Marantz AV7005 - serious ground loop hum

[darien87]

So just for kicks and since it was the most easily accessible, I put the cheater plug on the Behringer amp and guess what? The hum is almost gone now. I'd say it went from a 4 to a 1. I can't believe it. All that crap I went through and the solution was totally simple but not what I would have expected to work. Now I have to be within about a foot of the speakers to hear the hum. Funny thing though, I can swear I still hear it sometimes. Like I said before, once I hear something I can't seem to un-hear it.

But now at least I can put the 7005 through its paces and see if I like it enough to keep it. Thanks for all the suggestions guys.

 

[PENG]

I suppose the Behringer has a grounded chassis, i.e. truly 3 prong?

 

[AcuDefTechGuy]

So just for kicks and since it was the most easily accessible, I put the cheater plug on the Behringer amp and guess what? The hum is almost gone now. I'd say it went from a 4 to a 1. I can't believe it. All that crap I went through and the solution was totally simple but not what I would have expected to work. Now I have to be within about a foot of the speakers to hear the hum. Funny thing though, I can swear I still hear it sometimes. Like I said before, once I hear something I can't seem to un-hear it.

But now at least I can put the 7005 through its paces and see if I like it enough to keep it. Thanks for all the suggestions guys.

Told you so.

I'm trying to picture your outlet setup.

So the Belkin Surge protector connects to the wall outlet. And everything connects to the Belkin?

I would get a GF adapter for the outlet just to be safe. It's suppose to prevent electrocution.

So I would first connect the GF adapter to the outlet. Then connect the cheater plug to the GF adapter. Then connect the Belkin to the Cheater plug. Then connect everything to the Belkin.

I'm hoping that our resident electricians would chime in here.

 

[Rickster71]

the wife turned on the microwave which is in the kitchen about 30' to the right of the processor and the buzz got louder. Marantz thinks this points to an issue with my home's wiring. I would think the wiring would be good. The house is only 3 years old, but who knows.

Hey Darien, I was away for a week and missed most of this. So forgive me if this was already mentioned.
I'd start with going to home depot etc. and pick up one of these: Ideal Industries 61-035: E-Z Check Electrical Outlet Tester

It's very possible a neutral or ground connection is loose or not connected properly.
I used to always go back within a year to new panel installations and re-torque the connections.
Copper is soft and the connections, at times, need to be checked.

Since diagnosing this is really a long distance guessing game, keep in mind it will be a process of elimination.

I keep wondering if the unit it self is really a three pin with ground, and possibly (since it was an open box) someone intentionally broke off the pin at the back of the unit?
If you feel ambitious, you could unplug it and take off the cover and see if it has an internal ground wire going to the back of the plug.

 

[Adam]

I keep wondering if the unit it self is really a three pin with ground, and possibly (since it was an open box) someone intentionally broke off the pin at the back of the unit?

Nope - the image on Marantz's own site shows two pins (larger image here).

 

[Rickster71]

So just for kicks and since it was the most easily accessible, I put the cheater plug on the Behringer amp and guess what? The hum is almost gone now. I'd say it went from a 4 to a 1. I can't believe it. All that crap I went through and the solution was totally simple but not what I would have expected to work. Now I have to be within about a foot of the speakers to hear the hum. Funny thing though, I can swear I still hear it sometimes. Like I said before, once I hear something I can't seem to un-hear it.

But now at least I can put the 7005 through its paces and see if I like it enough to keep it. Thanks for all the suggestions guys.

While I agree cheater plugs are a quick and dirty fix.
They defeat the safety ground, and the real ground or neutral problem goes unchecked.
Units that come with a two pronged polarized plug are double insulated and don't need the ground pin.
A cheater plug, while it may be a short term fix. However, it leaves the chance of the outer case becoming energized, and being a shock hazard.

 

[Rickster71]

Nope - the image on Marantz's own site shows two pins (larger image here).

Thanks Adam!
That leads me to suspect a home wiring issue. A loose ground or neutral connection

 

[PENG]

While I agree cheater plugs are a quick and dirty fix.
They defeat the safety ground, and the real ground or neutral problem goes unchecked.
Units that come with a two pronged polarized plug are double insulated and don't need the ground pin.
A cheater plug, while it may be a short term fix. However, it leaves the chance of the outer case becoming energized, and being a shock hazard.

ADTG's suggestion of adding a GFCI adapter receptacle is a good one, not a 100% solution but certainly helps improve safeguard against shock hazard.

 

[PENG]

It just came to mind that for people who upgraded from a prepros that do not have a phono stage may in fact perceive the AV7005 as being more prone to ground loop. It is not necessarily more prone, but if it has a phono stage with sensitivity in the order of 2.5mV, it may inherently be more sensitive to an otherwise negligibly minor ground loop. It just a flash thought, could be completely irrelevant.

 

[darien87]

Told you so.

I'm trying to picture your outlet setup.

So the Belkin Surge protector connects to the wall outlet. And everything connects to the Belkin?

Pretty much. There are 3 outlets in the wall where my set up is. 1 up high that the TV is plugged into. 2 by the floor. 1 outlet has the Behringer plugged into it and nothing else. I did this because I figured the EP4000 needed the most power. The 3rd outlet has the Belkin and another power strip plugged into it. Plugged into the Belkin are:

AV7005
Emotiva XPA-5
Onkyo M-501
PS 3

And a couple of other things but I'm not sure which.

There are a few other things plugged into the other power strip like a couple of Netgear Ethernet to Wi-Fi adapters and the DirecTV stuff. I'm not sure but some of the DirecTV stuff might be plugged into the Belkin.

I screwed the little metal loop on the cheater plug to the screw of the outlet that it goes to. Does that re-establish the ground? I also tried moving the XPA-5 from the Belkin to the same outlet that the Behringer is plugged into since Emotiva recommends plugging their amps directly into the wall but that made the buzz come back a bit. With the XPA-5 plugged into the Belkin the buzz is quieter.

 

[darien87]

It's very possible a neutral or ground connection is loose or not connected properly.
I used to always go back within a year to new panel installations and re-torque the connections.
Copper is soft and the connections, at times, need to be checked.

I was hoping you'd chime in Rick. Thanks for the suggestion. Since the house is still under warranty I called customer service last week. Someone is supposed to be calling me to set up an appointment to check everything out.

 

[darien87]

So far I'm digging the AV7005. I ran Audyssey and got some pretty funky results though. The speaker distances were pretty close but a bit off. The crossover points it set were WAY off but I just put those where I wanted them. I don't like the EQ it came up with at all though. It sounds like a sheet was placed over my speakers. Everything just sounds dull and kind of muffled. But with the EQ off it sounds great. I haven't bothered to try to adjust the EQ manually since I've got the Carnegie's coming next week.

I've only encountered a few issues so far. I did have 1 audio drop today while watching TV. That's one of the reasons I wanted to get rid of the UMC-1.

Also, there are so many features that I don't know if I'll be able to get rid of the Marantz remote completely. Kind of a bummer. For some reason I don't get the on screen menu while watching TV through the 7005 and I'm not sure why. I'll call Marantz on Monday and see what I'm doing wrong.

But it sounds great and the HDMI switching is definitely faster than the UMC 1 and I don't have the issue of missing the first second or so of a song. The UMC always takes a couple of seconds to lock on to the audio stream and the beginning of songs would always get cut off.

 

[Rickster71]

There are 3 outlets in the wall where my set up is. 1 up high that the TV is plugged into. 2 by the floor. 1 outlet has the Behringer plugged into it and nothing else. I did this because I figured the EP4000 needed the most power. The 3rd outlet has the Belkin and another power strip plugged into it. Plugged into the Belkin are:

AV7005
Emotiva XPA-5
Onkyo M-501
PS 3

There are a few other things plugged into the other power strip like a couple of Netgear Ethernet to Wi-Fi adapters and the DirecTV stuff. I'm not sure but some of the DirecTV stuff might be plugged into the Belkin.

This may be a potential problem.
If a ground or neutral isn't as tight as it should be. they could be at different ground potentials.

I screwed the little metal loop on the cheater plug to the screw of the outlet that it goes to. Does that re-establish the ground?

It would. As long as all the other ground connections at each receptacle is tight.
What happens is, each ground connection, if not done properly, has the chance of building up resistance and having a different relationship or potential to true earth ground.

 

[Aras S]

Just an FYI. related: i had a hum issue after wiring my AV8802a with a new ATI at52xnc ... and resolved it by wiring the amp's ground to the phono ground. I verified that any copper chassis screw would have worked.

Note the AV8802a also has a 2 prong chassis port leading to a 3 prong plug. (ugh. I might modify the unit here.)