1. Home
  2. amps-preamps
  3. 142371-120446

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
stereo5's avatar
stereo5
2,766 posts
 
@tomiiv30...……………………..

McIntosh winds all their transformers in house.  Don't let anyone tell you different.  I toured the factory and watched the person doing it.  This person has been doing it for over 40 years at McIntosh.
tomiiv30 OP
63 posts
 
@stereo5 

Yeah but that doesn't mean that they don't use somebody else to do the transformers for the less expensive amps like mine.
There is another one or two threads on Audiokarma with the same problem as mine.
I mean this lady is getting old and is the only one at the factory as far as I know and how much more can she do - right?
gdnrbob
2,421 posts
 
Wow, what a clam bake this turned into...
@tomiiv,
If your dealer's wiring doesn't produce hum in your amps, I don't see why he didn't have his 'electricians' check your wiring.
But, considering how you have been treated, I would be circumspect about asking them to look at your wiring.
There must be a listing of Master Electricians locally. And, one who has experience in home stereo wiring.
Bob
stereo5's avatar
stereo5
2,766 posts
 
@tomiiv30............
There are two people that wind transformers at McIntosh.  That fact that the amp doesn’t buzz at the dealer is proof the transformer isn’t defective.  Weather or not there is noise on your line I am unable to debate.  There is not a part of the McIntosh factory that works on the “cheaper” equipment.  I can say this because I have toured the factory twice.  I do think McIntosh should do the right thing and give you all your money back.  They won’t be losing anything other than a quick refurbishing and it would reinstore your faith in the company.  Shame on them for not living up to their reputation in satisfying every customer. 

vt4c
27 posts
 
Toroidal transformers has no airgap like old E I laminations or c-cores which means they have a very small stray field.
A gap will minimize the DC saturation, so yes DC is bad but how much before the toroid starts humming from saturation. As the transformer is very heavy it is possible it may have shifted in transit.
Is it epoxy potted or mounted on a rubber disc?
Make sure nothing is connected to the center bolt as this could make a secondary turn on the toroid, inducing a load or a voltage. Been there...
 
More to discover