05-10-2015, 11:39 PM
I'm not sure how a 12au7 would perform in the b25... have you tried putting the 12ax7 in channel 2 to see if that channel behaves when it has the right tube in it?
the circuits in both channels are the same, so if channel 2 works with the 12ax7... its likely that the b25 doesn't like the 12au7.
the circuits in both channels are the same, so if channel 2 works with the 12ax7... its likely that the b25 doesn't like the 12au7.