Axiom Home Page Forums General Discussion Home Theater Help!! I have a sudden "mystery" hum from my EP500

Been enjoying my EP500 for a year now w/no issues. All of a sudden when I turn it on now, I get a very low level faint hum. When I turn the Yamaha Receiver on the hum intensifies quite a bit. I know this sounds like a ground loop, but NOTHING has changed w/my equipment and all connections seem firm? When I unplug the RCA cable from the receiver to the sub, but leave the power on the sub, the hum completely disappears? What has happened?

Thanks guys!

Do you have a dog or a cat that might have been chewing on the cable?

Try a different cable and see what happens.

darthkringle,

If the hum disappears from the EP500 when you unplug the coaxial sub cable, then there is nothing wrong with the EP500. Look on the back of the 500 for a Ground Screw. If you remove that, it may help.

Otherwise, you might have to insert a ground-lift transformer on your cable-TV input. Try disconnecting your cable or video antenna or satellite feed and see if the hum disappears. If it does, then that's the source of the ground loop.

Regards,

Alan- Thanks as always. Removing the Ground Screw did in fact help. Any ideas on why I would suddenly have a ground loop issue after a year and my equipment has not changed? Thanks!!

that is a good question, I was going to mention the screw also as it is mentioned in the pamphlet that comes with the 500/600.

Do you have a surge/line conditioner in your setup, this may help.

Randy

Alan,

What does this screw do? Seperate the amp from the mains ground? Does that make it 'float' and ground via the RCA to the AVR? I have to look - is there a screw on the 350?

This past weekend I had a hum problem with my EP350. I heard it regardless of whether the sub was on or not, and unplugging the RCA OR the power from the wall eliminated it. What I ended up doing was running an extension cord from the sub to the same surge suppressor/power strip my AVR is plugged in to. That fixed it, and i suspect the power strip isolated ground in some way. Now everything is plugged into the same strip.

-Brian

n8wrl,

Something like you describe. Without asking Tom, our engineer, I'm not sure what it exactly does, but it does not endanger anyone in terms of electrical shock (like putting a "cheater" on a 3-way plug does). I don't think there is a ground-lift screw on the 350.

Glad you solved your problem.

Regards,

darth,

Good. No idea why you suddenly got a ground-loop unless something subtle changed in your system. Perhaps you connected some video-related device or disconnected an aging VCR or something like that. Even a tiny shift in the ground potential will cause a hum.

Regards,

Hi. I had a bad ground loop hum. Removing the "screw" didn't help much. I ended up buying a SUB1RR from Jenson to isolate the sub from the receiver. The SUB1RR was expensive, about $100US, but it got rid of the hum. I subsequently purchased a surge protector. It seems that the surge protector by itself also removes the hum.
Too bad I wasted the $100.

Yes - this is a common problem on computer sound cards as well. A simple 1:1 isolation transformer on the audio lines is all you really need - that was going to be my next try if the extension cord didn't fix it.

-Brian