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


Thanks for the detailed explanation I very much appreciated it. All the suggestions from all the other members of this forum are very welcome and like I said I will try to do whatever it takes to find the problem and fix it, it may take some time but I will do it. I will make sure I take notes and maybe record if he is ok with it and will snap few photos.

But for now I think I need to relax and listen to some music because my head is gonna explode, I have to enjoy my stereo system little bit.

Will be back with some more info when I get some.
@ tomiiv30 OP

I decided to deleted my previous post because I didn’t think it was right for me to instruct/dictate how the electrician, you hired, should go about trouble shooting for possible problems on the electrical service and or wiring of your home.

I did save the first part of my post about the two ground rods that were installed for the equipment grounding of the two new dedicated circuits.

I would appreciate it though if you would note and post back what the Line 1, leg, to Line 2, leg, voltages are as well as Line 1 to neutral and Line 2 to neutral voltages are at the electrical service panel.
To high of an over voltage above the voltage rating of the torid transformer in the amp could also add to the cause for the transformer to buzz louder than it normally would.


@ tomiiv30 OP

Make sure you ask the electrician exactly what he did with the equipment grounding conductors for the new dedicated branch circuits he installed. TAKE NOTES! A picture is worth a 1000 words. Have him physically show you exactly what he did.

It is possible the electrician wired the new ground rods per NEC 250.54 ...... I’ll give the guy the benefit of the doubt.

If he did wire the 2 ground rods per NEC 250.54 "Auxiliary Grounding Electrodes", then the equipment grounding conductors for each IG receptacle are connected to the branch circuit wiring equipment grounding conductor and the equipment grounding conductor of the branch circuit is connected to the equipment ground bar in the electrical panel the branch circuits are fed from.

Per NEC 250.54 a ground wire is installed from the ground rod and is connected to the branch circuit equipment grounding conductor. He can use any any size wire he wants to use from the ground rod to the branch circuit equipment grounding conductor. Hell, it can be 20 gauge.

Does an Auxiliary Grounding Electrode really do anything to improve the sound of an audio system? It can act as an antenna and add noise. It also provides another path for a lightning high voltage transient to enter your home. Lightning loves aux grounding electrodes.


I went through something similar with an amp.  I tried dozens of fixes, from cheater plugs, extension cords, turning off all the breakers, different outlets, inexpensive filters, expensive filters, ground loop eliminators, DC blockser, power conditioners, power regenerators, isolation transformers, you name it.  Nothing worked.  Ultimately, sometimes it comes down to the electricity coming into your house and how it interacts with the component.  I hope you have an experienced electrician, because most don't measure/don't know how to measure/don't believe are important, the kind of things, to vanishing small levels, that can be causing the problem.  And if he does identify it, good luck getting your local electricity company to address it.

I'm also here to tell you that if you buy a similar priced amp from a different company, there's every likelihood that it won't hum.

As much as we like solving a problem once it's been identified, sometimes the expedient thing is the best route (i.e. I hope you haven't exhausted the store's return/refund policy).


It could be the electricity coming to the house form the outside, I've done everything I was told to do and more and nothing helped. The only thing left to do is convincing the electricity company to come out and maybe put a power analyzer on the entrance meter and record if there are any anomalies. 

The store has been pretty good with me as far as exchanges and getting new units to me but even I told them that I do not want them to get me new units but find a solution to the problem I am having,  it just that they should've know more about the product they are selling or they should have been trained from McIntosh of how to address this kind of problems. 
I wonder if one of our resident Audio Guru's could build a Heavy Duty DIY Noise Blocker and charge you accordingly?  I'm talking something better than the Emotiva which uses a circuit board?  I would think point to point wiring would be the way to go.