running RCAs by power

In short, running the RCA wires next to the power wire does NOT cause ANY interference whatsoever.  The power wire is carrying a DC current, which has a frequency of ZERO, and the RCA cables are carrying a frequency from 0~40khz.

These two wires will NOT cross talk as is the misconception.  How could they?  The power wire is putting absolutely NO interference due to the fact that its frequency is zero. 

Interesting.  So the electromagnetic field it generates doesn't actually produce any interference?  Can you explain more about the "frequency of zero?"

I've never bought into the idea that power wires had to be run seperate from RCA's b/c I've never solved a noise problem by seperating the two.  Good to hear I wasn't just lucky.

I recently read a similar article about this as well. And there were other points brought up too. Here is some of it...

There is no where on the chassis/floor of the car that will be isolated from noise.

Electrons flow from negative to postive. There is NO way to isolate anything going down the power wire from anything laying on the chassis/floor. Because anything that is going down the wires is also going down the chassis.

You do NOT get noise (or any audible noise) from running power wires and RCAs together.

You do get noise from bad grounds, poorly designed equipment, or a pinched cable.

Running power wires and low level signal wires together will not have an effect on noise. there is no statistically reliable evidence to show that it does matter, but there is a lot of evidence available to show that it doesn't.

Me

It was discussed at work, however I am not necessarily agreeing or disagreeing with the given info. For me to buy this, I might have to try it.

Unfortunately some of this info was pulled from Rcichard Clark and David Navone, which in my book are circus clowns.

dwarren wrote:

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Me

It was discussed at work

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You used the wrong smilie.  It should have been a .                  

No, stevdart I was graceful in my choice of smilies... Your purple guy was the wrong one!

To me it seems there are flaws to both arguments. But there shouldn't as these really are mathematical and technical expressions.

I have to disagree here.  Alternators produce rippling DC voltage because it can never be flattened out completely.  If you view this on an o-scope, it will look like a sin wave and will have a frequency.

I will agree that most of the time power wires will not induce any noise, but I, as well as others on here I'm sure have run into cases in the past where moving RCA's away from a power source solved a noise problem.

Its not that technical, audio cables WILL pick up electrical noise from ANY sorce, including the little bit of factory wiring it might come in near proximity too.

As dwarren stated....move the RCA's and the noise problem is solved. Its really that simple. no need for "o-scopes" or scientific mumbo jumbo chat.

haemphyst wrote:

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it was discovered that the battery (a big ol' noise filter, people) needed replacing or the alternator was in some way defective.

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Yes, so I have heard the battery acts as a filter, and can be biggest problem in a system. This is where most of the nosie is created.

haemphyst wrote:

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Take the same transformer discussed above, and disconnect the AC neutral from the one side. There is still POTENTIAL (the voltage component of power) in the coil, but because there is no CURRENT in the coil, there is no alternating magnetic field, therefore no EMI, and no primary magnetic field or secondary output...

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I was following everything fine until we got here.  Think I'll politely excuse myself now...

As the current flow through a cable in a DC circuit changes, the magnetic field it generates changes.  It is the changing magnetic field that can cause EMI in an adjacent circuit, just like in an AC circuit.  Of course there is no changing magnetic field as a system is "idling," as there is no changing current flow (or no current flow at all.)  But in an active car audio power system, the DC current draw is changing constantly.  This causes constantly variable (expanding and collapsing) magnetic fields around the DC power cables, which can induce noise (EMI) into other circuits.  It's been more than 20 years since college but I believe I still remember applications of Faraday's Law.....

haemphyst wrote:

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In my experience, ALMOST ALL noise induced into signal wires does not come from amplifier power cables, but from other electronics in the car - ECUs, fuel pumps; things like that.

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Perhaps I missed the explanation for this, but why then would it matter if the electrical component is not an amp, rather an ECU or fuel pump, how does it vary?

Dave, a magnetic field does not have to swing negative in order for it to collapse.  Indeed, if the current flow goes to zero, it collapses.  If the polarity swings negative, the field reverses polarity.  But "collapse" literally means it goes from some value to zero, and it will certainly do that in a DC circuit.  Faraday (and Maxwell) showed that anytime a magnetic field is moving in relation to a wire, an EMF is induced.  It does not matter the polarity.

The magnetic field change I am talking about is in the power cable for an amplifier, not in the signal cable.  This field change can be very radical as the amplifier draws more or less current, and this field is certainly more than sufficient to induce a voltage into adjacent wiring.

You are correct of course that the LARGEST contributors to EMI and other induction effects is more likely a noisy system (rippled DC, arcs and sparks in the alternator, other mechanical and magnetic devices, etc.) than from pure induction through magnetic field interaction.  But you cannot say it does not happen.  That was my only point: that it is certainly possible and in some cases very problematic.  Poorman's theory that it is a "misconception" is simply wrong.

Oh come, we'll give em each a glass room, Some wire, goggles, a big ol battery and a six month supply of Doritos. 

Then we just see who cracks first.  "or proves the theory first"  

Tegpilot wrote:

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Oh come, we'll give em each a glass room, Some wire, goggles, a big ol battery and a six month supply of Doritos.

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haemphyst wrote:

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The changing of the magnetic field in the power cable is always a positive - sometimes a little more, sometimes a little less - but ALWAYS positive. There is never a SWING from positive THROUGH zero, to negative.

There is simply not enough change in magnetic field with MUSIC signals to produce the necessary magnetic fluctuations required to induce a voltage high enough to go to the effort of tearing apart the entire car to run power down one side, and the signal down the other. There ARE fluctuations, but they ARE always POSITIVE. There is NEVER a negative swing - required to cause a total collapse of the magnetic field, inducing the voltage on the secondary - in this case the positive signal wire contained in the RCA wire.

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Looking specifically at "There is NEVER a negative swing - required to cause a total collapse of the magnetic field, inducing the voltage on the secondary"

explain how an ignition coil (which is nothing but a step-up transformer) works in this situation.. and why diodes are used on relay coil leads.

Jim

Tegpilot wrote:

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Oh come, we'll give em each a glass room, Some wire, goggles, a big ol battery and a six month supply of Doritos. 

Then we just see who cracks first.  "or proves the theory first"  

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haemphyst wrote:

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Tegpilot wrote:

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Oh come, we'll give em each a glass room, Some wire, goggles, a big ol battery and a six month supply of Doritos. 

Then we just see who cracks first.  "or proves the theory first"  

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...and I think he's talking about us, DYohn... you ready?

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I'd rather work with you than against you, my friend.  We could cook up some pretty good Frankenstein monsters if we wanted too.  I see large open frame plasma drivers.....  and plenty of Doritos and jerky... 

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.  

dwarren wrote:

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, rather it is a drop from one point 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.  

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... 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?

haemphyst wrote:

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Perhaps my statement translated to needing AC. While this is NOT true, a pulsed DC is a minimum. This is what is fed to the primary side of your ignition coil. ON, then OFF - the cycle of your ignition points (or in the case of most of today's cars, the solid state switching circuitry)... The OFF is when the spark occurs.

Diodes in relay coils are there to prevent the back EMF, produced when the field collapses, from feeding back into the driving circuitry. The diode is placed in opposite polarity of the driving voltage so it is "invisible" to the driving circuit.

When the field collapses, the back EMF produced is an opposite polarity of the voltage that produced the field to begin with. This is why the diode is placed the way it is... it will short the back EMF across the terminals of the relay coil, preventing the high voltage spike produced from being sent back into the driving circuitry.

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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

DYohn] wrote:

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QUOTE=dwarren]

, rather it is a drop from one point 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.  

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... 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. 

[/QUOTE]

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 (https://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. 

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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).

dwarren wrote:

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

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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.

haemphyst wrote:

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There's one I have never heard before...

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I am here to entertain! and something else, just can't remember.

Again this was gathered info from a physics professor. Your explanation is sound, however in your previous responses it was stated that AC current does produce a EMF, but the magnitude of this will not affect low level signal, but a metal wrapping in an RCA will amplify this interference. Yes a shield is used to block things so to speak, but after all it is a conductor.

Oh MY GOD..........come on "boys"...where is all of this taking us? And yes I said "BOYS".    You kids babble off this crap that is supposed to impress us, honestly it just makes the rest of us just want to "walk away with our tails between our legs" How many people do you think understand HALF of the crap you kids are spewing......and does it really help ANYONE. It's like the main objective has been forgotten....to help, and assist...the "not so experienced"

I would think this would be a perfect topic for you guys to PM the living crap out of one another over...........

Well Kar TuneMan you sure like to spoil other people's fun! Perhaps this topic is a little beaten, but at least it hasn't been reduced to name calling and other juvenille behavior (yet). Just because you can't join in doesn't mean you have to condemn it. (this should be read with a humorous inflection)

I for one have learned a lot from this thread, and am quite happy to have participated in it. It may take some time to figure this stuff out (there are some things I am not totally clear on) but there are answers to questions here. Be patient, this is after all a DISCUSSION forum...

KarTuneMan wrote:

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Oh MY GOD..........come on "boys"...where is all of this taking us? And yes I said "BOYS".    You kids babble off this crap that is supposed to impress us, honestly it just makes the rest of us just want to "walk away with our tails between our legs" How many people do you think understand HALF of the crap you kids are spewing......and does it really help ANYONE. It's like the main objective has been forgotten....to help, and assist...the "not so experienced"

I would think this would be a perfect topic for you guys to PM the living crap out of one another over...........

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If nothing else, use this to recognize things you don't know about and read up on them. Try to learn more. Is it surprising that DYohn and Hamfisted (sic) know stuff like this?.. they are two of the most knowledgeable people on the board. Do you think they ever stop trying to learn?

Jim 

Heh.. here's a post from another place I read..

"My Marks Manual lists the simplified final velocity of a rocket as delta V = I(s)*g*ln(w(i)/W(f)). This means that the specific impulse ( the I(s) term) times the natural log the final weight over the intial weight. Modern rockets often have a final weight of 10% of their initial weight (90% fuel), which gives about 2.2 for that part. I can not find the specific impulse of gun powder, but we can assume it is fairly low, which is why no one uses it and therfor it is not listed in my book. The lowest specific impulse listed is for hyrdazine, at 110 seconds. That give a maximum speed of 7,734 feet/sec. Escape velocity is around 33,000 feet/sec, so there is no way it could have reached orbit. If they fired it at a 45 degree angle, it would take about 170 seconds to reach its highest point, and another 170 seconds to hit the ground again. With a horizontal velocity 5468 feet/sec, that gives a max distance of 352 miles, which makes things at least possible."

Jim

Dwarren, just a quick correction.  This professor is telling you the braid would make more noise because in his mind it is like an antenna, paralleled with the center conductor.  The only problem with his view is the "antenna" is grounded at both ends.  Haemphyst's assessment is correct.