Bogen CHB-35 Preamp Mod

[gtrbryan]

Some time ago, I acquired a Bogen CHB35 for modification into a guitar amp. I am FINALLY ready to start it. However, I had a few questions to ask before proceeding.

I would like to leave one channel stock and modify the first stage of the second channel. The schematics for the original and my proposed mod are below. First, I need to know the voltage to put on the plate resistor of the modded stage. Second, I need to know the value of the new resistor in the power supply. I have added a stage to the power supply for the modded preamp stage. Any comments on that?

Also, I'm worried that the new preamp stage would be "too much." Any thoughts? Would a resistor in the signal path help, and if so, what value? Also, would a 470k resistor to ground at the junction of the 470pf cap and 470k resistor help? I got this idea off the AX84 High Octane, which has this extra resistor in place (schematic below - first stage only). I assume it acts as a voltage divider?

Any help is greatly appreciated.

Original schematic
http://i18.tinypic.com/2ce6drq.jpg

Modified Schematic (in progress)
http://i16.tinypic.com/2yyo7jr.jpg

AX84 HO first stage preamp
http://i17.tinypic.com/30k3pjo.jpg