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running power cable next to rca’s
- Thread starter mr sheep
- Start date
The theory behind the interference is simple, but high quality screened cable should prevent it from happening. Or even un shielded twisted pair. It doesnt stop the interference but splits it equally across the two channels thus cancelling it out.
ive never bothered about it before - always saved me from pulling trim apart on both sides of the car - lol.
Clio 197
On my first ever install, I ran them both down the same side, and luckily got away with it (I didnt know better anyway).
On my last two installs, I have kept them separate, just like I was told to.
The power cable has a (varying) electro-magnetic field. Believe it or not the voltage travelling down your power wire to your amp when your is engine running is a far from pure DC voltage, thus it can interfere with a sinusoidal signal.
This field is picked up by the signal cable, amplified, and can thus be heard out of the speaker as a buzz or a hum.
However, the shielding around the RCA cable prevents the magnetic field from affecting the signal carried by the cores.
Usually inteference in a car audio system is picked up elsewhere and not via crosstalk between cables.
Sorry if it doesnt make sense. Ill have to get me college notes out again. lol.
lagerlout pretty much said it. Its a good 10 years since I did electronics at uni, but basically any wires running alongside each other can induce a current in each other i.e. as if by magic, they can create current in the other wire. Thats how transformers work.
So if you ran a big power cable alongside an RCA pair which conduct a very low level signal, it is quite likely that the RCAs would pick up interference from the power cable because as Lagerlout said, its not direct current but is actually varying slightly. Not enough to knacker your amps, but enough to be picked up. This problem can be solved by running shielded RCA cable which most decent ones are anyway.
you could be lucky and get away with it. People probably dont bother, because its almost as much hassle to run cable down one side as it is to do both, so its not worth the bother of finding out youve got interference once the carpet it all back in again. If you do want to run the cables down the same side, make sure youre running shielded RCA cable, and try to keep them spaced apart. If youve got no choice about runnign them close, try to zig-zag the cables a bit so theyre not totally parallel.
Granted the ripple may be small . Im with you on this one mate, the effect, if any is negligble. Ive certainly never had a problem. I just thought you wanted to know the theory behind it!! Obviously you already knew!!
You do induce an equal amount on each RCA but this will not cancel out ( the average value of two indentical sine waves 90 degrees out of phase is zero, thus they cancel out) unless the RCA cores are in a twisted pair. Which they wouldnt be, as modern screened cable like co-ax is far more adept at keeping the interference at bay than a UTP is at cancelling it out!
[Edited by lagerlout1 on 09 February 2005 at 10:36pm]
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