Axiom Home Page Forums General Discussion Technical Questions PLESE HELP!!! EP-500 ands Denon 3805

I have DENON 3805, A 60VS810 Hitachi Rear LCD TV, 6 Axiom speakers and a EP-500 sub. Here's my issue. For SOME reason, I get a ground loop hum when the sub is connected. If I removethe ground loop screw from the sub, it reduces about 85% but it is still there. When I replace the ground loop screw AND add a 2 prog connector to the 3 prong AC sub plug, then the the hum goes away (but, this does not seem right since I should not have to add this. AND, the sound from the sub seems muddy. Also, just a background, all AV equipment is on a dedicated AC line with it's own circuit (no other appliances, lights etc on the circuit) AND I am using a Brick Wall Surge protector. Now here's where it gets even more bizzare -

I am without a doubt getting a magnetic field issue because I get nothing but an rumbling-type interference from the tuner when it is tuned to FM. AM is not really any better. The farther away I move the sub (it was never closer to RCVR than 5 ft), the slightly better the reception is but it is nowhere near of listening quality. The farthest I can move it it 13 ft and it was about 40% better but still, full of interference, runmbling etc.

Rearding other sources - The TV, CD etc. seem to work with sub but the sound is a bit muddy and unclear.

OK, part three - Axiom replaced the sub with a new one - SAME ISSUE! Today I am returning the Denon Receiver for a new one. (ABT electronics - also awesome guys to do business with)

All the equipment, cables etc are 3 weeks old.

I have done all the following troubleshooting -
1 - tried a different AC outlet
2- Tried a different RCA shielded sub cable
3 - Did NOT use the surrge protector
4- Tried a different AC outlet on a different circuit with combinations of items 2 and 3 above.
5 - Tried a GFI outlet - tried a non-GFI outlet.
6 - Tried bypass of crossover ; tried different ohm settings.
7) Disconnected all speakers except sub, tried various combinations.

I am calling Axiom today - is it possible I received two defective subs? That seems totally unlikely to me. Is the sub too bug for my room (16x20)? Is it normal to get such a strong magnetic force?

I am so lost and confused! I have spent over 8K and get tune in a radio station! I am also not convinced the muddiness I am getting from other components from the sub is how it should be responding.

What can I do next? The Axiom guys have been great but I don't want to have them keep paying for shipping this thing back and forth if there's something I'm doing wrong.

Please, PLEASE HELP!!!

Just checking -- does the interference with FM/AM go away when power is disconnected from the sub ?

Yes, it does.

Also, the room is about 16 x 18 or so.

Sorry... I got so tired of people asking "what kind of speakers should I get" without describing their room that I just added "how big is your room ?" to my signature

Do you have cable?

If so, have you tried disconnecting that from your system completely?

Check out this thread and this one and finally this one.

Sounds like it might be a ground loop problem and a cheater plug usually solves that (pretty cheap solution). Take a look at this thread and click on the cheater plug link that is provided.

Ok -

I am using a "cheater Plug" - 2 prong.

I have also disconnects all the cable TV as I know this is often the source of ground loop hum issues.

Still.. I'mm getting this, (what I am guessing is) magnetic interference. Also, with respect to the "cheater plug".. shoul I really have to do this? Aren't I defeating the ground if I use this?

kemrt23:
Boy! I am really interested in the outcome of this thread. I have almost the exact same situation occuring, except for the magnetic interference. But this I'll have to check on since I rarely listen to radio. At first I thought the cable tv was the culprit as when it was disconnected, the humming stopped. I purchased an isolator for it and everything seemed fine until a couple of days later the humming returned, though not as loud. When I removed the ground loop screw on the 500, the humming grew much louder. I disonnected all equipment except the 3805 and the 500, but it remained. I even went so far as to turn off all circuits. Did not help. The only thing I have not done is to remove all items from the back of the 3805. I'll do that today.

Let us know how the replacent 3805 does.

In reply to:

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Also, with respect to the "cheater plug".. shoul I really have to do this? Aren't I defeating the ground if I use this?

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I don't believe so. I could be wrong about this, my knowledge of this is pretty hazy, and those with more knowledge will correct me if I lead you astray.

The hum is caused by having TWO paths to ground, one through the third prong on your sub's cord, and one back through the wire connecting your sub to the receiver, which also has a ground connection. By using the cheater plug you merely lift one of those paths to ground. The other is still in effect, and grounding your sub. I hope I've got that right. All I know is I've been using cheater plugs for 40 years and have never had problems.

You can read more about ground loops here, and here, and other hum problems here.

Nowhere in these tutorials will you find them recommending using a cheater plug. They can't do that because it's "cheating."