Newsgroups: rec.audio.tech
Subject: Re: Convert rca to coaxial - audio only
References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]>
"Geoff Wood"  writes:

> "Richard Crowley"  wrote in message 
> news:[email protected]...
> > Disagree. In my experience, 100s (or even 1000s) of feet are not 
> > impractical in many cases. The main hazard is the
> > possibility of ground loops between the equipment at each
> > end. Cable made for TV is good for 100s of MHz. 20KHz
> > of audio is of no concern whatsoever.
> In/out  impedences of most consumer audio gear is totally unsuited for going 
> more that a meter of two at the most without hf drop-off.

The output impedances from consumer gear can vary widely. 
The impedances can easily vary from around 30 ohms 
(some sound cards) to five kilo-ohms (some CD players etc..)
The impedance is typically in few hundred ohms to two kilo-ohms. 

This is a greate difference on the effect of cable. 
The device with several kilo-ohms output impedance 
is unsuited for going more than few meters without noticeable 
high frequency roll-off. 
The device which has output impedance of jsut tens of ohms 
vile nicely run tens of meters with same or less high frequency 
loss than this kilo-ohms output impedance equipment gets on 
few meters of cable. 

> > Disagree. They are, in essence, identical. "TV coax" (i.e.
> > cable made for RF frequencies) is merely designed for
> > lower loss at high frequencies, which is actually better
> > for audio frequencies. 
> You have never seen the "screen" of an RF TV cable ? Coax cables work on  a 
> totally different concept to screened audio cable.

I have seen the "screen" of an RF TV cable. I have seen the 
construction of quite many coaxial cables. 

For audio application in coaxial cable there is a centre core 
and there's a screen, just like in the simple screened audio cable.
A top quality RG6 coax comes with the following features: 
solid copper center conductor, foam PE dielectric, 
>93% braided copper shield plus 100% foil shield. 
This coax fits for all audio-video cables, form cable TV 
to audio interconnections.

There are even plans how you can build your own audio/video 
cables from coaxial cables and RCA cables.
http://www.bus.ucf.edu/cwhite/theater/diycable.htm
http://www.bdcable.com/subwoofer-cable-kit.htm

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