Ground Cheater plug or....

Maybe this isn't a good idea, but I thought I'd ask anyway.

I have what I believe to be a persistent ground loop hum from my amplifier. It's quiet, inaudible if music playing or unless you're standing next to the speaker, but knowing it's there is annoying.

I've heard suggestions to use a cheater plug to defeat the ground, but it seems counterintuitive to stick a 35cent plastic plug between expensive cables and power supplies. My question is, couldn't you accomplish the same thing by disconnecting the ground wire in the outlet, and still exact the benefits of better cables?

I'm sure the fire marshall would disapprove, but I'd like to hear what the hi-fi nuts have to say.

If you believe the cable vendor's explanation of why an expensive three foot cable makes a difference at the end of a power line chain dozens of miles long, then using an inexpensive cheater plug between your ordinary wall outlet and the three foot über-cable should not diminish the impact of the über-cable on your system.
A couple of things you could do. One use the cheater plug, if you are using a standard wall outlet then there is an additional inch of the same grade of copper, brass etc that is used in the outlet. So you won't lose much from a performance standpoint. The trade off on the performance difference should be outweighed by the elimination of the hum. Two, try to wrap the ground pin in a thin layer of electrical tape to insulate the ground from conductivity. Make sure you leave enough tape on the plug itself so the tape can be pulled from the outlet whenever you move that cord for any reason. I would not disconnect the ground for a couple reasons. If you ever move and forget to reconnect it or you lose grounding for the other plug in on that outlet.
Try the cheater plug and see if that does away with hum,if it does take it off and unplug each component one at a time and see if you lose the hum. This way you can verify what is causing the hum. If it is your amp and it not audible when playing music I would not worry about it.
Someone clearly needs to produce an "audiophile" cheater plug for 50 bucks or so :-)
Grimace, you can get hum in many ways.

Sometimes it is because the system components are plugged into different breakers.
My JL Audio subs will hum because they are plugged into a different dedicated circuit and they are on the opposite side of the breaker box than the rest of the system. But once the rest of the system is wired up and powered on the hum goes away completely.

But many times it is caused by cable TV connections.
Be it interconnects, power cables etc. You can buy isolation adapters that connect to the cable coax that will eliminate that hum.

With all that being said, and if all else fails, hum can drive me absolutely crazy. If it could be determined which component is causing the hum, then I would disconnect the ground in the outlet that component is plugged into.
Here's another option & one I use myself on my CDP. Buy a Volex cord which is very good for around $7 from Newark & cut the grounding pin off w/some stout wire cutters. I do prefer to have my amp grounded. PS Audio & TG Audio sell ungrounded cords I believe.
On some PS Audio power cords you can remove the grounding pin.
I've been through all the components. The hum remains even if the ICs are disconnected from the amp. There are a lot of items in that room though: lamps, TV, ROKU box, DVD players, two seperate power supplies. The only thing I haven't tried is taking the amp to a different room/circuit breaker, mostly because I'm too lazy to haul the entire system along to test it.

RDav... you shouldn't assume that because someone is using aftermarket cables that they foolishly dropped a mortgage payment on them. There's nothing "uber" about my PCs, but at about $100 bucks they were an audible improvement over stock cords. Sorry if your hearing isn't that good. Maybe you should take up knitting.
Absolutely do not use cheater plugs. They defeat the ground that is there to protect you, your equipment, kids, wife, girl friend in the event of an electrical fault. Find and fix the electrical problem causing the need for a ground loop. Be it, bad interconnect cables, bad electronics, bad ground system in your home, however, you will find many people telling you to use cheaters. You are asking for trouble if you do this. No electrician in their right mind would tell you to defeat the home ground system by using cheater. It is relatively easy to find the cause of the problem, isolate it and fix or replace it.

if you have a hum or ground loop, I can tell you how to systematically find it, isolate it and what you can do to get rid of it. But do not use cheaters.

The hum remains even if the ICs are disconnected from the amp.
Then the hum is most likely not being caused by a ground loop, and it most likely would not be fixed by either a cheater plug or by disconnecting the safety ground inside the outlet.

The reason I say "most likely" is that there is a SLIGHT possibility that the hum is being induced by two different means in the two situations. By a ground loop when the preamp is connected, and by pickup of emi (electromagnetic interference) when it is not. With nothing connected to the amp inputs the possibility of emi pickup is increased, because without the preamp being connected the impedance at the amp inputs corresponds to the high input impedance of the amp, rather than the much lower output impedance of the preamp.

My suspicion is that the amp itself is generating the hum. To confirm that, put shorting plugs on its inputs, and turn off or unplug everything else that is nearby, that could conceivably be a source of emi. If you don't have shorting plugs, and assuming the interconnects are unbalanced, connect them to the amp, leave their other ends unconnected, and WHILE THE AMP IS TURNED OFF stuff some aluminum foil into the unconnected ends to short the RCA center pin and ground sleeve together. Make sure that the foil is securely in place, so that it won't dislodge when you turn the amp on. Do not let anything or anyone touch the RCA plugs while the amp is on. And after assessing the hum level do not remove the foil until a minute or more after you have turned the amp off.

Also, this paper may be of interest.

Finally, as I see it creating a code violation inside of an electrical outlet, where it might be forgotten about in the future, severely compounds the already non-negligible risk that using a cheater would represent.

-- Al
If you have cable or satelite hooked up on a dual use rig like many here unplug incoming signal wire to box and if hum is gone fix the earth ground, usually company will fix for free.
Just run a long extension ac cable from your amp to another outlet that you know is on a different circuit.This way you don't have to move your amp.
OMG Dopogue, I almost fell out of the chair laughing. They'll be shipping by next week and carried by Music Direct.
There is an audiophile cheater plug (IMO) that I employed in one of my systems because I was just too lazy to do the proper troubleshooting.

Ebtech Hum X - Plug-Style AC Voltage Ground Loop Hum Eliminator

The same effects of the cheater plug but safe.

Prices range from $60 to $90 depending on where you shop.
The hum remains even if the ICs are disconnected from the amp.


I agree with everything Al said.

I would add if the sound heard is truly a hum the problem could be a bad electrolytic cap/s in the power supply.
An oscilloscope connected to the DC output of the PS would tell you for sure.
The only audiophile cheater plug that I know if is the Ebtech Hum X. It retails for $60-$90 depending on the retailer you go to. It lifts the ground without any of the unsafe effects. I use it in one of my systems when I got too lazy to troubleshoot the hum I was hearing from my speakers.
Al is correct. This will not be solved by cheating the ground. Grimace, you've not mentioned your speakers; if they have an efficiency of over 100db or if your room is really really quiet this might be perfectly normal.
speakers are 89db Spendor S8e. I can only hear the hum from the listening position if there is no ambient noise - i.e. the fridge is not cycling - or if I'm standing right next to them, but not when music is playing. I sent the amp in for service and Cary said this was normal, but I'm not convinced. They said they weren't able to duplicate the hum.
great thread, commenting here so it is parked in my threads.
The plot thickens. I took the amp to a local tech who a) could not duplicate the hum and b) could not find anything wrong with the amp - although he did say it sounded very nice. Not quite believing it, I went and listened for myself, and he was right.

So, since that is now two places - Cary and my local guy - who've been unable to duplicate the hum, I guess that points to something in my AC system causing the problem.

So now what? Dedicated line? turning off the fridge is not an option.
In addition, I figured out which circuit the hi-fi is on, turned everything else in the house off, as well as unplugging everything else in the room, and the amp still hummed.

I also used a ground tester and the outlets were showing that they were in fact grounded.

Why not try a PS audio humbuster ?
I use cheaters on my mono blocks to solve the same issues - nothing else worked!

When you sent the amp to Cary did you also send along the power cord that is used on the amp?

How about the repair shop. Did you take the power cord with the amp?

I assume you have a multimeter.

(1) With the amp turned on measure the AC voltage at the wall duplex receptacle.

(2) With nothing plugged into the duplex receptacle measure the AC voltage.

(3) Check the AC voltage from the hot contact to the equipment ground contact.

(4) Check for AC voltage from the neutral contact to the equipment ground contact...
Make sure the meter is set to AC auto.
Make sure both meter test probes are making good contact.

Post back the measurements.
I had the same problem. Cause was the fact that one of my amps uses a grounded plug, the other not and they live on the same circuit, unfortunately. You may want to look to see if you have a similar situation. Two and 3 prong devices on the same circuit can cause this problem. Start disconnecting and reconnecting stuff and you will probably find out what is doing it. Chances are nothing is broken. I wound up using a cheater. No fires so far (10 years)
Yes all devices you have are grounded, some are chassis grounds (2 prong devices) and some externally(3 prong). The problem is that these grounds are just different enough to create a small current flow when they are on the same circuit and that is what you hear as 60 Hz hum. Rewiring all to be 3 prong will most likely fix, but that is pretty extreme. Not saying this is your issue, just that it was mine.
So here's what fixed it. I switched pre-amps, and suddenly the amp was quiet, but when I turned on the pre-amp the hum came back. It had mysteriously jumped between components! To finally get it to settle down, I stuck a cheater plug between the pre-amp and the power supply - the PS is still grounded at the wall - and that fixed it. I don't hear any sonic degradation from the cheater. Cheaters seem to be controversial, but at this point, and since the PS is still grounded, I'm not arguing. But hell's bells. it took a year to figure out.
Did you ever try shorting the amp's inputs, as I had suggested? Doing that would probably have led to the conclusion (which now appears to have been the case) that the hum that was heard while nothing was connected to the amp's inputs did not have the same cause as the hum that was heard while the preamp was connected. Knowing that would probably have led to a much quicker resolution. See my post dated 3-30-12.

Regarding the safety aspects of using a cheater, IMO it's your call. While the risk is very small, assuming that the equipment is in good condition, it can't be said that the risk is zero. And if that very small risk were to materialize the consequences could be very serious.

-- Al
Well again, the power supply - a PS Audio something-or-other - is still grounded. The cheater is between the preamp and the power supply, and the power supply still has a protection circuit, so I think the risk is pretty low. The amp, which is the big power draw, is still grounded.

I might check on the polarity thing though. It couldn't hurt.
I might check on the polarity thing though. It couldn't hurt.
07-30-12: Grimace


One of the questions I asked in my last post about the power cord used on the power amp.

There have been instances where the AC polarity of an aftermarket PC was reversed at the female IEC connector.

That is why I asked you if you sent the PC you use on the amp with the amp when you sent it to Cary........

You can check the polarity of the PC with a simple continuity test.
I didn't check the cord, but I did switch out my aftermarket PCs with the factory stock, in various combinations, and the hum remained.