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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
4,486 posts
 
4krow65 posts01-23-2019 3:17pm

And round and round we go. It’s this, it’s that, believe me. You made a simple case for me anyway. You took the unit to 3 different houses miles apart from each other with the same humming result. What more has to said? Defective unit, no?

He took the amp to 2 other houses, not 3, and it buzzed. Was it as loud as it was in his home? I don’t remember if the OP said.
He took the amp to the dealer where he bought it. It was put on a bench in the service department, plugged in, turned on, and no buzz. The OP said it was quiet.
Defective equipment? No. McIntosh was just too tight to incorporated a DC blocker in the unit. Like I said in an earlier post I bet the design engineer designed it using a DC blocker.
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tomiiv30 OP
65 posts
 
So I took the amp to 2 of my friends houses and I meant 3 total including my house. Why this unit has no been returned is that when I took it to the dealer it was dead quite, so if I was to send it back to McIntosh I would get the same answer back as the dealers, that the unit is not defective and by all means this unit is not defective it plays music and movies very well except that the buzz is so loud you can hear it in the other room. I am not complaining about a defective unit, I am complaining that McIntosh should've invented something to put in this kind of amplifiers so when we get them we don't hear this buzz.

And as far as naming the dealer, even if I told you who sold it to me, what difference would that make. They are just a dealer and a re-seller of a high end equipment. I think IMHO that it is up to the manufacturer to make sure this units work properly everywhere in every single household no matter what electricity, since we all cannot have perfect electricity right?

I mean this dealer just started selling McIntosh like not even a year ago and they did try to resolve this problem by getting me a second new unit that did the same thing, the thing is maybe the units are working as they should it just that they have this buzz that many of us get, that's all. Some are bothered by it (like me), some aren't.
And IMO when spending this kind of money we should not deal with this kind of problems.
4krow
80 posts
 
Ok, so from reading all this and assuming that everyone did the best that they could, I would be wary of buying a Mac unit, period. All the other equipment he owns has no trouble, but this unit, and even another replacement unit does.
amg56's avatar
Ag insider logo xs@2x
amg56
887 posts
 
Isotek make a nice inline DC blocker. I have one and does the job it was bought for. A might expensive though.
vt4c
31 posts
 
Try adding large paper/oil caps in series with one of the AC line wires, the type used for running AC motors and compressors, to see if it removes the hum. If does not resolve the problem the toroid could have enough of a magnetic field to excite some nearby ferrous object. Most likely the extremely toroid has shaken loose in shipping and/or is misaligned. Check the center mounting bolt for torque.
If it really is a DC issue, then you could look up some ultraisolation transformer.
I doubt you are using much the 5KVA of the transformer. Check the efficiency rating of your speaker and measure SPL one meter from your speakers and estimate how much power you are actually using. You can also plug in a Killawatt meter from Home Depot and measure power draw. This will help find a rating for an isolation transformer.
As the problem appears with no output very little power is used. 
90 dB SPL average is more than my ears can tolerate and with 90dB 1W speakers very little average power is actually used. 20 dB peaks will be at 100W.
Most of the music energy is in the bass, where powered sub does the heavy lifting. Low frequency sounds are mostly non-directional and are mixed to mono on vinyl. So the need for stereo at low frequency is just not there, minimizing large speaker requirements, if you have a sub. This could lead to improved domestic happiness and possibly more flexible speaker placement.


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