A ground-loop induced hum can come from any single ended source, and that is one of the problems with most receivers - all those single ended connections and not enough balanced inputs. In RLPIII's case I believe we got rid of most of the noise by providing a separate lower impedance path to a common grounding point on the receiver chassis for each of the power amps, than was possible though the interconnects. If I recall correctly, there was also a bit of shot (white) noise coming from the preamp output stage of the receiver too. RLPIII's Halcro was much quieter on all fronts.
Originally Posted by kennyt
Ground hums can happen in any system, they are not specific to receiver/amp systems. I have even had my cable be the cause of these from improper grounding as the main cable box for a multi unit building.
Just to also clarify, the idea of adding amps to a receiver is a stepping stone, more than an ends though for some it is sufficient.