Why does my amp sound different sometimes?

[jezzzz2003]

Tonight, I cranked up my 1987x for a play,
For about 30 minutes, the amp sounded as if it were working against me and felt hard to play, and a bit mushy, not in sound but feel.
When playing fast runs, the amps sort of missed some notes, if that makes any sense at all..
Come to think of it, the amp sounded like it had a slow tube rectifier when in fact it has a solid state diode rect of course.

5 minutes later, I came back and played for another half hour and my amp sounded awesome!

Im using Svetlana winged C 34's. play about 3 times a week, normally at fairly high volumes.
the last time I replaced them was 1 year ago.
I dont know if the tubes are the culprit though??
They dont seem to have lost any highs or lows, theyre not mushy either, the amp is still loud and generally sounds great most of the time.

Everybody knows that tube amps often sound different even when used on the same power outlet.
Some explanations Ive heard in the past include, tube temperature, transformer temp, and something to do with power itself, which Ive forgotten.

Basically what Im trying to say is, does anyone have any explanation for these types of symptoms in tube amps?

[slider313]

I think 3 times a week at high volume is a good reason to suspect the power tubes are in need of replacing. It could be one or two of the tubes drifting after heating up.

[brad347]

i would try an experiment. Next time your amp feels all "soggy," get a multimeter and test the AC voltage coming out of the wall socket that your amp is plugged into.

Then test it another time when the amp feels really 'awake' and when you love the tone.

The answer just might lie right there in your wall. I know I've noticed that sort of thing before. Wall power has more effect than many of us consider sometimes. Line voltages fluctuate throughout the day (less strain being put on the municipal grid at midnight than at 7 PM).

[jezzzz2003]

Thanks brad,
this sounds like one very reasonable explanation.
as for tubes, I think a good set of Svets should last about 2 years playing 3 times a week, I had a discussion with my Australian tube vendor about them and he told me that I had been wasting perfectly good tubes by replacing them every six months, Svets have been a very reliable tube within the past couple of years.

He said they should hold up to alot of abuse and to change mine every 1.5 years or so.

He also said that there is alot of current production tube myth about how "bad" they really are compared to the old ones, he says theyre really not that bad and urged me not to listen to the hype.

Mindsets regarding current production tube life I think, has been spurred on by books such as Aspen Pittmans Tube Amp Book aswell as internet myth and some buisiness men who work in the industry, tubes dont make a hell of alot of money for anybody dealing them so I wouldnt blame them for trying to get rid of as many as they can possibly unload, plus, it is a good idea to change them more regularly than not of course so its really not a scam on anyones behalf. whilst some brands and batches of tubes may be bad, others are not.

[jezzzz2003]

I think 3 times a week at high volume is a good reason to suspect the power tubes are in need of replacing. It could be one or two of the tubes drifting after heating up.

Thanks slider, I will check that out.

[jezzzz2003]

O.k.
Im just done replacing output tubes,
the new svets sounded exactly the same as my old ones, output at full tilt was also the same volume so I decided to keep playing the oldies and keep the new ones for when I really need to replace them.
thats not to say they could be drifting from time to time though but I think the occasional "bad" sounding amp has more to do with the power source itself.

[rob2001]

I think everything mentioned can contribute to a funky souding amp. But the main thing that has far more variables than the equipment is the human being playing it! Now i'm not knockin anyone. I've thought the same thing for alot of years and to a point, a tube amp changes, but not as much as our moods, listening environments, heck, even our ears change. I think some amps are more telling of these changes. I had an old JMP NMV that was just a brutally honest amp. I seemed to hear fluctuations in tone more with that compared to my JCM 800. An honest amp in itself but not like the JMP. I even hear these changes with an ADA tube preamp into a solid state power amp. My mood, how I attack the strings, the condition of my sinus's change way more than an amp will. But ya, I ran all the tests on my power etc.. that accounts for some change. Just a thought.

[Boogs]

Our hearing can be greatly affected by many variables. If you have been listening to music or a movie, the contrast can throw you off for a bit. Fatigue negatively affects our ability to percieve complexity in sound, and our enjoyment of it. Intoxicants like alcohol affect our hearing. Also, remember that our ears are complex and somewhat strange structures themselves, and our hearing varies a bit from time to time no matter what.

Then there's the amp warmup/voltages/humidity/tube condition/ air temperature/position of the moon, and of course the presence of any alien spacecraft. ;)

[SlyStrat]

I think I have a voltage problem too. Sometimes my tone is great, other times its very harsh, trebly, and not musical.
Too much can be a problem too. I need a volt meter.

[rockon1]

Ive noticed the same thing. Line voltage as mentioned. Ive seen mine swing from 124 volts to 114 volts. I also think changes in humidity must affect speaker cones to some extent also. There must be other causes Im not aware of too besides my perception too.

[brad347]

Not just speaker cones!

REMEMBER: We can control line voltage/wall power to an extent with power conditioners, variacs, etc.

What we CANNOT control is the air! The air is the final link in the chain between the speaker and our ears. Sound waves are air particles bumping up against one another. Now I don't want to make this whole thing any more ridiculous than it already is, but who is to say that the amount of humidity in the air wouldn't affect how quickly the air moves? What about the amount of nitrogen in the air that day? (ha ha!) I'd love it if there were a way to play an amplifier on top of a mountain where the air is really thin and then in new orleans where the humidity was high and you are below sea level. I wonder how it would change, all else remaining equal? Just a hypothesis...

[BBQLS1]

Could be the user. There are alot of times where my amps may sound different for whatever reason. I think ears adjust a little and change depending on all kinds of inputs.

[SlyStrat]

I live in a conjested suburb of Cleveland. The power lines are OLD. When it rains, my tone gets bad. With the cold and snow, my tone is HARSH.
I just ordered a voltage regulator made for computers and other electronics. $65 shipped.
And I'm gonna buy a Chinese 10 amp variac. $80.

[trisonic]

I've noticed big changes when I felt under the weather.
Sinusitis, Colds etc., all affect how you hear.
I sounded like shit yesterday and woke up with an earache and feeling like death warmed up this morning.
Congestion in the head is the worst.

Best, Pete.

[boobtoob]

I've had the same experience with my amp many times before...after the gig is about half over, the amp starts to sound "thicker" and better. Is it the amp warming up? Or is it my hearing browning out? I don't know.

[John Phillips]

I always think my amp sounds better - and the rest of the band quite often tell me it's louder :), even though I haven't adjusted it - after it's been on a while, typically a good half hour of playing. I think it's to do with it heating up, though I'm not quite sure why this should make it sound better, or louder. Every tube amp and quite a lot of solid-state amps I've used have done exactly the same thing.

Either that or it's something to do with beer ;).


BTW, changing tubes too often is only really a waste if you throw out the old ones, although there will come a point where you have a huge stack of partly used tubes :).

It's nice to hear a tube vendor say this though, I've always thought that the 'received wisdom' about changing them all every six months, or every year, or whatever, is wrong and driven by marketing. I change them when they fail or when they noticeably or measurably start to lose performance. It really saddens me to think how many great tubes have been tossed in the trash just because someone thought that since they were a year or two old, so they 'needed changing'. I've worked on many amps from the 70s and 80s, and even some older than that, with their original tubes in - including the power tubes sometimes - all in perfect working order.

I still think that old-production tubes are far better than new ones, it's just that my expected change interval for new tubes is slightly shorter than never, which is about when I change old-stock ones... ;)

[jyee]

if it's only the first 30 minutes each time you turn on, i'd suspect that it's a warmup issue.

[jezzzz2003]

I always think my amp sounds better - and the rest of the band quite often tell me it's louder :), even though I haven't adjusted it - after it's been on a while, typically a good half hour of playing. I think it's to do with it heating up, though I'm not quite sure why this should make it sound better, or louder. Every tube amp and quite a lot of solid-state amps I've used have done exactly the same thing.

Either that or it's something to do with beer ;).


BTW, changing tubes too often is only really a waste if you throw out the old ones, although there will come a point where you have a huge stack of partly used tubes :).

It's nice to hear a tube vendor say this though, I've always thought that the 'received wisdom' about changing them all every six months, or every year, or whatever, is wrong and driven by marketing. I change them when they fail or when they noticeably or measurably start to lose performance. It really saddens me to think how many great tubes have been tossed in the trash just because someone thought that since they were a year or two old, so they 'needed changing'. I've worked on many amps from the 70s and 80s, and even some older than that, with their original tubes in - including the power tubes sometimes - all in perfect working order.

I still think that old-production tubes are far better than new ones, it's just that my expected change interval for new tubes is slightly shorter than never, which is about when I change old-stock ones... ;)

It is a good thing our tube man tells the truth but theres a funny story that goes with it too,

Dad met the tube dude years and years ago whilst working in his old repair shop and he tells me he hates matching them, hes really slack on getting a batch out to us, Im talking months!
I dont know if its his only buisiness but he sure doesnt care about making money from selling tubes.

Last batch I personally ordered took 3 phone calls over a few weeks to get them out.
The third call I got his wife and left a message, she told me that hes going to be in trouble when he got back, We had them a few days later:D

[Quantumphysics]

About every month (or so) I fire up all the amps that I don't use on a regular basis and play about a 1/2 hour on each amp. I just feel it's not good to let gear sit with out using it. Also my studio/recording rig - I run that twice a month (unless I'm in the middle of a project) to keep the ghost's out of that rig. I use ear plugs every gig (but I don't put them in until the 3rd or 4th song so I know the stage mix) and towards the end the gig - I'll pull them for a minute or so - and regardless of which amp I'm running - my perception is it sounds better. I do believe that air quality makes a difference as well (especially with acoustics/microphones) Also - same thing with mixing a record - it always sound a bit different the next day. (and I know longer self medicate - so it's not the beer/shrub) It's all perception. I do know one thing for sure - an artificially aspirated engine with racing software runs better on cold night - that's a fact!

[Rik]

Since older days, I always waited for the tubes to get nice and toasty, it does have that warmer sparkely sound to me. seems like I just get it glowing and its time for a break. they had to drag me off stage.

I know its subjective, but humidity really changes the sound to me. muddy to clearer sounding.

I always read about guys changing tubes every 6 months to a year and I could not understand it, until I read where some people said its a must of you play constantly. I used to play at least four hours a day.. every day. the marshall el34 50/50, and the 100/100 monoblock amps I have used for years and years I had great results. (through most of the 90's). I guess it has to get really bad for me to notice they need changed haha.. but if it sounds good, why change them..

nowdays. I will turn on the amps, let them run for 10-15 minutes, then kick on the nitrous..

[Clearspider]

Not just speaker cones!

REMEMBER: We can control line voltage/wall power to an extent with power conditioners, variacs, etc.

What we CANNOT control is the air! The air is the final link in the chain between the speaker and our ears. Sound waves are air particles bumping up against one another. Now I don't want to make this whole thing any more ridiculous than it already is, but who is to say that the amount of humidity in the air wouldn't affect how quickly the air moves? What about the amount of nitrogen in the air that day? (ha ha!) I'd love it if there were a way to play an amplifier on top of a mountain where the air is really thin and then in new orleans where the humidity was high and you are below sea level. I wonder how it would change, all else remaining equal? Just a hypothesis...
I'm not a scientist, but I can guarantee that there would be a difference. Not only would the air pressure have an effect on the speaker movement, but also on your eardrum, which is a speaker in reverse (a mic for your brain.) The highs would be clearer, probably piercing as the lower pressure is pulling and tightening the membrane and causing a change in the pressure of the ear canal, causing the eardrum to be more susceptible to high frequencies. Of course the eustacian tubes would eventually release the pressure and equalize it between the ear canal and the air outside, but for a bit, it would be a tighter glassier sound. The speaker, operating under a lighter load, would be freer to move and probably distort a lot more, sounding crisp and possibly ragged, assuming that the high altitude air equates to drier air. Then you could take into account the amount of moisture in the air and factor all that shit in. Yes, your amp would sound markedly different, even to a layman.

[brad347]

further cementing the notion I'm getting to lately which is "we can't control it all, so why try to control any of it... just play!" Although the "shut up and play yer guitar" is a tired rolleyes-inducing sentiment on this message board and always has been.

[SlyStrat]

My problem isn't humidity, temperature, barometric pressure, I'm sick, etc.
I definately have power problems. This week my amps tone is so harsh its not even fun to play. Last night I turned down the presence control and it helped take away some unwanted trebly distortion. Its like a nasty buzz that rides on top of the notes. Hard to explain in words. Theres no harmonics, no warmth to the tone either. Very 2 dimensional.

[fullerplast]

As already mentioned, there are several major factors. I'd categorize them in this order:

1) AC voltage. A 10V swing in wall voltage can mean a 40V change in plate voltage. Definately an audible change. Solution: use a regulator (and a variac if necessary).

2) Heat: sonically affects many amp components from tubes to trannies. Solution: an internal fan (ala Fuchs and others) helps stabilize temperatures.

3) Speakers: surrounds loosen up, voice coils warm up, cones absorb moisture in the air. Not much to control.

4) Air: Humidity and temperature change the density and the way that sound moves. Not much to control.

5) Surroundings: More people in a club absorb sound and especially high frequencies. Room size and floor/wall/ceiling material change everything. Solution: EQ and volume.

6) Ear fatigue: The ears typically become less sensitive to highs and volume as the night goes on. Solution: None, other than ear plugs. Pull plugs and do periodic checks.

[brad347]

I'm not carting a variac to my gigs or putting a fan in any of my fender amps.

At some point my philosophy becomes "If you can't be with the tone you love, love the tone you're with"

[Dave_C]

i would try an experiment. Next time your amp feels all "soggy," get a multimeter and test the AC voltage coming out of the wall socket that your amp is plugged into.

Then test it another time when the amp feels really 'awake' and when you love the tone.

The answer just might lie right there in your wall. I know I've noticed that sort of thing before. Wall power has more effect than many of us consider sometimes. Line voltages fluctuate throughout the day (less strain being put on the municipal grid at midnight than at 7 PM).

Absolutely. I've documented this effect at my home and especially at clubs, so I bought a Furman voltage regulator (AR-15 Series II) and it has solved that problem. If you look around, they can be had for around $450...well worth it, IMO. It's also nice to know that whacky surges and brownouts at the dumps we play will have less likelihood of damaging my amp.

[Dave_C]

I always think my amp sounds better - and the rest of the band quite often tell me it's louder :), even though I haven't adjusted it - after it's been on a while, typically a good half hour of playing. I think it's to do with it heating up, though I'm not quite sure why this should make it sound better, or louder. Every tube amp and quite a lot of solid-state amps I've used have done exactly the same thing.

Either that or it's something to do with beer ;).


BTW, changing tubes too often is only really a waste if you throw out the old ones, although there will come a point where you have a huge stack of partly used tubes :).

It's nice to hear a tube vendor say this though, I've always thought that the 'received wisdom' about changing them all every six months, or every year, or whatever, is wrong and driven by marketing. I change them when they fail or when they noticeably or measurably start to lose performance. It really saddens me to think how many great tubes have been tossed in the trash just because someone thought that since they were a year or two old, so they 'needed changing'. I've worked on many amps from the 70s and 80s, and even some older than that, with their original tubes in - including the power tubes sometimes - all in perfect working order.

I still think that old-production tubes are far better than new ones, it's just that my expected change interval for new tubes is slightly shorter than never, which is about when I change old-stock ones... ;)

Definitely agree with the warm-up comments. I actually plan on adjusting high end as the gig wears on to compensate. I believe it's the tubes warming up first, followed by the trannies (it takes longer for the heavy thick iron to warm), followed by the rest of the components in the chassis. That's why it seems to take up to half a gig sometimes to reach that thicker, warmer tone. And, this effect occurs even with the Furman AR-15 Series II regulator.

[Dave_C]

As already mentioned, there are several major factors. I'd categorize them in this order:

1) AC voltage. A 10V swing in wall voltage can mean a 40V change in plate voltage. Definately an audible change. Solution: use a regulator (and a variac if necessary).

2) Heat: sonically affects many amp components from tubes to trannies. Solution: an internal fan (ala Fuchs and others) helps stabilize temperatures.

3) Speakers: surrounds loosen up, voice coils warm up, cones absorb moisture in the air. Not much to control.

4) Air: Humidity and temperature change the density and the way that sound moves. Not much to control.

5) Surroundings: More people in a club absorb sound and especially high frequencies. Room size and floor/wall/ceiling material change everything. Solution: EQ and volume.

6) Ear fatigue: The ears typically become less sensitive to highs and volume as the night goes on. Solution: None, other than ear plugs. Pull plugs and do periodic checks.

Nice list!

:AOK

[jspax7]

As already mentioned, there are several major factors. I'd categorize them in this order:

1) AC voltage. A 10V swing in wall voltage can mean a 40V change in plate voltage. Definately an audible change. Solution: use a regulator (and a variac if necessary).

2) Heat: sonically affects many amp components from tubes to trannies. Solution: an internal fan (ala Fuchs and others) helps stabilize temperatures.

3) Speakers: surrounds loosen up, voice coils warm up, cones absorb moisture in the air. Not much to control.

4) Air: Humidity and temperature change the density and the way that sound moves. Not much to control.

5) Surroundings: More people in a club absorb sound and especially high frequencies. Room size and floor/wall/ceiling material change everything. Solution: EQ and volume.

6) Ear fatigue: The ears typically become less sensitive to highs and volume as the night goes on. Solution: None, other than ear plugs. Pull plugs and do periodic checks.

+1! Get an AR-15 and plug your amp and FX into it. It will protect your gear and preserve your tone.

I had a line conditioner with a meter. Evey time my tone sucked, I looked at the meter. (114-117) Every time my amp sounded great the meter read 120 or above. It's the one variable that can (and should) be controlled.

[Dave_C]

+1! Get an AR-15 and plug your amp and FX into it. It will protect your gear and preserve your tone.

I had a line conditioner with a meter. Evey time my tone sucked, I looked at the meter. (114-117) Every time my amp sounded great the meter read 120 or above. It's the one variable that can (and should) be controlled.

I've got the AR-15 Series II and love it...so far. I'm powering my entire rig with it (see below - the top box in the rack is the Furman). I got it to stabilize the MIDI gear I'm using to switch the Fuchs, but have found it also helps to keep the tone consistent.

http://i2.photobucket.com/albums/y43/maz_master/Fuchs_Rig_Small_Cropped.jpg

[SlyStrat]

I ordered this voltage regulator. $60 shipped.
http://www.apc.com/resource/include/techspec_index.cfm?base_sku=LE1200

[fullerplast]

I ordered this voltage regulator. $60 shipped.
http://www.apc.com/resource/include/techspec_index.cfm?base_sku=LE1200

The reason it's only $60 is because the regulation is fairly loose. Its nominal 120V regulation is from 105.6V to 127.2V. Good for safety, but not for keeping tone consistent. That range allows for a plate voltage range of over 80 volts on a typical amp.

[SlyStrat]

The Furman also has a plus or minus 5 volts.
And I'm experimenting before I blow $450 on a Furman.
Next up: a variac.

[fullerplast]

You may find other differences as well.....like if they don't switch taps at the AC zero crossings you can get spikes causing noise. The APC really isn't made for audio applications, so you may find issues like this, besides the loose regulation.

FWIW, the Furman actually measured out to better than +/- 5V. It was more like +/- 2.5V in my tests. Maybe the APC will do better also.

Please post your results if you do test the APC.

[Dave_C]

The reason it's only $60 is because the regulation is fairly loose. Its nominal 120V regulation is from 105.6V to 127.2V. Good for safety, but not for keeping tone consistent. That range allows for a plate voltage range of over 80 volts on a typical amp.

Yeah, I believe I looked at this one too, as well as a few others in the lower price ranges, but their regulation was very poor (like this one) and they all had pretty skimpy conditioning and surge suppression. I couldn't find anything with better specs in the $450 price range than the Furman, but that doesn't mean they don't exist!

[Dave_C]

The Furman also has a plus or minus 5 volts.
And I'm experimenting before I blow $450 on a Furman.
Next up: a variac.

Yes, but in practice, I've found it's actually tighter than that. You need to look at their transfer function to see how the sweep through the taps works. The input voltage would have to be at the very edge of a tap to approach the +/-5V off the nominal 120V. In practice for about 7 months now, I've never seen the output voltage off by more than 2V. Plus, I've found that if I bias the amp at 120V, variations of +/- 5V from that center don't affect the tone enough to bother me. It's certainly not perfect, but it's a helluva' lot better than plugging straight into the wall...or, using a cheap regulator with poor regulation. Plus, I've heard too many horror stories about expensive boutique and/or vintage amps getting damaged by power spikes and surges. Also, given the MIDI stuff I'm using, the noise filtering is also a welcome feature.

A variac will allow you to dial in a precise output voltage, but it won't track variations automatically throughout the gig (I've seen the Furman use three different taps in one night, but usually it's just one or two) and it certainly doesn't have any surge suppression or EMI filtering.

Unfortunately, in this instance, you get what you pay for. But, I figure if I can spend $3500 on an amp and another $1000 on electronic "support" gear, it's kinda' dumb to not cough up another $450 to protect it all and keep it running in its optimal range.

[Dave_C]

You may find other differences as well.....like if they don't switch taps at the AC zero crossings you can get spikes causing noise. The APC really isn't made for audio applications, so you may find issues like this, besides the loose regulation.

FWIW, the Furman actually measured out to better than +/- 5V. It was more like +/- 2.5V in my tests. Maybe the APC will do better also.

Please post your results if you do test the APC.

All good points. There's a lot of technology in the Furman and it's all targeted for audio applications. Regarding the +/- 2.5V variation you saw, did you sweep the input with a variac? I just measured the output whenever I noticed it was using a tap other than the 120V tap. It never varied by more than 2V off 120V and I assumed that was because I just never caught it when the input was near the edge of a tap range.

[fullerplast]

Regarding the +/- 2.5V variation you saw, did you sweep the input with a variac? I just measured the output whenever I noticed it was using a tap other than the 120V tap. It never varied by more than 2V off 120V and I assumed that was because I just never caught it when the input was near the edge of a tap range.

Yes, I swept the entire input range. This is what I wrote last year:


Just an update on the regulated output of the AR1215 over the full input range from 95 to 140V. I was able to locate a variac with a step-up so wanted to check the range above 125V.

Over the entire range, the output stayed between 117V and 123V with eight tap jumps at about 5V intervals. There was no "tap gap" between 115 and 125 as reported by Furman. Over the more normal range of 115 to 125V, the output was generally between 118V and 122V. The worst case operating point for a tube amp would be if the input voltage fluctuated up and down right at a tap transition point. This could potentially result in an output fluctuation that was actually greater than the input fluctuation....nothing much you can do about it.

Overall the Furman performed much better than the 120 +/-5V spec and is probably one of the most cost effective regulators. The most noticeable benefits would be at voltages lower than 110 and higher than 125V. I give it a :AOK .
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