solderdude
Grand Contributor
This has nothing to do with that but rather the fact that one channel has original opamp and the other channel has the expensive one.There's one thing I find suspicious, though. Why does SINAD increase slightly on both channels when @amirm replaces the 5532 on one channel with the discrete op-amp?
Are there additional buffer capacitors on the discrete op-amp's circuit boards?
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No 2 channels measure exactly the same and even when he would have measured the same channel such 'differences' are to be expected and in the realm of tolerances.
Basically you are looking at the SINAD of the power stage (which is much higher in distortion than the opamps could ever add).
There is ... the output stage !There might be some other limiting factor in this particular amplifier as NE5532 can do better than THD+N 0.003.