crossline master volume?

[arfy]

I've been told that using the Matchless style master volume is a bad idea in amps like the Express that use negative feedback in the PI.
The MV I'm referring to is master volume "type-3" in the Trainwreck Pages.
Can someone explain?

[Darkbluemurder]

All post PI master volumes have the problem that the lower they are turned the more the PI will distort. This due to the fact that the feedback loop is broken when the control is set very low. They work OK if you just want to dial the volume a little lower (i.e. down to 6).

There is a thread in here entitled "Simplest Master Volume Ever". You might want to check that out.

Good luck!