Dispensing with the backstory and cutting to the chase....

Should your typical A/V receiver pre-out to powered sub connection be
done with 50-ohm or 75-ohm cable?

TIA

wrote in message
oups.com...
Dispensing with the backstory and cutting to the chase....

Should your typical A/V receiver pre-out to powered sub connection be
done with 50-ohm or 75-ohm cable?


No. Those are radio frequency coaxial cables with those characteristic
impedences.

You need regular screened audio cable, for which characteristic impedence is
largely irrelevant but screening and mechanical 'soundness' is. High shunt
capacitance may be a problem with extremely thin cable or extra-long runs,
but even this is of little consequence to a sub signal !.

geoff

Should your typical A/V receiver pre-out to powered sub connection be
done with 50-ohm or 75-ohm cable?

No. Those are radio frequency coaxial cables with those characteristic
impedences.

Granted, but apart from their bulk and cost, is there any reason *not* to
use them for audio?

"mc" wrote in message
.. .
Should your typical A/V receiver pre-out to powered sub connection be
done with 50-ohm or 75-ohm cable?

No. Those are radio frequency coaxial cables with those characteristic
impedences.

Granted, but apart from their bulk and cost, is there any reason *not* to
use them for audio?

Often inflexible, screening optimisated for rf.

The proper stuff is still low cost, unless you want snake-oil esoterica.

geoff

In article .com,
wrote:

Dispensing with the backstory and cutting to the chase....

Should your typical A/V receiver pre-out to powered sub connection be
done with 50-ohm or 75-ohm cable?

In all but the most exceptional of circumstances, it won't make a bit
of difference. A cable's characteristic impedance per se really isn't
relevant when carrying signals over a distance which is less than,
say, 10% of one electrical wavelength. Unless your sub is a mile or
more from your A/V receiver, don't worry about it.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"Geoff@home" wrote in message
...

"mc" wrote in message
.. .
Should your typical A/V receiver pre-out to powered sub
connection be
done with 50-ohm or 75-ohm cable?

No. Those are radio frequency coaxial cables with those
characteristic
impedences.

Granted, but apart from their bulk and cost, is there any reason
*not* to
use them for audio?

Often inflexible, screening optimisated for rf.

The proper stuff is still low cost, unless you want snake-oil
esoterica.

geoff



'...screening optimised for RF.'

What in heaven's name is that?


--
Woody

harrogate2 at ntlworld dot com

On Sun, 05 Feb 2006 08:28:48 +0000, harrogate2 burbled:


"Geoff@home" wrote in message
...

"mc" wrote in message
.. .
Should your typical A/V receiver pre-out to powered sub
connection be
done with 50-ohm or 75-ohm cable?

No. Those are radio frequency coaxial cables with those
characteristic
impedences.

Granted, but apart from their bulk and cost, is there any reason
*not* to
use them for audio?

Often inflexible, screening optimisated for rf.

The proper stuff is still low cost, unless you want snake-oil
esoterica.

geoff



'...screening optimised for RF.'

What in heaven's name is that?

Depends on the frequency. At vhf and uhf frequencies the screen doesn't
need to completely cover the core to be effective. At audio frequencies it
does. So, if you use TV coax for audio you are inviting hum problems.

--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info

On 4 Feb 2006 14:06:57 -0800, wrote:

Dispensing with the backstory and cutting to the chase....

Should your typical A/V receiver pre-out to powered sub connection be
done with 50-ohm or 75-ohm cable?

No, those are RF cables intended for a different purpose. Ideally, use
microphone cable, as this is designed to carry a low-level audio
frequency signal over long distances, and is also designed to be
insensitive to mechanical shock, aka handling noise.

RF cables can be overly stiff for domestic audio use, often have poor
shielding at LF (although not always), and can exhibit significant
noise pickup from vibrations - not ideal for a sub cable!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"mick" wrote in message
news
On Sun, 05 Feb 2006 08:28:48 +0000, harrogate2 burbled:


"Geoff@home" wrote in message
...

"mc" wrote in message
.. .
Should your typical A/V receiver pre-out to powered sub
connection be
done with 50-ohm or 75-ohm cable?

No. Those are radio frequency coaxial cables with those
characteristic
impedences.

Granted, but apart from their bulk and cost, is there any
reason
*not* to
use them for audio?

Often inflexible, screening optimisated for rf.

The proper stuff is still low cost, unless you want snake-oil
esoterica.

geoff



'...screening optimised for RF.'

What in heaven's name is that?

Depends on the frequency. At vhf and uhf frequencies the screen
doesn't
need to completely cover the core to be effective. At audio
frequencies it
does. So, if you use TV coax for audio you are inviting hum
problems.

--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info



He didn't actually say TV co-ax so I presumed since he said 50R or 75R
cable he meant something like RG58 and RG59. I don't know of a 50R Tv
co-ax, let alone one that is not fully screened.


--
Woody

harrogate3 at ntlworld dot com

wrote in message
oups.com...
Dispensing with the backstory and cutting to the chase....

Should your typical A/V receiver pre-out to powered sub connection be
done with 50-ohm or 75-ohm cable?


Just addressing the thread title - 50 ohm and 75 ohm are not resistances,
they are characteristic impedances.

If you try to measure the resistance of 50 or 75 ohm cables, you are
unlikely to ever see 50 or 75 ohms or anything like them on the readout of
your ohm meter.

If you measure between shield and center conductor, you'll find some really
high resistance, and if you measure either the shield or center conductor
from end-to-end, you'll see some really low resistance.

Stewart Pinkerton wrote:

[...]
RF cables can be overly stiff for domestic audio use, often have poor
shielding at LF (although not always), and can exhibit significant
noise pickup from vibrations - not ideal for a sub cable!

I find mini RG-8 to be quite flexible and well-shielded, nicely
suited to audio use. Stranded center conductor, foam dielectric,
braided shield - what's not to like?


Francois.

On Tue, 07 Feb 2006 03:58:01 -0000, ((null)) wrote:

Stewart Pinkerton wrote:

[...]
RF cables can be overly stiff for domestic audio use, often have poor
shielding at LF (although not always), and can exhibit significant
noise pickup from vibrations - not ideal for a sub cable!

I find mini RG-8 to be quite flexible and well-shielded, nicely
suited to audio use. Stranded center conductor, foam dielectric,
braided shield - what's not to like?


Francois.

The foam dielectric can be a pain - if you step on it, it crushes.
Sometimes it can break through and short. Generally though, RF cable
is made to a fairly high standard of dimensional tolerance to maintain
its impedance; this is a needless expense for audio.

d

Pearce Consulting
http://www.pearce.uk.com