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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
4,785 posts
 
clearthink607 posts01-24-2019 10:50am

If the claim that the amplifier was defective was valid, authentic, and genuine then why wouldn’t this person who came hear only to complain return the unit to McIntosh for repair, adjustment, or replacement and why wouldn’t he name the dealer who sold him this defective, damaged, or inferior unit?

The unit IS NOT defective, When the OP took the amp to the dealer it was taken to the service department. There it was plugged in, turned on, and the torid transformer did not buzz/vibrate. The OP said the torid transformer was quiet. The OP was in the room during the test.
Again, the torid DID NOT buzz/vibrate. It was quiet.

So what good would it do to send the amp back to the factory? The amp is not defective. It works as it was built to function. If the consumer has DC offset on his AC mains the torid transformer will buzz/vibrate. The more DC on the mains the louder the buzz.

Should the manufacturer have incorporated a DC blocker on the line side of the torid transformer? Yes. But the manufacturer chose to save a few bucks. Ron, a McIntosh representative, said they get maybe 5 complaints a year about mechanically buzzing torids. His advice to fix the CUSTOMER’S PROBLEM is to buy a DC blocker.

Probably most manufactures that use fairly large torid transformers, in their equipment, install a DC blocker. McIntosh does not.
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stereo5's avatar
stereo5
6,568 posts
 
"Probably most manufactures that use fairly large toroid transformers, in their equipment, install a DC blocker. McIntosh does not."

That is what galls me the most.  I own a lot of McIntosh equipment and am very happy, but it really galls me that  they couldn't add a DC noise blocker inside their amps with the large to largest Toroidal transformers.  IMHO, 5 customers a year is 5 too many customers.  I have been thinking of trading in my MC152 amp purchasing a MC462 amp but this buzzing sound really has me take pause.

I feel McIntosh is doing a big disservice to their customers by not adding the DC blocker, or adding one to the OP unit to make the customer whole.  The OP has a lot of money tied up in his amp to NOT use it because of the noise.  

I have dealt with our local electric company in the past and it is like pulling teeth to get any kind of satisfaction.  It took over 6 months for me to convince them that there was a power transformer across the street from my house and that the grid could easily support a 200 amp service for me.  I had to take pictures from every angle and go to a meeting with them to show there was a transformer there.  All they really had to do was go to my house and look across the street at the pole!  The OP would be fighting a losing battle with his electric co.  All they really car about is if you have power and is it safe, nothing more.

In conclusion to my rant, McIntosh should do something for this person at their cost.
gdnrbob
4,507 posts
 
@stereo5 .
+1
Bob
tomiiv30 OP
65 posts
 
And they do (Mc) read the forums and it sucks that not one of them made a contact with me to find a solution to the known problem. They were very quick to throw the ball at me saying that I have electricity problem (to which they never came to the house to test for it) and that I should deal with it, and that was the last thing I heard from them. And all they did was to tell me that I need a DC blocker to which I replied "Where do I buy one" and their reply "Search The Internet". Not even a direction to where I can buy one but they know that I need one. To my eyes they are all bunch clowns.
jea48
4,785 posts
 
@ tomiiv30 OP

I think the reason the DC blocker you got may not be working correctly is because it doesn’t have a large enough ampere rating. Does it give an, ampere rating on it anywhere? I believe you are going to need one that is made for a big power amp.

There is an Agon member that used to build DC blockers. I will see if I can find his user name.
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