Axiom Home Page Forums General Discussion Home Theater Am I going insane?

I am having a problem that is driving me crazy. It began when I hooked up a 15" driver to my left main channel to run some test tones (building DIY subwoofer). I realized I had a pronounced hum. I put my front speaker (10 plus year old B&W 2004) back on - realized there was a hum there also.

So I researched ground loop hums - possible culprits include cable TV, wrong polarity of plug, etc. After confirming the polarity of my outlets with my polarity tester, I proceeded to disconnect cable, etc.

In the end, I was left with my receiver (old Sony STR-D1090) and only my speakers. I removed all other connections to my receiver - EVERYTHING. With the volume at listening levels, there is an audible hum a few to several feet away from all speakers, although not very loud. I hook up the 15' driver - slightly louder hum. Even my rear QS8s have a hum from a few feet away. The receiver is grounded to a grounded outlet, but still there is a hum.

Note, no other funky appliances (like a bank of flourescent lights) are on in the house. The house is only 12 years old and the wiring is solid.

Is it just that my receiver a piece of crap? (yes is the default answer, but is that the problem?)

Or is this normal?

When nothing is being played through the receiver, should any hum be heard from speakers?

Any aid for my sanity will be greatly appreciated.

Pete

Do you still hear the hum if the volume is all the way down?

Yeah, that would be my question. Does the hum vary with the volume? I've heard a bit of a hum from my M50s with the volume on the H/K 525 turned almost all the way up (and nothing playing).

It's the fridge

Yes, I hear it with the volume all the way down, but it does get louder with increasing volume.

Pete_D, if I read your posts correctly, the cable tv is not the problem? Try using one outlet and see if the humming stops. If not, borrow another receiver to see if yours is having an issue.

You can try one of these. It has worked for me a few times.

To be more clear, when I turn the volume all the way down, I can still hear a hum. Granted, my ear needs to be within a few feet of the speaker to hear this.

I assume it should be completely quiet in this scenario. Right?

Right now, my polarized plug on the received is plugged into a properly polarized and grounded outlet. I also have a grounding wire running from the grounding terminal on the back of the receiver to the outlet. I have hooked this wire up to the screw on the outlet as well as inserted it into the hole for the grounding prong on the outlet itself.

It seems to me (I am no expert) that this plug may not help in my situation. Have you used it with success in this scenario?

Pete,

What you are describing is exactly how a ground loop occurs to create the hum and the "cheater plug" that has been suggested is the usual, inexpensive and effective fix. Give it a try.

Thanks Ray.

For $3, it is certainly worth a try!

You might want to try it without the grounding wire and try the cheater plug.

I've used it on a sub amp and once on an external power amp and it did the trick. BTW, they are about .59 cents at target/wal-fart/home depot etc., can't hurt to try it.

I have to use one of those "cheater" plugs with my Hsu subwoofer. Without that in place, she hums. With it...she rocks!

Same here but when I got rid of my old TV, the hum went with it. So I no longer need the cheater plug on the HSU.

Peter,

2x6 had a valid option - the fridge. Try this. Turn off every circuit breaker in the panel except for the one supplying power to the outlet that the reciever is plugged into. Unplug everything else from that circuit. If the hum is gone, turn on 1 breaker at a time until it comes back. Then, check everything plugged into that circuit that has either a motor or a power supply.

Good luck,

Great idea Mike & 2x6. I would not have thought of that myself. Plus, you get the added bonus of ending up right in front of the fridge when you are done and in need of a cold one!

Good point Michael. I took your suggestion.

I turned off all of the breakers except the one controlling the outkets in my HT. Then, I unplugged every device plugged into that circuit, except for the receiver. The receiver has nothing plugged into it except for 4 speakers.

There was still a hum!

BTW, I tried a cheater plug with no luck. I did not reverse the polarity by filing down the plug and inserting backwards, though.

Again, the hum is audible from a few feet away with the volume all the way down and then with increased volume, a hum gets louder. It actually sounds like a different hum gets louder, if that makes sense.

Here are my current theories:

1. I have unrealistic expectations of how quiet a recevier should be.

2. My old Sony receiver (and another old Sony receiver I have) have poor quality amps that produce noise.

3. I have noise in my power that is carrying though to my speakers. I previously did not believe this was possible, but I am not sure anymore.

Maybe I need an AC isolation transformer??

Help!

I'm guessing a combo of 1&2, but mostly 2. Could be very wrong, however...

Yep, I was thinking that testing another receiver in the mix might be the answer if the cheater plug didn't work. Can you borrow one from somebody just to test the theory?