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_
Even if you were not within the return period, Parasound’s warranty is one of the best I have ever seen. They are extremely pleasant to deal with and will go out of their way to make things right. I would just ask AudioAdvisor for a new unit. I’m really a fan of the Halo Integrated.
I had some more contact with the folks at Audio Advisor. I had to follow up, but they are actually really nice folks to work with. They were willing to get a new unit and listen to it themselves before shipping anything out. They claimed the unit they listened to still had some noise, but was (according to their technician) slightly less bad. I ended up agreeing to having the new unit sent over, figuring it was within spec.

It turns out this new unit is much better than the one I returned. In a quiet room, if I literally put my ear within an inch or two of the driver I can still pick up a very faint hum but much less than it was before. If I remove my ear more than a few inches, however, it becomes inaudible. 

So it appears this hum does vary from unit to unit and what I have picked up on is probably within spec. That said, I would never have heard it on this new unit and I am happy with what I got.

It was nice of Audio Advisor to send me a new unit to replace my refurbished unit. Customer service from Parasound and Audio Advisor has been outstanding.