What are your thoughts on using a 14AWG speaker cable to make a 20m RCA lead ?

We need a point to point RCA run through a property but the cable hasnt been installed at first fix stage, but we have a spare 14AWG un screened speaker cable in this location.

If we put RCA ends on it do you think it would work, or do you think it would pick up to much interference or have other issues ?

If it’s not shielded it’s not worth it.

For line audio? I would never recommend doing it but I guess you could test it.

If we where able to run a new cable what would you suggest ? We will probaly run a cable and make off the ends ourselves, but not sure what cable to run

For just stereo audio?? RG59 or 6, CatX, planetwaves cable, 18 or 22/4 stranded and shielded.

Pick your poison.

If it's a 14/4, you could try putting XLR ends on it, then adapt it back to un-balanced with an XLR to 1/4" adapter. I don't know how well it would work in terms of noise, and it would also require 3 conductors to get only 1 channel of audio, but it's an idea.

With a Cat5/6 this would be easy work for any passive balun, I think. I've used the Liberty AVO-A4 for that.

Line audio needs to be shielded or at the least, twisted pair. Speaker cable has no way to reject noise. That said, the soil should limit this, but if it's run parallel to powerlines, nothing is off the table. XLR isn't made or used for high power and the losses post amplification over long distance makes this a tricky problem.

Is this in conduit? Would the replacement cable be in conduit? I would recommend direct burial cable, even if conduit is used- there's no way to guarantee moisture won't enter.

I used thin Belden cable when I had to run audio from a house to a shed, in conduit, with an Art Clean Box to convert from high impedance to low impedance line audio with level controls.

For sure, it just sounds like this isn't amplified (maybe I missed that). The 1 pin would be a 'ground' less than a 'shield'; I'm not sure how the whole common mode rejection thing would work with a conductor that's not a shield...so I probably should have put a heavier emphasis on the 'try' part.

In a home theater where we had a 35' RG59 and a 16/4 ran between a surround receiver and a powered sub...

The RG59 was causing a crazy hum in the sub. The 16/2 was ran JIC we went with a passive sub. Out of desperation i soldered an RCA male at each end of the 16/2 and it worked just fine.

Whatever caused the hum with the RG59 wasn't bothering the 16/2. I don't remember what the RG59 was but we used it often for line level audio back then. Never had any issues with it until that subwoofer.

Most Category cable isn't shielded, it's twisted. That twist rejects common mode interference.

The OP mentioned that it would be for a 20 meter RCA lead- Pin 1 is for grounding/lifting ground if needed and pins 2 & 3 carry the signal, on a twisted pair but by original design, with balanced LoZ circuits. There's no need for large conductors but the cable usually has shielding of some kind, as you probably know.

I agree that it's worth a shot, but I'm not confident that it would be noise-free. Some kind of balun/isolation would be a good idea, too.

I can’t find them at the moment, but in the past I’ve seen RF ‘boxes’ that can encapsulate and send audio or video over just about any conductor. They were from companies that I would not normally do business with, but they had impressive demos at trade shows.

Probably not very appropriate for this case, but here’s an example ‘box’.

The RG59 was most likely causing a ground loop. Differential in electrical phases would be my guess. The circuit used for your rack was on a different phase than the circuit being used for the sub.