It lives. I'm using a Context Engineering case, I need a 1/4" cardboard shim to keep the PCB from sliding front to back, but it still slides side to side about 1/16" (slots are 3" wide exactly). It's mounted in the 3rd from the top slot. Big caps are mounted under the PCB. The 24V reg is mounted underneath to the angle bracket show. I couldn't get the second screw (wiring difficulties mentioned below) in there so I used only the screw closest to the middle of the case.
I'm using a 120-ohm output resistor on each channel. I mounted it directly to the output jack instead of in the PCB slot.
Changes from the BOM:
- different jacks.
- different switches.
- different case plenty of room on the front panel for a decent sized knob.
Snags I hit...
1) Put C3P in reverse, promptly blew out Q1P and Q2P on power up. Reoriented C3P and replaced Q1P and Q2P and all was good.
2) Wiring the input jack in the back. PITA! The wire I used is too stiff (Kaptan shielded twisted pair), but would make a good whip. The amount of time to "stuff" the wires into the case was about 30 minutes, that's how much of a PITA it was. I needed extra length so I can pop the panels off as I bottom mounted the 24V reg onto an angle bracket.
Other than that, all is good. If I ever need to open this again, I'll need to find more flexible wiring for the input jack to pot.
It's pleasing so far using the EH 12AU7 tube, but too early to really comment. I may switch to RCA 5963 soon. It's still a bit too much gain for high sensitivity low-Z headphones, even with the 120-ohm output resistance. I dare not go over 120-ohm.