PRE-AMPS: What do V1-V4 control?

[mwalluk]

My VHT came stock with this set up.

V1: Sovtek 12AX7WB
V2: Shuguang 12Ax7
V3: Shuguang 12Ax7
V4 (driver) Shuguang 12Ax7


What do all these V's control?

[the guy who invented fire]

Re: PRE-AMPS: What do V1-V4 control?

Check the manual, it will tell you.

[misterwhizzy]

Re: PRE-AMPS: What do V1-V4 control?

It definitely depends from amp to amp. And remember that each tube has two amplification stages, at least in a 12A*7. In a typical Marshall-style amp, I think the setup is something like this:
V1 - First input gain stage, to bring the level up to something the preamp can work with.
V1 - Second gain stage, where you might get a bit of clipping, depending on the drive levels.
V2 - Third gain stage.
V2 - Current driver for the power section. If I understand things correctly, this may not be terribly important in overall tone, especially compared to the V1 gain stages.
V3 - Phase inverter, where one stage passes basically an unaltered preamp signal, and the other stage passes the same input signal 180 degrees out of phase. Basically the opposite. I'm not sure anything other than a class A/B amp has the phase inverter.

I think the Fryette designs use that extra tube for the two drive knobs. One controls the first, and one controls the second. If I were a betting man (or if I had the schematics), I would guess that V1 is the most important, and V4 is the PI.

[mwalluk]

Re: PRE-AMPS: What do V1-V4 control?

Wizzy - so ddef get really good ones for one and four? How important are 2 and 3?

[misterwhizzy]

Re: PRE-AMPS: What do V1-V4 control?

In my experience, your most noticeable tone changes are in V1. If I were you, I'd buy a Tung-Sol, a Sovtek LPS, and a JJ. I hate JJs, but if I were forced to choose one, I'd take the long plate. I'd try each of those in V1, and keep what you like in there. I'm going to assume for a second you like the Tung-Sol best there.

Then, take the JJ and put it in V4. That'll give you a comparison against what are typically considered bright tubes (the Chinese ones). Then, put the Sovtek in there and see what you think. My thinking is that some detail and clarity will be heard with the Sovtek that you don't hear in the JJ.

Finally, whichever tube you have left over, try it out in V2 and V3 to see if there's a noticeable difference. If you like it, great. If not, keep what you have or buy some EHX tubes. But I think that's a good starting point that won't break the bank. It'll also give you an idea of what type of tubes you like in what position.