New cable=subwoofer buzz

[DS]

My home theatre system came with a powered subwoofer and a 4' RCA cable to
hook it up to the receiver. It always had a very quiet hum (you could barely
even make it out if your ear was right next to it), but it was low enough
that the autosensing power circuit would turn it off.

I recently moved the room around and picked up a longer cable (24' to get it
to the other side of the room along the baseboards). Now I get a quiet (but
noticible) hum all the time and the autosensing power circuit doesn't power
it down. This is regardless of if the receiver is on or not.

Even if I run the cable across the carpet it still has the hum. Could I put
some sort of filter on the subwoofers end to get rid of this interference?
If so, how do I go about making it?

Thanks in advance..
-Dan

 

[Little Monster]

On Sun, 23 May 2004 21:28:09 +0000, the world was enlightented by DS, unto
whom the words are attributed:

My home theatre system came with a powered subwoofer and a 4' RCA cable to
hook it up to the receiver. It always had a very quiet hum (you could barely
even make it out if your ear was right next to it), but it was low enough
that the autosensing power circuit would turn it off.

I recently moved the room around and picked up a longer cable (24' to get it
to the other side of the room along the baseboards). Now I get a quiet (but
noticible) hum all the time and the autosensing power circuit doesn't power
it down. This is regardless of if the receiver is on or not.

Even if I run the cable across the carpet it still has the hum. Could I put
some sort of filter on the subwoofers end to get rid of this interference?
If so, how do I go about making it?

Thanks in advance..
-Dan

Your cable is acting as a great big antenna to pick the mains frequency!
Why not shield it? Or use shielded cable? You only need to wrap it in
foil, for example, and connect the foil to an earth connection at the
reciever end. Simpler than building some kind of LF bandstop filter. If
that doesn't work, one of the guru's on here will have to help out...

Monster
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http://www.the-monstruum.co.uk

 

[Jim Thompson]

On Mon, 24 May 2004 20:38:35 GMT, Little Monster
<root@localhost.localdomain> wrote:

On Sun, 23 May 2004 21:28:09 +0000, the world was enlightented by DS, unto
whom the words are attributed:

My home theatre system came with a powered subwoofer and a 4' RCA cable to
hook it up to the receiver. It always had a very quiet hum (you could barely
even make it out if your ear was right next to it), but it was low enough
that the autosensing power circuit would turn it off.

I recently moved the room around and picked up a longer cable (24' to get it
to the other side of the room along the baseboards). Now I get a quiet (but
noticible) hum all the time and the autosensing power circuit doesn't power
it down. This is regardless of if the receiver is on or not.

Even if I run the cable across the carpet it still has the hum. Could I put
some sort of filter on the subwoofers end to get rid of this interference?
If so, how do I go about making it?

Thanks in advance..
-Dan

Your cable is acting as a great big antenna to pick the mains frequency!
Why not shield it? Or use shielded cable? You only need to wrap it in
foil, for example, and connect the foil to an earth connection at the
reciever end. Simpler than building some kind of LF bandstop filter. If
that doesn't work, one of the guru's on here will have to help out...

Monster

The receptacle across the room is probably on the other phase or has
hot and common reversed. Check it out with a receptacle tester.

Might also try and audio transformer at the _source_ end. Ground
cable _only_ at the woofer end.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
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