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? 
I had a Halo Integrated and experienced the same issue. I used 6 different pairs of speakers with the amp, in addition to different outlets, cables and source components. I also checked the ground points inside the amp. The noise always remained at the same level, however, it was low enough that it was rarely noticeable during playback.

 The only other amps I’ve had in my system that produced similar noise were all 3 Rogue Audio integrateds. My experience led me to believe that it’s in the nature of the H-Int’s design, not a QC issue.
Thank you all for the responses.

@erik_squires , @oddiofyl
I do not have cable TV, so I am afraid that can’t be the cause. I do have cable internet and an antenna, but I have tried the integrated with those unplugged. In fact, I have literally unplugged everything in the same room and the issue persists.

I do have AVRs in my apartment (both Denon). One of them is on the same outlet and is completely quiet. So it likely is the integrated, or as @helomech mentions, it could be the design of the amp.

That said, I’m not sure if I want to accept that a $500 Denon AVR performs better than a $2,500 Parasound in that regard. Also, @stereo5 above says his Parasound Halo Integrated was dead silent. It could be that the Parasound is just more sensitive to some sort of interference, I suppose.

In an effort to take the wiring in my apartment out of the equation entirely, I will see if I can test the integrated at a friend’s house sometime this week.

In the meantime I have also emailed Parasound. I have had some communication with the CEO(!), who is asking me the usual ground loop related questions.
I also have a Halo Int, I've had it for a few weeks.  It does not have any hum, and is dead silent.  I do have it plugged into a Furman power conditioner though.

The long and the short of this is that there are several variables here, and methodologically it's really hard to pin down exactly what is happening.

1. AC quality coming into house varies.

2. Design of particular brand/model will have more or less hum.

3. Individual example of model will vary, according to quality of particular parts used to build it and the care with which it was built.

Although hum/no hum can be something of a predictor of performance of the piece of equipment in your hands in your house, it's never a guarantee that it will perform in the same way.

I am also having a hum buzz problem with my 2.1 in the phono section. The amp is integrated is about 14 months old with problem starting approximately 5 months ago.Like you I unplugged everything except the speakers problem still present, moved the amp to another area and outlet still hum. The noise seems to get louder and softer at different times, it is also much louder in the mc position(my cartridge is mc)Every other section is dead silent.