JTM45 cascading gain mod

[dai h.]

Just for clarity, here's a redraw of the PPIMV with the pots flipped and the safety resistors removed. This is how I proposed it for use with bias wiggle trem some years ago and it's reported to work well.

saw this described on Headfirst Amps' youtube, and it looked interesting:

https://youtu.be/q6YL7uk_0w4?t=2956

what's described sounds like Chuck's but without the added series R. ((Assuming I understood correctly,) basically you add on a 250k-ish dual pot wired as variable resistors over the existing grid load/bias return Rs.) Though it looks a bit strange (since they aren't wired as potentiometers and the PI is loaded down more (since the added pot lowers the load) and even more as the MV is turned down and less low end should pass to the power tube grids as a result), (according to David Friedman) it works well. (I guess an MV has to be after the PI since it provides some distortion and the 5F6-A/1987/1959 circuit won't sound the same if you try to put it before?)

(PPIMV related thread--good descriptions by Helmholtz on the workings) :

https://music-electronics-forum.com/...-master-volume

[loudthud]

The output impedance of the PI limits the LF loss as you turn down the Master.

[Helmholtz]

For my calculations I used an LTPI output impedance of 40k per side.