Mordpol X2 Guitar Poweramp13.11.2019:
I started working on the matching power amp for my X1 preamp, so here's the current state of this thing. Tubes are a pair of 5881s, operated at a relatively low B+ voltage of around 420VDC. My choice fell on 5881 because of their compact physical dimensions especially of the tung-sol one, because I don't have that much height to spare even in a 3U rackmount chassis.
I designed the PCB myself - some features are: two switchable inputs which can be padded to line levels, two switchable volume controls (+ presence and depth also switchable), everything switchable via MIDI. The test build seen on the pic is working flawlessly except for the PWM fan control, which is giving me the ugly noise, so I'll probably abandon it. Even heating all tubes with AC (also preamp tubes on PCB) doesn't give me the least hint of 50/100Hz hum, which I didn't expect. Next step is getting the matching enclosure - expected to happen in December.