Question about running power/RCA's

[91Chevy 10+ year member]

Due to the specific setup of my vehicle, I have found that the easiest way to run the RCA cables and Remote lead is behind the glove box, and then straight down under the carpet. The problem is, the grommet in my firewall is directly below the glove box, about a foot to the left. I plan on running the power wire pretty much down the middle of the cab, as that would be easiest. Unfortunately, with the RCAs on the same side, at some point in time they will need to either cross on run very near to the power wire. I'm just worried about potential noise, and am wondering: How close do the RCA's and Power wire have to be for me to worry about noise, and are there any effective 'shielding' methods I could use?

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[x1le 10+ year member]

What guage wire? And how much power are you planning to run?

And there is always a way for them to not cross paths. Just gotta think creative.

Why not run the power wire down the middle and the rca's through the dash and then down the pass. side of the vehicle?

 

[PSturmer 10+ year member]

just try it. most of the time there are no problems when running power wire with rcas

 

[IHaveItGood 10+ year member]

Due to the specific setup of my vehicle, I have found that the easiest way to run the RCA cables and Remote lead is behind the glove box, and then straight down under the carpet. The problem is, the grommet in my firewall is directly below the glove box, about a foot to the left. I plan on running the power wire pretty much down the middle of the cab, as that would be easiest. Unfortunately, with the RCAs on the same side, at some point in time they will need to either cross on run very near to the power wire. I'm just worried about potential noise, and am wondering: How close do the RCA's and Power wire have to be for me to worry about noise, and are there any effective 'shielding' methods I could use?

I would just wrap it in foil right where they cross. That's all shielding is anyway.

 

[Torgus 10+ year member]

properly grounded rcas should be fine...

 

[loopkiller 10+ year member]

Having the RCA and power wires cross is not the problem. Having them run parallel is the issue. If you have to cross them, do so at a 90 degree angle (perfect cross) and it will be fine. However if you run them in parallel runs, even for a short distance, you will for sure need to shield the RCAs.

 

[n2audio 5,000+ posts]

dc power wires don't induce audible noise in signal wires.

This is a problem in a home with 120v ac, but 14v dc, no.

I thought this myth had pretty much been busted at this point??

You can braid your signal wires along with you power wire if you want. There is no noise there.

Avoid the hvac blower motor - there is definitely emi coming from that.

 

[oni 10+ year member]

dc power wires don't induce audible noise in signal wires.This is a problem in a home with 120v ac, but 14v dc, no.

I thought this myth had pretty much been busted at this point??

You can braid your signal wires along with you power wire if you want. There is no noise there.

Avoid the hvac blower motor - there is definitely emi coming from that.

LONG POST INC!

Mostly correct. AC induces a current by the Electromagnetic field it generates. This creates noise by inducing a current other than your signal in your RCAs/Speaker Wires/etc. This "should" not be an issue with DC current, i.e. car battery.

BUT if your stock electrical isn't uber, i.e. you're running stock alt with 1 or 2 batts because you really aren't running that much wattage or you just aren't running what you should for what you have, you may have an issue.

When your subs hit a loud note, what happens? Your amp needs to pull more power for a "bigger" note. This causes your voltage along the power wire to "dip" as the amp needs more power. The better your electrical system, the less it dips. Using, lets say, a run of 1/0 to a distro block with 4 AWG exiting to multiple amps will also cause this. Ok, so what happens to your current? To keep this post small, I'll skip out on the math, your amperage draw on your power wire will change as power demand by the amplifier changes as well. So what do we call it when current isn't constant? ALTERNATING CURRENT!

Now the change in DC current is much less than in actual AC, but it is there none the less. And as I said, with AC, you have induction. So in actuallity, you can gain some noise from DC power wires, it's just extremely diminished versus AC. In a perfect world DC would be real DC. Like home electronics, for instance. Think of your house electrical being fed from an infinitly large AC battery. It'd be like running a 50 watt rms amp off of 4 Kinetik 2400s on a 500 amp alternator(overkill I know). The voltage dip is almost a tickle for the electrical, so your DC is pretty much really DC.

But due to the limit of space in a vehicle (not to mention cost) it isn't practical for most daily drivers to upgrade their electrical enough to not cause minimal noise on a power wire. For competition folk, those with big vehicles, or people with more money than the rest of us,, it may be very likely that you can upgrade your electrical enough to see almost no noise in these lines. And I stress again, the variance in DC "CAN" cause noise (in theory by the math), but I myself have never measured it so I cannot speak to its strength and prevalance, only that it's there. It may just come down to how sensitive your ear is and if you can even hear it.

 

[nimrod 10+ year member]

LONG POST INC!
your amperage draw on your power wire will change as power demand by the amplifier changes as well. So what do we call it when current isn't constant? ALTERNATING CURRENT!

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[91Chevy 10+ year member]

Alright, thanks. I'll just wrap it in Tinfoil so they can't read my mind. I mean, so there isn't any noise. Then I'll just try to run it as far from the power cable as possible.

 

[n2audio 5,000+ posts]

No, it was all correct. You just added a bunch of details people don't care about anyway.

The fact of the matter is you're more likely to pick up noise from ground currents flowing through the chassis in general (some of which is ACV) than the 12.5-14v fluctuations in the power wire. The tests have been ran, the data is out there somewhere. Power wires just aren't noisy.

I have heard cases where an alt's rectifier doesn't work very well and leaves a substantial ac ripple in the system (and amp power wire) which can be noisy, but I don't know if that actually happens or if it was just an interesting explanation for a problem someone didn't completely understand.