Macintosh MC205 ground loop problem with a twist


Hi everyone. I recently purchased a Macintosh MC205 Power amp, and I have detected a slight hum/buzz coming from my Front right channel. I know its a ground loop because a cheater plug on the power amp makes the buzz go away entirely. Not wanting to permantly use the cheater plug, and to eradicate the problem I have been trying to track down the source. My rack is on a dedicated circuit and I am using a Monster Power HTS 5100 coupled with a Monster power voltage regulator. With everything except the Macintosh pre/amp and the Macintosh power amp plugged in I still get the buzz. taking the monster power center out of the picture I have plugged the amp into the wall and still no joy. This just does not make sense to me but anyway I still am convinced that there is something in the circuit that is causing the problem simply because the cheater plug makes the noise go away.. However it could be the amp itself but since the hum is so low (have to put your ear about a foot away from the speaker to hear it) I decided that I am not going to pack this beast up and return it to the store. So I have decided to either live with the hum/buzz or use the cheater plug. Now I understand the risks of using a cheater plug, and even with extremely low odds of getting electrocuted I still would like to make those odds even lower by actually grounding the chassis of the power amp. However there is no grounding post on the rear of the chassis. I think however if I can find a way to ground the chassis this would eleminate me getting shocked say if in the unlikely event that something shorted to the chassis. However I am no electrician by any means so my question is this: Can I effectively run a group wire between one of the chassis screws and one of the other outlets in my rack to ground the chassis only if indeed this happens or would this essentially be the same as leaving the cheater plug off? Not sure how this whole ground thing works to be honest so excuse me if this sounds like an idiodic question.

I tried running a ground cable from the cheater plugs little grounding loop to one of the outlets but this actually brought back the hum, which I suspected it would but I thought it was worth a try. Essentially I am tying to create a ground only for the chassis and not the power cable. In theory it sounds good but just want to check to see if anyone else may have done this or if there is someone on the forum that maybe more knowledgeable about electricity than I. Im sure you guys get tired of talking about ground loops but if this will work I will at least feel pretty safe in using the cheater plug.


P.S.

One more thing because I know the question will be asked. I am using decent power cables (audioquest) and the more I think about it its very possible that the macintosh mc205 and the MX121 could be the loop lol. No way to separate the two unless I run another dedicated line to the rack which I guess would not be that difficult.

Thanks in advance
Keith
barnettk
If you use the cheater plug and run a ground from the chassis to the ground screw on the outlet ,it will be as safe as the ground in the power cable. If that works and you have no hum then you can leave it like that. 
It is possible that the power cable that is producing the hum is not wired correctly, I have seen this before!
Thanks Yogiboy. I have tried 3 different power cords of which all of them still had the hum. What you described is exactly what I had planned to try next. I know the cheater plug is floating the ground from the power cable, but I just want to make sure that I am covered from shock from the chassis so I will try it and let you know if it works. I am hoping that this will not just loop the noise right back into the system, but Im thinking that the two will stay separate unless the chassis is grounded with the power receptacle in the power amp.

Thanks  
Ok attaching a ground wire from the chassis to the ground screw on another power outlet in my rack produces the hum. This is actually a good thing because I know that the screw I selected is indeed going to ground so the noise is working with me here. So HERE is what I did instead. I ran the ground wire from the chassis on the Power amp to the ground post on the pre amp and BINGO no hum... only that very faint sweet soft white noise hiss I was expecting. Problem solved! feel like dancing. I think that the ground loop is being cause by the only two components that I could not unplug to test with...the power amp and the pre amp lol. Thanks again Yogiboy. 

Keith
I'm glad you fixed the problem.
Enjoy!