As usual, lovely work, Damir. I actually picked up a "Cobra" head from a Songbird garage sale (back when they were Songbird), and keep meaning to rebuild it into something else. Right now, the contenders are brownface Vibrolux, Tremolux, Deluxe, or Princeton. But I'm also wondering about other possibilities. In your experience, is the power transformer capable of powering another 12AX7 on top of the two already in there?This is complete remake of Cobra mk2 amp from 70s, I was asked to add master volume end effect loop at first, but it finished as full rebuild with added master, buffered effect loop and EF86 channel to existing diagram (copy of Fender Princeton reverb sans reverb )
These amps, cobra is same as riviera 725 from pepco, are cool amp, but very noisey (hum) , with poor tubes layout and heather wiring.
Amps is very quiet now (at idle LOL), very loud for two 6V6 in the output.
If I had to do same job again, I would make a new chassis, it was a hassle to reuse existing one.