Sorry to digress (again), but I see that 2x6spds loves tube amps...
I was an electronics nerd in my youth, and built quite a few DIY tube amps in my highschool days back in Japan. My pinnacle "opus" was a 60W x 2 output-transformer-less power amp, which used as many as 8 big power tubes (called 6336) per channel to lower the output impedance. That was a heck of finicky beast, but when set up correctly, it sounded so sweet (well, at least to me!). I still have that amp in the closet, but I do not have guts to power it on anymore. Talk about getting old...
Indeed, a fresh-off-the-bench tube amps always needed some "break-in." The big final-stage tubes kept changing their electrical properties during the first 20-30 hours or so of operation, only after which I could stably set the bias voltage, etc.
I also built a high-sensitivity tube pre-amp for moving coil pick-ups (remember those?). The tough part was the calibration of the RIAA curve... You can readily hear a 0.5dB deviation, and it was fun!
My memories long for those good ol' days with low dumping factors, RIAA deviations, and easily measurable levels of harmonic distortion... Those days you could easily detect a
real sound difference between amps, I guess even without a blind test!
Each amp used to have its own "character," much like loudspeakers still do today...
By the way, those days (late '70s) it was very fashionable among Japense audiophiles to use a thick, heavy-duty, outdoor-spec power cord as speaker wire. Talk about low resistance and high reliability! I guess the hobby was then much healthier than it is today...? LOL
Cheers!
