Parasound Halo Integrated Buzz/Hum


Hi all. I bought a Parasound Halo Integrated last week and discovered there is a faint low frequency buzz coming from my speakers from all inputs except the home theater bypass (more on that below). In a completely silent room I can hear it from my listening position about 8ft away from the speakers, but it's not very loud at all. After a quick Google search and some reading, the most likely cause seems to be a ground loop issue.

Unfortunately, I am not sure if it is as simple as that. I disconnected all inputs and plugged it in an outlet with no other devices connected. I also moved it to a different outlet in my apartment, again with only speakers connected, and it still buzzes. Different model speakers have been tested as well.

The buzz only comes from the speakers, not from the amp itself or if headphones are plugged in. This integrated amp has home theater bypass inputs and there is no buzz when this input is selected. However, if I connect my AVR to these inputs, there is a buzz. This buzz can also be heard through headphones connected to the Parasound. Unlike the buzz from other inputs, this buzz does not increase when I increase the volume.

My apartment is in an old building, which in all likelihood had its wiring redone over the past decade or so. I used a 3 wire receptacle tester on some of the outlets. It indicates there is an open ground in my living room (something I should probably bring to my landlord's attention!), but other outlets appear to be wired correctly. The buzz is there regardless of what outlet I use, however.

The amp was bought from an authorized dealer and I am still under warranty, so I can certainly get it replaced or repaired. Before I do that, however, I would like to make sure I have exhausted all of my options. Do any of you knowledgeable folks have any idea if I am missing something? 
tod_
AC power quality is not the issue. I’ve worked in mitigating ground loop and EMI noise in avionics for years, and I’m sorry to say the problem is in the amp. The AC coming into my home is as clean as any. I checked the internals of my Halo Integrated thoroughly and I could only conclude that the amp has a less-than-ideal circuit layout or connection issue that would require extensive disassembly to find.

If you Google some internal pics of the H-Int, you’ll notice there’s some variation to the wire routing. I know they also had a rash of bad volume pots in some of these amps (though that’s not the culprit in this case). So I’ll retract my prior statement and say that it is potentially a QC issue, but I think it’s far more likely that they simply revised portions of the design/layout at some point.




@helomech
I fully expect it to be the amp as well. I will still test it at a friend's house, just to be sure. If it also hums there, which I expect, I will contact the dealer. Thanks for your input. 
Quick update:
The Parasound CEO actually had someone from the dealer cc'd on our correspondence. He asked the dealer to have it shipped back. They are mailing me a label and I will return it at some point next week. Everyone involved seems really pleasant, thankfully. I am hopeful I will end up with a dead silent unit.
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