Cary SA500.1 mono blocks

I just added the 500.1 mono blocks and I have a hum on both that I can't get rid of .I've tried to lift the ground pin on the PS audio AC12 power cables with no change. I tried different power cables with no effect. The amps are on their own 20amp circuit plugged into a Richard grey 400 . Any help would be appreciated thanks .
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Showing 1 response by almarg

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.

-- Al