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Talking Sub with components turned off.

post #1 of 20
Thread Starter 
Hi guys,

Have a bit of a problem that I was hoping you all could help me with.

System : Pioneer LX-53 amplifier with Kef KHT2005 system with second Yamaha sub conected via a Y spliter. The Kef sub is at the rear of the room ved via RG6 quad sheild cable with audio plates at each end.

I have recently upgraded my amp to the LX53 wihich I must say is very good. I noticed the other day that my KEF sub was not automatically powering down to standby which at always used to do. I did notice that it still had a slight hum to it with all the components in standby. I went to the back of the amp expecting there to be some kind of interference from a power cord. As I was moving the Y splitter I started to hear muffled voices from the SUB (Kef Only). All the components i.e. set top box, amp etc. were in standby (off).
Any Ideas what could be causing this?
post #2 of 20
Quote:
Originally Posted by Doogsy View Post

Hi guys,

Have a bit of a problem that I was hoping you all could help me with.

System : Pioneer LX-53 amplifier with Kef KHT2005 system with second Yamaha sub conected via a Y spliter. The Kef sub is at the rear of the room ved via RG6 quad sheild cable with audio plates at each end.

I have recently upgraded my amp to the LX53 wihich I must say is very good. I noticed the other day that my KEF sub was not automatically powering down to standby which at always used to do. I did notice that it still had a slight hum to it with all the components in standby. I went to the back of the amp expecting there to be some kind of interference from a power cord. As I was moving the Y splitter I started to hear muffled voices from the SUB (Kef Only). All the components i.e. set top box, amp etc. were in standby (off).
Any Ideas what could be causing this?

If the cable run is long and not shielded properly you may be picking up a radio station.
post #3 of 20
Thread Starter 
It did sound like a radio station. But it is quad sheild cable and it never used to do it.
post #4 of 20
Thread Starter 
This is the first time it has happend in 3.5 years.
post #5 of 20
Quote:
Originally Posted by Doogsy View Post

This is the first time it has happend in 3.5 years.

That should be shield enough does it do it with the cable disconnected from the sub?
post #6 of 20
Thread Starter 
No. I can get the voices to disapear if I move around the cabling at the back of the amp where it connects to the wall plate. But I cannot get rid of noise completely (with all components switched off)
post #7 of 20
Just to clarify here: You said "quad shield cable" but you also said "wall plate"... Is the cable run inside the wall also quad shielded?

Have you tried disconnecting at the other end of the run closer to your amp or receiver?
post #8 of 20
Thread Starter 
I Istalled the run of quad sheild when I had the house built to allow me to have a sub at the rear of the room. The run is aprox 12 meters. THis terminates to a wall plate at each end. at the sub end I have a standard audio conector from wall plate to sub. At the receiver end I have a Y spliter from the amp connected to two standard audio conectors. One to the fron sub the other to the wall plate (feeding the rear sub).

Thanks for your input.
post #9 of 20
Could be a new radio station signing on very close to your home. If its close enough and powerful enough all the shielding in the world wont keep all RF out of your amp.
post #10 of 20
Quote:
Originally Posted by Doogsy View Post

I Istalled the run of quad sheild when I had the house built to allow me to have a sub at the rear of the room. The run is aprox 12 meters. THis terminates to a wall plate at each end. at the sub end I have a standard audio conector from wall plate to sub. At the receiver end I have a Y spliter from the amp connected to two standard audio conectors. One to the fron sub the other to the wall plate (feeding the rear sub).

Thanks for your input.

Is the Y splitter and the cable running from the wall plate to your sub shielded?
post #11 of 20
Thread Starter 
I was thinking that the W spliter could be the problem. Maybe puting a very small amount of current into the quad sheild turning the cable into some sort of powered antenna? I will mess around with things when I have a bit of time and report back.
post #12 of 20
If it's a really powerful radio station nearby (maybe they upgraded their transmitter), the signal will get in *everywhere* -- through the power lines, through the signal lines, even by way of the wiring internal to the speakers and electronics. They all act like antennas In the worst cases, ferrites have to be added to the internal power and signal wiring, chassis have to have copper mesh added over all their openings and seams have to be made electrically tight along their full lengths. Hopefully that won't be needed!

But do check all of the connectors. While you were moving cables, maybe one or more of the ground leads came loose internal to a connector.

Edited to add: there are ways to drape a cable loop (in a figure 8 and then folded back to look circular) so that signals induced in one part of the coil cancel signals induced in another part. Also, avoid long straight runs: an S run is better. Either might help if you have cables that are longer than the minimum necessary.
post #13 of 20
Thread Starter 
Sorry to resurect an old thread. I managed to aliviate the original problem by swapping the subs around (moving the rear sub to the front( kef) and the front sub to the rear(Yamaha) ). I have had to replace the Kef sub as it stopped working with a Mordant Short MSW20. I have had to place the MS sub at the rear due to its size and again place the Yamaha sub at the front. Guess what? The interference has returned. My question is why does the interference only manifest itself with the Kef & MS but not the Yamaha? as its bloody annoying. Any suggestions how to get rid would be most welcome. Thanks
post #14 of 20
Quote:
Originally Posted by Doogsy View Post

The interference has returned. My question is why does the interference only manifest itself with the Kef & MS but not the Yamaha? as its bloody annoying. Any suggestions how to get rid would be most welcome. Thanks

Have you added a choke to the subwoofer cable. You might find something useful in this thread.

See post number four.

"To expand on what Q.E.D. said: Some appliances are susceptible to radio frequency interference (RFI). It is often found that common-mode RFI enters the appliance via an electrical cable. One way to correct this problem is to install a low-pass (LP) filter on each conductor just before it enters the appliance; the filter will attenuate RF noise while passing lower-frequency signals. This can be done many ways, but probably the easiest way is to install a series inductor for each conductor. (A choke is another name for an inductor.) This inductor, when combined with the input resistance-to-ground of the appliance, constitutes a first-order LP filter. A nifty way to insert an inductor is to wind each conductor around a ferrite core a few times. Alas, the “snap-on magnetic choke.”"

Magnetic chokes are readily available.



Here's a bit more on the subject of RFI and magnetic snap-on chokes.

Good luck.

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post #15 of 20
Thread Starter 
Thanks BeeMan, I will give it a try. I think I have a couple of them lying around. I will let you know how I go.
post #16 of 20
Quote:
Originally Posted by Doogsy View Post

Thanks BeeMan, I will give it a try. I think I have a couple of them lying around. I will let you know how I go.

Hope to read that doing so fixes your talking sub problem. My next suggestion would be an exorcism. Talking subs are just plain creepy. tongue.gif
post #17 of 20
Thread Starter 
Lol too true. I did wonder what the hell was going on at first. Just about to get up in the loft to have a look. I will keep you posted.
post #18 of 20
Thread Starter 
Ok. The coils made no difference. But being an electrician and having a good idea of how the network operates here (Australia) I removed the earth ( ground) wire from the sub power lead. Voila no more talking sub. I now think the satellite company's way of earthing their system has introduced some interference. I shall track it down. Thanks for the help BeeMan.
post #19 of 20
Quote:
Originally Posted by Doogsy View Post

Thanks for the help BeeMan.

................biggrin.gif

Ground loops are a pain as they can be caused by any dissimilar touching going on between units. Even something as innocuous as an equipment rack can be the cause. My understanding, one's choices are, remove contact with any ground, which you did, or isolate all contact points and wire everything together under a single common ground; string a bunch of green wire all over everything so as to tie all the gear together under a common ground.

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Edited by BeeMan458 - 1/2/13 at 4:26am
post #20 of 20
dbl post.
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