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XLR cables are picking up radio/TV hash...

Hi everyone,

This is an ongoing dilemma so I'll try my best to be short and to the point. I recently got 1 m Cardas Neutral Reference XLR to use between my Sim Audio W-5 power amp and my Marsh P2000b preamp. My system sounds a lot better, but I am picking up audible radio and/or television sounds on my speakers (Quad 22l). I do not have a functioning cable tv connection (I don't have a television, period!) but my power outlet is near a cable tv jack. Could this be the problem? I read on some other fourm that the cable connection may need to be grounded.

I have tried to go troubleshoot in a thorough fashion; I tried using cheat plugs; I disconnected all my cables, power cords and speaker wires, then reconnected them slowly. I discovered that only when I powered up my preamp did I got noise...and it did not increase or decrease whatever I did with the volume knob. Something is obviously acting as an antenna and picking up signals.

I think this may be a problem unique to the Sim Audio W-5; it has two sets of RCA connections, where, if you choose you can use both sets in a sort of single-ended "balanced" configuration. There are two dummy plugs inserted into the negative inputs, and the positive inputs are used in a normal single ended configuration. Thing is, I had no noise when using the Marsh and the Moon in single ended mode. I am certain that my new Cardas cables are fine...I had them checked out at a dealer...I also replaced them with a brand new pair of Transparent balanced cables with the same resultant hash. I did find that if I placed the two dummy plugs into either the left or right set of RCA connections I did not get any hash on that channel but it obviously degraded sound quality as it shorted out that particular channel.

I have had suggestions ranging from changing my preamp with another balanced one to check to see if that is having problems, to using Cardas caps to cover unused XLR and RCA connections, and even clamping ferrite clamps on the XLR interconnects.

Also, I am using a Rega Planet 2000 (in single ended config) and a Rega Planar 3 with a Pro-ject Phono Box SE; I am pretty sure they are not the cause of my problems but I am just being thorough for the record!!

Please help!
Thanks,
Khalid
128x128aurlieus
aurlieus's avatar
aurlieus OP
11 posts
 
Hi everyone,

I have moved to a new house and NO problems! No noise, all xlr connections work just fine. Still, it would be great if someone could come up with a technical explanation of what happened at my old place.

If someone has the spare time and insight, it would be helpful for others pulling their hair out over this.

Khalid
kirkus
502 posts
 
This is a classic symptom of interference from an AM radio transmitter. For FM and television (which uses FM for the sound), RF interference won't actually de-modulate the audio from the station.

The most likely cause of what you describe would be a mistake in the design of the ground traces or wiring on either your preamp or power-amp, whereby the RF crawling around on the interconnect shields (which is where it's supposed to be), gets somehow injected into the signal conductors.
aurlieus's avatar
aurlieus OP
11 posts
 
Thank you for that Kirkus. I hope that this weak point has been addressed by Simaudio in their newer designs.

Khalid
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