running RCAs by power

I decided to investigate this matter further. I went to a physics professor today and brought the situation to him.

He said that yes AC current does produce EMF. However will we hear the noise, no. It is dependant on what the amperage the wire is pulling. The higher the number the more it will produce.

As far as the swing of polarity, negative doesn't necessarily mean it goes negative, rather it is a drop from one poin to another. So DYohn Faraday's theory is applicable but the magnitude of what we are dealing with (relatively small numbers) EMF will not have and effect on low voltage signal cables.  

... assuming the low-level signal cables are properly shielded.  If they are cheap 99 cent unshielded cables, the EMF induced from the changing magnetic field around a power cable can create audible hum, buzz or thumps.  I know, I've heard it. 

I can't believe y'all are still going at this!  Interesting theories even tho they're beyond my understanding level.

So to bring this to a more practical level, how many of you have actually solved noise problems by seperating RCA's & power lines?  Those who have, how often, out of say 100 noisy systems, would you say that the power lines were responsible?

It was a rhetorical question... my point was to show that it's certainly possible to run a transformer off DC.. you have to pulse it, yes, but even though there's no zero crossing, it'll still work.

to go a step further, if you accept that the higher the current flow the stronger the magnetic field, a current change from 400 amps to 50 amps in a wire would change the magnetic field enough to generate a current in another nearby wire... yes?

Jim

Shielding (the foil wrap) in rca's acts an amplifier for noise here, so they may make things worse, not better.

C'mon, let's not make DYohn do all the research too!  Here's one answer from a source we all know well ( http://www.bcae1.com/rcacable.htm):

RCA Cable Construction

The RCA cable, which is used in virtually all car audio installations, is a specialized cable which is designed to transmit audio while preventing noise from entering the audio stream. As you can see in the diagram below, the center conductor is "shielded" from noise by completely enveloping it in a braided copper shield conductor. The shield is connected to the reference terminal of the audio source. You remember that every measurement has to have a reference. The same is true when you are sending a signal (audio in this case). This is so because the next device in line must "measure" the level of the incoming signal. If it does not have a good reference, the signal quality will suffer. I will explain "audio grounds" in a section to come. 

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

That's funny, I went to sleep after posting yesterday.  I wasn't going to get as indepth as Dyohn or Haemphyst because I wanted to make my point in a somewhat easy-to-read manner.

Steve, I like the comment about stirring up the nest and leaving (594).

well i love it when everybody gets techanical . it shows the knoldedge we are all capable if we apply ourselfs. well i was just going through my symmetrys handbook and this is how fosgate solved this problem in the early 90's,  they used a missing link transmitter for the signal processor system, witch i believe is one of the best systems ever designed. just my opinion though, so here it is, most systems use low voltage,unbalanced cables to transmit audio signal from one end to another. unfortunately,these unbalanced lines are very suscepible to ignition noise,fan motors,and alternator whine. to alleviate these problems the missing link transmitter comes into play.

it takes unbalanced lines witch are immediatly converted to fully balanced,differentially driven output.these outputs,witch are similar to the ones used in recording studios,are amplified to 30 volts peak to peak and then routed to preamplified module(pam) via db25 multiconductor cable (computer cable) the (mlt) is designed to be mounted as close to the source unit as possible to obtain the lowest possible noise figure.since the output of the (mlt) is fully balanced,any noise introduced into the cable between the (mlt) and the (pam) will be eliminated due to common mode rejection.in addition,by amplifying the signal at the (mlt) and then reducing it back to unity at the preamplifier, any noise that escapes the common mode rejection will be reduced at the same time the signal is reduced to unity at the preamplifier.

so there you go you can have all that for the 500 to a 1000 dollars they are selling for today. oposed to the 2500 dollars when they came out in 1992. i personaly own one and love it the options are endless but thats my opinion and just thought i would add that to this topic. they are not for evryone.