Well, this is a very good post. Distorted op amps give solid state a bad name. This is evident in most all receivers and amps that started using them in the late 70,s and early 80,s.
Changing out the op-amp Ic,s and the capacitors makes all the difference. One of the top audio engineers has confirmed this, adding that the plus and minus power supplies are not right in some of the amplifiers that power the op-amps.
One thing I noticed is that Mac uses a unbalanced to a balanced
configuration in their op-amp preamp circuits.