Wife working from home started me on a silent rig quest that led me this and now I'm in headphone heaven.
It's a full Dumble ODS preamp with Russian 6n17b submini tubes in a 1590XX enclosure. I used grill cloth to cover the heat vent ports for the tubes.
Well-worn 555 SMPS with about 140V at the plates.
I added a high-voltage mosfet buffer on the output (Dumbleator style) and it even works really well as a boost/OD pedal into another tube amp. Mostly I run it into a delay > diy Surfy Bear reverb > Two Notes Cab M+.