terrible sound at extremely master volume

[EETStudent]

Ive got my amp configured with 3 different volumes. Volume I(after stage 1), Volume II(after tone stack, before PI) and Master Volume(between PI and power tubes) Well, with the master volume at a very low setting, hardly even 1, and Volume II at max the distortion is terrible. It sounds terrific when you bump the master volume up to where the signal audibly passes through, so Im hoping someone will just assure me that the terrible distortion at extremely low settings is to be expected. If it helps any, the power amp config. is as follows: split-load PI(Paul C mod, comments?), driver stage, power amp.

[Steve Conner]

Sometimes with the master volume turned right down, you can hear a little signal getting through due to stray capacitances in the circuit. It sounds like a kind of thin, fizzy, funky distortion, because the capacitive coupling causes a 6dB/octave treble boost.

You could probably get rid of it by rearranging the wiring. But I never thought of it as a problem, since it's hardly worth using the amp turned down that low anyway. If I was using it like that most of the time, I'd get a power soak or make a smaller amp. Or turn it off and try again when the neighbours are out :-)

[pdf64]

The major benefits of a post PI MV is the extra gain from the long tail pair and it's overdrive characteristics.
A split load PI has no (voltage) gain, yet you've got a volume pot before and after it - what's the design rationale for this?
Is your post PI MV the single or dual pot typeA, lin or log tracks, of value?
Peter.

[daz]

If i'm reading your post right, i had the same issue using a post tone stack master and a post PI master. If i leave the post PI all the way up so it's basically not attenuating at all, then use the one after the TS as master, everything sounds normal at any volume. yet if i turn the post TS master up past as 10 or 11:00 and use the post PI master as master, I get this horribly ratty nasty distortion no one would want. The odd thing is i had this with both my builds and no matter where the circuit was at. (i modded them in every way imaginable at one time or another) The only thing that makes any sense is that the PI is distorting horribly. But that doesn't seem to jibe with what others say like in the post above. And having used many PI values on all the components including traditional marshall values, i can't understand why this would be.

[EETStudent]

Well pdf, Im still a newbie at this stuff so I have no rationale Ive got a master volume in about every spot possible just for the sake of having them and learning the different characteristics. The volume pot after the split-load is a regular ol 500k audio, and the circuit is one I snagged from the Matchless Cheiftain( i think). maybe Im not going about this the right way, or maybe the split-load isnt the best choice, but when I crank volume II the power amp distortion is really awesome. I use volume I for some dirt and for dialing in the clean settings