Does lower supply V always=less dynamics?

[daz]

Say you drop the preamp supply on the first 2 cascaded stages of a marshall style somewhat high gain amp down a good deal....say 100V from 280 to 180 for the sake of example. Your clean sound is gotten the traditional way by rolling back the guitar. Do you now lose a lot of dynamics in that tone with the lower voltage, or are there other things that can be changed to get it back w/o bringing the supply V back up? I ask because i get a bit richer and springier tone when i lower the voltage, but i want the dynamics to be as wide as it was.

So in short, is it possible to have great dynamics with a lower supply voltage to the first stages? Or are the two mutually exclusive?

[MWJB]

100v on a 12AX7 is VERY low, typically most guitar players might find this gives poor fidelity & poor note separation, knowing that you have a 820r cathode resistor, I doubt that 100v would be workable.

150v with a 1.5K cathode resistor would be around my lower limit, add 20-30v for an 820R cathode? Usually you would just tweak the preamp supply resistor to get the best compromise, once you have decided on the cathode & plate resistor values you like the sound of.

As for correcting at later stages, it's often seen that amps with a very grindy first stage (like you are suggesting), generally bump up the B+ at later stages (with larger cathode values and/or higher B+ supply) to avoid compounding the situation later in the circuit. You could have an additional voltage dropping node between V1a & V2b to accomplish this, be aware that one 12AX7 triode doesn't draw much current, so a large value dropping resistor is in order (try around 100K?) don't forget you need an additional filter cap.

On a 2 channel amp (I know yours isn't) you can have both halves of V1 running at preferred voltages for grind & clean.

Generally I might also suggest a stiffer rectifier/bumping up the B+ voltage & B+ filtering (100uf), but I seem to remember that you already have a SS rectifier. You could try a larger value cathode bypass cap (100uf/220uf) at the power tubes. Maybe reducing the B+ drop at later stages like the PI might help?

[daz]

100v on a 12AX7 is VERY low

No, i said 100v LOWER, not 100v on the plates total. In other words, if you had 280 and dropped it to 180. however, badcat does use 99v on the first stage on at least one of thier amps.

You could try a larger value cathode bypass cap (100uf/220uf) at the power tubes

It is a 220uf

But anyways, i guess what you are saying is there is no single common tweak that does make for good dynamics as with higher supply V. so i guess it just a matter of the best compromise in voltage. I like it both ways so maybe a resistor 1/2 way between where it was and where i have it now.

[MWJB]

Oops, my bad. But response says the same.

Undoubtedly you will find amps that buck the general trends (like very high, or very low preamp plate voltages) but often you will find something else unusual about the circuit that compensates. You'll notice the Badcat's voltages rise as we get nearer the power amp & the tone shaping & gain controls at virtually every stage...also note the "clean channel" ...if you have 2 channels you get the option to make either, or both, more focussed towards a particular flavour.

[daz]

You'll notice the Badcat's voltages rise as we get nearer the power amp & the tone shaping & gain controls at virtually every stage

Same with mine. I only lowered the first 2 stages by raising the last dropping resistor. I've had it like this before but i always had lower voltages at the later stages too. this time just in the first 2. I'm not sure it's really much less dynamic, as i have yet to really play with it much due to neighbors. I should have a chance today tho.