Preamp voltage targets?

[mlp-mx6]

I apologize if my search did not find something that has been discussed before, but...

I'm converting a Fender Blues Jr. to a small Liverpool-style circuit. What are the target plate voltages for the 12AX7s in a Liverpool and/or Express?

She's working already - and sounds pretty cool, but perhaps a little crunchy/brittle. Very nice single-coil tones, though. I was thinking that the target voltages for the preamp tubes are likely lower than I have now.

Thanks, folks!

[mlp-mx6]

OK, just to clarify - so you folks don't think of me as an idiot (well, maybe not as much, anyway).

I was asking about the actual voltages on the plates of the 12AX7s, not at the power supply node, for the amps you have been most pleased with tonally.

I know that many of the schematics have the power supply voltages, but my question was measuring the voltage at a different place in the circuit.

OK, that's enough explanation. If I'm still an idiot, so be it.

[Fischerman]

You can't just go from plate voltages. The supply voltage, plate voltage, and cathode voltage are all 'related'. If you have a 400vdc supply and a 100K plate resistor and a 1K cathode resistor then that tube is going to draw a certain amount of current because of where it's biased. That current through the 100K plate resistor causes a certain voltage drop (which when subtracted from the supply voltage gives you your plate voltage). And your cathode voltage is the current times your 1K cathode resistor. Now if you change your cathode resistor you change the bias...thus the current...thus the plate and cathode voltages. And if you changed the supply voltage everything would change.

[mlp-mx6]

I completely agree with you.

I have also seen different brands of 12AX7 idle differently in a circuit when the only thing changed was the tube. (meaning that the voltages on the plate and cathode changed - tubes are NOT consistent!)

Nonetheless - for some circuits there appears to be a "sweet spot" for the voltage at the plate. Specifically, for the "other" amps on this forum, the ODS circuit seems to radically prefer approximately 200V on the plates for the first tube. Over and over folks have admitted that when they finally worked to set the plate voltages on V1 to 200V the tone they were seeking began to show up.

I'm simply asking if folks have found a value that seems to work consistently for their tone in the Express/Liverpool type circuits.