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

I'm surprised that Niagra didn't resolve it.
Expensive piece. 
Sounds to me like "Mac" needs to get back to their roots.......perfect example of "bean-counters" making the final decisions that directly affect the output product's level of quality and/or performance.

But, instead, let's regurgitate the response regarding the rolled-off highs!

Never seizes to amaze me!

It’s not BS. DC filters use chokes. Chokes function are to roll off the highs. So DC filters are colored.
The Niagara was added after the improper grounding was added. 
jay23145 posts02-11-2019 8:49pm


It’s not BS. DC filters use chokes. Chokes function are to roll off the highs. So DC filters are colored.

No.....  A DC blocker does not use chokes. A simple purely DC blocker uses a couple of diodes and a couple of electrolytic capacitors. No chokes.
See post #3 in this DIY Audio thread.


The top schematic DC blocker is one used in piece of Bryston equipment. I’m guesting a power amp. The schematic below the one for the Bryston is one used in a Crown amp. Again no chokes.

Now some stand alone DC blockers sold do have filtering too. But purely DC blockers without filtering can also be bought. Chokes are not needed.

I’m not a robot.


The improper grounding outlet has nothing to do with the Niagara, the Niagara was plugged in different outlets that have nothing to do with the outlet that was improperly added.