"Power Dampening" effect with Hiwatt PI

[DanShibz]

Hey guys,

Ive had a lot of my questions already asked and answered by others on this forum, so this is my first post. I'm a big fan of the Mojave "power dampening" effect on cathode biased phase inverters. I'm planning to start a Hiwatt build soon, but I wanted to figure out a way to get this effect with its unusual PI setup. I know in the particular preamp version I want to replicate, the PI bias voltage is supplied by a dc cathode follower and the bias voltage appears to be selected via a voltage divider before the grid of the CF. My initial thought is that I could replace the grid leak resistor with a potentiometer so that I could bias the PI colder and colder just like the cathode biased PI version.

My concerns however, are that there will be a certain point where the voltage becomes too low to be effective, and putting a potential divider hear I guess would also act as volume control for the audio signal too... So maybe the resistance before the grid leak should be what is adjusted.

Does anyone have some ideas, or has anyone tried something like this?

[gingertube]

I think it is something you would need to try.
I would suggest replacing that 1M with say a 470K + 500K pot wired as a variable resistor (that is just use 1 end + the wiper).
See what that does. It should not affect the audio signal as teh top arm of the divider (the top 1M) is bypassed by the cap.

Cheers,
Ian