Do you insulate RCAs?

If so, what would you use? Is there a specific place to run the cables from the HU to the boot? Mine just go down the drivers side, just under the carpet. The speaker cables go along side, and power cables go down the other side.

I have alternator whine that comes and goes every so often, and I've been trying to keep the RCA's and power cables as far apart as possible to try and prevent it. I've just spent a while making sure the amp end is neat and tidy, but it's made no difference to the whine. Is there anything behind the HU that the RCA should be kept away from?
 

NeX

You're after my robot bee
Club Member
If so, what would you use? Is there a specific place to run the cables from the HU to the boot? Mine just go down the drivers side, just under the carpet. The speaker cables go along side, and power cables go down the other side.

I have alternator whine that comes and goes every so often, and I've been trying to keep the RCA's and power cables as far apart as possible to try and prevent it. I've just spent a while making sure the amp end is neat and tidy, but it's made no difference to the whine. Is there anything behind the HU that the RCA should be kept away from?
for a quick fix just fit a ground loop isolator and the noise will go away,

all cables in your car generate a magnetic field around them which can cause problems in RCA leads if they are too close, but we are talking about an inch away should be fine, especially if the RCAs are shielded. but that is not what is causing the problem.

the noise comes from one or more devices getting its ground connection via the RCAs instead from its dedicated ground point.

so step one, find all the ground points, for the headunit, amps etc, make sure they are very good contacts, the best would be to wire them all directly to the battery. make sure the wires are the same or thicker than the positive cables, make sure they are attached properly, crimped properly, etc just make the ground connections as close to perfect in every way.

if the noise is still there it may be a ground connection from the engine to the battery, it would be a good idea to fit a nice new ground to the engine and a new cable to the alternator while you are at it, and make sure the battery is properly grounded to the chassis too.

if the noise is still there, make sure your RCAs are built properly, they should have a positive and ground cable inside for each phono, then around that is a braid which should be connected to ground at the sender end (HU) but free at the other end. then over that should be foil which is not connected to anything at either end. that is how proper RCAs should be put together.

if all else fails then you will have to resort to a ground loop isolator, but its not really getting to the root of the problem
 

Seb_

Give me some frogs.
Site Supporter
the best would be to wire them all directly to the battery.
What Nex said. Battery - is the best ground you can find on the car, and the most secured if it's tighten correctly. Remember me when I fitted my Panasonic headunit on the 1.0, the stock ####ty ground behind the headunit slot wasn't good enough and the headunit wouldn't even start, so I ran a wire directly to the battery and then never had a problem.
 
Thanks for your replies. As for ground loop isolators, are they much the same or do you get what you pay for?

Is there any reason why it might come and go like it does? When I've had it before it's been constant.

Cheers,
Tom
 

NeX

You're after my robot bee
Club Member
Thanks for your replies. As for ground loop isolators, are they much the same or do you get what you pay for?

Is there any reason why it might come and go like it does? When I've had it before it's been constant.

Cheers,
Tom
if it comes and goes, i would be 99% sure its a bad ground or loose contact. as for ground loop isolators they are so amazingly basic that i really doubt you could buy a bad one. £5 from ebay? they are nothing more than a couple of 1:1 transformers inside
 
as for ground loop isolators they are so amazingly basic that i really doubt you could buy a bad one. £5 from ebay? they are nothing more than a couple of 1:1 transformers inside
I'm afraid I've bought a bad one ;) Was £6 from eBay, and don't get me wrong it works - the sound quality however is just awful! Sounds like a cheap ipod dock. On removing it I get the buzzing and whining again, but the quality of sound is incomparable. I'm looking for ones from reputable companies now, then in theory I can send it back if it's crap.

Tom
 
Just tried a more substantial one and have exactly the same problem. It takes out the midbass and lower end sound. Will be taking it back in the morning.

Are there any other ways to remove the whine without stripping the cables and relaying?
 

r-reg-sr

-------
Site Supporter
what amp is it,,they sposeed to clean that noise out
old jvc here,with all wires running down pass side under carpet,no buzzing:)
 
is a good idea to keep wires as short as possible. do not coil the rca if it is too long. this can induce the whine.
I have cable tied the excess wires behind the amplifier. I'll try laying them under the back seat to reduce that, and see if it helps the problem.

what amp is it,,they sposeed to clean that noise out
old jvc here,with all wires running down pass side under carpet,no buzzing:)
It's a Fli 900 amp :/ I know, I know! :p Rainbow Componants in front and Vibe Blackair ltd. ed. 1600w 12".
 
I have relayed all cables in the rear half of the car and made sure not to coil anything, but there's no change to the noise.
 

Retepetsir

King of Subsonic
As above, re-do your earths on the amp/amps along with a new dedicated earth on the headunit.

Do you get alt whine/intereference on all channels or just one/some?

Running signal cables near power cables shouldn't be a problem, but signal cables near speaker wire isn't so good. Try running a separate RCA just straight from the headunit front to back without laying it under the carpet and see if that solves your problem.
 
Thanks, I have re-done the amp earths, and am now about to re-earth the HU itself. Is there a specific point to use on the HU, or can I take it from anywhere on the metal casing? Or should I use the original earth on the loom but re-locate it?

Does the size of the cable used matter? I've got a standard amp earth cable I could use, or some remote turn-on cable.

Whine seems to be on all channels. I'll have to source another RCA from somewhere to try it...
 
I've added a ground to the HU metal casing by a screw at the back and a bolt on the chassis, but it's made no difference to the whine.

The speakers have also started to "pop" recently when powered on or off, or when adjusting volume. The HU went into "protect" too a couple of days ago but hasn't since I had it out and checked the wires.

Is it possible that:

a) the wiring loom is dodgy - when you move the wires around, sometimes the whine stops
b) the RCA terminals at either end could cause this - same findings as above
c) the amp itself is nackered - I had a similar problem in the Peugeot with the same setup
 
I'm fairly confident my amp is buggered, and that's what's causing my issues :/ Might try and convince Halfords to let me plug in an unboxed one to confirm... :S
 

Retepetsir

King of Subsonic
Sounds like a combo of dodgy amp and bad earth on the headunit....run the headunits own ground wire (from loom) straight to a clean earthing point. See what happens.
 
Sounds like a combo of dodgy amp and bad earth on the headunit....run the headunits own ground wire (from loom) straight to a clean earthing point. See what happens.
Thanks, I fitted a new earth a couple of weeks ago from loom to an existing earth point in the passenger footwell, but it hasn't affected the noise.

Today I tried again running an RCA from the HU over the headrests to the amp in the boot, which also made no difference, so I can rule out the RCAs picking anything up. It's also not anything between the amp and the speakers as the gain determines the volume of noise. For now I've cut the gains from just under half to minimum, which reduces the noise to live-able level.

If the gain changes noise level and RCA's aren't to blame, does that suggest HU as the problem?

I'm going to try and scrounge a HU with pre-outs from somewhere to eliminate this as a cause.
 

James

Chairman
Earth tracks on the HU's circuit board may of gone.
Pioneer headunits were notorious for this sort of thing, both mine have had a little surface mount fuse pop (due to my own negligence) when the RCAs to the amp touched the body of the car, or down to some poor earth on the amp itself.

There were two ways round it in that case:
  1. Replace the fuse in the headunit with a beefier one (not easy to do)
  2. Take a load of wire from the ground in the headunit and wrap it round the RCA shields, like this:
    508955.jpg
 
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