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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
jea48
4,526 posts
 
atmasphere6,924 posts01-22-2019 10:38am

Amplifier buzz is a thing to fix- but it really shouldn’t have anything to do with the electrical system.
@ atmasphere

It’s not the amplifier that is buzzing loudly. It’s the power toroidal transformer buzzing, vibrating, loudly. It’s a big toroidal transformer capable of delivering 35 amps, continuous. At the vary least the torid would have to be at least rated at 3500Va. And that would really be pushing the torid beyond its’ limit using a 125% SF.

In case you missed the OP post. He took the amp back to dealer. The service dept plugged the amp in, powered it up, and the torid transformer was quiet. No loud buzzing as the OP experiences at his home.

tomiiv30 OP37 posts01-21-2019 6:26pm@stereo5

I still have the amp, a member of another forum sent me his two Emotiva CMX2 DC blockers and told me to put them in series and after doing so there is still buzz in the amp but quieter than without the dc blockers.
@ atmasphere

Any thoughts why the blockers didn’t stop the buzzing of the torid?  Bad distorted waveform. Harmonics?


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twoleftears's avatar
twoleftears
5,320 posts
 
Because the toroid isn't manufactured properly; probably not wound properly.  More than one example hums because whole batches probably made with sub-par QC.  It's all down to the sub-contracted company that M. buys their transformers from these days.  Evidently not the same QC, and probably not the same company, as in the old days.  Once you stumble over a product that hums regardless of whatever else you do to remedy it, the only thing to do is get rid and move on to a different (and hopefully better) manufacturer.  That's what I did.  The monoblocks I own now (admittedly not massive) are absolutely silent.
stereo5's avatar
stereo5
6,486 posts
 
You must have nerves of steel, I would be a basket case.  I would have thrown the amp in question through the stores window just out of spite.  I would call McIntosh and ask if they could install the DC offset filter inside the amp for a nominal fee.  If they balk, tell them you will be calling the states attorney general to file a complaint and also bad mouth them all over social media and in the different online forums.   Anything to get their attention.   Or, put it up for sale on Audiomart and move on.  
tomiiv30 OP
65 posts
 
@twoleftears 

If that's the case McIntosh should pick up my bill and make it right for all the troubles I went thru.
The salesman from the dealer I bought my amp from told me that they had specialty electrical companies come to the building every so often to make sure everything works properly, and said that they have the best in business when it comes to electrical wiring, installation, construction and whatnot, it is a specialty hifi store and I bet their electrical is top notch.
This amp buzzed at three different houses all about 20+ miles apart, and I am still not sold on that it's only me and my electrical. But it is what it is and I have to live with it.
tomiiv30 OP
65 posts
 
@twoleftears 

Do they really buy their transformers from somebody else and are not wound in-house?
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