Ultimate Attenuator

[jnug]

i just got an Ultimate attenuator and :crazy:AOK this thing is awesome. though nothing will beat a cranked amp by itself, but this thing is very close. i couldn't believe it. i wasn't expecting it to sound so good, i can barely tell there is anything there. mine has the plexi switch and the bedroom switch which i don't really like. the bedroom switch you can tell there is an attenuator in your signal. so i don't use any of the features.

i can finally use my slo with the guys i playing with. we have a very low stage volume so the slo is to much for most of our situation, not any more. even the guys i play with commented on how clear it was. it didn't alter my sound, it didn't change the way the slo feels, very good product.

of course i'm not gonna rely on it all the time, just use it in situation where i need a low stage volume, which i hope will not be all the time. though this is a really good attenuator nothing will beat a cranked amp with out one

[JubileeMan 2555]

I agree. I have a Ho Attenuator on its way and I've had a UA a while ago. Great product.

Even though many here do their best to scare users off the unit, I think enough players using the unit have proven its safety and I personally believe the concept to be a massive step forward in the technology of guitar gear.

[wedewer]

get the plexi switch. If I understand it correctly, the switch actually turns that feature off. without the switch it is in the circuit. To me, it sounds way better with the switch set to off. That is my preference. But.... the switch allows you to choose.

And I will say it again. I know I sound like I get a kick back from the UA guys but I don't. It is an amazing piece of equipment. It unlocked the possibilities on my Straub Cantus. I played non stop for like 3 days and used it at a gig and was floored.

[Jon C]

I am very impressed with what I've heard too. Agree on the bedroom switch. I may or may not keep it long term for reasons having nothing to do with how good it sounds, but it pleasantly surprised me too based on my expectations (neutral).

The Plexi switch seems to bump up the highs a bit though its effect seems to vary on diff. amps.

Compared to "ordinary" use, with the UA on the power tubes are definitely getting slammed, e.g., my Deluxe Reverb (SF) with volume at 6, knocked down to less than ear splitting basement volume. You can see the light show if you watch the tubes compared to playing at lower volume, so yes, more tube wear to be sure.

[JubileeMan 2555]

The plexi switch is intended to add the highs that you PERCEIVE is lost with lots of attenuation. As I understand it, because our ears hear frequencies very different at different dB levels, the Plexi switch, when adding something to the sound, is simply compensating for the lack of highs you hear at lower volumes.

IMO, its a fun option to have, but not necessary.

[bjjp2]

I just got a Ho. I was really enjoying it with my cranked Germino Club 40 head, until, around the 4th or 5th time I was using it, the amp faded out and died, refusing to produce a sound. The amp's now in the shop. Could just be a coincidence, but I doubt it. I have no interest in "scaring anybody away" from the UA/Ho, but I wanted to pass my experience along.

[Timster]

Probably just burnt out a tube, or a fuse blew. Because the UA allows you to crank your amp, tubes can wear out quicker than normal...

[jnug]

The plexi switch is intended to add the highs that you PERCEIVE is lost with lots of attenuation. As I understand it, because our ears hear frequencies very different at different dB levels, the Plexi switch, when adding something to the sound, is simply compensating for the lack of highs you hear at lower volumes.

IMO, its a fun option to have, but not necessary.

i agree it is a fun option but really not necessary. i like it off and just stock. the bedroom switch is nice for really low volume. i just don't like having options to interfere with the signal any more than what's already there. when both options are ingaged i feel they really effect the original tone, but this is my opinion with my gear, it may be diiferent with other gear.


I just got a Ho. I was really enjoying it with my cranked Germino Club 40 head, until, around the 4th or 5th time I was using it, the amp faded out and died, refusing to produce a sound. The amp's now in the shop. Could just be a coincidence, but I doubt it. I have no interest in "scaring anybody away" from the UA/Ho, but I wanted to pass my experience along.

alot of times it isn't the attenuators fault. when your driving things hard parts will break, same as in race cars, and any machine. this is where high quality parts comes in handy

[JubileeMan 2555]

I just got a Ho. I was really enjoying it with my cranked Germino Club 40 head, until, around the 4th or 5th time I was using it, the amp faded out and died, refusing to produce a sound. The amp's now in the shop. Could just be a coincidence, but I doubt it. I have no interest in "scaring anybody away" from the UA/Ho, but I wanted to pass my experience along.

Fading out and died with a cranked amp sounds like a dead tube to me. Did you first try swapping out tubes before sending it in?

[bjjp2]

Fading out and died with a cranked amp sounds like a dead tube to me. Did you first try swapping out tubes before sending it in?

I did. Power, pre and recto.

[Timster]

fuse?

[bjjp2]

fuse?

Fuses are intact. I have a thread on this in the Amp Technical forum. I didn't want to hijack this whole thread. I'll let people know when I hear from the tech.

[Rod]

That's interesting...The Ultimate attenuater actually reamps your amp, sending a line signal to a 100 watt solid state power amp.....If you can't hear the difference, that's great.....

[Yossi]

I just got a Ho. I was really enjoying it with my cranked Germino Club 40 head, until, around the 4th or 5th time I was using it, the amp faded out and died, refusing to produce a sound. The amp's now in the shop. Could just be a coincidence, but I doubt it. I have no interest in "scaring anybody away" from the UA/Ho, but I wanted to pass my experience along.


There is a "switch" of sorts in the UA that requires you to hit a note or chord on your guitar to "wake up" the UA. Sometimes it's a bid annoying that I want to play and the UA is stubborn and doesn't wake up as fast as I would like. Usually the culprit is that I have one or more of my stomp boxes on with a lower volume that isn't quite enough to start the UA.

If you tried your amp without the UA and it didn't work you would know if it is your amp.

I posted a note of caution on another thread about making sure that your amp is set at 16 ohms before hooking it up to the UA. The mis match of impedance nailed me when I just got my UA and my Germino 55LV hooked up to a 2x12 speaker cab set at 4 ohms. I made the mistake of matching the Amp to the ohms of the speaker cab rather than the UA. Fortunately I only killed a fuse and some tubes. Greg Germino fixed the amp on warranty, which makes him Number 1 in my book on customer service. He strongly recommended that I only use the ohm setting that I mentioned above, when using the UA, regardless of the ohms of the speaker cab.

[bjjp2]

There is a "switch" of sorts in the UA that requires you to hit a note or chord on your guitar to "wake up" the UA. Sometimes it's a bid annoying that I want to play and the UA is stubborn and doesn't wake up as fast as I would like. Usually the culprit is that I have one or more of my stomp boxes on with a lower volume that isn't quite enough to start the UA.

If you tried your amp without the UA and it didn't work you would know if it is your amp.

I posted a note of caution on another thread about making sure that your amp is set at 16 ohms before hooking it up to the UA. The mis match of impedance nailed me when I just got my UA and my Germino 55LV hooked up to a 2x12 speaker cab set at 4 ohms. I made the mistake of matching the Amp to the ohms of the speaker cab rather than the UA. Fortunately I only killed a fuse and some tubes. Greg Germino fixed the amp on warranty, which makes him Number 1 in my book on customer service. He strongly recommended that I only use the ohm setting that I mentioned above, when using the UA, regardless of the ohms of the speaker cab.

Wow, I had no idea about this. So with my 8 ohm speaker cab, I should set the Germino to 16 ohms when using the Ho?

[Yossi]

Wow, I had no idea about this. So with my 8 ohm speaker cab, I should set the Germino to 16 ohms when using the Ho?

Yes. Your amp has to run into a 30 ohm UA. The UA is what is pushing your speakers after that. I had my problem when I set my amp at 4 ohms. You may not have the same problem at 8 ohms, but Mr. Germino said that the 16 ohm setting would be the safest.

[jnug]

i contacted the guys at the UA about this, they say you don't have to do that. i don't get it? even says you don't have to run it at 16ohms in the instructions that came with it. either way nothing will beat a amp running with out one but it is still a great piece of gear.

[Yossi]

i contacted the guys at the UA about this, they say you don't have to do that. i don't get it? even says you don't have to run it at 16ohms in the instructions that came with it. either way nothing will beat a amp running with out one but it is still a great piece of gear.


I know they say that, but at the same time I had a brand new amp develop the above mentioned problems and an expert amp builder tell me otherwise. The bottom line is you can run your amp however you want, it's up to you. There happens to be two different views.

[Geetarpicker]

If one has a UA, doesn't have the plexi switch, and wants to hear what you're missing it's an easy mod. The "load" on the UA is two resistors AND a choke, ALL in series. The choke effectively adds some highs. The plexi switch basically shorts out the choke, so that the signal is only going though the resistors and skipping the choke. So, if one only needs the darker tone of the plexi switch in the "off" position (but doesn't have one) just run a jumper wire in place of the choke in the load circuit. That said, I added a "plexi switch" to my UA, but I doubt I'll ever use it in the "on" position. I tend to go for darker tones mostly as my amps are all on the brighter side and I usually don't need any more highs added in the signal chain. To my ears the UA sounds a little brighter than "flat" with the switch "on", and a little darker than "flat" with the switch "off" and the choke bypassed.

[hasserl]

i contacted the guys at the UA about this, they say you don't have to do that. i don't get it? even says you don't have to run it at 16ohms in the instructions that came with it. either way nothing will beat a amp running with out one but it is still a great piece of gear.

That's because they don't know what they are doing or what they are talking about. Send them your amp repair bill.

[Rod]

There is a "switch" of sorts in the UA that requires you to hit a note or chord on your guitar to "wake up" the UA. Sometimes it's a bid annoying that I want to play and the UA is stubborn and doesn't wake up as fast as I would like. Usually the culprit is that I have one or more of my stomp boxes on with a lower volume that isn't quite enough to start the UA.

If you tried your amp without the UA and it didn't work you would know if it is your amp.

I posted a note of caution on another thread about making sure that your amp is set at 16 ohms before hooking it up to the UA. The mis match of impedance nailed me when I just got my UA and my Germino 55LV hooked up to a 2x12 speaker cab set at 4 ohms. I made the mistake of matching the Amp to the ohms of the speaker cab rather than the UA. Fortunately I only killed a fuse and some tubes. Greg Germino fixed the amp on warranty, which makes him Number 1 in my book on customer service. He strongly recommended that I only use the ohm setting that I mentioned above, when using the UA, regardless of the ohms of the speaker cab.
Yossi...that symtom sounds like you might have a dirty jack somewhere

[Yossi]

Yossi...that symtom sounds like you might have a dirty jack somewhere

I don't think so. There is something in the UA that requires a signal to switch on. It's part of the design.

[jnug]

That's because they don't know what they are doing or what they are talking about. Send them your amp repair bill.

that's funny, that's what they said about you guys.

[cjshaker]

That's because they don't know what they are doing or what they are talking about. Send them your amp repair bill.

So let me get this right. They build what is probably the best sounding attenuator on the market, which is pretty well agreed on by all people (that I know of anyway) but yet they dont know what they are doing.

Interesting.

[bjjp2]

Just an update. My amp tech said the "high voltage section of my power supply was shorted". Since this happened on one of the first times I ever had the amp cranked through the Ho attenuator, I have a hard time believing that it's just a coincidence. (As mentioned, if I was supposed to run the amp at 16 ohms with the Ho, I was unaware of that).

[JubileeMan 2555]

...My amp tech said the "high voltage section of my power supply was shorted"....

Thanks for the update!

I'd like to get a more specific detail of what he's talking about, though. Thats extremely vague. Two components too close that get bumped together could be considered a "short". Did the tech have to replace anything?

The club 40 uses a Tube rectifier. I wonder if that tube caused the short.

I'd love to hear some more tech-knowledgeable folks comment on how the attenuator (or load/reamp like the UA) might effect a power supply.

Also, did you ever play the amp cranked for any period of time before you bought the attenuator?

[jnug]

So let me get this right. They build what is probably the best sounding attenuator on the market, which is pretty well agreed on by all people (that I know of anyway) but yet they dont know what they are doing.

Interesting.

i find it interesting as well. i contacted them about this very topic before i purchased mine they said you don't have to set your amp to 16 ohms. i even asked my tech who knows his shit and he checked out the UA and did some research and he said that you don't have to set your amp to 16 ohms. it would seem that if this was the case there would be more people with busted amps complaining. i just see one and his problem wasn't the attenuator

i'm gonna beleive the people that made the UA instead of somebody posting on TGP. :AOK

[LunarSF]

So let me get this right. They build what is probably the best sounding attenuator on the market, which is pretty well agreed on by all people (that I know of anyway) but yet they dont know what they are doing.

Interesting.

If I understand the situation correctly, a quick read of previous UA forum threads shows there's a flaw in your logic: UA may appear to have designed and built the UA, but in reality they just market the UA. The UA was an existing product designed and handbuilt in Canada by someone not so interested in marketing or style, so the product excelled at function but lacked any style. So the UA guy just licensed the design and subcontracted the labor (I have heard it is all or partially built in China now) and put a nicer faceplate on it.

Apologies if I am incorrect.

They may not know specifics, then again they might by now. It does look much nicer.

[soldano16]

There is a "switch" of sorts in the UA that requires you to hit a note or chord on your guitar to "wake up" the UA.

Per Mr Ho, it's a relay put in there for safety to make sure the amp and speaker are plugged in correctly. I find the easiest way to start up is to turn the UA volume completely down and guitar full up and wack a chord. Then just bring up the UA volume.

[soldano16]

Apologies if I am incorrect.


Basically correct.

The hand made Ho's (some have the Ultimate Attenuator label, some don't) have the volume on the right. The newer, Made in China ones have the volume on the left. And I believe you can only get the two volume model from Mr. Ho. The footswitchable 2 volume is a FANTASTIC feature.

http://i438.photobucket.com/albums/qq108/Soldano16/rig.jpg

[hasserl]

that's funny, that's what they said about you guys.

I'd be happy to debate them right here on TGP. IT's obvious they haven't a clue. Let me ask you a simple question, would you plug your 4 or 8 ohm amp into a 32 ohm speaker cabinet? No? Why not? Your answer to that is exactly why you shouldn't plug it into a UA. It's not rocket science guys, it's really prety simple. You all seem to understand this when it comes to speaker cabs but for some reason you throw that out the window when it comes to this UA contraption. Strange.

So let me get this right. They build what is probably the best sounding attenuator on the market, which is pretty well agreed on by all people (that I know of anyway) but yet they dont know what they are doing.

Interesting.

If I understand the situation correctly, a quick read of previous UA forum threads shows there's a flaw in your logic: UA may appear to have designed and built the UA, but in reality they just market the UA. The UA was an existing product designed and handbuilt in Canada by someone not so interested in marketing or style, so the product excelled at function but lacked any style. So the UA guy just licensed the design and subcontracted the labor (I have heard it is all or partially built in China now) and put a nicer faceplate on it.

Apologies if I am incorrect.

They may not know specifics, then again they might by now. It does look much nicer.

That appears to be correct, the designer is a guy that is known around here as Ho. Besides that, there have been several posts of these same kinds of problems from UA users right here on TGP. The fact is, there is a problem with running your amp into too high of a load. It stresses the output transformer and the power tubes and tube sockets, everything connected to the primary side of the output transformer. That is why amps have impedance selector switches, and that is why we match cabinets to amps.

[Paul86]

I've been playing my amp through a Ho since January - everyday. No problemo so far. As soon as my amp blows up in smoke and burns my house down I'll let you guys know;)
It's switched to 16 ohms, but I've also tried the 8 ohms position. Again, so far so good. By the way, I'm using the built in socket, which is delivering 100 volts to the amp. Not only does the amp work cooler, it sounds a bit sweeter too.

[Timster]

I think this Hasserl dude has a hidden agenda

[epluribus]

Not taking sides in this, my jury is still out, but I've been hashing out tech ideas with Hasserl for several years here in the amp pages. His info is well-researched and he calls 'em the way he sees 'em--even when I wished he'd call 'em my way. :)

Frankly, my impression of this thread and the discussion thus far is that there really doesn't seem to be any big agenda. You guys are sticking to some very intriguing issues regarding attenuation and it's been a very cool thread for that reason.

From a clinical standpoint what Hasserl is saying has significant and demonstrable merit. I'd have to see results that can be duplicated on a good workbench to the contrary to convince me UA has indeed discovered something new. Not to say they haven't, just saying I haven't seen any measurable and reproducible data yet. Don't know of anyone else that has yet either.

--Ray

[cg]

I love mine and couldn't live without it. Very transparent to my ears.

[cg]

Wow, I had no idea about this. So with my 8 ohm speaker cab, I should set the Germino to 16 ohms when using the Ho?

That's how I run my Germino with the UA.

[jnug]

someone besides a guy on TGP is gonna have to prove this to me. if he can provide evidence with pictures or some outside resource besides "this is how it is, i don't know why you guys don't get it" then i will change how i run it. but there is not information from UA saying that you need to run your amp at 16ohms and they are even saying you don't have to. my amp tech is also looking into it, and i respect him and his work because it is top notch.

so show me where it says the UA has to have the amp run at 16ohms? i have yet to see proof. i'm not trying to start and arguement, but someone is claiming something and is expecting everyone to follw his word without posting proof. post s'ome proof to back you statement don't post "because i said so, it's very clear" back it up, with pictures documentation what ever prove the guys at UA wrong. i'm interested to what pops up.

only on TGP will someone argue with the manufactors of a product about how it is supposed to be run.

[jackaroo]

Howdy guys...I think most of this ground has been covered in the old threads on this subject, but here a little retread...


I believe that the device is safe after running mine for nearly a year with my amps. I set my amp to the highest Ohm available- 16. Yes the Ho/UA is a 30 Ohm...not 32 BTW load. Anyway the risk that guys are concerned about is called "flyback voltage"...and If I understand it correctly, a bit of voltage can go backwards and fry the tranny if things are mismatched by too large a degree. The likelihood of this increases with driving the hell out of an amp.

That's the against side of the deal.

The "for" people such as myself look at the fact that the mismatch from 16 to 30 Ohm isn't a big deal. I'm told that the load on the amp is constantly changing when we play directly into a cab. So even without attenuation the the load is all over the place...sometimes just as high as with the HO/UA. There's also the fact that the load isn't changing, it's a fixed load and in theory may be protecting the amp from irregularities in voltage and flyback by providing a steady load.

All issues I've heard about that have a UA/Ho in the mix have been simple...like a tube going out or something. This type of thing is common if you're running the amp hard. Which is something you get to do with the Ho/UA. Also these folks seem to set the head and the cab to match, when they should get the head and the Ho/UA as close as possible.

By setting the amp to 16 you're just minimizing any risk to the amp, but 8 is fine...4 is pushing it- 2 is a no no. If it's really a concern, Ho will make the unit at whatever Ohm you want...so the point is basically a non-issue.

If you're really interested in the subject, do a little research as well as participating in this thread, you'll find plenty of opinions. Hasseral understands this stuff well, and theoretically he's right. It's not a great idea to mismatch these things. But, in real world applications those theories/facts don't come into play with a minimum of precaution. I don't think he's got an agenda, just a firm opinion that tends to come out in these threads. All in all, he's a good source of technical information, and I see him as an asset here...though a little disagreeable on this one topic.

Peace and best of luck with the Ho/UA, obviously I'm a big supporter. I love mine and consider it a must have for my amps of choice.


J

[jnug]

straight form the guy at the ultimate attenuator maybe this will help with out little delima:

We can mod the UA to 16 ohms but I don't recommend it. Here is what
I'm posting to my blog on the UA site that addresses these concerns.
Thanks!
Impedance matching on the UA
There are two serious considerations for load devices like the UA or
other attenuatos. They are
1.Flyback voltage from the load
2. High heat and high voltage from the amp
Both are dangerous to your amp. The higher the impedance of the load
and the more voltage an amp produces, the more flyback voltage can
become a concern.
The lower the impedance of the load, the more heat and voltage is
produced. It’s kind of a balancing act.
We have been asked why we don’t match the impedance of the load more
closely to an OT’s winding spec?
There are two reasons. One is tone. The 30 ohm load sounds better. The
other is safety. At 30 ohms, the amp doesn’t work as hard or produce
as much voltage and heat which are your amp and tube’s enemy. In
principle and practice, the 30 ohm load is safe for the amp and
doesn’t introduce unacceptable risk for the amp and tubes at any
impedance in theory and practice until about 2 ohms. That’s pushing it
a bit with the mismatch but generally amps with 2 ohm taps are lower
wattage and lower voltage which helps. If you are nervous about it,
plug your amp into the UA’s 100v tap. It drops the voltage about 10%,
not low enough for cathode stripping of the tube to be a concern, but
low enough to make the amp and tubes run safely when the amp is
cranked for long periods of time. Is it as safe as running straight
into a cabinet? Yes, maybe more so at the same playing volume and
intensity (while using the 100v tap). Why then, do techs and amp
makers not recommend using attenuators (except their own brand?). I
suspect that anyone that warrants a product or repair would prefer not
dealing with issues like current tube production failure rates that
can cause damage to an amp. Who can blame them. Playing hard can
reveal problems with tubes and amp circuits and playing through an
attenuator encourages playing hard. That’s my take on it. If your amp
runs at an unusually high voltage or you have a shaky output tube, I
don’t recommend using an attenuator. Otherwise, play the amp. That’s
what it’s there for.
Mark Gregg, Magus Innovations.

[Geetarpicker]

I agree with UA that the higher load is safer. My '68 plexi 100 Superbass runs a fairly high plate and screen voltage for the era, and can red plate slightly (when dimed under sustained notes and chords) with many modern EL34 tubes even when biased properly. It definately runs a little cooler and the tubes are less apt to do this with an ohms offset. Typically I run the amp on 8 ohms with a 16 ohm cabinet or 16 ohm THD attenuator, or set to 16 ohms with the 30 ohm resistive load UA. The amp seems happier this way, and I've been doing this way with most speakers/attenuators for 5 years now with no problems. Actually the amps goes through tubes quicker matched "properly".

[Yossi]

I don't have an agenda and I don't see an agenda here regarding the load issue. I am always using my UA with my Germino 55LV and I am using the lower voltage 100v option, and the amp set at 16 ohms. That seems to be the consensus of the best way to set the ohms switch on the amp. That doesn't mean that 8 ohms will fry your amp, and that my not be a problem either.

When I got my UA I did not understand that it was a fixed 30ohm load and I matched my Germino to my 2x12 cab @4ohms. When I took the UA for a test run with the amp cranked up to a 10 using the UA to get the volume way down, my amp blew. If I didn't dime the amp maybe that wouldn't have happened. If the amp wasn't brand new out of the box when I did that, it may have been easier to blame the amp as having a bad tube,etc and attribute the extra volume for coaxing the problem out much faster than it would have at a lower volume. Fortunately I was able to learn what a gentleman Greg Germino is when he fixed my amp, including replacing the tubes at no charge. I could have justifiably addressed my issue with UA for giving the "Green Light" to run the amp at the ohms that I did.
I sent both the Amp and the UA to Germino to test them both and as I said before the recommendation of running the UA at 16ohms when using the UA came from him. So it's not just an uninformed TGP opinion vs the Manufacture of the best attenuator on the market.
If I do have an "agenda" for posting my story, it is only to be taken as helpful advice to anyone who chooses to listen and hopefully avoid the same problem that I had.

[Mark Gregg]

Hi. Mark Gregg here from Magus Innovations. Yossi, I spoke to Greg about this and if I recall correctly it was a tube issue. I would just like to be clear on this that the tube blew and not the amp as you stated. You are free to extrapolate what you like from Greg's recommendation but I would like to clarify what actually caused the problem. A shaky tube which according to Greg, accounts for 99% of the amp problems he sees. Not trying to confront, just trying to keep the accounts straight.

[Yossi]

Hi. Mark Gregg here from Magus Innovations. Yossi, I spoke to Greg about this and if I recall correctly it was a tube issue. I would just like to be clear on this that the tube blew and not the amp as you stated. You are free to extrapolate what you like from Greg's recommendation but I would like to clarify what actually caused the problem. A shaky tube which according to Greg, accounts for 99% of the amp problems he sees. Not trying to confront, just trying to keep the accounts straight.


Hi Mark. I apologize if my layman's terminology is incorrect. I had a fuse that blew and tubes too, that's what I meant when I said amp. I was speaking in broad terms. I don't believe that I was merely extrapolating that the running the amp at 4ohms into the UA at 30ohms was the cause of the fuse and the tubes blowing based on Greg Germino's advice of running the Amp at 16ohms. Greg told me that he thought that the 4ohm into 30ohm caused the fuse and the tubes to go and that it was luck that the damage to the amp was limited to that.

I want to be clear that I think that UA is a wonderful product and I highly recommend the Maggus UA. I would suggest that your product literature be more clear about matching the ohms from the amp to the UA.
Best Regards,

Yossi

[Paul86]

AFAIK old Marshalls, and old amps in general let's be fair, blew up from time to time. Before there were attenuators. If you crank an old amp to get that sweet distortion cooking you are already 'putting it at risk'. It was not designed to work on the edge, all the time, for long periods. Period.
When people buy attenuators and start getting the goods without the earbleed, they tend to go overboard a bit.
As for the theoretical stuff, well, it's just theory. As the name implies, it may work in practical terms, but then again it may not. Theoretically, the Blues was all 'wrong'! Rock'n'roll was even wronger! If you don't try it yourself, you'll never know. I don't think theoretical types have an agenda, though. If they do have an agenda, it's their own private thing of putting too much stock on a theory, especially if they tend to think along the same lines. Rock'n'roll amps ain't no rocket science.

[kindburro]

I must step in here. There are multiple threads on TGP regarding the issue of blown output tubes and use of the Ultimate Attenuator. Currently another thread is running regarding the use of the UA with a Traynor amp that experienced difficulty, both a tube issue and bad output tube socket as a result of being used with the UA.
It is my opinion from years in the field of repairing every type of tube amp out there as well as years of experience with my own line of amplifiers that running a 30 ohm fixed load such as the UA uses, with an amplifier set on anything other than 16 ohms is harmful. Even at 16 ohm setting your are at a 50% mismatch. Most amplifiers are tolerant of this. Settings of 8 ohms or lower with the UA I don't agree with...again my opinion. Everyone here can make their own judgement, but for safety and IF someone chooses to use the UA with any Marshall or Marshall style amp I would strongly urge you to use a setting of 16 ohms with this product.

I see a few comments with people impedance mismatching their heads and cabs and wonder why their amps tolerate this while others have problems with using the UA. The answer is quite simple as a 30 ohm fixed load is quite different that a speaker load of 30 or 32 ohms. The fixed load does not change where the reactive load of the speaker fluctuates as the speaker is moving.

What happens when you play an amplifier into a load even one "notch/setting/impedance" (choose one) higher than what the amp is set for, you are doubling primary impedance of the output transformer.
That would be a 50% mismatch. A dual EL-34 OPT goes from 3.3K to 6.6K.
Now set an amp at 8 ohms, run this into a 30 ohm fixed load and the primary impedance doubles again, now at 13.2K. If you go to 4 ohms you double again....!!!!! The result is flyback arcing at the tube socket due to the tubes seeing such a high impedance. Tubes will arc, fuses will open and loss of output tubes and possibly screengrid resistors as well as arced tube sockets can be and are the result.

Plainly and simply a tube amplifier must be in good working order to obtain top performance. Attention to condition of an older amp is imperative if you are using the amplifier in gig situation or pushing the amp to get certain sounds. I can tell you running an amp at full volume or near full volume will not hurt anything as long as the amp is in good working order.
Tubes are not what they used to be, this is something we all know, many current production tubes are not tolerant of impedance mismatching and experience failure as a result. Many current production tubes are not stable at voltages above 480vdc. This is a far cry from the European and US manufactured tubes of years past.

I would like to second the suggestion that the product literature for the UA be more specific about recommendation of how amplifiers should be used with their device.

This is not a strike against the UA, my post is to be taken as informative for those who have the product or have interest in the product as there are repeated threads with the same concern.

My best to all,
Greg Germino
www.germinoamps.com (http://www.germinoamps.com)

[ripoffriffs]

I wish YuKong Ho himself would address this issue on this forum (or some other site we can link to) and provide a rationale for why his design is this way. Could a TGP member in Vancouver BC go to his shop and give him a printed transcript of this and other threads about the UA and why it's designed this way?

I'm sure if he saw the amount of discussion (that's the polite word) that has gone on about this product, he would feel compelled to respond. Or is this too much to hope for?

[Timster]

I am glad we have some experts in-house to help clarify the issues.

For what it's worth, I have been using an Ultimate Attenuator for 2 + years now with no problems whatsoever... I have, however, always used it with the amp at 16 ohms.

[soldano16]

I wish YuKong Ho himself would address this issue on this forum (or some other site we can link to) and provide a rationale for why his design is this way. Could a TGP member in Vancouver BC go to his shop and give him a printed transcript of this and other threads about the UA and why it's designed this way?

If I remember, I'll give him a call tomorrow.

[Lavely]

Randall & Greg - Thanks for your contributions here. I love my UA, but I have minor worries in the back of my head...curious what HO has to say.

Lavely

[Belmont]

you guys make this sound like it's a new product. palease, give it a giant rest, he's been making these for a decade or more. do you guys honestly think he hasn't heard all of this before? he's not an inter dweeb and could care less about silly forums like this. I've known him for years, trust me he's heard it all before. if you want 16ohms, call him, he'll make it for you. I use mine with a Super Lead and a Hiwatt DR-103, it works better than I would have believed. I'm commenting strictly on the Ho Attenuator, not the new made in China Magus UA, those I can't speak for.

[epluribus]

These scope photos clearly show...

Nice methodology Randall, much appreciated. Not only has controversy raged around the UA lately, but it's surrounded attenuators in general pretty much since they came out. It would be very enlightening to see shootout-style bench tests of several attenuators to try to clinically pin down the beefs and rumors as much as anything. Not sayin' btw, that you or anyone else should run right out and do it, just an obeservation. The whole attenuation thing is proving to be quite the complex beast to rassle.

--Ray

[Yossi]

you guys make this sound like it's a new product. palease, give it a giant rest, he's been making these for a decade or more. do you guys honestly think he hasn't heard all of this before?.

It's my fault. I got my UA and it was new to me and when I used it with a 4ohm mismatch into the 30ohm fixed load my tubes fried. I wasn't so concerned about HO or Magus hearing about the problem as I was about the people on "Silly forums like this"


he's not an inter dweeb and could care less about silly forums like this. .

OUCH!!


I've known him for years, trust me he's heard it all before. if you want 16ohms, call him, he'll make it for you. I use mine with a Super Lead and a Hiwatt DR-103, it works better than I would have believed. I'm commenting strictly on the Ho Attenuator, not the new made in China Magus UA, those I can't speak for.

I like mine also. The point of the contention is not to set your amps output below 16ohms when using the UA or Ho Attenuators. After reading some of the most recent posts from highly respected amp builders and experts in the field about the subject I think the issue of mismatch loads can not be put into any category other than Expert Valid Advice.

If someones amp only has an output of 8ohms or 4ohms, then your suggestion of having Ho make one with a 16ohm or 8ohm fixed unit would prevent problems.

[Belmont]

I trust Ho far more than any unknown amp builder, check out who's using his products, and then check who's using theirs.

[Jon C]

you guys make this sound like it's a new product. palease, give it a giant rest, he's been making these for a decade or more. do you guys honestly think he hasn't heard all of this before? he's not an inter dweeb and could care less about silly forums like this. I've known him for years, trust me he's heard it all before. if you want 16ohms, call him, he'll make it for you. I use mine with a Super Lead and a Hiwatt DR-103, it works better than I would have believed. I'm commenting strictly on the Ho Attenuator, not the new made in China Magus UA, those I can't speak for.

that would be interesting ... for the safety factor, someone who has only 8 ohm and 4 ohm amps (like me), could just go with an 8 ohm version (?) ... though I recall someone saying that Mr. Ho thought the other versions did not sound as good as the 30 ohm he settled on as a default.

[fullerplast]

I trust Ho far more than any unknown amp builder, check out who's using his products, and then check who's using theirs.

:jo

How about you checking out the scope snaps showing 3080 volts across the primary OT winding? Or check out the screen grid current measurements Randall made?

It's like walking across a frozen lake with marginally thick ice.....a bunch of people may make it across, but that doesn't mean it's safe. It just means a bunch of people were lucky.

[OutterLimits]

First off, to call Randall Aiken or Greg Germino anything but experts on the subject is ignorant. Have some respect for crying out loud.

Second, I have used the UA with two amps, it sounds great, best I have heard, but if there are potential problems with the design then these should be noted in the instructions. That's all. Still a great unit.

No need for any nastiness, especially against the two electronic gurus who were nice enough to contribute to the thread.

[GuitarNorton]

Thanks Greg and Randall much appreciated!

[GearHeadFred]

I trust Ho far more than any unknown amp builder, check out who's using his products, and then check who's using theirs.

Dude are you serious? These are some of the most highly regarded guitar amp gurus on the planet! :bow

[GuitarNorton]

I trust Ho far more than any unknown amp builder, check out who's using his products, and then check who's using theirs.

I have some ocean front property I'll sell you in Arizona

[hasserl]

This is getting funny! Thanks for the laugh. :D

[FAC]

Mr. Aiken was kind enough to take the time to scope some impedance mismatches, and demonstrated that there are potentially unsafe voltage swings. That is, he produced data rather than conjecture. He also qualified his results by saying he did not use an actual UA. However, it's probably a decent assumption that a mismatch is a mismatch...

How many UA/Ho threads have there been in the last few months? Seems like a lot...this seems like the first one with actual data. I'm not a supporter/detractor (I don't own one, but I have thought about it)...but I do appreciate seeing data.

[Belmont]

Thanks, Harris, I appreciate it, but he has a right to his own opinion. Even if he has a poor sense of humor. :)

Randall Aiken
all I said about your product is that I've never heard of it, which is the truth. I didn't criticize it, or question it's design. you are the one who has done that, regarding the Ho. you are the one who went so far as to make slight of his name. there's too many of these things in use to take any critic seriously, keep the scope pictures and tutorials coming if that's what fulfills you.

I'm just a guy sticking up for a friend, maybe one day one of your customers will do the same. anyway there's more important things in life.:BEER

[Belmont]

I can respect that...I apologize for making a joke of his name, it just struck me as funny when I typed it, that's all.

Randall Aiken
no apology needed, I knew you weren't being serious. peace:BEER

[Ian]

Hey Guys!

Thanks Randall Aiken for showing some pics that demonstrates what you were referring to! It helps us with lesser (haha....MUCH lesser) technical knowledge on these issues.

I have a dumb question......The THD Hotplates are produced at specific ohmages (4, 8, 16). I think the whole idea behind doing this was to pair the proper Hotplate with your amp and speaker cabinet.......16 Ohm amp / 16 Ohm Hotplate and 16 Ohm cabinet.

Wouldn't it make to me to run your rig in this fashion just to make sure that nothing blows up?

I don't see why people would want to fool around with all the mis-match possibilities......Is there some "voodoo" that I am missing here?

I'm planning on getting the new 16 Ohm Faustine Phantom (when available) and running it with my 16 Ohm Blankenship into my 16 Ohm cabinet....

Thanks!

[ripoffriffs]

If you know him well (Mr. Ho that is), then why not ask him to provide a rationale for the 30 ohm load. Ask him how he reconciles the huge voltage being produced with mis-matched loads demonstrated by Randall Aiken. I'm serious.

Randall never attempted (in his original post with the picture of the oscilliscope) to critizice Ho or the UA. He just demonstrated the consequences of such a large mis-match between an amp and 30 ohm resistive ohm load when the amp is set at 4 & 8 ohm taps.

Belmont: if you had any inkling of an education you would realize how seriously genuine his demonstration was and what a truly legitimate point Randall demonstrates.

Based on your posts you haven't a clue how to interpret Randall's original post. It doesn't make it any less true.

There are truly more important things in life, your ignorance is surely not one of them.

all I said about your product is that I've never heard of it, which is the truth. I didn't criticize it, or question it's design. you are the one who has done that, regarding the Ho. you are the one who went so far as to make slight of his name. there's too many of these things in use to take any critic seriously, keep the scope pictures and tutorials coming if that's what fulfills you.

I'm just a guy sticking up for a friend, maybe one day one of your customers will do the same. anyway there's more important things in life.:BEER

[Belmont]

If you know him well (Mr. Ho that is), then why not ask him to provide a rationale for the 30 ohm load. Ask him how he reconciles the huge voltage being produced with mis-matched loads demonstrated by Randall Aiken. I'm serious.

Randall never attempted (in his original post with the picture of the oscilliscope) to critizice Ho or the UA. He just demonstrated the consequences of such a large mis-match between an amp and 30 ohm resistive ohm load when the amp is set at 4 & 8 ohm taps.

Belmont: if you had any inkling of an education you would realize how seriously genuine his demonstration was and what a truly legitimate point Randall demonstrates.

Based on your posts you haven't a clue how to interpret Randall's original post. It doesn't make it any less true.

There are truly more important things in life, your ignorance is surely not one of them.
why don't you call him and ask him, dazzle him with all your knowledge, tell him where he went wrong, I'm sure he'll take notes as he listens intently.
we're waiting...........

[Nuclearfishin]

Hey fellas, back on topic here--I found this explanation of the UA from the guy who produces Mohave amps although I don't fully understand the explanation. Can any of you techies elaborate? Also, they seemed to mention that the 100V power tap on the back makes them safer on older amps. True?

With the Ultimate Attenuator, your amps current is reduced leaps and bounds.
For instance, if your amps set for a 8 ohm load, the UA is only going to see a maximum of around 25 watts made by your 100 watt amp. That is because the load is approximately 4 times larger. The result is the power amp is full throttle but the power output is low. That is good. It saves not only your output transformer but your power transformer. This is probably a good answer to the Mercury Magnetics concern now that the amp is not actually making any where near its full power even though the power amp is full tilt. The power transfered from the amp to the laod simply can't be any higher then the equation allows for.

The UA has a built in low impedance power amplifier. The term low impedance means strong high frequency response and with their well crafted internal audio coupling, they have managed to retain and preserve the sound quality while keeping the amp at a low volume. The reduction of actual power is safer and the audio quality is preserved and enhanced via the audio coupling circuitry as well as the built in low impedance power amplifier, which does exactly what you need for low volume high frequency preservation.

Because of these two basic facts, the Ultimate Attenuator is definitely the safest product you can use and it delivers that low volume sound with the least impact which results in a very accurate quality of sound reproduction.

[Bussman]

Mr. Aiken was kind enough to take the time to scope some impedance mismatches, and demonstrated that there are potentially unsafe voltage swings. That is, he produced data rather than conjecture. He also qualified his results by saying he did not use an actual UA. However, it's probably a decent assumption that a mismatch is a mismatch...

How many UA/Ho threads have there been in the last few months? Seems like a lot...this seems like the first one with actual data. I'm not a supporter/detractor (I don't own one, but I have thought about it)...but I do appreciate seeing data.

Amen to that! Some people need to leave emotions aside, it's only a piece of gear.

Kudos to Randall Aiken for providing hard data for us to ponder.

[hasserl]

Hey fellas, back on topic here--I found this explanation of the UA from the guy who produces Mohave amps although I don't fully understand the explanation. Can any of you techies elaborate? Also, they seemed to mention that the 100V power tap on the back makes them safer on older amps. True?

With the Ultimate Attenuator, your amps current is reduced leaps and bounds.
For instance, if your amps set for a 8 ohm load, the UA is only going to see a maximum of around 25 watts made by your 100 watt amp. That is because the load is approximately 4 times larger. The result is the power amp is full throttle but the power output is low. That is good. It saves not only your output transformer but your power transformer. This is probably a good answer to the Mercury Magnetics concern now that the amp is not actually making any where near its full power even though the power amp is full tilt. The power transfered from the amp to the laod simply can't be any higher then the equation allows for.

The UA has a built in low impedance power amplifier. The term low impedance means strong high frequency response and with their well crafted internal audio coupling, they have managed to retain and preserve the sound quality while keeping the amp at a low volume. The reduction of actual power is safer and the audio quality is preserved and enhanced via the audio coupling circuitry as well as the built in low impedance power amplifier, which does exactly what you need for low volume high frequency preservation.

Because of these two basic facts, the Ultimate Attenuator is definitely the safest product you can use and it delivers that low volume sound with the least impact which results in a very accurate quality of sound reproduction.

Translation: Vic is working on UA as an advertiser on the Plexi Palace forum, or has signed them up already. It's all about the money.

What Vic is saying in the above description is the UA is safer for your amp because the impedance mismatch will result in less current draw thru the transformer. The problem with that assessment is that the danger to the output transformer from excessive current draw is much less dramatic than the danger from the high flyback voltage spikes. Now add to that the concern over excessive screen grid current and there is a second avenue for failure exacerbated by the high impedance mismatch of the UA.

[reaiken]

Translation: Vic is working on UA as an advertiser on the Plexi Palace forum, or has signed them up already. It's all about the money.

What Vic is saying in the above description is the UA is safer for your amp because the impedance mismatch will result in less current draw thru the transformer. The problem with that assessment is that the danger to the output transformer from excessive current draw is much less dramatic than the danger from the high flyback voltage spikes. Now add to that the concern over excessive screen grid current and there is a second avenue for failure exacerbated by the high impedance mismatch of the UA.


To be fair, what he says is mostly correct (except that the power output is half at 4x mismatch, not at 2x mismatch, so it is more like 70W if you run a 2x mismatch and 50W if you run a 4x mismatch). Also, if you don't drive the amp into hard clipping, you don't get the excessive screen current or voltage spikes, so in theory, the thing is perfectly safe - it's just when you drive the output stage into hard clipping with duty-cycle modulation that things start to get out of hand with excessive screen current and voltage spikes.

By the way, I deleted all my other posts on the subject. As a manufacturer, it is impossible for me to be perceived as unbiased when commenting on another manufacturer's products, even when presenting data that is only peripherally associated.

Randall Aiken

[Timster]

If I remember correctly, even Hogy, from Komet amps uses a UA...go figure.

Bottom line, using the UA should be safe if you set your amp to 16 ohms

[hasserl]

By the way, I deleted all my other posts on the subject. As a manufacturer, it is impossible for me to be perceived as unbiased when commenting on another manufacturer's products, even when presenting data that is only peripherally associated.

Randall Aiken

That's too bad, but understandable. I was just thinking I should capture those images in case this thread gets deleted like so many others.

Thanks for posting them anyways, that was good info to see.

[meterman]

My $.02 - I for one appreciate the input from expert amp builders like Randall Aiken and Greg Germino, thanks for your time and if there are those who don't see the value, that's too bad. I personally think it's a good thing to hash this out as I own one and want to know the full story, so I can balance any potential risks with my increased enjoyment of my amps.

I've had a Ho for a few weeks and have to say it works as advertised, very smooth reduction in volume keeping high end intact almost all the way down, very nice. I still don't like the feel when it's way down low but it may still record well that way, haven't tried it yet. It does allow me to crank my larger amps (35w and 50w TopHat heads) much more than I ever could before, without damaging my ears. Yes I am concerned about risk to the amp but rarely ever run the amps flat out. If I did blow a tranny I could always get a replacement from TopHat - it's the guys using vintage amps with these, where a blown tranny could devalue the amp significantly, that are really putting it to the test....

Anyway, overall I'm very impressed, build quality is nicer than some photos I've seen, and Mr. Ho was very pleasant and interesting to talk to on the phone, answered all my questions very patiently. Price with options was the same as the UA base model....only one little gripe, the cooling fan was pretty noisy, more than my two PCs together, so I had to replace it with a super quiet 60mm computer case fan b/c my primary use will be for low volume recording. Other than that, very satisfied so far....

[hasserl]

If I remember correctly, even Hogy, from Komet amps uses a UA...go figure.

Bottom line, using the UA should be safe if you set your amp to 16 ohms

Better check w/ Hogy on what impedance setting he uses it with. IIRC from past threads he doesn't advise it with 8 or 4 ohm amps (or set to those impedances on amps with switchable impedance settings). And that's all I've ever commented on with the use of these units. Perhaps he'll clarify that here, but if not, go check with him.

[Yossi]

By the way, I deleted all my other posts on the subject. As a manufacturer, it is impossible for me to be perceived as unbiased when commenting on another manufacturer's products, even when presenting data that is only peripherally associated.

Randall Aiken

That's a shame. It was great of you to post your experimental results and your expert opinion on this topic. I would much rather have the emotional posts from some other members deleted , rather than your educational posts. I find it difficult to put up with some of the personal slams that are hashed out on TGP, but I tolerate them because I can still find informative posts from people, such as you, who make the time I spend on TGP worth while. So please don't withhold your knowledge from those of us who value it!

[epluribus]

And so it was the Juries of Salem were sated...

[silencer eleven]

Ok here's my question. I have a 1965 BF tremolux that is 4 ohms and i'm running it into a 4 ohm cabinet. I have had the amp recently looked at and everything is in great working condition. My sweet spot for the amp is around 4 maybe 4 1/2, so since i'm not running the amp full tilt or even at half volume would it be safe the use the UA?

[soldano16]

If I remember, I'll give him a call tomorrow.

I just go off the phone with Mr. Ho on this exact issue. He agrees that a 4 ohm Fender amp turned all the way up and run for hours could be an issue. He offers a 30/8 ohm switch as an option to cover the Fender fellows.

[valcotone]

I just go off the phone with Mr. Ho on this exact issue. He agrees that a 4 ohm Fender amp turned all the way up and run for hours could be an issue. He offers a 30/8 ohm switch as an option to cover the Fender fellows.


Did he say why it could be an issue?

(Though from earlier posts in this thread it's clear, I'm just curious on Mr. Ho's comments on the issue).

[Nuclearfishin]

I just go off the phone with Mr. Ho on this exact issue. He agrees that a 4 ohm Fender amp turned all the way up and run for hours could be an issue. He offers a 30/8 ohm switch as an option to cover the Fender fellows.

I also just read that a resistor can be removed to make the UA run at 16 instead of 32 ohms. Are there any amps running at more than 16 ohms where it would make more sense to run at 32 vs. 16?

[silencer eleven]

Is it only an issue with a 4 ohm amp if your running it at max or close to max volume?

[fish78]

I just go off the phone with Mr. Ho on this exact issue. He agrees that a 4 ohm Fender amp turned all the way up and run for hours could be an issue. He offers a 30/8 ohm switch as an option to cover the Fender fellows.
Help my ignorant rear end out...what is a 30/8 switch...I presume...well, I am not going to presume...

I have another question, i have been talking with Mark Greg about using the UA to INCREASE the volume in a low wattage amp for gigging purposes, in addition to the normal attuator use...he says that there is a watt doubler switch that can be added...OK, I get how that would work, but he also says if you had a 8 ohm amp and run it through the UA into a 2 ohm speaker cabinet that you will also double volume...I don't want to pester Mark with repeatedly saying, I don't understand how this works...could someone be so kind as to fill me in as well as comment on the safety issues with such an arrangement...Mark says it is safe...

[soldano16]

Did he say why it could be an issue?

(Though from earlier posts in this thread it's clear, I'm just curious on Mr. Ho's comments on the issue).

I mentioned the concern here about the flyback voltage. He said that could be an issue if the amp is very cranked up. I then mentioned that many folks would be using their amps that way - cranked all the way up. That's the point where he mentioned the 30/8 switch, which would change the resistance load of the UA from 30 ohms to 8.

[hogy]

If I remember correctly, even Hogy, from Komet amps uses a UA...go figure.

Bottom line, using the UA should be safe if you set your amp to 16 ohms

Yes, I do use an UA for ultra low volume home playing. But I have also said that I use it with 16 Ohm amps only. I would personally not use it with 4 or 8 Ohms.

I have used the UA for a few years now and have not experienced any problems.

[Nuclearfishin]

One more quick question for the experts--is there less chance of the flyback voltage if the amp is running at a lower volume? Also, do any of the settings on the UA (such as less attenuation) decrease the chance of problems?

Thanks!

[stratovarius]

Does using the 100v tap change the effective output impedance?

[fullerplast]

is there less chance of the flyback voltage if the amp is running at a lower volume?


Yes, the lower the volume, the less flyback.

Also, do any of the settings on the UA (such as less attenuation) decrease the chance of problems?
Thanks!

It's not really an attenuator, so reducing the output level won't affect the load mismatch, or reduce the flyback danger. Only a reduction in load resistance will decrease the chance of problems, on the UA's end.

Does using the 100v tap change the effective output impedance?

No.

[fullerplast]

I have a dumb question......The THD Hotplates are produced at specific ohmages (4, 8, 16). I think the whole idea behind doing this was to pair the proper Hotplate with your amp and speaker cabinet.......16 Ohm amp / 16 Ohm Hotplate and 16 Ohm cabinet.

Wouldn't it make to me to run your rig in this fashion just to make sure that nothing blows up?

I don't see why people would want to fool around with all the mis-match possibilities......Is there some "voodoo" that I am missing here?

Thanks!

All speaker/OT's exhibit a phenomenon called "back EMF" where the cone movement actually generates a voltage that is fed back to the OT. It's part of the natural dynamics of the speakers, and will be different for different series/parallel speaker setups, but it is a larger effect as volume increases.

I have a theory that the higher 30 ohm load of the UA more closely (than lower load values) mimics the higher back EMF created by a speaker at high volumes and acts almost like a Fletcher-Munson dynamic EQ correction. The downside is that it becomes too much of a good thing at cranked levels, just as F-M EQ compensation does. But unlike EQ compensation, this also can create a potentially damaging situation via the extreme flyback voltages demonstrated earlier.

[Mark Gregg]

If you use a variac, it changes the voltages. That’s why the UA has an 100v tap. I always recommend it. Maybe Mr Aiken can do another comprehensive analysis of the way different voltages will affect the different impedance mismatches. This will change much of the data.
Flyback voltage it seems, higher wattage amps like Marshall 100 watt amps, tend to have higher plate voltages which will cause arcing.
What I don’t think is sinking in here is that flyback voltage, while immediate and dramatic, is not the only potential problem. Lower impedance loads can go through tubes much faster and don't sound as full.It’s The higher impedance load and the 100v tap work very well for tone and safety. Lowering voltage will definitely lower the likelihood of flyback voltage. Use the 100v tap.
If someone wants a 16 ohm load, we will do that.
Thanks a lot for all the interest, Mark.

[JubileeMan 2555]

If you use a variac, it changes the voltages. That’s why the UA has an 100v tap. I always recommend it. Maybe Mr Aiken can do another comprehensive analysis of the way different voltages will affect the different impedance mismatches. This will change much of the data.
Flyback voltage it seems, is also more encouraged by higher wattage amps, more so in my opinion than wide impedance mismatches.
What I don’t think is sinking in here is that flyback voltage, while immediate and dramatic, is not the worst potential problem. It’s heat. Heat will take longer to melt the dielectric coating of the transformer’s wire but over time shorts will accumulate and the tranny may fail. The higher impedance load and the 100v tap protect against this very well. Lowering voltage will definitely lower the likelihood of flyback voltage. Use the 100v tap.
Personally, I would prefer almost anything to happen to my vintage Marshall rather than have the OT blow. If a tube goes and takes a socket, your amp will still sound the same. If the OT goes, you may never get the same sound or feel out of that amp again. Ever.
Mr Germino has asked that we be clear on how to use the UA. I thought we had been clear, but I can be more specific.
The UA may be used with amps in good working order with good tubes that include:
2 ohm (OT transformer tap) amps 45 watts and under
4 ohm amps 85 watts and under
8 ohm amps any wattage
16 ohm amps any wattage
If someone wants a 16 ohm load, we will do that but we don’t recommend it.
Thanks a lot for all the interest, Mark.

I used to be in the camp that any ohms (4-16) could work with a UA, until I recently had major Arc on one of my tube sockets blowing out the brand new EL34 and forcing me to replace the tube socket. I was using the 8ohm tap with a dual EL34 amp thats got 470v on the plates. Everything well in the "Safe" zone you mention.

Mark G: Because of my personal experience, and others that I'm reading here and other places, you might want to rethink your recommendation of using the UA with any output OHM other then 16. Its dangerous. I'm just lucky my tube socket arc'd and not my internal Tranny windings. I'm also lucky I'm handy with a soldering Iron and am able to quickly diagnose my problem and was able to fix it. Otherwise, this mishap would have cost me hundreds of dollars.

[Mark Gregg]

Hi Tyler. Please tell me why I should be convinced that it's not a tube issue? And if it is, why I should change my recommendations based on a few tube problems? New tubes never have problems? Please!
Also, how do you know your tranny windings haven't arced?
There are thousands of UA's out there. I'm sure I know about the majority of problems. 99% of them can be resolved with tubes. All you know is what you read on boards and your bad tube experience. I'm willing to get together with your amp and if this can't be resolved, I might be willing to consider changing my recommendations.
Thanks!

[JubileeMan 2555]

I know its not the amp because I had been swapping around tubes and playing the amp cranked without the UA for weeks. I had put in the new set of Tubes the previous week and had been cranking the amp tweaking the circuitry everyday. Never had one issue ever.

Plugged in UA. In less then 2 min. of playing my tube socket arced and blew away a tube. If I had bad tubes, wouldn't I have had arcing or a tube blow when the amp was on ten for about a week?

What other possible test can anyone have that the UA is what caused it? Since its documented heavily that Flyback voltages can cause arcing over pins 2 and 3. Its sounds like if anything gets blown, its the part's fault and not the UA. What evidence is needed to show its not the part?

You don't recommend using it with 4ohm and 2ohm. Why... what evidence have you come across that shows that to be dangerous and not the 8ohm setting? Obviously you understand the risks of the missmatch, or you would simply state there is no issues with any amp and any OHms.

I love the UA for what it does, I'm not trying to put down the unit (in fact this is my second owned unit...first used with a Super Trem years ago on the 16ohm setting without issue). I just know I'm lucky the UA didn't destroy my tranformer. Stating that thousands of UA units that don't cause problems isn't proof, its even more coincedental then my experience. Who knows, maybe 999 of those 1000 are using it with a 16ohm tap. Most amps have them. And I betcha 90% or more of your buyers are using them with Marshall amps set at the 16ohm setting. Which I strongly believe is perfectly safe.

My theory is that the "tube issues", that are the only problem you've encountered, are because modern tubes simply can not handle the massive flyback voltages that occur with such a missmatch. Technically it IS the tube thats failing due to its lower quality, but the UA is causing a failure that would not happen otherwise.

btw. after reinstalling a new tube socket and new tubes I have played the amp cranked (sans-UA) since without any problems. Same brand tubes throughout.


Hi Tyler. Please tell me why I should be convinced that it's not a tube issue? And if it is, why I should change my recommendations based on a few tube problems? New tubes never have problems? Please!
Also, how do you know your tranny windings haven't arced?
There are thousands of UA's out there. I'm sure I know about the majority of problems. 99% of them can be resolved with tubes. All you know is what you read on boards and your bad tube experience. I'm willing to get together with your amp and if this can't be resolved, I might be willing to consider changing my recommendations.
Thanks!

[Mark Gregg]

Hi Tyler. Yes, we know that the more you mismatch impedances, the more chance of flyback voltages. It's one of the reasons we incorporate the 100v tap. Did you use it? As far as your guess of what amps my customers use, the first thousand or so UA's purchased through my site which at that time accounted for about 80% of all UA sales, a feedback form was included which had a questionnaire that asked what make and model amps were being used by the customer. You guessed it, Marshall type amps were #1 at about 50%. This ratio seems to be still holding true. Not everyone plays Marshall's through the UA.
As far as thousands of people using the UA safely being more coincidental than your problem, let's just say I'm scratching my head at that statement. Send me your amp and let's see if we can get it working at 8 ohms with the UA.
I'm not sure where you got the quote that I don't recommend using the UA with 4 or 2 ohm amps. Please see previous post.

[JubileeMan 2555]

...I'm not sure where you got the quote that I don't recommend using the UA with 4 or 2 ohm amps. Please see previous post.

This:
The UA may be used with amps in good working order with good tubes that include:
2 ohm (OT transformer tap) amps 45 watts and under
4 ohm amps 85 watts and under
8 ohm amps any wattage
16 ohm amps any wattage
If someone wants a 16 ohm load, we will do that but we don’t recommend it.
Thanks a lot for all the interest, Mark.

Its not directly saying don't use the 2ohm or 4ohm. But the restrictions imply not to with higher wattage amps. Why are there restrictions if everythings safe? Then of course, we get into the fact that amp wattage is sort of a myth since a 100 watt marshall doesn't put out 100watts. Sometimes less...sometimes more.

I'm obviously not going to convince you of anything. I can't send you my amp. I need the amp here for my band. Maybe if you sold me some tubes that you've given the green-light for. If your idea is correct, then I could use the tubes in my amp and nothing would ever go wrong.

I'm just weary with the idea that if something goes bad, its the parts fault and it was going to fail anyways. I honestly used to feel that way with the UA, but now its starting to form in my mind that thats a tricky way out of any responsibility since its practically impossible to prove.

[Fred Farkus]

All speaker/OT's exhibit a phenomenon called "back EMF" where the cone movement actually generates a voltage that is fed back to the OT. It's part of the natural dynamics of the speakers, and will be different for different series/parallel speaker setups, but it is a larger effect as volume increases.

If this is the case, how is it a problem with a resistive load (as opposed to a speaker)?

[soldano16]

If there are ANY issues about what can safely be used with what, that should be CLEARLY marked on the product. People shouldn't have to find an internet forum to know that their setup is risky.

[JubileeMan 2555]

If there are ANY issues about what can safely be used with what, that should be CLEARLY marked on the product. People shouldn't have to find an internet forum to know that their setup is risky.

Big +1... but it looks like the makers don't feel there is any danger no matter what.

[fullerplast]

If this is the case, how is it a problem with a resistive load (as opposed to a speaker)?

Several ways: the magnitude of the impedance mismatch, magnitude of the reflected voltage (a moving cone does not reflect large damaging voltages), and the dynamic nature of speaker impedance (it actually varies considerably from the "rated" impedance as a function of frequency). See the 4 ohm response curve below. The speaker impedance also has inductive and capacitive components that vary with frequency.

All that said, a 4:1 speaker mismatch can be as damaging as a 4:1 fixed load mismatch....but that's not due to the cone's back EMF.

The back EMF results in a damping effect, that may be why the 30 ohm load sounds better at lower volumes, in that it is emulating reflected voltages that would not exist with a no-cone perfectly matched resistive load.

http://upload.wikimedia.org/wikipedia/en/thumb/e/ec/Znom3.png/800px-Znom3.png (http://upload.wikimedia.org/wikipedia/en/e/ec/Znom3.png)

[Fred Farkus]

Okay, gotcha. Thanks! I've read this for years but never completely understood this phenomenon.

Seems to me the solution to all this is simple:

Either

1) Get them to build a UA with the load matched to your amp, or

2) Use a dummy load and re-amp your amp to another via a line-out. That's basically what this is- a "re-amp in a box".

[fullerplast]

Okay, gotcha. Thanks! I've read this for years but never completely understood this phenomenon.

Seems to me the solution to all this is simple:

Either

1) Get them to build a UA with the load matched to your amp, or

2) Use a dummy load and re-amp your amp to another via a line-out. That's basically what this is- a "re-amp in a box".

Add a way to make it all sound realistic and I'm on board.....but that's exactly what makes things not so simple.... It's easy to make it safe or it's easy to make it sound good. It's the combination that's tough.;)

[JubileeMan 2555]

Add a way to make it all sound realistic and I'm on board.....but that's exactly what makes things not so simple.... It's easy to make it safe or it's easy to make it sound good. It's the combination that's tough.;)

lol...exactly. If we wanted it to be ultra safe...we'd all be playing acoustic guitars! :)

[Fred Farkus]

Well, I've done re-amping at home with my home-built (mass based) attenuator as a dummy load, and a line-out I installed. Did it sound exactly the same as the original amp? No. But I was using a guitar amp instead of power amp, and a different speaker- both colored the sound. In my defense, I was using it to experiment with wet/dry and wet/wet setups with an fx loop and etc. I wasn't trying to do "accurate attenuation". But it *did* sound very consistent at all volume levels (as you would expect). Seems like it would be fairly easy to do this sort of thing with a load, line-out divider network, and a chip amp.

[fullerplast]

Well, I've done re-amping at home with my home-built (mass based) attenuator as a dummy load, and a line-out I installed. Did it sound exactly the same as the original amp? No. But I was using a guitar amp instead of power amp, and a different speaker- both colored the sound. In my defense, I was using it to experiment with wet/dry and wet/wet setups with an fx loop and etc. I wasn't trying to do "accurate attenuation". But it *did* sound very consistent at all volume levels (as you would expect). Seems like it would be fairly easy to do this sort of thing with a load, line-out divider network, and a chip amp.

Well, I think that basic premise was the genesis of the UA...

[bolero]

Ampeg SVT has a 2 & 4 ohm output, doesn't it? at 300 watts....wow, that would be an amp to test!!


:hide


*edit* although cranking a 300w tube amp & attenuating down to bedroom levels has to be on the far side of practicality, lol

[pepperco]

Tyler, it's easy to prove. Send me your amp. Put up or shut up. A smart successful guy like you could surely find an amp temporarily to use for 3 weeks while we do this. I'll post a youtube video on this forum.
BTW, there are no 2 ohm tube amps over 45 watts or very many if any 4 ohm amps over 85 watts. It was meant somewhat tongue in cheek.

HOLY CATS !!!

I thought Jubileeman was being particularly supportive and restrained
about the his experience with the Ultimate, at the very least he is
respectful !! I think the "send me your amp / put up or shut up"
comment is way out of line. Just sayin.

FWIW I am a proud and longtime Ultimate attenuator user, I have
recommended it to people on this forum many times, I still use it
for nearly every gig. I have no bone to pick at all. But there are
people here who have concerns, and legitimate questions. A little
forum decorum helps a lot.

[Timster]

holy cats !!!

I thought jubileeman was being particularly supportive and restrained
about the his experience with the ultimate, at the very least he is
respectful !! I think the "send me your amp / put up or shut up"
comment is way out of line. Just sayin.

Fwiw i am a proud and longtime ultimate attenuator user, i have
recommended it to people on this forum many times, i still use it
for nearly every gig. I have no bone to pick at all. But there are
people here who have concerns, and legitimate questions. A little
forum decorum helps a lot.

+1
,,,,,,,,

[Timster]

...................... :)

[soldano16]

Big +1... but it looks like the makers don't feel there is any danger no matter what.

No. They both admit there can be issues. Even Mark says only so many watts with 4 ohms. But that's not marked on the UA itself. There is no warning for that.

2 ohm (OT transformer tap) amps 45 watts and under
4 ohm amps 85 watts and under

[fish78]

I hate to be the turd in the punch bowl, but just because there are no big letters on the unit saying 2 ohn <45 watts and 4ohm <85 watts, does not mean any negligence on the part of the maker...in the old days befor UL tags you bought anything electric at your own risk...way too much of this you must protect me and all of my stuff from everything...you assume risk, just by living. Let me ask a question...has anyone had an incident directly the fault of the UA that either Mark, or Ho has not made good? We now all know the risks involved...as I see it run your amp at less than full tilt, the risk is reduced greatly or have them set it up for 16 ohm if you are concerned...btw, just how many amps need to be at full tilt to find the sweet spot? Just the rambling thoughts of a doughtering old coot, who believes in taking responsibility for his own decisions.

[Yossi]

....has anyone had an incident directly the fault of the UA that either Mark, or Ho has not made good? .


I am sure that Mark would stand behind the UA if he thought that his unit was at fault. My situation was perhaps unique in that I was using a brand new UA and a brand new Germino Lead55LV, both out of the box and I had a fuse blow. I replaced the fuse and used both again, followed by another amp stoppage within aprox. 10 minutes period. I sent the amp to Germino after speaking with him and the store where I bought it. I went back to the manufacture of the "broken" unit and the more expensive of the two. I sent Germino both the UA and his amp because I wanted to know if the UA had anything to do with the amp quitting.
Germino repaired the amp at no charge by replacing tubes (perhaps sockets?-I don't remember) and putting in a new fuse. He tested the UA. He warned me against using his amp with the UA at any setting other than the 16ohm output because of the mis-match of 30 ohms.
Forgive me for repeating myself. You asked the question and may not have read my previous post on this.

From what I've learned since having my problem I've learned that I did something that I shouldn't have with my UA and the Germino.

1. I was running the Amp at the 4ohm setting
2. I had the amp dimed into the UA and set at high attenuation, most likely causing some heavy fly-back voltage
3. I wasn't using the 100volt tap on the UA at the time.

If after my experience and the expert opinions on this subject, anyone would like to ignore my lessons learned it would because there is no indication in the UA instruction manuel that supports my findings.
I am not sure if Mark Gregg even agrees that the UA was at fault. If he did it would mean changing the literature and perhaps warranting the tubes that blow while using the UA. If the literatue had warned against the impedance mis-match and I did it anyway it would have been my fault. I didn't know about this concern until after I experienced a problem.

If Mark would have replaced the tubes in my amp had I sent it to him?
I don't know.

[hasserl]

If you use a variac, it changes the voltages. That’s why the UA has an 100v tap. I always recommend it. Maybe Mr Aiken can do another comprehensive analysis of the way different voltages will affect the different impedance mismatches. This will change much of the data.
Flyback voltage it seems, is also more encouraged by higher wattage amps, more so in my opinion than wide impedance mismatches.
What I don’t think is sinking in here is that flyback voltage, while immediate and dramatic, is not the worst potential problem. It’s heat. Heat will take longer to melt the dielectric coating of the transformer’s wire but over time shorts will accumulate and the tranny may fail. The higher impedance load and the 100v tap protect against this very well. Lowering voltage will definitely lower the likelihood of flyback voltage. Use the 100v tap.
Personally, I would prefer almost anything to happen to my vintage Marshall rather than have the OT blow. If a tube goes and takes a socket, your amp will still sound the same. If the OT goes, you may never get the same sound or feel out of that amp again. Ever.
Mr Germino has asked that we be clear on how to use the UA. I thought we had been clear, but I can be more specific.
The UA may be used with amps in good working order with good tubes that include:
2 ohm (OT transformer tap) amps 45 watts and under
4 ohm amps 85 watts and under
8 ohm amps any wattage
16 ohm amps any wattage
If someone wants a 16 ohm load, we will do that but we don’t recommend it.
Thanks a lot for all the interest, Mark.

Tyler, it's easy to prove. Send me your amp. Put up or shut up. A smart successful guy like you could surely find an amp temporarily to use for 3 weeks while we do this. I'll post a youtube video on this forum.
BTW, there are no 2 ohm tube amps over 45 watts or very many if any 4 ohm amps over 85 watts. It was meant somewhat tongue in cheek.

OK, there's a problem here. You say your post was "meant somewhat tongue in cheek", yet others won't take it that way and they'll go away with the understanding that somehow wattage is the issue. Wattage isn't the issue, it's the impedance mismatch that is the issue, and wattage doesn't change that. An impedance mismatch for a 20 watt amp is just as bad as an impedance mismatch for a 100 watt amp. So let's be clear here, this device is flat dangerous for a 2 or 4 or even 8 ohm amp regardless of wattage, period.

(BTW, you do realize there are plenty of 100 watt amps out there with with impedance switches enabling 4 ohm output, right?)

This is just another example of the misleading you seem to have a habit of doing regarding the use of your product. While excessive heat can cause damage to a component, normal heat from use is not damaging. What kills a transformer is the breakdown of the winding insulation due to high flyback voltage, not heat from normal use.

Here is what RG Keen has to say about it:

It's almost never low impedance that kills an OT, it's too high an impedance. The power tubes simply refuse to put out all that much more current with a lower-impedance load, so death by overheating with a too-low load is all but impossible - not totally out of the question but extremely unlikely. The power tubes simply get into a loading range where their output power goes down from the mismatched load. At 2:1 lower-than-matched load is not unreasonable at all.
If you do too high a load, the power tubes still limit what they put out, but a second order effect becomes important.
There is magnetic leakage from primary to secondary and between both half-primaries to each other. When the current in the primary is driven to be discontinuous, you get inductive kickback from the leakage inductances in the form of a voltage spike.
This voltage spike can punch through insulation or flash over sockets, and the spike is sitting on top of B+, so it's got a head start for a flashover to ground. If the punchthrough was one time, it wouldn't be a problem, but the burning residues inside the transformer make punchthrough easier at the same point on the next cycle, and eventually erode the insulation to make a conductive path between layers. The sound goes south, and with an intermittent short you can get a permanent short, or the wire can burn though to give you an open there, and now you have a dead transformer.



http://geofex.com/



Also note, it is not the operating voltage that results in flyback voltage (more misleading statements from you), it is leakage inductance in the transformer that causes spikes. Operated at correct impedance ratios spikes are minimized or prevented entirely. With an impedance mismatch however, where the load is greater than ideal, spikes are generated, the larger the mismatch the greater the spike. That is just what Randall's screen shots showed. Reducing the operating voltage reduces stresses on the amp, but it doesn't eliminate inductive kickback voltage. And he was only playing with a 4:1 ratio such as using an 8 ohm amp with a 30 ohm UA. Take that out to an 8:1 ratio or 16:1 ratio as with a 4 or 2 ohm amp and the situation gets extreme. Telling people to go ahead and use it like this is irresponsible at best, personally I have some sharper words in mind that I won't put here out of respct for TGP.

I've noticed you tend to blame every problem someone has on bad tubes. While there are plenty of failed tube issues to be dealt with, arcing between the pins is not usually one of them. Arcing between the pins is most commonly caused by either an open circuit in the output transformer secondary, such as a disconnected speaker cable, poor connection in the jacks, plug, cable or speaker; or an impedance mismatch (such as one would see when using a 2, 4 or 8 ohm amp into a UA).

But now it appears that there is another issue of excesive screen grid current, that may be a result of excessive impedance mismatch. So it may NOT be just a case of a bad tube, but a case where the tube failure was a RESULT of using the UA; the excessive impedance mismatch causing excessive screen grid current resulting in a failed screen grid, internal shorting of the tube, a blown fuse and possibly failed screen grid resistor. You tell the customer it was just a bad tube and accept no blame, and he gets stuck with a repair bill plus the lack of use of his amp while it is being repaired, and possibly shipping charges if he has to return it to the mfgr.

Please tell me why I should be convinced that it's not a tube issue? And if it is, why I should change my recommendations based on a few tube problems?

I just did.

I might be willing to consider changing my recommendations.

That would be a good thing to do.

[jnug]

:munch

[drbob1]

I've been worried about the UA's high input impedance in the past, but after playing one with a 100w Marshall style amp last weekend I'm not worried about it any more. Simply, the benefit of the UA over my Weber mass at minimal attenuation levels (like the 3-6 dB I use to protect my 69 Greenbacks from my 100w metal panel Superlead) is minimal. And, with ANY degree of attenuation, both attenuators change dynamics and eq balance (felt as a loss of bass thump). Even just turning the UA on with no attenuation causes this change. So, it may be a good tool for some people, for me, I'll just stay with ear plugs and no neighbors...

[Stu Blue]

I repeat what I said on a similar thread...

People here are being very polite about UA and other 30 ohm attenuators. Either the manufacturers don't know about flyback voltage arcing problems, in which case they don't know enough to be designing and marketing professional gear, or they do know but would rather not reduce sales by warning anyone. I suspect it was one followed in time by the other.

It is Mark Gregg who needs to put up or shut up... since he's got to show that all the degree level textbooks on electrical engineering in the world are wrong and he's right... well good luck mate.

_________________

[Fred Farkus]

One point I'd like to make- I think worrying about overheating an old output transformer in a vintage amp is a poor justification for mismatching the load. If you are worried about overheating the OT, you shouldn't be running the amp full-out anyway- with or without an attenuator. Or- you should get a new OT, get it rewound, etc, etc...

Given that arcing due to flyback is an issue with too high of a load, the real question is how much of a mismatch can be tolerated before this happens.

[fish78]

I want to caution you all. You may have your concerns about the dangers of flyback voltage and any other matters, and they may well be valid. BUT without empirical evidence that a particular devise used AS THE MANUFACTURER recommends is INHERENTLY dangerous, you risk ruining a person's livlihood. I probably know less than anyone here about electronics, but Mark Gregg has stepped up and agreed that flyback voltage CAN be a problem, Mr HO has related through a forum member that flyback voltage can be a problem. Mr Aiken gave us some very good testing information that demonstrated how flyback voltage can occur when the amplifier is driven to HARD CLIPPING with an impedence mismatch. Just how good is any amp going to sound in hard cliping? What I think we all have learned here is that impedence mismatch CAN create serious problems and because it can, the device under discussion here has some recommendations to LESSON that risk...can it ELIMINATE the risk, probably not, but before you categorically declare a device unsafe and unfit, consider you are really messing with another person't ability to make a living and feed his family...how would you feel, if someone did it to you?

[jnug]

so if you are running the amp at 16ohm this is still a mismatch since the UA is 30ohms right? the only way to solve the problem would be to get a matching UA right? what is the solution to this problem? :dunno

[TTripp]

so if you are running the amp at 16ohm this is still a mismatch since the UA is 30ohms right? the only way to solve the problem would be to get a matching UA right? what is the solution to this problem? :dunno

16 to 30 is still a mismatch. Most agree that a one step mismatch isn't the end of the world in and of itself. Throw in a CRANKED amp and that could change. (Heck, throw in a CRANKED amp with a matched load and that might end unpleasantly as well). I think the only thing you can really do is not crank the amp.

[rick13]

Would not the use of a Weber impedance matcher "lessen" the potential for a problem???? The only real way to insure you don't have a problem with any possible scenario....don't do it in the first place. You don't think that cranking a 100 watt vintage amp to capacity with the expectation that a manufacturer is going to pat you on the back and tell you it's OK and warranted is not foolhardy? Nobody can make these types of claims in this litigious society. If you want to crank your amp beyond whats reasonable given natural human error in any manufacturing process...be willing to live with the consequences. You drive fast, don't complain about crashing.
Rick

[Fred Farkus]

BUT without empirical evidence that a particular devise used AS THE MANUFACTURER recommends is INHERENTLY dangerous, you risk ruining a person's livlihood.

Wow...

You "risk ruining a person's livelihood" by expressing an opinion on a web forum? :huh

That's a new one... :jo

[Yossi]

.....Mark Gregg has stepped up and agreed that flyback voltage CAN be a problem, Mr HO has related through a forum member that flyback voltage can be a problem.

Mr Aiken gave us some very good testing information that demonstrated how flyback voltage can occur when the amplifier is driven to HARD CLIPPING with an impedence mismatch. ........


What I think we all have learned here is that impedence mismatch CAN create serious problems and because it can,

the device under discussion here has some recommendations to LESSON that risk...can it ELIMINATE the risk,.......

The manufacturer of UA has not accepted responsibility of the problem caused by fly-back voltage and their literature doesn't warn users of the problem or instruct the user to limit the output to 16ohms into the 30 ohms fixed load. Mark Gregg maintains that the mis-match does more for the amp by reducing the heat buildup than the fly-back voltage risks damage. He has said on this forum that it's OK to use 4ohm & 8ohm amps into the UA, a point that has elicited some serious questions from experts in the field.

While I commend you on your concern for an other's livelihood, I see TGP as the appropriate venue to address this concern. How many people are now aware of the potential problem who would not have been otherwise?
If a manufacturer claims that the tubes were at fault, perhaps he's correct. Once many users come forward with similar problems, that causes doubt to the validity of the manufacturer's claim of no responsibility. Perhaps that will lead the manufacture to put warnings into product literature and lead to the protection of future customers.

Ralf Nader did a lot to harm the sales of GM cars in the 60's but he did a tremendous service to the safety of consumers.

[dewman]

Ultimate attenuators- unsafe at any speed....

I think I'll be ok using it to knock the volume down a wee bit. Anything more may be asking for trouble. And say no to impedance mismatching and cranking that vintage amp.

[jnug]

Ralf Nader did a lot to harm the sales of GM cars in the 60's but he did a tremendous service to the safety of consumers.


:AOK i see nothing wrong with pointing out issues, nobody wants a fried amp or worse right, in respect this is a service of safety towards our amps which are not cheap.

[dumbell78]

Im willing to send my UA to someone like Mr Aiken do run some tests for all of us to see. We need some hard evidence of what we are looking at when using the UA. From that point ppl can make clear choices as to what you should or shouldnt do.

This is in no way of trashing Mark or Ho, I have used the UA for about two years and love it. I just want to help and get some firsthand testing with the UA under playing circumstances.

If Mr Aiken, Mr Germino, or someone like that wants to take me up on my offer, please let me know. For the record Im not trying to single out any amp builder here. Aiken has been kind enough to chime in here and Germino has first hand expierence with the UA, so thats why I mention them.

[rydogg_sc2]

Ultimate attenuators- unsafe at any speed....

I think I'll be ok using it to knock the volume down a wee bit. Anything more may be asking for trouble. And say no to impedance mismatching and cranking that vintage amp.

Since it is a re-amping device it does not matter if you are using to only lower the volume a tad or using to play the amp at bedroom volumes. You are running the same risks both ways.

[JubileeMan 2555]

Im willing to send my UA to someone like Mr Aiken do run some tests for all of us to see. We need some hard evidence of what we are looking at when using the UA. From that point ppl can make clear choices as to what you should or shouldnt do.

This is in no way of trashing Mark or Ho, I have used the UA for about two years and love it. I just want to help and get some firsthand testing with the UA under playing circumstances.

If Mr Aiken, Mr Germino, or someone like that wants to take me up on my offer, please let me know. For the record Im not trying to single out any amp builder here. Aiken has been kind enough to chime in here and Germino has first hand expierence with the UA, so thats why I mention them.

Problem is the conflict of interest. Testing another vendor's product isn't gonna fly. AIken already deleted his posts because of this. For testing, one would probably have to find a neutral party and pay for the testing for there to be any validity.

[dumbell78]

Problem is the conflict of interest. Testing another vendor's product isn't gonna fly. AIken already deleted his posts because of this. For testing, one would probably have to find a neutral party and pay for the testing for there to be any validity.


Well that sucks!!!

[Belmont]

they've been in use for years upon years now, it's a little late for testing, dontcha think. if your don't have the brains, or a set big enough to use one, there's lots of other (inferior) attenuators out there, buy one of them. this is nothing more than an atteck on a designer who has over 40 years of amp teching/designing/building experience. someone point out the pile of wrecked amps, or get a life, maybe take up accordion.

[Yossi]

they've been in use for years upon years now, it's a little late for testing, dontcha think

No. There are experts who have presented convincing arguments that there is a problem with the resistance issue. Yet the manufacturer contends differently. There are customers who have had problems. For the sake of being able to continue to sell this product and provide adequate instructions, I think that Magus/Ho should settle this issue.
A problem "for years upon years" doesn't just go away because you choose to ignore it.


if your don't have the brains, or a set big enough to use one, there's lots of other (inferior) attenuators out there, buy one of them

I don't know why you think that littering your posts with immature jabs does anything other than make YOU look bad???:dunno

this is nothing more than an atteck on a designer who has over 40 years of amp teching/designing/building experience.

You are 100% Wrong. It is pointing out a problem with a product. Period.

someone point out the pile of wrecked amps,.

I pointed out the problem that I had with my amp and the advice that I got from Greg Germino after sending the amp and the UA to him. It's not a pile but then again it happened to all the amps that I used with UA set at a 4ohm load. If you read these posts you will see that there are others who have had the same type of problems and that there are people who haven't but run their amp at 16ohms. The evidence is very overwhelming that you shouldn't run at least a Marshall type amp at any output other than 16 ohms into the UA. Open up your eyes and see that this is an issue.

or get a life, maybe take up accordion.

:nono

[dumbell78]

No. There are experts who have presented convincing arguments that there is a problem with the resistance issue. Yet the manufacturer contends differently. There are customers who have had problems. For the sake of being able to continue to sell this product and provide adequate instructions, I think that Magus/Ho should settle this issue.
A problem "for years upon years" doesn't just go away because you choose to ignore it.




I don't know why you think that littering your posts with immature jabs does anything other than make YOU look bad???:dunno



You are 100% Wrong. It is pointing out a problem with a product. Period.



I pointed out the problem that I had with my amp and the advice that I got from Greg Germino after sending the amp and the UA to him. It's not a pile but then again it happened to all the amps that I used with UA set at a 4ohm load. If you read these posts you will see that there are others who have had the same type of problems and that there are people who haven't but run their amp at 16ohms. The evidence is very overwhelming that you shouldn't run at least a Marshall type amp at any output other than 16 ohms into the UA. Open up your eyes and see that this is an issue.



:nono

Gotta agree! We arent here bashing Mark or Ho, in fact we want to continue using their product. We just want to be safe and rational about it. No need for the jabs at the guys here, its a topic worth discussing.

[alivegy]

Problem is the conflict of interest. Testing another vendor's product isn't gonna fly. AIken already deleted his posts because of this. For testing, one would probably have to find a neutral party and pay for the testing for there to be any validity.

I can do this. Someone send me a Germino and another UA and I will let everyone know how it goes. I just want to help out the community.

[meterman]

Has anybody actually blown up or damaged an amp that wasn't running flat out on 10 and that was set at the "correct" impedance of 16ohms?

That's all I care about really, I don't plan on diming my amps into the thing at 8 ohms....

[QRSS]

they've been in use for years upon years now, it's a little late for testing, dontcha think. if your don't have the brains, or a set big enough to use one, there's lots of other (inferior) attenuators out there, buy one of them. this is nothing more than an atteck on a designer who has over 40 years of amp teching/designing/building experience. someone point out the pile of wrecked amps, or get a life, maybe take up accordion.

:roll

[Mark Gregg]

Has anybody actually blown up or damaged an amp that wasn't running flat out on 10 and that was set at the "correct" impedance of 16ohms?

That's all I care about really, I don't plan on diming my amps into the thing at 8 ohms....
I just want to say one more time, if you use the 100v tap, it's safe. The voltages will be safe and the tubes won't arc. We have tested this to our satisfaction. At any impedance.
If that's not enough to assuage your concerns, we will install a switch for 8 or 30 ohms. 30 ohms will sound better and your tubes will last longer. Many many people use it at different impedances including a guy from Seattle I just got off the phone with. He's using it with a 300 watt SVT @ 4ohms for 3 years now with no amp or tube problems. Google ML3 band myspace to confirm this. 3 rehearsals a week, 2 to 3 hours and many gigs. I know it's circumstantial evidence and not scientific but I think that's par for the course here.

[pickslide]

This may be a dumb question, but I am far from a technical guy. I have a Ho and like it quite a bit. My amp has 4, 8 and 16ohm settings. My cab is wired for 8ohms. What I am hearing here is that it is totally ok to run the amp at 16ohms with attenuator into an 8ohm cab?

[jackaroo]

yes. The connection between the UA and cab can be mismatched. The important thing is to use the 16 Ohm speaker out from the head when possible.



J

[pickslide]

Sweet. Thanks.

[Paul86]

Still using it regularly and still not burning / blowing fuses / arcing / schmucking. (Even though I am a schmuck, go figure.)

[767400]

I posted this on another thread and I thought I would repost it here

(Repost)
My amp tech (great guy!) fixed my Bluesbreaker when it had a tube socket short, using an attenuator for the first time none the less. He installed a ceramic sockets and a little extra mod. He connected three diodes (IN-4007) in a series from pin 3 to ground for spike protection. I am hoping this modification will save any of my NOS tubes from damage. I love my Ho (I also love saying that) attenuator and the tone I can maintain while not blowing my ears out. This picture is a 1959HW 100w head with the diodes in place. I marked just one of them with a red arrow.


http://216.77.188.54/coDataImages/p/Groups/176/176331/folders/154603/2398353CopyofHPIM2582.jpg

[soldano16]

I just want to say one more time, if you use the 100v tap, it's safe.

And what about units that don't have the 110v tap?

And what about people who don't know they should use the 100v tap?

[345]

And what about units that don't have the 110v tap?

And what about people who don't know they should use the 100v tap?

Then there may be problems depending on the output impedance of the amp.

I think for everyone to be happy ... there needs to be a little booklet with instructions, disclaimers etc. sent with these attenuators.

I use mine with both 8 ohm and 16 ohm output impedances of my amps with no problems so far ... I did have some crackling in one and that turned out to be bad tubes that were exposed by the attenuator. I put in some NOS Mullards and all is fine.

[jnug]

Has anybody actually blown up or damaged an amp that wasn't running flat out on 10 and that was set at the "correct" impedance of 16ohms?

That's all I care about really, I don't plan on diming my amps into the thing at 8 ohms....

i believe that is still a mismatch and not 100% good (somebody clear this up for me). but it is not as bad as the 8ohm and 4ohm setting. it is the safest setting

I just want to say one more time, if you use the 100v tap, it's safe. The voltages will be safe and the tubes won't arc. We have tested this to our satisfaction. At any impedance.
If that's not enough to assuage your concerns, we will install a switch for 8 or 30 ohms. 30 ohms will sound better and your tubes will last longer. Many many people use it at different impedances including a guy from Seattle I just got off the phone with. He's using it with a 300 watt SVT @ 4ohms for 3 years now with no amp or tube problems. Google ML3 band myspace to confirm this. 3 rehearsals a week, 2 to 3 hours and many gigs. I know it's circumstantial evidence and not scientific but I think that's par for the course here.

so how do you use the 100v tap, do you plug the amp into the tap instead of the amp jack and the speaker cab into the speaker cab jack on the UA?

[TTripp]

so how do you use the 100v tap, do you plug the amp into the tap instead of the amp jack and the speaker cab into the speaker cab jack on the UA?

The 100v "tap" is an outlet on the back of a the UA that lowers the wall voltage by 20 volts. The UA is plugged into a wall outlet as usual, but instead of plugging the amp into another wall outlet, you plug the amp into the UA's 100v outlet instead.

[hasserl]

I just want to say one more time, if you use the 100v tap, it's safe. The voltages will be safe and the tubes won't arc. We have tested this to our satisfaction. At any impedance.
If that's not enough to assuage your concerns, we will install a switch for 8 or 30 ohms. 30 ohms will sound better and your tubes will last longer. Many many people use it at different impedances including a guy from Seattle I just got off the phone with. He's using it with a 300 watt SVT @ 4ohms for 3 years now with no amp or tube problems. Google ML3 band myspace to confirm this. 3 rehearsals a week, 2 to 3 hours and many gigs. I know it's circumstantial evidence and not scientific but I think that's par for the course here.

Again Mark, this just isn't right. Reducing the operating voltage is not going to eliminate the flyback voltage, the first is not the cause of the second. It will reduce stress on the amp, but it isn't a cure for an impedance mismatch. Or you say you've done testing, post the results of your testing so we all can see it. Let's see some more scope images.

Besides, what effect does this have on heater voltage? There are amps out there on the market that operate at the low end of heater voltage range already, reduce the primary voltage to the power transformer and the heater voltage is going to drop even further.

[Paul86]

Last time I checked a UA?/Ho atten. kind of thread (there was a great one started by Ulysses - by the way, Ulysses, thank you, great sounds!) there were lots of guys who actually play their amps and use or have used the UA without any issues. Including some respected builders around here, like one Mr Hogy.
To me it is quite simple, actually. You either buy the godamn thing or you don't. If anyone who plays rock'n'roll and is afraid of blowing a fuse / tranny / arcing a tube, well there's jazz for you guys! Or acoustic folk ballads - I've never heard of those guys blowing trannies / fuses whatever.
Like any other piece of equipment, guitar amps do malfunction. Sometimes when I read the kind of boogey man stories some tgp member tell around here, I wonder what would have happened if guys like Hendrix, Clapton and Angus Young, just to cite a few, were, er, scared of blowing an amp:roll
We would all be playing polkas - Now, that will keep your amp safe, guys.

[dumbell78]

Last time I checked a UA?/Ho atten. kind of thread (there was a great one started by Ulysses - by the way, Ulysses, thank you, great sounds!) there were lots of guys who actually play their amps and use or have used the UA without any issues. Including some respected builders around here, like one Mr Hogy.
To me it is quite simple, actually. You either buy the godamn thing or you don't. If anyone who plays rock'n'roll and is afraid of blowing a fuse / tranny / arcing a tube, well there's jazz for you guys! Or acoustic folk ballads - I've never heard of those guys blowing trannies / fuses whatever.
Like any other piece of equipment, guitar amps do malfunction. Sometimes when I read the kind of boogey man stories some tgp member tell around here, I wonder what would have happened if guys like Hendrix, Clapton and Angus Young, just to cite a few, were, er, scared of blowing an amp:roll
We would all be playing polkas - Now, that will keep your amp safe, guys.

Hendrix, Clapton, Young could/can afford to blow amps left and right. Some of us actually cant go around buying a new Germino, Metro, Marshall plexi everytime. So thats why we are asking bro.

[QRSS]

Last time I checked a UA?/Ho atten. kind of thread (there was a great one started by Ulysses - by the way, Ulysses, thank you, great sounds!) there were lots of guys who actually play their amps and use or have used the UA without any issues. Including some respected builders around here, like one Mr Hogy.
To me it is quite simple, actually. You either buy the godamn thing or you don't. If anyone who plays rock'n'roll and is afraid of blowing a fuse / tranny / arcing a tube, well there's jazz for you guys! Or acoustic folk ballads - I've never heard of those guys blowing trannies / fuses whatever.
Like any other piece of equipment, guitar amps do malfunction. Sometimes when I read the kind of boogey man stories some tgp member tell around here, I wonder what would have happened if guys like Hendrix, Clapton and Angus Young, just to cite a few, were, er, scared of blowing an amp:roll
We would all be playing polkas - Now, that will keep your amp safe, guys.

"godamn"?

lighten up francis!

[Stu Blue]

Hendrix, Clapton, Young could/can afford to blow amps left and right. Some of us actually cant go around buying a new Germino, Metro, Marshall plexi everytime. So thats why we are asking bro.

:dude Exactly. There is extensive empirical, theoretical and expert designer evidence on the dangers of flyback voltages dating back from before the second world war. Electricy will follow the path of least resistance. Given a high enough voltage it will jump across (arc) across any distance to a lower resistance. That's why your car starts in the morning (spark plugs). Push the voltage high enough and it will jump clear across the sky (lightning). The laws of physics do not bend for friendship, or the hopes and dreams of a handful of guitarists.

If you think the major amp manufactures are happy with replacing increasing numbers of blown output trannies under warranty with 4x mismatches as recommended by UA (and the damage to their reputations) then you are very mistaken.

On this very thread, real experts have shown flyback voltages approaching 4,000 volts. Your amp may appear to be working fine but, unseen inside your output tranny, those volts are jumping and slowly but steadily degrading its performance. Just because it hasn't gone bang doesn't mean that everything is OK.

The spokeman for UA on this thread has shown that every arcing amp failure with the UA will be written off as poor quality valves/transformers or people running their amps too hard, (despite the fact that the only sane reason to buy an attenuator is to do precisely that).

When europeans wish to be rude about the USA they they say that yanks cannot tell the difference between an explanation and a sales pitch. The defenders of UA on this thread are rather proving the truth of the jest.

[Stu Blue]

Then there may be problems depending on the output impedance of the amp.

I think for everyone to be happy ... there needs to be a little booklet with instructions, disclaimers etc. sent with these attenuators.

I use mine with both 8 ohm and 16 ohm output impedances of my amps with no problems so far ... I did have some crackling in one and that turned out to be bad tubes that were exposed by the attenuator. I put in some NOS Mullards and all is fine.

No. You had a flyback voltage arc and your NOS Mullards will go the same way unless you change what your doing...

[jnug]

Hendrix, Clapton, Young could/can afford to blow amps left and right. Some of us actually cant go around buying a new Germino, Metro, Marshall plexi everytime. So thats why we are asking bro.

exactly:AOK i just lost my job, and i am not trying to repair a busted amp do to a problem from the UA, to me a mismatch is a mismatch and that isn't good. :facepalm things are always to good to be true

[plexistack]

This is why I run my NMV MKII at 8 ohms into 2-16 ohm 4x12 cabs with no attenuator.

Instead of paying $800 for an attenuator, I spent $8 on a box of earplugs, which work fine.

I even leave a box on the stage for the fans, but most people don't want'em.

[Belmont]

so now we've concluded that only rockstars with unlimited funds should be using these. could someone please tell me how many amps Doyle Brahmhall, Sonny Landreth and Peter Stroud have cooked? I guess that those guys are tone deaf idiots for using them right? according to all you """"" experts """"

[GearHeadFred]

Instead of paying $800 for an attenuator, I spent $8 on a box of earplugs, which work fine.

Hey, thanks for adding that useful nugget of knowledge to the discussion!

[JubileeMan 2555]

...When europeans wish to be rude about the USA they they say that yanks cannot tell the difference between an explanation and a sales pitch...

Oooh! I really dig this line. I gotta use it someday:)

This is why I run my NMV MKII at 8 ohms into 2-16 ohm 4x12 cabs with no attenuator.

Instead of paying $800 for an attenuator, I spent $8 on a box of earplugs, which work fine.

I even leave a box on the stage for the fans, but most people don't want'em.

Haha! Great story:) I bet sound guys just LOVE you!

[tedzepplin]

so now we've concluded that only rockstars with unlimited funds should be using these. could someone please tell me how many amps Doyle Brahmhall, Sonny Landreth and Peter Stroud have cooked? I guess that those guys are tone deaf idiots for using them right? according to all you """"" experts """"

What amp impedence are Doyle Brahmhall, Sonny Landreth and Peter Stroud using with the UA?

[indravayu]

Doesn't it seem sometimes like every other thread on TGP turns into a flame war? To quote the prophet Rodney King, "can we all just get along"? :)

[JubileeMan 2555]

Doesn't it seem sometimes like every other thread on TGP turns into a flame war? To quote the prophet Rodney King, "can we all just get along"? :)

nope. Too many humans on earth for all of us to get along:)

[wedewer]

This is why I run my NMV MKII at 8 ohms into 2-16 ohm 4x12 cabs with no attenuator.

Instead of paying $800 for an attenuator, I spent $8 on a box of earplugs, which work fine.

I even leave a box on the stage for the fans, but most people don't want'em.

Plexistack,
What planet are the clubs on that you are playing a cranked mkII with earplugs? I just played a gig last night using my Straub Cantus(50watts) and the UA. I had the knob on the UA about 10 O'clock. I don't know what level of attenuation that is, but that was the max the soundman was allowing. PERIOD! And I must say, the tone was killer. With that said, my goal is to have a great mix out front, not show the people( who could give a sh*t), what power tubes be driven sound like.
Not to mention the other guys in my band who would like to be able to hear themselves as well. So if you can, do all of us on here a favor and list the clubs you play. That way, we can all get booked there, show up with a marshall, turn it up to 10 and play. Unless of course, you have an amp that goes to 11.

[Roe]

I've been giging various metro plexis w/o an attenuator. the band is used to the volume and most of the sound guys thinks it is ok. some of them actually like it. I've used a 45/100 with 400 people and the jtm50 and 45 with 200 people

[rick13]

waaah....I want to play my 100 watt amp full tilt and be assured that nothing is ever going to happen, because I can't afford to fix it. Are you kidding? I have a UA....if I break my amp...I fix it. I know the risks, nothing but common sense logic.
Rick

[Stu Blue]

Doesn't it seem sometimes like every other thread on TGP turns into a flame war? To quote the prophet Rodney King, "can we all just get along"? :)
Well some people come to drink from the pool of knowlege and others just like to splash about a bit....

[Paul86]

"Hendrix, Clapton, Young could/can afford to blow amps left and right. Some of us actually cant go around buying a new Germino, Metro, Marshall plexi everytime. So thats why we are asking bro."
:thud :worried :rotflmao
You know, that makes a lot of sense. Why didn't I think of that before...?
Ah, I know. I was too busy having fun with my amp.
You guys remind me of a friend in third grade. He bought this brand new football, and he kept it just like that, brand new, for the whole year!
But he didn't play that godamn ball, he was too busy cherishing it, you know?
More power to you guys (ahem, less power, that is.). "

[dumbell78]

Im done with this thread, ppl are just missing the point. Flame on!

[Stu Blue]

Im done with this thread, ppl are just missing the point. Flame on!

:agreeYup bye babes....

[Tone_Terrific]

I had the knob on the UA about 10 O'clock. I don't know what level of attenuation that is, but that was the max the soundman was allowing. PERIOD! And I must say, the tone was killer. With that said, my goal is to have a great mix out front, not show the people( who could give a sh*t), what power tubes be driven sound like.
.

Does everybody understand that the UA does not provide partial attenuation? Your amp is 100% attenuated all the time i.e. you have just turned it into a giant preamp/fuzzbox and are using the UA SS amp to drive the speakers, re-amping!
The best reason for using one IS to drive the tubes so people can hear what OD'n tubes sound like.

Maybe I missed the basic concept lesson, somewhere, or some others did or there is a misunderstood interpretation amongst us. Again.

[wedewer]

Does everybody understand that the UA does not provide partial attenuation? Your amp is 100% attenuated all the time i.e. you have just turned it into a giant preamp/fuzzbox and are using the UA SS amp to drive the speakers, re-amping!
The best reason for using one IS to drive the tubes so people can hear what OD'n tubes sound like.

Maybe I missed the basic concept lesson, somewhere, or some others did or there is a misunderstood interpretation amongst us. Again.

You are missing the whole point of my post. It wasn't about how the UA works from an attenuation stand point. Re-amping or attentuating. I was saying that there is no way I could play my amp at the actual volume without the UA. I mentioned that the knob was at 10 o'clock to give people a frame of reference to where the clubs that I play, allow me to set volume. Since the UA is different, I can't say -4,-8, or -12. So please, save your "master of the gear universe" tone for people that care.

[drgonzoguitar]

http://theelectrostore.com/shopsite_sc/store/html/media/resistors/nhl-100-06z-15k-100w-dale-new-s.jpg

+

http://diyaudioprojects.com/Gallery/albums/userpics/normal_LM3875-Gainclone-Protoboard.jpg

=

http://www.musictoyz.com/img200802/ultimate.jpg



Any questions? :stir

[tedzepplin]

Any questions? :stir

Yes. what are you trying to say?

[fullerplast]

Yes. what are you trying to say?

I think he is simply illustrating that the UA is not really an attenuator, but is a fixed load followed by a SS amp. IOW, a re-amp device.

Your risk of flyback is totally independent of your reduced UA volume settings. The risk of flyback may be slightly reduced by use of the 100V AC for your amp, at the expense of the "brown tone" resulting from reduced plate voltages and heater voltages. IOW, your tone/sag/response won't be the same as 120V. Also, if you see nearly 3000V flyback at 120V, then a 20% reduction is still 2400V.....

I think all the pertinent facts have been presented in this thread by this point. It is clearly a "use at your own risk" type device and if one chooses to use one, the most significant way to reduce your risk of amp damage is to use the highest possible impedance setting available.

[drgonzoguitar]

Yes. what are you trying to say?

From the gut shots that I saw, the UA looks like a large resistor (similar to other resistive attenuators) and a really clean solid state amp to reamplify the signal. This is why the designer can add a "double power" switch---it is a SS amp. You can make the amp as big as you want and it will take up very little space.

I am willing to suspect that in exchange for less heat (by using 30 ohms of resistive attenuation), you have a moderately safe environment for SS amp. It really looks like the tube amp is being attenuated to a line level signal and then reamplified by a solid state amp.

I could be wrong....:hide

[drgonzoguitar]

I think he is simply illustrating that the UA is not really an attenuator, but is a fixed load followed by a SS amp. IOW, a re-amp device.

Your risk of flyback is totally independent of your reduced UA volume settings. The risk of flyback may be slightly reduced by use of the 100V AC for your amp, at the expense of the "brown tone" resulting from reduced plate voltages and heater voltages. IOW, your tone/sag/response won't be the same as 120V. Also, if you see nearly 3000V flyback at 120V, then a 20% reduction is still 2400V.....

I think all the pertinent facts have been presented in this thread by this point. It is clearly a "use at your own risk" type device and if one chooses to use one, the most significant way to reduce your risk of amp damage is to use the highest possible impedance setting available.

:agree

[Belmont]

:agreeYup bye babes....

and you think we care?

[Stu Blue]

and you think we care?
Enough to post about it, obviously. It doesn't surprise me that you are good friends with the guy from UA. You've both been gratuitously rude, arrogantly dismissive of expert information, and utterly indifferent to other peoples problems/interests. You have lots in common.

But thanx for the excuse to use the IGNORE feature on this forum...click and you're gone from my computer and click and I'm unsubscibed from this ( forgot to do it.)

[irwin4star]

The impedance of a real speaker varies with frequency, with a substantial peak at the 'resonant frequency', and a more general rise towards the high frequencies, typically up to four or five times the nominal impedance. It's common for a 16 ohm speaker to have impedance of 80 ohms or more. A fixed resistor of any value doesn't exhibit those tendencies. Does anyone understand that?

[hasserl]

The impedance of a real speaker varies with frequency, with a substantial peak at the 'resonant frequency', and a more general rise towards the high frequencies, typically up to four or five times the nominal impedance. It's common for a 16 ohm speaker to have impedance of 80 ohms or more. A fixed resistor of any value doesn't exhibit those tendencies. Does anyone understand that?

That is not correct, here is a link to a data sheet for a 16 ohm speaker. http://eminence.com/pdf/texasheat-16.pdf

Take a look at the graph that shows the impedance by frequency, do you see at what point it reaches 80 ohms? About 12kHz. Sorry, but that is way, way, WAY above the range of a guitar amp, it will NEVER see that impedance. Do you understand that?

[irwin4star]

lol

#1. i wasn't trying to be a smart a$$.. i was asking if anyone could explain it or had experience with the situation.

#2. So, at about 130hz and 1.7k it's 30 ohms.

#3. When I push up the 12k frequency band on my eq, I damn sure hear a difference.

#4. I'm glad you posted that chart. It makes me feel alot more comfortable using my UA for another 3 years!!!!

#5. At the resonant frequency, 370 ohms???

#6. ROCK ON BRAINIACS!!!!

[JLee]

For those that might be paranoid about the UA or any other attenuator and impedance mismatches-
https://taweber.powweb.com/store/attenmatch.htm

[rick13]

Why worry? If it breaks, fix it. If you can't afford to fix it...don't use an attenuator, and buy an amp with power scaling.
Rick

[phsyconoodler]

I'm not making any argument about the UA,but maybe I'm a little thick about voltage selector settings.Did I read correctly that the amps voltage set at 100v is safe to use with the UA?
Correct me if I'm wrong here,but when the amp voltage selector is set at 100v and you hit it with 123v(my peak voltage) the plate voltage climbs to unacceptable levels.
What is the rub with the 100v !!!!!!??????
100v in=468v out
120v in = 468v out
230 in = 468v out (100watt marshall as test mule)

So does that mean 120v into the 100v tap means 468v out?Not in my book!

[fullerplast]

I'm not making any argument about the UA,but maybe I'm a little thick about voltage selector settings.Did I read correctly that the amps voltage set at 100v is safe to use with the UA?

So does that mean 120v into the 100v tap means 468v out?Not in my book!

No. For your amp, the safest settings for using the UA would be to use the 100V output of the UA into your amp, with the amp set to the 120V setting. Concurrently, you would set your amp speaker output to 16 ohms. That both lowers the plate voltage and gets you as closely matched to 30 ohms as you can get. That is the safest mode you can operate the UA. (Note that the 100V UA supply will also change the tone and response of the amp to some extent.)

[JubileeMan 2555]

No. For your amp, the safest settings for using the UA would be to use the 100V output of the UA into your amp, with the amp set to the 120V setting. Concurrently, you would set your amp speaker output to 16 ohms. That both lowers the plate voltage and gets you as closely matched to 30 ohms as you can get. That is the safest mode you can operate the UA. (Note that the 100V UA supply will also change the tone and response of the amp to some extent.)

I don't recommend the 100v tap. It brings the Heater voltages down 20% which is enough to cause cathode stripping and decrease the life of your preamp tubes significantly.

[jackaroo]

I hear cathode stripping starts at around 80v.


I think you're wrong. I don't use my 100v tap though. It's too soft/squishy sounding

[JubileeMan 2555]

I hear cathode stripping starts at around 80v.


I think you're wrong. I don't use my 100v tap though. It's too soft/squishy sounding

Tone-lizard.com has a good run-down why you should never lower the voltages on an amp. But here is a good graph:

http://www.tone-lizard.com/images/Tremaine.gif
from the book Audio Cyclopedia, by Howard M. Tremaine

[fullerplast]

I don't recommend the 100v tap. It brings the Heater voltages down 20% which is enough to cause cathode stripping and decrease the life of your preamp tubes significantly.

I'm not supporting use of 100V, only answering a question regarding its use to minimize risk of amp damage.

I have seen the graph you presented, but I don't believe it simply because it shows 3 hours of tube life at 85% heater voltage....equivalent to running an amp at 106V vs 125V. I don't know where he got his numbers, or what tubes he is discussing in his book, but I am sure that 12AX7's are not going to be dead in 3 hours. So to me, that makes the data at least suspect. I don't have that book, maybe you do and could elaborate?

In any event, the point UA supporters are making is that there is far more total risk to the amp and trannies running at 120V+ combined with flyback due to extreme impedance mismatching (4x or greater).

Pick your poison. It's about minimizing risk of damage.:worried

(FWIW, I don't use a UA and I do use a voltage regulator set to 120VAC)

[Husky]

More modern research using real data instead of estimated data does show some benefits to lower heater voltages, longer life, more consistent and less distortion.
10% less is no problem at all and the actually sound better in many situations. 5V is used very often in the Audio world
http://www.tubecad.com/july2000/img45.gif

http://www.tubecad.com/july2000/page10.html

[fullerplast]

More modern research using real data instead of estimated data does show some benefits to lower heater voltages, longer life, more consistent and less distortion.
10% less is no problem at all and the actually sound better in many situations. 5V is used very often in the Audio world
http://www.tubecad.com/july2000/img45.gif

http://www.tubecad.com/july2000/page10.html

Thanks for that link John. I had seen 5V recommended before as a practical lower limit on heater voltage but had not seen supporting data. That makes much more sense than the previous graph.

[JubileeMan 2555]

more modern research using real data instead of estimated data does show some benefits to lower heater voltages, longer life, more consistent and less distortion.
10% less is no problem at all and the actually sound better in many situations. 5v is used very often in the audio world
http://www.tubecad.com/july2000/img45.gif

http://www.tubecad.com/july2000/page10.html

thanks! Good to know! :)

[hasserl]

I agree, I've seen certain amps that run the preamp tubes at ~ 5 volts, I've even seen some down to 4.7vdc (the current is rectified for the first two preamp tubes) and they can last for years depending on how much the amp is used.

RDH4 says "If the filament or heater is operated for long periods at reduced voltages, the effect is reduction in emission, but no damage is generally done to the valve unless the cathode currents are sufficient to exhaust the "space charge"" "".