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McIntosh MC205 hum

My McIntosh MC205 hums. It is set up with all the proper interconnects and I use a Krell HT Standard as the processor. It hums and is a bit annoying. Is this natural? I went back to my dealer and they said I had improper grounding. It is plugged into a surge protector which goes into a 3 prong wall outlet. The surge protector indicated protected but not grounded. I have an old house. There are walls that I've opened elsewhere in the house and there ground wires running from the box. So I bought a green ground wire and grounded the wall outlet to the box. Surge protector still did not show grounded.

However, I did go to my dealer, put my ear up to their MC205 and their's hums too.

So is this something natural for an $8000 amp? Any feedback is appreciated.
128x128tobaccoleafpie
swampwalker's avatar
swampwalker
5,138 posts
 
If the sound is from the amp itself and not through the speakers, its likely a transformer vibration which I call buzz. Try telling your dealer its a transformer buzz and ask them to tighten the hold down bolts. These are sometimes difficult to prevent, but if you bought it from a retail dealer he should help you out.

If the sound is through the speakers it may well be a grounding issue, but since you say you have an HT processor, it may be your cable TV. Try disconnecting the cable co-ax and see if it goes away. If it does, try a ground isolation transformer which can be purchased at radio shack.
theo's avatar
theo
2,660 posts
 
I just bought a MC205 as well and replaced an MC7205 which had the same issue. My hum was in the speakers and presented itself as a buzz more than a hum. I do have a slight hum at the amp and that according to McIntosh that hum at the amp is the enormous power supply. OK OK so why does my MC402 not have that hum? The buzz at the speakers I solved with a PC Audio power cord and removed the ground plug. Someday when I have time and patience I want to track down the source of the hum as it may be an interaction with phone, cd or something. I think I can eliminate the hum at the amp (power supply hum) by adding a sorbethane footing under that amp I just haven't done that yet. I will add the 7205 did not hum at the amp except at turn on which all my Mc amps have doen once they reach full warm up (about 1-2 seconds) it goes away.
tobaccoleafpie's avatar
tobaccoleafpie OP
35 posts
 
Well, the hum is definitely not thru the speakers. Its in the amp. I kinda figured the hum would be explained away by the manufacturer that it is due to the enormous power supply. (Thanks Theo) Don't you think for $8000 it should be quiet too? (I paid $6K for mine before the price went up.)

I have no cable TV. Too cheap. I mainly use my system for listening to music, DVDs and vinyl.

I was shopping at my dealer with my buddy yesterday (he wants a system too) so I sneaked away to the room where they keep their McIntosh amps. Lo and behold, their MC205 did it too. A salesperson was wondering why I had my ear pressed against their amp.

So Theo, what is a sorbethane footing and where do I get one? Aren't there air vents underneath the amp and would it interfere with venting and cooling?

Thanks all.
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