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
6,563 posts
 
I don’t believe anyone commenting here is a licensed electrician for your area nor knows your areas electrical codes.   I would trust your licensed electrician before any of us.  While everyone is trying to be helpful, we are merely speculating at best.   If everyone got to you and you are truly worried, have a different licensed electrician come by to look at everything for a second opinion.   It will be money well spent for your piece of mind.  

Do do you still have the Mac amp or did you take the refund?
tomiiv30 OP
65 posts
 
@stereo5 

I still have the amp, a member of another forum sent me his two Emotiva CMX2 DC blockers and told me to put them in series and after doing so there is still buzz in the amp but quieter than without the dc blockers. 
Couldn't return it because I was over my returning period. The sales man could do so much, management would not even bother look into my matter, McIntosh is nowhere to be found.

It was an expensive learning experience for me and was a first one for me. 
jea48
4,736 posts
 
stereo52,661 posts01-21-2019 6:16pm


I don’t believe anyone commenting here is a licensed electrician for your area nor knows your areas electrical codes. I would trust your licensed electrician before any of us. While everyone is trying to be helpful, we are merely speculating at best. If everyone got to you and you are truly worried, have a different licensed electrician come by to look at everything for a second opinion. It will be money well spent for your piece of mind.

I will bet you the AHJ in Chicago does not allow the equipment grounding conductor of an IG receptacle to be connected to an isolated earthed ground rod as the OP described the electrician did it.

OP said:
The other 20 amp outlet is grounded directly from the outlet to the outside rod with a clamp that is attached to the rod itself, I saw that with my own eyes. It is a straight wire that goes from the outlet to the outside and has nothing to do with the inside panel or anything else in the house.

OP said:
What is the difference between the ground wire that is connected to the panel itself and the one that goes to the outside, it still goes thru the panel but it is not attached to the panel itself it just goes thru the pipe that goes outside where the meter is and from there it is attached to the rod.

//


2014 NEC® section 250.146 Connecting Receptacle Grounding Terminal to Box


(D) Isolated Ground Receptacles


Where installed for the reduction of electrical noise (electromagnetic interference) on the grounding circuit, a receptacle in which the grounding terminal is purposely insulated from the receptacle mounting means may be permitted. The receptacle grounding terminal shall be connected to an insulated equipment grounding conductor run with the circuit conductors. This equipment grounding conductor shall be permitted to pass through one or more panel boards without a connection to the panel board grounding terminal bar as permitted in 408.40, Exception, so as to terminate within the same building or structure directly at an equipment grounding conductor terminal of the applicable derived system or service. Where installed in accordance with the provisions of this section, this equipment grounding conductor shall also be permitted to pass through boxes, wireways, or other enclosures without being connected to such enclosures
http://www.cooperindustries.com/content/dam/public/wiringdevices/BuyersGuides/AHBG/I/AHBG-I-09.pdf

Wording is word for word right out of 2014 NEC, page 70-133.

Nothing said about connecting the equipment grounding conductor to a ground rod.
I see no NEC exception given for the OP’s electrician. I also doubt the Chicago AHJ would approve what the guy did either. It’s dangerous! Surely you would agree?

AS for the OP getting another electrician out to house I agree he should. First thing he should do is land the IG equipment grounding conductor on the ground bar in the service electrical panel where it should have been landed in the first place. Then the OP should have the electrician inspect the rest of the work the other guy did.

.
jea48
4,736 posts
 
@ tomiiv30 OP


Chicago? I didn’t think the city of Chicago AHJ allowed NM sheathed cable, (Romex is a manufacturer’s Trade Name for NM), in residential occupancies. My understanding all branch circuit wiring has to be installed in EMT conduit. Did the electrician install Romex? Is your house wired with Romex? Do you actually live within the city limits of Chicago? 
Jim
.
cleeds
6,186 posts
 
jea48
Chicago? I didn’t think the city of Chicago AHJ allowed NM sheathed cable ...
If this guy lives in Chicago, then the work he described would require an electrical construction permit from the city. It would also require that an electrical inspector approve the work before the circuit could be energized. While the permit may cost a few $$$, it would be cheap insurance against the sort of hazardous connections described here.
More to discover