Capacitors in the audio signal path are BAD, m'kay. Capacitors belong in power supply sections, and nowhere else. Capacitors used to compensate an amplifer generally mean that the amplifier is otherwise unstable with poles in the right half plane and is therefore a bad design.
Transformers belong in linear power supplys and nowhere else.
That basically means anything with an op-amp in it. Op-amp circuits with open loop gains of 10,000 or more require large amounts of feedback to make them usable. While this reduces THD, the intermodulation products, and especialy the transient intermodulation products are much higher than they should be. Servo loops MUST NOT be in the audio feedback loop. This one is also very important.