Leaking crossline master

[Leevi]

I'm working with GEM Deluxe reverb and added a crossline master to it.I'm wondering why the master does not mute the amp when turned off?The pot is working and it does not mute even if you short the lugs.
/Leevi

[pdf64]

A type 3 AKA crossline usually achieves signal muting because when the 12AX7 LTP anode to anode impedance drops below about 10k, the outputs flip from being balanced to single ended, ie same signal at both anodes.
The balanced output stage should largely reject such common mode signal inputs.
But the rejection won't be perfect unless the balance is perfect.
So I suspect that the balance of your output stage may be a bit off. And the high gain of EL84 may be exacerbating the bleed.

Swapping from a shared bias resistor to a bias resistor for each cathode may help, but they would probably then each need bypassing (a shared push pull cathode resistor has a degree of self bypassing effect at lower signal levels).

[Leevi]

The problem disappeared after I put a brand new power tube set to the amp.So the issue was caused by the unbalanced/bad power tubes?
/Leevi

[pdf64]

The problem disappeared after I put a brand new power tube set to the amp.So the issue was caused by the unbalanced/bad power tubes?
/Leevi

That seems a reasonable conclusion :)