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

Showing 4 responses by atmasphere

Amplifier buzz is a thing to fix- but it really shouldn't have anything to do with the electrical system.
I wish there was a video or some kind of a drawing of how to make this simple low-pass filter device but yet too complicated for me and some others.
I am a graphics designer by trade and not an electrician but I am willing to give a go to make one I am no afraid but only if I see it how it is made. I do have a soldering Iron and solder plus those alligator clips so I am half way there.

Google, first hit:

https://www.stereo.net.au/forums/topic/75460-diy-main-dc-blocker/
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.
Not all transformers will respond the same.
+1
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.
DC on the line is caused by things like an electric heater that is only running at half power and so only using half of the AC waveform. That causes that half to be lower amplitude- thus the DC on the line.
Its solved by a DC blocker, which is a simple and inexpensive circuit. Why Mac didn't include that in the amplifier, when toroids are known for being particularly sensitive to DC (and thus make a substantial amount of noise) is curious to say the least.

IOW the amp may be perfectly fine. The DC Blocker can be installed in the outlet junction box, or it can be a separate box of its own. Its probably a good idea to find one and try it, as its likely less expensive than the shipping of the amp.