Higher plate voltage equals better tone?

[SactoBass]

For power tubes, does a higher plate voltage translate to better ("tubier") tone?

I know that, in my experience, and in my opinion, high voltage (~300V) tube preamp circuits sound better than lower voltage tube preamp circuits. My question is, does that also apply to the power tube section? It seems that logic would suggest that it would, but I am not sure, so I thought I would post and ask some of the tube amp experts here on TB. I read alot on TB about varying plate voltages on the power tubes with various amp designs, and I am wondering if higher plate voltage is better for tone.

[billfitzmaurice]

EVH used (he may still) a Variac with his amps to adjust the voltage. He used it to decrease the voltage, to brown-out levels, as that allowed saturation at lower levels. Increased voltage would have the opposite effect, so whether you want higher or lower plate voltage is a matter of whether you want cleaner or dirtier sound.

[JGR]

Yup. Too many other variables in the circuit to make any major generalizations, with the exception perhaps of some of the tube driven pedals that run 12ax7's at starved voltage levels... though that has it's own sound too which some folks seem to like. For power tubes, I would stay within their design guidelines, though there is plenty of room to vary within that as well. There are an infinite amount of factors that go into circuit design, but on a very general level, as Bill already mentioned in part, lower voltages and supply capacitance will give you a dirtier, more compressed sound in the preamp and more "sag" in the power section, while higher voltages and bigger supply caps will be cleaner, less compressed, and yield a faster response. A circuit designer will tailor these parameters to each gain stage as well as the power section, along with a bunch of other things to get the desired effect.

[DrSmaggs]

Interesting topic. On sort of a related note... I know guys that swear by using almost-dead batteries in their distortion pedals, wether or not the pedal has a tube in it or not.

Good read, though... I never really thought about the dynamic of browning-out for saturation at a lower volume.

I prefer a moderate stage volume... one that still allows for talking amongst bandmates!

[SactoBass]

Originally Posted by billfitzmaurice

EVH used (he may still) a Variac with his amps to adjust the voltage. He used it to decrease the voltage, to brown-out levels, as that allowed saturation at lower levels. Increased voltage would have the opposite effect, so whether you want higher or lower plate voltage is a matter of whether you want cleaner or dirtier sound.

Thanks Bill. That makes perfect sense!

[DrSmaggs]

I didn't realize voltage had such an effect on tone. I was always under the assumption that properly matched speaker-to-amplifier ratio and proper wattage to speakers (with headroom, of course) was the main factor in having a nice fat and clean signal/tone.

I had just never heard of sagging voltage on purpose before. Do people actively practice this technique for bass amps?

[billfitzmaurice]

Originally Posted by SactoBass

Thanks Bill. That makes perfect sense!

When it was first revealed that he used a Variac the details were left out, and guitar'd players naturally assumed he used it to boost the voltage to go louder. And that's why we call them guitar'd players.

[Fuzzbass]

Originally Posted by DrSmaggs

I had just never heard of sagging voltage on purpose before. Do people actively practice this technique for bass amps?

One example I can think of is the Tube Gain control on the Ampeg SVT-3 Pro. I think it controls the voltage going to one or more preamp tubes.

It works counter-intuitively (for me, anyway): turn it all the way up and you get the cleanest signal, because that's the most voltage. As you turn it down you get more sag, so it's easier to clip the preamp when turning Gain up. This could possibly be called "underdrive" instead of "overdrive".

[JGR]

I'd say it is less of an issue/factor with bass amps since they are generally designed to be clean. High gain guitar tones are where it really comes into play. High gain is a difficult beast to tame. I spent about nine years tweaking my high gain amp design -tone chasing indeed.

[billfitzmaurice]

Originally Posted by Fuzzbass

It works counter-intuitively (for me, anyway): turn it all the way up and you get the cleanest signal, because that's the most voltage.

You could reverse the leads on the pot.
As it is higher would be more clean headroom, lower would be less.

[DrSmaggs]

Oh NICE... I used to own an SVT 3 Pro... it was my first head. I have the 4 pro now.

I thought the tube gain worked the other way around... thanks for the info.

I always wondered why the boost of that tube gain would make it cleaner. Now it makes much more sense. Whenever I would turn that knob down, I did notice my sound was a tad..... overdriven? I mean, not by a big amount, but it sounded duller and dirtier, but not extreme... make sense?

[Jim C]

Originally Posted by billfitzmaurice

When it was first revealed that he used a Variac the details were left out, and guitar'd players naturally assumed he used it to boost the voltage to go louder. And that's why we call them guitar'd players.

Funny you should say that; I knew a shop back in the day that did a bunch of repair business for that very reason.

Seems like the whole idea of changing line voltage is to make the amp sound different from the design goals and not necessarliy "better".

[Calaverasgrande]

well you can get overdrive both ways. Either by reducing the available voltage for the circuit (reducing headroom) or by increasing the signal strength to the point that it exceeds what the circuit can reproduce without clipping. My favorite fuzz pedal mod is to put a pot on the volt supply for the distortion element so I can "starve" it.
One of my favorite amps is a Traynor YBA1a. They run the power tubes very hard (cant speak for the pre tubes, but interesting question?).
I think in the neighborhod of 7-800 volts? As they put out 90 watts (at least) from a pair of EL34.
http://en.wikipedia.org/wiki/EL34
My last one would go thru a pair of tubes about once every 6-8 months when playing a lot. It would also blow up about once a year but thats another story (YBA1a dont seem to like being run into 4 ohms!).

I can't think of an amp that sounds more "tubey" than that guy. The one word that keeps coming to mind is ballsy. Not so much distorted but very insistent and angry souding. I guess it must have been producing lower order harmonics? Either way, love the clean tone on those heads. Keep meaning to get a stack of 3 with 3 4x10 cabs.