Marantz AV7005 - serious ground loop hum

[Grador]

A cheater plug will do no harm, but it will certainly not solve the problem. It will just be lifting the ground that's not there. Effectively you would just be adding a very short length of wire to the power cable.

 

[slipperybidness]

A cheater plug will do no harm, but it will certainly not solve the problem. It will just be lifting the ground that's not there. Effectively you would just be adding a very short length of wire to the power cable.

Correct me if I'm wrong, but technically the 2-prong plugs are indeed grounded through the neutral spade of the plug. Back at the service box, the neutral is tied to earth-ground. It just doesn't have the separate ground at the outlet that is an advanced safety feature (and not required with the double-insulated chassis).

 

[Grador]

Correct me if I'm wrong, but technically the 2-prong plugs are indeed grounded through the neutral spade of the plug. Back at the service box, the neutral is tied to earth-ground. It just doesn't have the separate ground at the outlet that is an advanced safety feature (and not required with the double-insulated chassis).

I'm not an electrician, I will make no comments on double-insulated, but to my knowledge everything you've stated is correct. The cheater plug eliminates the 3rd plug used as the earth-ground safety feature while leaving the neutral intact (if the neutral were disconnected you wouldn't have a circuit to run your device).

 

[darien87]

But does a cheater plug serve any purpose if the power cord on the Marantz is aleady 2-prong? I thought you only used that on 3-prong cords?

 

[adk highlander]

I think you would want to use it on the amp or anything with a three prong to lift the ground. The balanced cables are quieter on mine than the single ended. The Marantz is not dual differential like my amp is but all I can say is it did make enough a significant difference.

 

[Grador]

But does a cheater plug serve any purpose if the power cord on the Marantz is aleady 2-prong? I thought you only used that on 3-prong cords?

As I was trying to say with my first post, none at all. A cheater plug is used so that the 3rd prong isn't connected to ground. Given that there's no 3rd plug it will do nothing.

 

[PENG]

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?

I agree "all" will have ground loop hum if there is a ground loop, that goes the same for "all" of your AVR, prepros. Preamps are quite capable of amplifying low level signal, that's their job so if there is a loop, they will do the rest. Now if you come to my house and honestly can say my 7005 has a problem you could have it for free plus my AV8001, not that you would, but you could.

 

[PENG]

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!!!

If they don't have another unit for exchange, can't you get the money back? If they said they had another one in stock, you should take your Onkyo with you to make sure you tested that other unit before taking it. If that hums too, then you can just refund the first unit.

 

[darien87]

I agree "all" will have ground loop hum if there is a ground loop, that goes the same for "all" of your AVR, prepros. Preamps are quite capable of amplifying low level signal, that's their job so if there is a loop, they will do the rest.

Well with my exact same system, I didn't have ground loop hum with my UMC-1. Just sucks that this Marantz seems to be prone to it. Guess the Emotiva has a better design in regards to ground loops. I can certainly return the unit but that's a major bummer because I got it at a good price. The salesman says he's got a 7701 for a decent price but I don't see how this one would be any different. I would assume the 7701 has the same architecture as the 7705. The techs at Marantz think that there may be something wrong with the 7705 and I could send it in for a warranty repair if something is wrong. But how long will I be out the processor? Probably 2 weeks at least.

 

[PENG]

Well with my exact same system, I didn't have ground loop hum with my UMC-1. Just sucks that this Marantz seems to be prone to it. Guess the Emotiva has a better design in regards to ground loops. I can certainly return the unit but that's a major bummer because I got it at a good price. The salesman says he's got a 7701 for a decent price but I don't see ho??w this one would be any different. I would assume the 7701 has the same architecture as the 7705. The techs at Marantz think that there may be something wrong with the 7705 and I could send it in for a warranty repair if something is wrong. But how long will I be out the processor? Probably 2 weeks at least.

Again, I am not a believer of the 7005 being prone. I think the tech is right, that there is something wrong with your unit. I repeat, if the 7005 as a whole is 'prone' how come mine is silent, with 5 different power amps already.

By the way, Rich returned an ATI that also hum, yet ADTG has a few of them that are dead silent, I guess I rest my case. So either get Marantz to fix it, or trade up or get a refund from BB.

 

[AcuDefTechGuy]

But does a cheater plug serve any purpose if the power cord on the Marantz is aleady 2-prong? I thought you only used that on 3-prong cords?

On my Denon I think the plug that goes into the wall outlet is 3-prong, even though the part that goes into the Denon is 2-prong. So I'm thinking it could still be picking up something.

I don't know why the cord is 3-prong on one end and 2-prong on the other end?

But at this point, if I were you, I would try just about anything, especially for $1 or $2.

 

[AcuDefTechGuy]

I agree "all" will have ground loop hum if there is a ground loop, that goes the same for "all" of your AVR, prepros. Preamps are quite capable of amplifying low level signal, that's their job so if there is a loop, they will do the rest. Now if you come to my house and honestly can say my 7005 has a problem you could have it for free plus my AV8001, not that you would, but you could.

I think the power is just cleaner in Canada.

In the USA, we have all kinds of hum and hiss and crap.

 

[AcuDefTechGuy]

Well with my exact same system, I didn't have ground loop hum with my UMC-1. Just sucks that this Marantz seems to be prone to it. Guess the Emotiva has a better design in regards to ground loops. I can certainly return the unit but that's a major bummer because I got it at a good price. The salesman says he's got a 7701 for a decent price but I don't see how this one would be any different. I would assume the 7701 has the same architecture as the 7705. The techs at Marantz think that there may be something wrong with the 7705 and I could send it in for a warranty repair if something is wrong. But how long will I be out the processor? Probably 2 weeks at least.

I just don't know about having to get it fixed when you just bought it.

 

[darien87]

So I called up Best Buy and they've got another one at another store that I'm going to swap out this weekend. I think I'll take Peng's advice and bring my Onkyo amp with me and have them hook it up there to see if it hums. One bummer about the 7005 though is that it won't let you set the sub crossover any lower than 80hz. I would think that's kind of high. I don't know how well that's going to integrate with my Carnegie's when I get them.

 

[PENG]

So I called up Best Buy and they've got another one at another store that I'm going to swap out this weekend. I think I'll take Peng's advice and bring my Onkyo amp with me and have them hook it up there to see if it hums. One bummer about the 7005 though is that it won't let you set the sub crossover any lower than 80hz. I would think that's kind of high. I don't know how well that's going to integrate with my Carnegie's when I get them.

If you are making the effort to bring along the Onkyo, please ask to hook it up in a quiet environment because unless the hum is really loud you may not hear it in the bestbuy shop floor even if it hums just the same as the first one. Also, I would make sure they know if the second unit does not work out, you will want your money back.

 

[PENG]

I think the power is just cleaner in Canada.

In the USA, we have all kinds of hum and hiss and crap.

But yours are dead silent, yet Rich's hummed, so I am thinking it is not that ATI is prone to the GL thing, but more likely he had ended up with one that is defective, albeit likely a very minor defect. I really wish I could be there toubleshooting for them so I don't have to guess or speculate this and that.

 

[RichB]

But yours are dead silent, yet Rich's hummed, so I am thinking it is not that ATI is prone to the GL thing, but more likely he had ended up with one that is defective, albeit likely a very minor defect. I really wish I could be there troubleshooting for them so I don't have to guess or speculate this and that.

There is transformer hum and speaker hum. I have had both but the speaker hum was tamed by connecting most components to the same circuit and using balanced connections. The transformer hum was fixed by switching to a Parasound A51.

ATI tested mine when I returned it and said there was some hum but it was so minor that they considered it to be within spec. My Outlaw 7500 traveled twice across the USA and still has quiet transformers after globe trotting.

I think it may:

• vary unit to unit,
• is related to power quality,
• can be exacerbated the environment (rug versus hardwood), and
• is subject to individual sensitivity.

BTW, in my web searches I have read hum complaints about many different amps including the Epoxy encased transformers.
I think most experience ground-loop hum which I have had with many different amps.

- Rich

 

[PENG]

There is transformer hum and speaker hum. I have had both but the speaker hum was tamed by connecting most components to the same circuit and using balanced connections. The transformer hum was fixed by switching to a Parasound A51.

ATI tested mine when I returned it and said there was some hum but it was so minor that they considered it to be within spec. My Outlaw 7500 traveled twice across the USA and still has quiet transformers after globe trotting.

I think it may:

• vary unit to unit,
• is related to power quality,
• can be exacerbated the environment (rug versus hardwood), and
• is subject to individual sensitivity.

BTW, in my web searches I have read hum complaints about many different amps including the Epoxy encased transformers.
I think most experience ground-loop hum which I have had with many different amps.

- Rich

Agree, if you sample large enough quantity of one brand, you will likely find one or more that will hum for you. So far I have been lucky, no ground loop hum whatsoever, but do have some very minor transformer hum that can only be heard when the room is totally silent and ear touching the enclosure. That, I am sure will fall within or below most manufacturer's so call within specs.

 

[darien87]

So my "instant gratification" desire kicked in last night and I ended up driving to pick up the other 7005 last night, (about an hour each way ). I got home about 8:45pm and still had to cook dinner. But I'm happy to report that I hooked up a couple of XLR cables for the hell of it and no hum. The other one hummed even with only 1 XLR cable connected. So it looks like I had a defective unit after all.

 

[j_garcia]

You said it was an open box didn't you? That's why it was an open box IMO. Someone else returned it; it probably had a bad ground and the person who returned it either damaged it or didn't bother to tell them it had hum.