trainwreck pages master volume question

[funkmeblue]

I'm interested in info on ken's master volume mod number 2 where you replace the two 220k resistors in the phase inverter with a dual 100k pot. Can this be done on a cathode biased amp as well. Also I read that DR Z used one of Ken's dual ganged master volumes on his new prescription JR amp. Close inspection of some pictures revealed the two 220k resistors still in place. Is it possible to still leave them there and maybe change the value of the dual pot. I don't believe he used the type 1 master because there are no added .1uf caps. Here is a link to the picture http://www.proguitar.de./ProGuitarPreis ... liste.html

[billyz]

Looks like that is exactly what the good Dr has done. give it try and tell us what you find.

[funkmeblue]

would it still " function" with a dual 100k pot and the 220k resistors still in place? Would like to not burn anything up, thanks

[billyz]

I'll take a stab at it. Looks like it's parallel to the 220K resistors which are grounded. So I thinks it's just grounding out the PI signal to the power tubes.

I would try a dual 1 meg pot.

[KT66]

I modded this amp: http://www.classictubeamps.com/6v6plexi.html with a fixed bias / cathode bias switch per the purchaser's request. It has a KF type 2 master in it and it works fine when in cathode bias mode.

If someone knows why this is not a good idea, please tell me because I am in the begining stages of an AC30 build that I plan to use this type of MV in.