Cars-N-Cans
Addicted to Fun and Learning
It is impressive performance for the time and its a shame they could not get the PSU noise down. They did add UFR diodes presumably to eliminate some of the spikes from the reverse recovery time of slower diodes with the transformer's leakage inductance. I would assume that the noise was there from the start when it was first made, and probably due to the fields coupling into the audio circuits and/or maybe poor PSRR, but not a EE so cant say for sure what the true culprit may be.It was actually one of the first silicon amplifiers. Solid state amplifiers before this were using Germanium!