I think you might be going about this incorrectly.
When you said you disconnected the amplifier what exactly did you mean?
The first step should be turn amp off, wait until it plays down. Then disconnect the input cables to the amp at the amp so the amp is only connected to the speakers. Then turn amp on and check for hum. If its gone, its not the amp's fault. If the hum is still there you might have low level DC setting on your AC power line, although this will usually make the power transformer talk to you through the case rather than showing up in the speakers.
If you have interconnect cables connected to the amp only with the the other ends open this will cause lots of noise hum buzz hiss, don't do that!
Interconnect cables - are they well shielded? Goofy unshielded interconnects are hum city.
Do some of the components have a two conductor power cord and others or maybe the new amp, have a three wire power cord? This can sometimes cause ground loop hum because there can be two ground paths between components. Sometimes a 3 to 2 cheater plug on the 3 terminal power plug will fix this.
Finally, maybe the new amp just does not know the words.
good luck and happy New Year,
Frank Van Alstine
