Ultimate Attenuator?

[John Phillips]

Originally posted by tonedaddy
Not sure if you saw this previously, but the UA is available in 100w and 300w versions, and he does suggest going to the 300w version for 100w amps (e.g. Super Leads).

I didn't know that. So is the UA intended only for up to 50W amps? If so, it shouldn't be called a '100W' model. For the avoidance of confusion, a '100W' attenuator should be capable of taking the full distorted output of any 100W amp on the market, IMO.


Yes, flyback voltage is a problem even with resistive loads, because the OT itself is still highly inductive. That's the same as why no load (which by definition is not inductive) is dangerous.

(That's also why over-high loads are not usually a problem to solid-state amps, which almost always don't have an OT.)


If the Airbrake is around 14 ohms, it sounds like it is ideal for 8-ohm amps, since that is also about the average of an 8-ohm speaker over the audio range. It should be definitely safe for any 8 or 16-ohm amp, and almost certainly not a risk to 4-ohm ones, in the same way as the UA is probably safe with 8-ohm amps. If you're going to make a 'universal' (ignoring 2-ohm) attenuator, that's the right value to make it.

Originally posted by pluto
That would be my power chord that was melted almost all the way through!! Almost started a fire in my house and almost killed my amp without knowing it!! That was my fault though because I didn't know part of the chord was resting against the UA when I was playing it and I knew it was going to get hot.

That wasn't your fault - that's a design fault. If something is going to get that hot, it should be fitted with a high-temperature power cord (like a kettle or toaster). That's one reason it would fail CE certification. Anyway, a properly-cooled attenuator shouldn't ever get hot enough to melt plastic. If it does, many of the components inside are at serious risk too.


Sorry to keep going on about this, I just don't think it's right that a pretty amateurish, poorly-built, not very thoroughly tested unit should be on the market, branded as 'Ultimate', with all sorts of claims for it's 'universal' application, when in fact it could cause major damage to some amps, and possibly even a quite serious safety risk - when not all potential users have the technical knowledge to know the risks they may be running.

It's not specifically this product I have an issue with either - I'd say the same about anything which looked similar inside or whose maker (or is that distributor?) makes claims which are simply wrong.

[tonedaddy]

Originally posted by John Phillips
I didn't know that. So is the UA intended only for up to 50W amps? If so, it shouldn't be called a '100W' model. For the avoidance of confusion, a '100W' attenuator should be capable of taking the full distorted output of any 100W amp on the market, IMO.

I didn't ask him about what he would recomend with the 100W model, but I think that's what you have to infer from the info on his website, e.g.:

"A word about Scaling and Watts.
Scaling is the UA's ability to go from zero db's to the matched full volume of your un-attenuated amp. For example, The UA is rated for 100 watts and the average Marshall Super Lead amplifier with 4 EL-34 power tubes can produce 150 watts before clipping. That is a 30% deficit between the UA And the Super Lead. In other words, the UA with the volume maxed will be less loud by about 30% or approximately 2db's.

"You might say, "I bought the UA to turn the volume down, so what's the difference?" This is a good argument and we have lots of UA's on tour with players using Marshall Supers. If you want full scaling for amps rated up to 300 watts, I would recommend the SuperUltimate Attenuator."


I agree with your comments, and I have the same issue with confusion you've been speaking to. Until I found out it was a reamp, I was under the impression is was a true attenuator. I've already got a reamp solution, I could have ended up making a costly investment I didn't need if not for doing the research I did. Not exactly easy to get the straight story.

For that, I think he's actully hurting himself in the long run. Reamp solutions are great, and I'm glad the UA is working for those who are using it effectively. But for no additional cost, he could clearly explain the functionality of the unit on his website, and explain the advantages of it along with some more technical info on how it should be used safely.

Hello. Thanks for all the interest in the UA. I appreciate the chance to participate in this forum and would like to clear up some assumptions and reply to some statements about the UA.
The first is that it is the same as a dummy load and amp. It is not. The circuit does consist of a dummy load and an amp, but there is more to the picture and no one seemed to pick up on it. It is not technically a re-amp. It is something else. Maybe something you've never heard of. Let's see if anyone can guess what it's technical name is. I will describe it compared to a dummy load amp scheme.
The dummy load, line out re-amp will give you back whatever power the amp is capable of with the volume maxed. In other words. if your amp is 100 watts and the re-amp is 300 watts, you can get 300 watts back. With the UA, if you have a 100 watt amp and turn the UA to the max, you will get 100 watts. If you have a 50 watt amp and turn the UA up to the max, you will get 50 watts and if you have an 18 watt amp (or any wattage up to about 130 watts), you will get just that wattage back. That alone should get you thinking. In other words, you can't do this with a Hotplate and amp.
The next issue with a re-amp is sound quality. Some seem to assume that a Hotplate and amp would sound the same as the UA. That would be wrong. Those of you who own the UA could easily test this theory. I would be interested to see your results. I know what mine have shown. There is no comparison. Don't assume that you know what is in the UA circuit. Nobody on the forum has described it yet. There is nothing like it on the market so it's safe to assume that unless you've actually tried one, you don't know.
The other issue is attenuation. With a re-amp setup, you can't tell at a glance if you are attenuating or even actually making your rig louder. This is why I call the UA a true attenuator; When you turn the UA all the way up, it is as loud as your amp. Not louder. Then, you turn it down or attenuate your amp. Attenuation simply means to turn down.
John Phillips, you are wrong on a couple of counts. First that a fixed load at 30 ohms will cause flyback to a 4, or 8 ohm load. This could be true of a fluctuating load, but not a fixed load. Second, that the UA is a shoddily built device. I guess you surmised that by the photo. I'm not sure what you are referring to. The fact is, the UA is a professionally hand built device and a very well engineered piece of gear for professional guitarists and is fully warranted for the life of the unit by Magus Innovations. With several hundred units in service in the last few years, we have not had any incidence of amp damage or injury whether used properly or improperly. I would not stay in business very long building shoddy products. We have done extensive real world research with some of the top guitarists in the world to develop this product and I stand behind it Sir.
Lastly, I stand behind all claims on the Ultimate Attenuator website. I urge you to look there for more insight to this amazing and unique device. Feel free to contact me anytime and thank you for your consideration. Sincerely, Mark Gregg. PS, We will be at Winter NAMM in the '65 amps booth with Peter Stroud, former Hotplate user.

[wrecked]

Mark,
I'm glad you are able to address out concerns on this forum. That being said, there are still some valid issues that I hope you can further clarify.

Are you the actual designer of this unit, Mark? If not, I certainly don't want to jump on you for misunderstanding what leakage inductance is, but flyback voltage spikes do not require a non-fixed load. In a simple equivalent circuit model, the leakage inductance is represented by an inductor in series with a transformer winding. Voltage across an inductor is proportional to the rate of change of the current that flows through it meaning any discontinuity in current can easily generate very large spikes.

Furthermore, I don't think that the argument that the UA is popular among high-profile guitarists has any bearing other that the subjective tone, and that isn't what we're really trying to dispute here. I completely agree with John that based on the report (which you didn't mention) that the unit got hot enough on the surface to melt a power cord, there should be a serious review of the safety of this design. The production quality and design is in my opinion not engineering of a professional caliber, as stated in your post, principally because it would not meet the requirements of any safety standards organization. Some construction points like what appears to be a floating vector board are debatable, but I personally would be very worried to have "hundreds" of any product constructed with a heat problem like the above in circulation. I'm not a lawyer, but I'd imagine that, aside from the ethical consequences, monetary liability in the case of an accident with this product would be rather extreme, especially since you've now been given at least one report (that, again, you've not addressed) that your product might be unsafe for consumers.

Matt

[Hipster Dofus]

Originally posted by pluto
That would be my power chord that was melted almost all the way through!! Almost started a fire in my house and almost killed my amp without knowing it!! That was my fault though because I didn't know part of the chord was resting against the UA when I was playing it and I knew it was going to get hot. To Mark's credit, he fixed it for free and put in the high gain option for no charge at all. The one thing that bothers me about the UA more than anything else right now is that when I first spoke on the phone to Mark about the UA, he made it sound like it was his design, his product, etc. But it isn't at all-he's simply distributing for Ho who had been making this product for awhile. You can buy the same UA directly from Ho for a LOT cheaper than how much Mark is charging for the UA.

Are you saying the unit was so hot it melted the plastic insulation, or the cord itself was hot from the Current draw of the unit..?

[55 Jr]

Wow.

Great read, this place is pretty cool!

I saw one of these on the'bay a while back, went for a fair buck too.

I'm still not sure what to make of this unit or the apparent cost mark up and claims of who actually invented the UA.

I will say that I ended up bidding on a used Airbrake and I am very happy with it.

Thanks for the information.

Brian

Hi Matt. Glad to be included. The alleged cord burning incident first of all, probably never took place! I repaired this gentleman's cord and he told me what happened. The fact is, the burn mark was there when I shipped it , from a soldering iron! The smell he reports was not the cable but the resistors heating up. I think I still have the cable around here somewhere. If you use a 4 EL-34 amp with the standard unit, it gets very hot. Remember, it's only rated to 100 watts (although I know of several people who use it with 4 EL-34 amps and I think this gentleman may have been as well). We recommend the SuperUltimate for up to 200 watts continuous and I think it could easily handle 300 watts.

I'm not sure I understand what you are saying about discontinuity. In relation to impedance? There should be NO discontinuity.
As far as flyback, I consider it no more or no less likely with a matched speaker impedance than with the amp set from 4-16 ohms and a properly designed 30 ohm load. The impedance is actually 30 ohms (When measured you get resistance which is why someone got 32 ohms. The reason for 30 ohms? It sounds best!
I did not invent the circuit, ( to answer your question) and have never tried to imply that I did. I was, however instrumental in it's devolopment to it's current state. We build to my specs which are evolving a bit as far as some materials and cosmetics. In the near future we will probably move away from hand building (We will be up to euro safety standards then) as we are inundated with orders from individuals and have many inquiries for retail outlets. I think these early ones should be regarded as somewhat special as they are hand built. You are of couse entitled to your own opinion about the build quality (I don't agree) but I maintain that the unit is safe if used as directed and very well built. BTW, the floating board is part of the circuit protect and is not in the circuit. We are now mounting it on the heatsink. Thanks! Mark.

[908SSP]

I run a 35 watt amp into my Ultimate I have never noticed it getting hot. It sounds better then any other attenuator I have tried. If they weren't so much money I would have a few more.

[reaiken]

Originally posted by Mark from UA
Let's see if anyone can guess what it's technical name is.

Sounds to me like it's a 30 ohm resistor loading the amp, followed by an emitter follower (or MOSFET source follower) driving the speaker (which is the reason for the power supply). Do I win? A free UA, maybe?

Oh, by the way, an amplifier with unity gain is still *technically* an amplifier, so it is a "reamp", for what it's worth.

Randall Aiken

[wrecked]

Hi!

That's a very fair response Mark. I looked up a few numbers, and found that it would actually be quite hard to "melt" what I would assume is electrical-grade PVC insulation without having the resistor toast first. I certainly accept your explanation, since the resistor would derate down to zero before the PVC would really softnen all that much, let alone burn (which happens right around soldering iron temperature). I think I just misconstrued Pluto's wording as meaning that he noticed the fault occur (i.e. saw it on the hot part, moved it, and saw a correlating burn mark).

I'm glad to hear that you plan to re-evaluate the construction methods used in the UA, and I'm also hopeful that you'll strongly consider adding an impedance matching function or at the very least using another power resistor to allow the unit to handle a true 100W and avoid disasters. At less than 0.7% of the base price, I'm sure the extra 50W resistor would pay for itself in repairs many times over.

Concerning the leakage inductance thing, I probably should have specified primary leakage inductance as being the culprit. I'm also really refering to any sharply changing input stimulus as being approximately "discontinuous", something like an idealized square wave input. When the current flow is cut sharply in the primary (like the "fall" portion of a square wave), the transformer's collapsing magnetic field will generate a voltage on all the mutually coupled inductors (the windings) to dissipate that energy. In an imperfectly coupled transformer, not quite all of this energy is used in the secondary to drive the speaker; the remainder manifests itself as core losses and inductive kickback on the primary side. The problem with a higher than expected mismatch ratio is that it means that higher voltages are reached on the primary (and also the secondary, naturally, since the impedance is higher) before the energy is dissipated. To address what Hasserl asked, the inductive nature of the speaker isn't required for a kickback voltage spike, although it will probably exacerbate it a little. In calculation, the leakage inductance of the secondary will also be in series with the load, so an ideal resistor on the output will still present as being a little bit reactive overall. There's really no easy way to determine, short of using HV probes and a 'scope to test the peaks, if running into a 30-ohm load will hurt any given amp design. This is because the flyback voltages will be based on a pretty complex mix of things including the output stage slew rate, power tube inter-electrode capacitance, the voltage insulation rating of the OT primary wires, the power tubes and sockets, the amp's B+, frequency resonse, etc. There will certainly be a higher probability of an arc occuring when running a higher load impedance than intended across the audio range though, so I probably wouldn't chance the 30-ohm load with something irreplaceable without first seeing what kind of an effect a slighter deviation from the ideal load (like say 20ohms for a 16ohm output) has on the peak value of the kickback peaks.

Anyway, sorry if my explanation above is a little long or hard to follow, and I'm definitely open to any comments or corrections.

Good luck!
Matt

[PStroud]

All technical concerns of a new unit like this are always warranted. But, I can say from a user's standpoint that I'm thoroughly pleased with my UA. I have a standard UA that I've used for the past couple of years with my hot-rodded 100 watt Super Lead (540 plate volts) and as the unit gets damn hot, it has never failed. Eventually, I'll pick up one of their 300 watt models. It's clarity and reaction to dynamics makes it my favorite attenuator out thus far. I've used the Hot Plates for the past 8 years and still like and use them. It's a great, reliable unit. Just think the UA design is raising the bar. Rids of that flattening compressed sound that you hear with most current attenuators.

As with any newer product, I'm sure there is room for improvement in design. But neither I nor any of my other friends who I've turned onto these UA's thus far have had an ounce of trouble, be it with their amps or safety issues. All I can say is...Keep up the good work guys and I don't mind being a guinea pig!

[loverocker]

<scratches head> So it is a re-amp? Congrats on the extra control that lets you re-amp to the original input signal - that's clever - but it's still a reamp.

FWIW: I happen to think re-amping is a great idea. I've got a Guytron and I also re-amp 18-100W Marshalls via Palmer PDI-03/04 or Hotplate all the time.

FWIW2: I'd have added a Send/Return loop just before the amp in the UA to make it easy to get good-sounding (post-distortion) FX, too.

The issue for me is the use of the word "attenuator". In a market full of very conservative and valve-loving purists who would never normally use a solid-state amp - i.e. who are happier with a passive attenuator that just cuts down their valve amps' volume - it's great stealth marketing.

[wrecked]

Originally posted by loverocker
The issue for me is the use of the word "attenuator". In a market full of very conservative and valve-loving purists who would never normally use a solid-state amp - i.e. who are happier with a passive attenuator that just cuts down their valve amps' volume - it's great stealth marketing.

Hi!

Loverocker, I hope those aren't the same valve purists who use dirt pedals into a clean amp! I appreciate how SS has come to have its negative reputation, but they're not bad for clean reproduction. Many a great live tone has been blasted out of an SS PA amp, too!

The UA does re-amplify signal, but since "Reamp" is a trademarked name we can't really fault Mark and Co. for not wanting to call it that. As for the use of "attenuator", well that's what it does, so I don't know how that could be argued against (especially while all those "Class A" amps are still around). The only potential problem with the name that I can see is that if you search on Yahoo! a similarly named product for HiFiers comes up. I believe if either party has a problem with that, the first group to use it in commerce is given precedence as far as a trademark goes, but as I said before I'm not a lawyer.

Welcome to the forum Peter, and thanks for sharing your impressions of the ultimate attenuator with us!

Matt

[pfrischmann]

Peter Stroud and Marg Gregg. Welcome! Please stay around a while!

[John Phillips]

Originally posted by Mark Gregg
The fact is, the burn mark was there when I shipped it , from a soldering iron!

So you shipped a unit with a burn in the power cord and you are claiming to have professional standards of construction??!!!

Unbelievable.


Yes, I did "surmise" the quality of construction from the pic. That is a pic of one of your products, yes? If so it is quite clearly not built to the highest professional standards. If you really can't tell why, or why a burned power cord is not acceptable, you shouldn't be in the business of making electrical products to sell to the public. IMO.

It's things like the cheap line fuseholder, DIY circuit boards, untidy wiring, layout, and the general inaccurate assembly - very little is even square (yes, I know this doesn't actually affect the operation, but it's an indicator of poor workmanship standards). 'Hand built' does not have to mean poorly built.


BTW, 'scaling' the output power to the input should be straightforward, since the voltage developed across the dummy load is dependent on the amp's power. More power, more voltage. If you amplify that voltage linearly (as a simple SS output stage will), the output power will be proportional to the input power. So all you need to do to achieve what you mention is to calibrate the input voltage to the power amp such that when the volume control is up full, the same power is developed.

And it's still NOT an attenuator. It's a dummy-load/re-amp system, no matter if it has a bit of extra circuitry to achieve good tone and power matching.


I've never disputed that it sounds good, BTW. I admit to being surprised, but if it does, then it does. I think it needs to be built better, and I'm still very skeptical about the impedance matching (read Matt/wrecked's post).