D
Deleted member 50971
Guest
These are things that your average person doesn’t realize, or even think about it myself included.I was really curious how this amp should perform and how it could have performed when it was new. As the circuit is simple, I have put it into MicroCap, trying to keep parts as close as they were.
This is the schematics
View attachment 228185
and it was designed by a competent circuit designer. R4+C2, R27+C9 and C6 make very interesting and perfectly working frequency compensation. Small signal frequency response looks like this
View attachment 228186
It is wide and flat. Remember I speak about the power amp section only, without bass/treble eq.
The idle current is quite low, due to simple bias circuit with 5 diodes in series. This is the point that might have been grossly improved. Because of the low idle current, distortion is rising at low power. However, the value of distortion above 100mW is fully acceptable.
View attachment 228187
In this distortion/power simulation, please take into account that ideal voltage sources are used to supply the amp.
I will investigate the PSRR as well, and I expect it will not be as good as these basic parameters.
I have a feeling that even though this amplifier was lovingly put back together, it’s not quite performing like it originally did.