Newsgroups: rec.audio.tech
Subject: Re: Hum with Kimber Kable
References: <[email protected]> 
Kalman Rubinson  writes:

> Endymion Seiler  wrote:
> >      My Kimber PBJs have been giving me hum recently in both channels
> > and it is not obvious to me why as they've never given me any
> > appreciable hum before.  If I swap in radio shack cables the hum is
> > reduced substantially and with fully shielded cables the hum is down to
> > almost nothing...This cable is between the preamp and amplifier.
> 
> PBJ is simply a twisted pair; there is no shield.  

Which is quite unsuitable wire type for carrying low level
(line level) audio signals from unbalanced audio interfaces
(RCA connectors). The RFI and other noise shielding in this 
kind of configuration with this kind of cable is poor.

And still high end audio cable companies sell this kind
of cable with very high price to customers. Propably it
makes the difference to the sound because it lets the
interference to enter to your audio system...

Can anyone tell any other feature on the twisted pair
wire connecting two RCA connectors than lower
capacitance and cheaper price compared to a proper
coaxially constructed shielded audio cable ?

> Something has changed in your
> environment which is inducing the hum.  

That's what I think also.

> Find it and/or replace the PBJ with a shielded cable.

First replace that poorly shielded cable (if that claim
of it being unshielded twisted pair is true) which 
is a proper type to carry audio signal from unbalanced
interface: a normal shielded audio cable.

Whn you have made that, you have reduced very many noise
sources nicely away. If you still get humming, then
you have to start looking around if you have ground loop
related problems. If you have any, you can find
information how to solve them at
http://www.hut.fi/Misc/Electronics/docs/groundloop/

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/