So here's something interesting, the globe RCA 841 have super low distortion. Like, solid state level distortion in this amplifier, especially with high impedance headphones.
THD 1mW into 32ohm (low impedance switch) - 0.017%
THD 1mW into 120ohm (medium impedance switch) - 0.007%
THD 1mw into 300ohm (high impedance switch) - 0.0054%
Whereas the shouldered Hytron 841 distortion figures are double or triple the RCA, second harmonic dominant. This has an audible effect, the globes offer a more clean listening experience, compared to the slightly more smooth Hytrons.
With the RCA 841, this amplifier is very revealing of poor recordings, bad ones sound very bad, good ones sound incredible. Will be interesting to see how the sound evolves. I haven't ruled out experimenting with different output caps or even different source follower FETs.
Here is the full circuit once more, taken with my phone, my nice camera is getting a little long in the tooth and has pretty poor low light performance, hence the potato photos before.
B+ circuitry, featuring 1101 Audio's /
@A2029 's exquisite HV regulator.
The output impedance switch from hell. Thankfully I diagrammed the wiring months ago so didn't have to think about it much, but it was still a PITA to say the least.
Source follower board, CCS board, Auricap XO coupling caps, Sowter 8665A output transformers, Goldpoint V47 stepped attenuator, filament bias resistor.
And closed up.
Don't think I showed the rear panel before.
Here is a long exposure shot with the RCA 841 on my desk.