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Ground Issue

I have two McIntosh Amps - MC402 and MC252 - There's a buzz in my system recognized in the midrange and high-end (mostly midrange). Even with the pre-amp off there's still this buzz. A friend suggested I put A/C adaptor on the end of the power cord of each amplifier and the buzz went away. The other way to reduce the noise was to remove both shielded coaxial wires from two source pieces in the system - the noise reduced but not totally eliminated.
Each amp (and my other source equipment) are all plugged into a RG power conditioner. Any suggestions how to eliminate the buzz while using the ground wires of the amplifiers?
stusurf86
stops
56 posts
 
I think you have a ground loop issue. Turn off all the equipment.

PLEASE REMEMBER TO TURN OFF THE POWER AMPS EVERY TIME YOU CONNECT/DISCONNECT THE INPUTS TO THE AMP.

Disconnect the inputs to the amp at the amp side and power up the units. If the buzz is gone then you are creating a loop with the interconnects and power ground. Try using a cheater plug on one of the units. If the problem goes away leave it like that. All the units will be connected to each other via the interconnect grounds and will have ONE connection to the power ground when you reconnect the interconnects.
frepec
17 posts
 
Had the same problem with my MC2102. My dealer told me to install a 3 prong to 2 prong plug adaptor in the power cord. Took the noise away.
dan_ed
2,451 posts
 
Frepec, did your dealer explain to you why that is very dangerous to do with a power amp? A cheater plug is useful for finding ground issue, but using one in this manner is not a good idea, and my be against code in some places.
stops
56 posts
 
If the cheater plug works on the preamp then an isolating power transformer will break the ground loop (1:1 ratio). I suggest you use it on the preamp so it does not need a lot of power output.
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