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DC Offset Blocker/Killer - where to buy in the USA

   I have McIntosh MC8207, the first unit I bought from an authorized dealer came with a loud buzzing coming from the left transformer, and was replaced with a new unit which came with even a louder buzzing. The buzzing can be heard from 8 feet away. Then I was told to have install new 20 amp outlet that has its own isolated grounding.
   That was done professionally by an electrician who installed two isolated 20 amp outlets, two 20 amp circuit breakers, two copper polls for grounding for each outlet, each outlet has its own neutral and power line. After all this done the buzzing sound was still there.
   I was then told to buy a power conditioner which I did (Audio Quest Niagara) which was like $4000 and that did not help. Called back McIntosh and was told that I might have DC offset in my AC line and was told by McIntosh that I would need a DC Offset Blocker/Killer to which when I asked them where to buy one they told me to go on the internet and search to find one, to which I cannot find one.
  This bothers me a little bit, if you as a company think that I have dc in my ac and i need a dc blocker wouldn't you need to sell one as well. I brought this amp to my friends house and it was the same no improvement, so my guess is that he has dc in the ac line as well.
   So If anyone of you knows where to buy a DC Offset Blocker/killer please let me know, but even if this helps kill the buzzing wouldn't you guys think that this expensive somewhat hifi amp/brand should be silent from the factory. I mean this is two units in a row all purchased brand new.

My house is 5 years old, everything is brand new, the whole neighborhood is about 8-9 years old, my electrician says that I have perfect power coming to the house and everything looks fine.

Thank You

tomiiv30
stereo5's avatar
stereo5
2,766 posts
 
I own a Mac MC152 power amp and a MA6600 200wpc integrated and both are dead quiet. I have never heard of that. I will ask over at Audio Aficianardo Mac forum and see if others may have a clue. I’ll report my findings back here.  Did you or the dealer check to see if the transformer is bolted down tightly?

This is what I posted on Audio  Aficionado:

McIntosh MC8207 Transformer buzzing

I am asking this for an Audiogon member who is having a hard time with this amp. He bought from a reputable authorized dealer and the left power transformer buzzes so loud he can hear it from his listening chair 10 feet away. He returned the unit for another amp and it has the same problem. He contacted McIntosh service on 3 different occasions. They first told him he needs dedicated lines so he had a licensed electrician do that, having 2 lines installed both with separate grounds, but no change. Then service told him to buy a power conditioner and he bought an Audioquest Niagra to the tune of 4 grand and still no change. The last time factory service told him he needs a DC Offset Blocker.

It seems to me they are taking stabs in the dark. He brought both amps to his friends house 10 miles away and the same problem, the left toroidal transformer buzzes. His house is new, only 5 years old with a 200 amp service. He is quite ticked to say the least. I feel bad for the guy and I am trying to help him out. Anyone??
tomiiv30 OP
63 posts
 
@stereo5 

I just got an email from the salesman I bought it from and told me that he would talk to service dept. to see if they can check or have checked the one I returned. I would also be bringing this one to them as well and have them plug it in while I am there no matter how busy they are.

And thank for posting in the other forum for me, I really appreciate that. I just don't want to spend another cent on trying to fix something that may not be fixable by me.
stereo5's avatar
stereo5
2,766 posts
 
3 members of the forum told me there was a bad batch of the potted transformers which was confirmed by McIntosh.  Let the dealer know about that.  Best of luck and let us know how you make out.
jea48
2,944 posts
 

@ tomiiv30 Your profile list country as N/A. By chance do you live in the USA?
I have McIntosh MC8207, the first unit I bought from an authorized dealer came with a loud buzzing coming from the left transformer, and was replaced with a new unit which came with even a louder buzzing. The buzzing can be heard from 8 feet away. Then I was told to have install new 20 amp outlet that has its own isolated grounding. That was done professionally by an electrician who installed two isolated 20 amp outlets, two 20 amp circuit breakers, two copper polls for grounding for each outlet, each outlet has its own neutral and power line. After all this done the buzzing sound was still there.


Then I was told to have install new 20 amp outlet that has its own isolated grounding.
That was done professionally by an electrician who installed two isolated 20 amp outlets, two 20 amp circuit breakers, two copper polls for grounding for each outlet, each outlet has its own neutral and power line. After all this done the buzzing sound was still there.

If you live in the USA the so called electrician is no electrician. Definitely not a qualified licensed electrician. No way in hell!

two copper polls for grounding for each outlet,
I assume you mean two earth driven ground rods.

DANGEROUS and not electrical safety code compliant. Not NEC or any AHJ in the USA.

IF the branch circuit wiring is Romex an isolated grounding type receptacle serves no purpose what so ever. Per NEC code the insulated equipment grounding conductor that connects to the isolated ground terminal on an IG receptacle shall terminate on the ground bar in the electrical panel the branch circuit is fed from.
Exception: NEC allows the insulated IG equipment grounding conductor to pass through a sub panel and to be connected to the equipment ground bar in the main electrical service panel.

NO isolated ground rods allowed for IG receptacles.


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cleeds
2,065 posts
 
stereo5
3 members of the forum told me there was a bad batch of the potted transformers which was confirmed by McIntosh.
That certainly wasn't publicly posted in the forum. Are you saying that AA users told you that privately?
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