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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
jay23
210 posts
 
Did you ever try a power conditioner or DC blocker after not using the improperly grounded outlet?

McIntosh should be more helpful. At the same time, it wouldn't make sense to put a DC blocker in all its products to make a small percentage happy. DC blockers are colored and roll off the highs. Why would audiophiles want a manufacturer to make their gear colored in an unintentioned way, when the customers with problems will benefit from cleaning up their power? The amplifier working at the dealer shows it's not broken.
stereo5's avatar
stereo5
6,476 posts
 
I have  been in contact with Tom who has the problem.  He is done with both his dealer and the manufacturer.  No one is extending a hand to help.  One of our esteemed Audiogon members badgered him so badly on McIntosh's forum @ AudioAficiando that Tom said he would rather set the amp on fire. as it was his money and his right.  Well, the guy still wouldn't let it go, words were said and Tom got banned from the group.  Had I been Tom, I would have lost my cool with this person way before that.  Personally, I think Tom got screwed.  I am the one who posted his problem at AF, so I have a strong opinion on this whole ordeal.  That is all I will say about this.
jea48
4,510 posts
 
DC blockers are colored and roll off the highs.
BS!


atmasphere6,979 posts

01-03-2019 1:06pm



DC blocking circuits are expensive to do right, and are very rarely needed.

That’s why they aren’t included in almost any linear power supply I know of.



You can find them on ebay for less than $100.00. We build them into all our amps.

Repeat..... atmasphere said:
We build them into all our amps.


Bryston also does.


Bet there are plenty of others too.
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jea48
4,510 posts
 
@ stereo5

As I said in an earlier post tomiiv30 needs to hire a Power Quality testing company to check the quality of the power in his home. Some electrical contractors may have the needed test equipment to preform the test, but most don’t. For many electrical contractors it is cheaper to hire a Power Quality company than buy the testing equipment. In my area a certified, qualified, power quality testing company charges about $125 an hour. A good single phase power quality analyzer can run around $10,000. And then you need a tech that is trained, certified, for its’ use. The tech will explain the problems, if any, and then recommend the solutions to solve the problem/s.

If the power quality problem/s is coming in on the electrical service entrance conductors the tech will provide the necessary, certified, print out test results for the customer to give to the utility power company.

Jim



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Ag insider logo xs@2x
cleeds
6,014 posts
 
jea48
tomiiv30 needs to hire a Power Quality testing company to check the quality of the power in his home.
Agreed. And if the OP seeks a definitive assessment of the unit itself, he'll need to send it back to McIntosh or to an authorized service center for a complete evaluation. That's something his dealer - which he for some reason won't identify  - apparently isn't equipped to conduct. Simply plugging it in to see if it buzzes isn't the equivalent of a proper bench test.
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