Does cap voltage affect tone?

[olddawg]

I don't know guys.. I'm enjoying reading this thread as much as the next guy... but. Didn't most legendary amps use 20% Carbon comp resistors, have even worse tolerances on very primitive caps, and to this day tubes are all over the place to the point that you choose the ones you like by trial and error. Seems to me it's like Enzo always says: "It's just a guitar amp!" It's an instrument... not a refferance amp as has been said before. You play the one you like. You repair one with the appropriate parts. Everything else gets pedantic at some point. To address the OP.. the answer seems to be "maybe", it's very subtle and definitely subjective. Try it and see what YOU think? Lol!

[nosaj]

I don't know guys.. I'm enjoying reading this thread as much as the next guy... but. Didn't most legendary amps use 20% Carbon comp resistors, have even worse tolerances on very primitive caps, and to this day tubes are all over the place to the point that you choose the ones you like by trial and error. Seems to me it's like Enzo always says: "It's just a guitar amp!" It's and instrument. You play the one you like. You repair one with the appropriate parts. Everything else gets pedantic at some point.

Unless your a cork sniffer ..everyone wants to be the one that really finds something special that the early tube guys never found or they think they worked out something better. There are few things new under the sun. I think some builders use it to justify their high prices.
nosaj

[Chuck H]

I think some builders use it to justify their high prices.

Huh... And I though it was because designing and making amps as a small operation was expensive and difficult.?. I learned something today

[nosaj]

Huh... And I though it was because designing and making amps as a small operation was expensive and difficult.?. I learned something today

For some there's not much design when they just copy a design and sell it as their own. Like I said some not all or most.

nosaj

[olddawg]

Unless your a cork sniffer ..everyone wants to be the one that really finds something special that the early tube guys never found or they think they worked out something better. There are few things new under the sun. I think some builders use it to justify their high prices.
nosaj

Yeah I sometimes wonder if I’m aesthetically deficient in some way. I still can’t tell the difference between a $200 tone control cap and a $2 one in my guitars.. and I even owned some of those legendary guitars back in the day. We would even cut the lead on those “magic” caps to get a tiny bit more out of the pickup. I was at a jam Tuesday night and my old Japanese Squier Strat and Chibson parts LP Jr through a Bugera with stock Chinese tubes sounded as good or better than the guy’s Custom Shop stuff through a Mesa across from me to my ears. The crowd certainly didn’t care, nor did other the musicians that weren’t guitarists and the guitarists thought the Chibson was real. Also used a $149 electric acoustic by BC Rich that held up fine along with the 60s vintage Gibson’s and Martins. It’s all subjective. I never once worried about my filter cap voltage ratings. You plug in... the rig works or it don’t.

[Chuck H]

"...through a Bugera with stock Chinese tubes sounded as good or better than the guy’s Custom Shop stuff"

I think the biggest tonal difference between cheap amps and expensive amps is in the speakers. Maybe a tad in the transformers. Maybe. And I don't have any issues about tone WRT such products. People like to say their cheap "this" or "that" sounds as good as the more expensive stuff because the people selling the expensive stuff HAVE TO say that the expensive stuff SOUNDS better to justify the price. The tonal difference (speakers not withstanding) is tiny AND subjective.

"My" issue with such products is that they aren't all that charming and they aren't all that durable. They lack provenance of any sort and dilute the value and usefulness of craftsmen and artisans. Which I don't like whether their value and usefulness is declining, outmoded, outdated or otherwise.

I also don't like that their buying power is so great that I not only can't even buy parts to build an amp for what their finished product costs, but I can't even get quality parts like tubes and reverb pans consistently because the premium units go to preferred customers. Basically we're eating their leftovers. And you can chalk this up to whining if you like. I don't much care. All I know is that where I live there use to be effective laws to prevent monopolies from smothering smaller competitors. But not anymore because those amps aren't made where those laws exist. They're sure as $h!t sold there though. And they're almost all copies of circuits developed by the businesses they're crushing. That's not healthy competition. That's more like a parasitic infection. And it won't end any better either if we keep supporting the Walmart mentality while greedy corporate moguls and the overseas manufacturing machine eat our sick economy so they can $h!t money.

[Enzo]

Just my opinion, but I think in discussions like this, many times someone becomes aware of some phenomenon, then takes it out of context. Once stated, it becomes a "protect my turf" thing.

This whole thing started if I recall, when the OP wondered if his 500v cap would be OK in place of a 25v cap of came value as a cathode bypass. Now it is conceivable that the capacitance of that HV cap might be off from its nominal value used at low voltage, but that assumes the cap of "proper" voltage is on value to start with. But ignoring that, just how much difference? Never specified. Half a uf? 400%? Instead the thing wanders into ceramic or tantalum caps, which that 20uf 500v cap wasn't.

Every phenomenon we encounter needs to be put into its context.

Steel expands as it gets warmer, until it melts. My furnace gets hot. MY ductwork is steel. I know that my ducts expand as the hot air courses through them. But do I really need to worry they will expand enough to cause a problem? And should I concern myself they might melt? COntext.

[Chuck H]

This whole thing started if I recall, when the OP wondered if his 500v cap would be OK in place of a 25v cap of came value as a cathode bypass.

And almost TEN YEARS AGO!!!

By resurrecting this what our new friend has effectively done is key up to solve this old yarn where he believes we have failed. I don't see where a turf war is avoidable and we weren't the first to start shoving.

[olddawg]

"...through a Bugera with stock Chinese tubes sounded as good or better than the guy’s Custom Shop stuff"

I think the biggest tonal difference between cheap amps and expensive amps is in the speakers. Maybe a tad in the transformers. Maybe. And I don't have any issues about tone WRT such products. People like to say their cheap "this" or "that" sounds as good as the more expensive stuff because the people selling the expensive stuff HAVE TO say that the expensive stuff SOUNDS better to justify the price. The tonal difference (speakers not withstanding) is tiny AND subjective.

"My" issue with such products is that they aren't all that charming and they aren't all that durable. They lack provenance of any sort and dilute the value and usefulness of craftsmen and artisans. Which I don't like whether their value and usefulness is declining, outmoded, outdated or otherwise.

I also don't like that their buying power is so great that I not only can't even buy parts to build an amp for what their finished product costs, but I can't even get quality parts like tubes and reverb pans consistently because the premium units go to preferred customers. Basically we're eating their leftovers. And you can chalk this up to whining if you like. I don't much care. All I know is that where I live there use to be effective laws to prevent monopolies from smothering smaller competitors. But not anymore because those amps aren't made where those laws exist. They're sure as $h!t sold there though. And they're almost all copies of circuits developed by the businesses they're crushing. That's not healthy competition. That's more like a parasitic infection. And it won't end any better either if we keep supporting the Walmart mentality while greedy corporate moguls and the overseas manufacturing machine eat our sick economy so they can $h!t money.

You are correct of course Chuck. That Bugera is HEAVY for what it is because it is made of MDF not Baltic birch plywood. I'm constantly having to tighten the screws that hold it together too. It also has a digital Reverb and no tremolo. It probably will not endure 50 years of gigging. And a jazz guy would probably hate it. Honestly the speaker is ok.. but I think it's an Emenence clone and well broken in.

[J M Fahey]

This whole thing started if I recall, when the OP wondered if his 500v cap would be OK in place of a 25v cap of came value as a cathode bypass. Now it is conceivable that the capacitance of that HV cap might be off from its nominal value used at low voltage, but that assumes the cap of "proper" voltage is on value to start with. But ignoring that, just how much difference? Never specified. Half a uf? 400%? Instead the thing wanders into ceramic or tantalum caps, which that 20uf 500v cap wasn't.
Every phenomenon we encounter needs to be put into its context.

Agree and add: cap tolerance may be a big issue or nothing to worry, depending on intended use ("context").

In a resonant circuit, such as in a gyrator in a Graphic Equalizer?
Yes, definitely.
We will definitely hear a difference between it being tuned to 2500Hz instead of 2000, because it is a sharp peak (high Q resonance) and smack in the middle of our ear peak response (ever wonder why sirens, alarms, buzzers, doorbells, etc. all seem be producing a lot of output at those frequencies?)
And even so "error tolerance" isnīt even half as bad as it seems.
There is a parameter called "parameter sensitivity" involved in circuit design, which tells us how much circuit results change with parts tolerance variation.
Some are very sensitive, and a small variation spells disaster, others are linear (10% tolerance means roughly 10% variation in results) and some are robust and tolerant, result variations are *smaller* that parts tolerance
Resonant circuits are one such example, in LC tanks resonant frequency varies with the square root of either L or C variation.
So 2:1 C variation changes Frequency by 1.4:1 ("smaller variation")

BUT: on a Cathode bypass Cap?
Even more, the mythical 25uF value which is so deeply ingrained into our genes that we use it without asking?
Unless we want a *specific* Bass cut , such as Marshsllīs .68uF/2k7 combination.

The ubiquitous 25uF value (and notice that almost never it is , say, 10uF or 47uF ... why?) , if you think about it, is weird because it acts way below audible frequencies
http://www.sengpielaudio.com/calculator-RCpad.htm
tells us that typical 1k5 + 25uF has a crossover frequency (somebody would love to call it a Pole instead, but wonīt speculate on the preference) of .... drumroll!!! .... 4.24Hz !!!!!
Hardly an Audio Frequency, huh?

And in fact, my hypotethical 10uF or 47uF would change that to 10.6 or 2.26Hz .... all of them well below Audio range (and doubly so in the Guitar World).

So it can not be for *audible* reasons.

Well, actually it is, but none of the above.
Sometimes Truth is SO simple ... after you learn it that is.

Old Tube datasheets , *when* referring Hum and Noise, (not all did) suggested some conditions to minimize it.

Just found this for reference, but saw about same on others: since tubes "have the enemy inside" meaning the AC powered filament VERY near to cathode and grid, one trick was to use the cathode itself as a shield, so it needed groundingf ... AC grounding that is.

So a way larger than needed decoupling capacitor was suggested, usually 100uF:

Now a 100uF cap, even standing only 25V, must have ben something in the old days, specially in the $$$ department, and many were used, so I bet Leo who was very cost conscious (letīs put it mildly) might have experimented and found 25uF was as low as he could go and yet have a useful effect.

But absolutely unrelated to *Audio* response and as shown above, variations or tolerance would have no audible effect, so we canīt *ignore* them but definitely shouldnīt *overthink* it .

[printer2]

So this chemical is a good fire retardant on clothing. But does it have adverse effects on people? Let's grab 100 university students, give them $25 each to keep this patch on their arm for a day. After a day goes by the students get checked, nothing visible under the patch, the chemical gets the green light. What is wrong with this picture? The patch is not a real world application, this is not how the cloth will be worn. The clothing will be worn on the whole body in environments less temperature controlled than a classroom. The same cloth that passed in a patch test can cause burning of the skin when some people get hot and perspire. Real case.

Now the question of a pair of electrolytic caps and them behaving differently in a circuit when one is rated at 6.3V and the other for 350V. And since we have used 22 uF caps as bypass caps for our signal stage cathodes do you think trying a typical circuit with a 12AX7, 1.5k and 100k resistors would be in order? Well I thought so also when about six years ago the question came up in a forum at tdpri.com. I didn't know the answer but a knowledgeable member said the high voltage cap would not work as the low voltage one. I had some 22 uF 350V caps and I looked through my box of parts I was too lazy to sort and found a 6.3V 22 uF cap. It was tiny.

So I bread boarded a stage of gain using the 12AX7 and the normal Fender complement of parts, set up my signal generator, scope, and ran through the normal guitar spectrum swapping the low voltage part for the high voltage one (before I forget, checked the capacitance with my meter and selected from my 350V ones to get the same reading as the 6.3V one). I took pictures of the scope traces, and so everyone remembers the bias on the cathode is roughly 1V, (I know from seeing familiar names most know this, more directed to the new guy as I do not know his frame of reference). With the traces of both side by side you could see the gain was exactly the same, the sine wave looked exactly the same. And if Photobucket would not have gone to the dark side I could pull up the pictures for you. You may have to take me on my word for that.

A network analyzer would have been something that might have been useful when I did some work for a aerospace manufacturer that had me come up with a filter network to keep RF out of rocket wiring so they do not light off prematurely. They gave me nothing for a budget and had no idea what it took to get the job done. Oh yea, make it small, great rejection, and try to keep the cost low. When I did get a bunch of parts together that I thought would do the job I decided to test it in a TEM Cell, (an expanded coax cable of sorts. Made one with the center conductor using some copper sheet, the cell was made of cardboard that I glued tin foil on (ok everyone, let's get our hats on). I got laid off before I could test it, a week after I showed them the prototype. Came back a year later for my original department (What the heck did I know about 20 GHz anyway? The top frequency it was suppose to reject.) I asked how it worked when I met the engineer that took over (he was suppose to have had the job but the satellite project was running late). He said it seemed to work and that he used my arts and craft Tem cell up to half a Gig.

Moral of the story? Don't underestimate people, as an Instrument Technologist my world ends about 20 Hz, 50 Hz if you want to push it. And if there was one person on the forum that I take seriously it would be Mr. Fahey. But then again I have read many of his posts and have found they were backed up by experience. Just saying.

[Chuck H]

Hey Juan. What about the sub harmonic frequencies that occur with stiffer power supplies (like Marshall used) that result in "beating".?. Sum/difference harmonics that occur IN the audio spectrum BECAUSE there are frequencies below the audio spectrum. This is actually a cool effect sometimes and probably wouldn't happen if the amp weren't trying to reproduce frequencies below "guitar amp" spectrum. It's just another mojo part of the coveted tonal qualities of our vintage favorites. I'm sure there are similar phenomenon happening in the HF as well. May be more or less relevant here. Just keeping it real

EDIT: Then there's Enzo's consideration of context. At this level it's more about listening tests than it is about loop and pole theory (I think). Actually understanding "beating" probably won't even help a designer to reproduce it short of the original designs that do it already because there are, indeed, other complex influences in play. Trying to isolate them with even the most advanced bench gear (or believing you have?) hasn't proved out much in the real world. Nothing should be ignored, but anything claimed should be proven. I think that's where we are in this thread.

[Malcolm Irving]

… What about the sub harmonic frequencies that occur with stiffer power supplies (like Marshall used) that result in "beating".?. Sum/difference harmonics that occur IN the audio spectrum BECAUSE there are frequencies below the audio spectrum. This is actually a cool effect sometimes and probably wouldn't happen if the amp weren't trying to reproduce frequencies below "guitar amp" spectrum. It's just another mojo part of the covented tonal qualities of our vintage favorites. ....

I connected my guitar through the sub-woofer channel on a big PA once, just to see what happened. I was amazed how much stuff comes out at frequencies below the 82Hz of the low E. It was how you strike the strings (palm muting and such like) that caused the low thumps and bumps. OK, a guitar speaker would not reproduce this stuff very well, but if we allow it through stage 1 of the amp it could have a significant effect on blocking distortion etc. in later stages.

[Chuck H]

...if there was one person on the forum that I take seriously it would be Mr. Fahey. But then again I have read many of his posts and have found they were backed up by experience.

Which is exactly as you have done here. And very well IMO. Here's my second

[J M Fahey]

Oh, the sub-audio frequencies (I tend not to call them sub-harmonics simply because they are not exact multiples and submultiples of the note being played, although they are created by playing) canīt be heard by themselves, as a pure sinewave tone, but we can be definitely hear their effect on very audible sounds.

Just think *tremolo*: a 2 to 10Hz band oscillator modulates audio frequencies and is so strong and easy to hear that we use it as a special effect

By the same token, string to string beating can create all sorts of low frequencies, even as low as 1 Hz of even less if they are *almost* in tune, what matters is difference and you can get as close as you wish.

And no need for tubes or even *electronic* stuff in the path, Piano tuners for ages have counted beatings per second between double and triple strings hit by a single hammer key for a richer sound and consistency.

So in an overdriven amp, which is the King of Intermodulation by definition, and where chords are being played, and you feed it the proper material to intermodulate, yes, lots of things will appear, as experienced by Malcolm Irving.

As another easy to experiment fact: just look at, say, Twin Reverb speakers with the grill cloth off.
I mention that particular amp because itīs easy to pull it out of the way and because the amp has "too much Bass", and itīs easy to see (specially if you look at it from one side) speaker cones pumping in and out a lot, at very low frequencies, a few Hertz and definitely inaudible by themselves.

And they are created by intermodulation, not fed from the input or part of input program.

Long ago when I worried about that I tried to stop that wasteful movement (does not contribute to acoustic output and wastes resources) so added an active 60 Hz highpass, 12dB/Oct between preamp and power amp .

End result?: lowered wasteful movement but definitely didnīt stop it , far from that, so it was clearly being created inside the Power Amp itself when driven balls to the wall.

On the other end, in a single non overdriven stage, when components behave politely well within their ratings, "nothing weird happens" as shown by printer2 :

So I bread boarded a stage of gain using the 12AX7 and the normal Fender complement of parts, set up my signal generator, scope, and ran through the normal guitar spectrum swapping the low voltage part for the high voltage one (before I forget, checked the capacitance with my meter and selected from my 350V ones to get the same reading as the 6.3V one). I took pictures of the scope traces, and so everyone remembers the bias on the cathode is roughly 1V, ...... With the traces of both side by side you could see the gain was exactly the same, the sine wave looked exactly the same. And if Photobucket would not have gone to the dark side I could pull up the pictures for you. You may have to take me on my word for that.

Oh, we do, you are confirming by experiment what is the "normal" experience.

Now if you were going *contrary* to it, then we would ask for evidence, not out of distrust by the way, but out of curiosity.