What spec for RCA cable?

[AnotherGuy]

1st fix electrics is going in on my house refurb and following on from my previous question I need to run a phono/rca cable across my extension from the sub location to the av receiver underneath the stairs.

I will have Scolmore wall plates at both ends (like this) so I just need the actual cable. But what cable? Google suggests that normal coax like the stuff used for tv aerials is fine, apparently RG6 spec. Any views (or better ideas) as it seems a bit bulky/overkill compared to the bellwire stuff that I've seem interconnects made from. The total run is about 15 metres.

[JimbobVFR]

I used RG6 coax. Its cheap and does the job.

[legzr1]

https://www.amazon.co.uk/RCA-Audio-Video-Coaxial-C...

[AnotherGuy]

Thanks JimbobVFR for confirmation. RG6 it is then.

legzr1 - appreciate the link, but a ready-made cable is no good for me.

[Mr Pointy]

RG6 will work but it's not really the right cable & is, as you say, bulky. Assuming the sub is active & you are connecting a line level signal (ie not the amp output) then there are number of cables you could use here:

https://www.maplin.co.uk/c/household-diy/diy/cut-c...

This one is suitable:
https://www.maplin.co.uk/p/vdc-contractor-series-p...
Red to center pin, black & screen to outer.

This would do as well:
https://www.maplin.co.uk/p/van-damme-yellow-classi...
There are lots of colours & for some reason blue is cheaper

If youre running two cable for stereo (unlikley):
https://www.maplin.co.uk/p/vdc-contractor-series-2...

If you are running the amplifier output then you need a heavier cable from this page:
https://www.maplin.co.uk/c/household-diy/diy/cut-c...

You can buy all of these by the meter ordered via the website.

[Red 5]

AnotherGuy said:

1st fix electrics is going in on my house refurb and following on from my previous question I need to run a phono/rca cable across my extension from the sub location to the av receiver underneath the stairs.

I will have Scolmore wall plates at both ends (like this) so I just need the actual cable. But what cable? Google suggests that normal coax like the stuff used for tv aerials is fine, apparently RG6 spec. Any views (or better ideas) as it seems a bit bulky/overkill compared to the bellwire stuff that I've seem interconnects made from. The total run is about 15 metres.

Hi there,

Please don’t buy any speaker cable type wires to do this! Some of the links above are not correctly designed for your use.

You are correct, in that and RG6 style cable is basically correct. However, that regular TV coax designed to be 75ohm and as such, move the emphasis a little away from your main needs.
You’re going to run 15m to an amplified box, not a TV.

The main problem with long rca cables, is that they can be pick up noise from various sources.
You need a very sturdy solid centre core, with separating dielectric, then a correctly designed woven screen / earth. This might also be 75ohm, but then that’s of no consequence to you.

Also, don’t use those wall plates if you can help it. This is just an unscreened area at each end and also another join.
Run the cable to a deep plaster back box, which can store a little extra slack, then exit from a brush plate. Looks tidy, no joins and messing about.
You go from 3 connections at each end, to only 1.

If you do it wrong, you’ll have no cable slack and little chance of a remedy!

The issue is, Subs will amplify any interference and cause a hum. Very annoying.
An incorrectly designed cable can in essence, act like an antenna and pick things up, which you’ll then plug into a massive amplified box. Not a good idea.

While you’re at it, as these are cheap cables.....
Run 2x sub cable, just in case. Like this as it has a great design for this application over such a long run.
http://www.qed.co.uk/qed_professional/qxdav1_flx.h...

1 x CAT6, because you always should whenever you can, for all sorts of possible further reasons.

1 x jacketed speaker cable. So if you want, you can upgrade to a passive sub and rack amp later. These offer advantages and are more widely used these days, over a wider range of prices.

You’re only doing this once

I hope this helps

Edited by Red 5 on Wednesday 17th January 23:25

[Mr Pointy]

What a load of old cobblers. Coax is NOT the "right" cable for line level analogue audio signals although it will do the job. Any properly screened cable will work well. Hum is due to earthing issues not a short stretch of unscreened cable at a wall point, although this might have a very slight effect on pickup from mains spikes if there is a mains cable near by.

[Red 5]

Mr Pointy said:

What a load of old cobblers. Coax is NOT the "right" cable for line level analogue audio signals although it will do the job. Any properly screened cable will work well. Hum is due to earthing issues not a short stretch of unscreened cable at a wall point, although this might have a very slight effect on pickup from mains spikes if there is a mains cable near by.

I’m sure I probably speak cobblers sometimes, but I know you do!
I’ll not respond further to the rudeness though. Please let’s knock that on the head!

A humming subwoofer can be caused by a number of issues. One of which, as you say is earth bourne noise. The cable won’t stop this, whatever the design.
If this is an issue then other problems are afoot, to all of which there are solutions too.

Coax is the only sensible design of cable for the LFE application. It’s what all (I’ve ever seen in 25years) specifically designed sub cables use, as it’s reliable.
The screening is extremely effective and the cable is compact and strong.

Other styles of screening are well suited to short single ended applications for full frequency connection. So yes, with further qualification, you’re quite right.

‘Spikes’ from nearby mains cables though? That’s not a thing.
That is a rather involved subject, not really needing further exploration here.
Just stay away from mains with your signal cables and all will be well on that front. Especially parallel runs within 300mm or so.

Shall we suggest the OP use a non coax design of cable, with six joins from amp to sub, some of which are not screened? Why whould anyone take that advice, as it’s a recipie for problems?

There’s no point in discussing theory further than this. The OP wants to know how to best achieve the LFE cable run.
I have answered that query above, using the most sensible, affordable, reliable and easy method.