Cary SA500.1 mono blocks

Mechanical hum from the transformer is caused by DC on the line, which can result from many sources regardless of whether you have dedicated lines.

60Hz hum that you can hear through the speakers is sometimes a grounding issue and sometimes something else.

I believe the 500.1s accept balanced and single-ended inputs. Whichever you are trying, try the other. In particular, if you are trying to run balanced cables to the balanced inputs but your source/preamp is not fully balanced, and especially if you are using adaptors, then that could cause an issue. BTW, I also owned the 500.1s and they were dead quiet in my system too.

Well this sucks I'm done with the amps . After 4 hours yesterday and a few hours today I'm about to put my system back together. I did everything I could think of to silence the amps with no effect. Nothing in my room has power to it but the amp and speakers no rca connected just speaker cable with no effect. Something is wrong with my power and all my amps that I've owned are not this sensitive to bad power I've never had a ground loop hum that I couldn't get rid of. Thanks for the responses. I guess I will stick with my rotel amps and be happy maybe buy a new prepro or a Sony 4k projector.

Is it mechanical hum of the transformers inside the amps, or a hum/buzz coming through the speakers? Does it come through both amps/speakers or just one? Do you have any similar (although maybe lessened) effect from your Rotel amps? Try a cheater plug and see if that makes a difference (indicating a ground issue). Hopefully, they are new amps and you don't have to keep them or pay for them. Good luck.

04-18-15: Mitch2
Is it mechanical hum of the transformers inside the amps, or a hum/buzz coming through the speakers?

Kwa69, you should clarify this. As Mitch2 indicated earlier, "Mechanical hum from the transformer is caused by DC on the line, which can result from many sources regardless of whether you have dedicated lines." But if the hum is coming from the speakers, I see no reason to conclude (as you have stated both here and in your system description thread) that the cause has anything to do with "bad power."

If the hum is heard through the speakers, and if I am correctly interpreting from your system description thread that you are driving Martin-Logan Odysseys with these amps, I'm thinking that the following statement in the SA-500.1 manual may have some relevance, even though you are apparently not connecting a sub to the amps:

Caution! Do not under any circumstances connect the amplifier to a subwoofer through its high level (speaker) inputs. There is a potential of damaging the amplifier using this type of connection due to differences in grounding schemes used by some subwoofer manufacturers.

Although the Odyssey does not incorporate a powered woofer or subwoofer, as a hybrid electrostatic it nevertheless receives AC power. I'm wondering if as a result there may be an incompatibility between the amp and how AC ground and signal ground are handled in the speaker, resulting in effects similar to what might happen if a powered sub were connected to the amp.

What I would suggest, assuming that the hum is coming through the speakers, is that you try the amps with different speakers, that do not require any AC power. Also, if you already haven't, try plugging the amps directly into the wall, without any of the power conditioners that are mentioned in your system description.

Regards,
-- Al

Al, good catch as usual. KWA should call Cary on this. If this is the issue, he could damage the amps. BTW, the first iteration of the manual did not have that warning. It was added after the issue was observed by owners.