Marantz AV7005 - serious ground loop hum

[darien87]

Hey guys, I bought a Marantz AV7005 today to replace my UMC-1 and unfortunately I'm not very happy so far. I've got a FAT ground loop hum and pretty loud speaker hiss. The hum comes out of all 3 of my amps. I didn't have this issue at all with the UMC. Right now most of my electronics are hooked up to my Belkin power center. I think tomorrow I'll try plugging the Marantz directly into the wall and see if that helps. One thing though that I thought was weird is that the Marantz came with a power cord without a ground prong and the power plug in the back of the unit itself only was the 2 prongs. This seems strange to me. Also, it sucks that Marantz service is only available M-F 9-5. Don't they know most people work during the week. How am I supposed to walk through trouble shooting with them if I can't be in front of my system?

 

[Adam]

Hi, Darien. I'm not surprised by the two-prong cord on the Marantz, but only because I can't recall any of my receivers ever having three-pronged cords. I agree that it seems like they should, but they don't seem to.

You say that most of your electronics are hooked up to the same power center. Which ones aren't? Also, do you have any cable connections coming in from outside of the system (e.g. TV antenna, cable TV)? After years of never having an issue, I got a hum one day after making some changes. Long story short, it was the coax line coming from my external TV antenna. Once I routed that through my Belkin power center, the hum disappeared. The Belkin that I was using connected the coax inputs/outputs to the same ground as the electronics plugged into it, so it eliminated the hum. You might be able to do the same.

Sure, their CS might only be at work when you are...but that's why you have us.

 

[AcuDefTechGuy]

Even my AVP-A1HD & AVR-5308 don't have 3-prong.

I guess it's not even grounded to begin with since it's only a 2-prong?

If nothing works, I'd just use a cheater plug from Walmart plugged into a portable ground-fault protector plugged into the surge protector.

Anyway, nothing new with pre-pro & AVR having hum when connected to external amps. Unfortunate, but pretty common.

 

[PENG]

Even my AVP-A1HD & AVR-5308 don't have 3-prong.

I guess it's not even grounded to begin with since it's only a 2-prong?

If nothing works, I'd just use a cheater plug from Walmart plugged into a portable ground-fault protector plugged into the surge protector.

Anyway, nothing new with pre-pro & AVR having hum when connected to external amps. Unfortunate, but pretty common.

That seems true as we do see this kind of reports popping up once in a while on forums. I have had my AV7005 hooked up simultaneously to 3 separate amps or 7 if I count the 4 sub amps and never experienced any hum and hiss. I also have it individually paired with two other amps with no such issues so I highly doubt this is an inherent problem with a particular prepro or AVR pairing with separate amps.

I would suggest the OP try disconnecting everything and then start connecting one piece of gear at a time, to find out which one triggers the prepro to hum, and go from there.

 

[Irvrobinson]

Hey guys, I bought a Marantz AV7005 today to replace my UMC-1 and unfortunately I'm not very happy so far. I've got a FAT ground loop hum and pretty loud speaker hiss. The hum comes out of all 3 of my amps.

If the AV7005 isn't defective, the hum you describe is almost certainly originating in one of your sources. Disconnect them all, and reconnect them one by one. Are they both connected with HDMI?

 

[Speedskater]

Most likley the Marantz is designed to meet the Class II or double insulated electrical appliance is one which has been designed in such a way that it does not require a safety connection to electrical earth/ground rule.

The way to troubleshoot is:

a] unplug everything. AC power, interconnects and (internet, cable TV & telephone cables)(especially power conditioners)
b] use only one AC wall outlet & one outlet strip.
c] Plug-in the receiver/amp does it hum?
d] Plugin one music source at a time. interconnect then AC power. Does it hum.
e] Continue with other music sources, one at a time.
f] Then power conditioners and the like.
g] Finally internet, cable TV & telephone cables.

 

[adk highlander]

I believe the AV7005 is overly sensitive to ground loops. I have had a nearly identical experience as Darien. I had an Onkyo PR-885 with absolutely no noise, hiss or hum. Installed the AV7005 with identical setup and spent the better part of two weeks tweaking cables, connection types and outlets to get the noise to an acceptable level. I even had my dealer get me a second one with was WORSE than the first one.

 

[Cos]

I tried the AV7005 and had similar problems with it, so I ended up returning the two that I tried.
1. I had it plugged into the PVA 7 Anthem, the Speakers and that was it, it would still hiss.
2. I was able to get it down to a lower level, but still was loud enough to hear from about 4 Feet.

- Try attaching one piece of equipment to your pre pro at a time, it might be a ground loop fault in your Cable/Direct TV, so see if still hums with that unplugged

If this is the issue, i.e. no noise when its unplugged, you can get something like this that might fix the issue:

Amazon.com: Viewsonics VSIS-EU Cable TV Ground Loop Isolator: Electronics

Other Ideas have already been suggested: Good Luck

 

[Irvrobinson]

Amazing, maybe the AV7005 has some sort of design problem. Has anyone tried using the balanced connections versus the single-ended ones?

 

[PENG]

Amazing, maybe the AV7005 has some sort of design problem. Has anyone tried using the balanced connections versus the single-ended ones?

I only used the single ended rca and had no hum and hiss with multiple amps, 4 powered sub,sat box, 4 bdp, 1 hddvd, ps3 (all hdmi inputs used up), plus CV, analog inputs, and even an ext preamp connected, can't get it to hum or hiss. It can't be overly sensitive, more likely defective units. Hard to see how AK could have 2 defective units though. But if it is so sensitive, then mine would have been humming like bees. I also have my stuff plugged in to two separate 20A and 2 15A ccts.

I had even tried it with my other 2 channel system in another room pairing with a 35 years old amp, still no issue. Anyone interested in buying it?

 

[Alex2507]

Anyone interested in buying it?

The 7005? Where in Ontario? I hope it's not Thunder Bay.

 

[darien87]

Thanks for the responses guys. The only change made to the system was the addition of the AV7005. I just put that in place of the UMC-1 with all of the same connections so it sure seems like the AV7005 is the problem. I unplugged everything and none of the sources were doing it. The hum came back as soon as I tried connecting any of the pre-amp connections so that seems to be the culprit. I tried swapping different RCA cables, plugging the 7005 into different electrical sockets, I even bought a $50 Humx ground loop isolator. Nothing worked. I ordered some XLR cables from Monoprice. I'll have them on Tuesday. Hopefully that does it. But even if that works, I'm screwed on my Onkyo 2-ch amp. I need to find some way to ground the 7005 to that amp.

 

[darien87]

Here are pics of the back of the Onkyo amp and the 7005.Middle of Onkyo amp Right side of Onkyo amp Back of 7005. I don't see any type of ground plug on the back of the Onkyo amp. But the 7005 has an AM and a phono ground. Would it work if I was to attach a wire from one of the screws on the back of the Onkyo to one of those grounds on the 7005?

 

[Adam]

You might be able to use the Phono grounding post on the Marantz to connect it to other equipment. I'll leave it to the smart sparkies here to say if/how you can, though.

 

[Irvrobinson]

Thanks for the responses guys. The only change made to the system was the addition of the AV7005. I just put that in place of the UMC-1 with all of the same connections so it sure seems like the AV7005 is the problem. I unplugged everything and none of the sources were doing it. The hum came back as soon as I tried connecting any of the pre-amp connections so that seems to be the culprit. I tried swapping different RCA cables, plugging the 7005 into different electrical sockets, I even bought a $50 Humx ground loop isolator. Nothing worked. I ordered some XLR cables from Monoprice. I'll have them on Tuesday. Hopefully that does it. But even if that works, I'm screwed on my Onkyo 2-ch amp. I need to find some way to ground the 7005 to that amp.

Without knowing the implementation in the Marantz it's a shot in the dark regarding whether or not the balanced connections will make any difference. If Marantz just stuck a phase splitter in the outputs you'll just get the same hum with a slightly better SNR. But I hope it works.

 

[PENG]

The 7005? Where in Ontario? I hope it's not Thunder Bay.

Within the GTA, sort of kidding, someone is taking it already just not yet, will so find out if it would hum for him but of coure I doubt that..

 

[PENG]

Right side of Onkyo amp Back of 7005. I don't see any type of ground plug on the back of the Onkyo amp. But the 7005 has an AM and a phono ground. Would it work if I was to attach a wire from one of the screws on the back of the Onkyo to one of those grounds on the 7005?

No harm trying but I bet it will not work. Do you have another amp to try? If it does that with another amp then you should contact Marantz and see what they have to say and try to get it replaced on warranty. The reason why I responded the way I did in my previous post was to let you know that it is highly unlikely the 7005 would be inherently (by design) more ground loop sensitive that others because it it was then I should have been experienced such hum for the fact I have so many things connected to it, including all of the preouts, zone 2, and other analog outs. Once you have this issue resolve you will love this prepro, it worked well and to me it sounded every bit as good as my more expensive 8801 except the XT32 did fix my most of my bass dip issues that the 7005 couldn't.

I think if you Google hard enough you will find people experienced such hum regardless of which prepro they own. The AV7005 happens to be probably one of the most popular prepro sold in recent years due to its price point and the perception (IMO just a perception) that Marantz = SQ first. So more units so, equate to more defects/issues reported, I am just speculating though. My suggestion is that you should push to get a replacement unit before giving up on this great prepro (relative to its price), but at least try a different amp first.

 

[darien87]

No harm trying but I bet it will not work. Do you have another amp to try?

My Emotiva XPA-5 also hums. Come to think of it, I think that at first I might even have had hum from my EP4000 and that it connected with an XLR cable so maybe the XLR cables won't work after all. Crap!

 

[darien87]

Just called Marantz and the tech guy thinks there's a grounding issue in the AV7005 itself. He recommended I get it exchanged but I don't know if Best Buy will do that since it was an open box. I guess worst case scenario is I can ship it to Marantz to repair. The closest service center to me is in Sacramento!!!

 

[AcuDefTechGuy]

Just called Marantz and the tech guy thinks there's a grounding issue in the AV7005 itself. He recommended I get it exchanged but I don't know if Best Buy will do that since it was an open box. I guess worst case scenario is I can ship it to Marantz to repair. The closest service center to me is in Sacramento!!!

You bought it from Best Buy?

Did you go to Wal-Mart or Home Depot and get a $1 cheater plug to diagnose ?

I bet it will eliminate the hum.

Tell BB you've talked to Marantz and they recommend you get it exchanged.

I think all of the Marantz AV7005 units will have ground loop hum. Some systems are just more prone. Unfortunately, your system is one.

My question for our local electricians is, since these units have 2-prong and are NOT grounded anyway, would a "cheater plug" do any harm if they work to remove the hum?