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interference of engine noise thru stereo 

 

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 Post subject: interference of engine noise thru stereo
Posted: Wed Aug 08, 2012 10:48 am 
Getting Side Ways
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so after finally putting new power cable thru my car i have a annoying whine while engine is running and the pitch goes up with the revs.

what can i do to get rid of it and where have i gone wrong?

 

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 Post subject: Re: interference of engine noise thru stereo
Posted: Wed Aug 08, 2012 11:11 am 
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Benny D wrote:
so after finally putting new power cable thru my car i have a annoying whine while engine is running and the pitch goes up with the revs.

what can i do to get rid of it and where have i gone wrong?


Are the RCA cables running along the power cable? If so, move them the RCAs to the other side of the car. Check your earth cables...especially at the head unit. Did you use the original earth wire from the wiring loom or the wire with the washer fitting from the aftermarket head unit? (assuming you are running an aftermarket head unit).

Also supposedly, RCA plugs on the head units may have a bad earth as well, causing the interference you hear.

That's all I can think of at the moment.

 

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 Post subject: Re: interference of engine noise thru stereo
Posted: Thu Aug 09, 2012 3:32 pm 
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second that.
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 Post subject: Re: interference of engine noise thru stereo
Posted: Thu Aug 09, 2012 3:38 pm 
Getting Side Ways
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hey phong, sorry but thanks for the help.
ive been running around getting paperwork ready for home loan and all sorta and been a bit busy.

now that you mention it, it has only really been happening since the new power cable went in. and i believe it was right nexto or at some points in contact with the RCA leads that head down to the amp.

and sorry for not much info. yes aftermarket head unit. cant remember exactly about the earth lead. 8-) .

gonna pull the trims apart probly saturday and get the power cable clear of the RCAs for a start and will report back :P

 

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 Post subject: Re: interference of engine noise thru stereo
Posted: Thu Aug 09, 2012 4:03 pm 
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Does its pitch and frequency change with engine revs ? If so you have got a ground loop . A ground loop is caused by individual components ie head unit and amp being earthed at different places in the car . Earth is NOT earth . You most probably have your head unit earthed much closer to the battery than your amp . If the voltage at the head unit earth point is 12.6 volts and the voltage at the amp earth point is say 12.55 volts you have an instant ground loop . Voltage differences as little as 1/10th of a volt will result in a very noticebale ground loop . There is a slight possibility it is inductance generated interference from having power wires and signal wires running too close but odds on it is a ground loop .

Is it a Pioneer head unit ? They have notoriously bad rca grounding that can be remedied like this .

http://s42.photobucket.com/albums/e319/ ... eerFix.jpg

Also pioneer head units have a little internal fused circuit called a pico fuse , when it pops you'll receive bad ignition whine. The ground wires on the rca help a little maybe 75% but it will still be there. To confirm this is your problem you can use a dmm and do a continuity test of your rca ground to the radio case , if its open that's your problem. Get it fixed so you dont damage your amp and or speakers. If this is the case it was most probably caused by a hot swap of your rcas while deck had power on...when you plugged rcas to amp under power ...it grounded back through rcas popping this pico fuse to save your deck
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 Post subject: Re: interference of engine noise thru stereo
Posted: Thu Aug 09, 2012 4:18 pm 
Getting Side Ways
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wrongwaynorris wrote:
Does its pitch and frequency change with engine revs ? If so you have got a ground loop . A ground loop is caused by individual components ie head unit and amp being earthed at different places in the car . Earth is NOT earth . You most probably have your head unit earthed much closer to the battery than your amp . If the voltage at the head unit earth point is 12.6 volts and the voltage at the amp earth point is say 12.55 volts you have an instant ground loop . Voltage differences as little as 1/10th of a volt will result in a very noticebale ground loop . There is a slight possibility it is inductance generated interference from having power wires and signal wires running too close but odds on it is a ground loop .

Is it a Pioneer head unit ? They have notoriously bad rca grounding that can be remedied like this .

http://s42.photobucket.com/albums/e319/ ... eerFix.jpg


Hmm.. Its a sony head unit.
What would be the best way to remedy this ground loop?
Seems impracticle to send ground wire either from the amp in the boot to the HU or vice versa..

 

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230RWKW@5250 rpm. 625NM.

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 Post subject: Re: interference of engine noise thru stereo
Posted: Thu Aug 09, 2012 4:24 pm 
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" Hmm.. Its a sony head unit.
What would be the best way to remedy this ground loop?
Seems impracticle to send ground wire either from the amp in the boot to the HU or vice versa.."

Hi Benny : It may be impractical but it will solve your problem instantly and permanently . Are either the head unit or amp ' s earthed directly to the cars bodywork ? If so remove the earth cable and sand / file the paint off till you have bare clean metal and try reearthing via this new earting point . If that doesn't work its back to a common earthing point . If you do go down this route use a good quality oxygen free copper lead as it has zero line impedence .
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 Post subject: Re: interference of engine noise thru stereo
Posted: Thu Aug 09, 2012 4:29 pm 
Getting Side Ways
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Ok I can't remember about the earth on the HU but I'll try sand the one on the amp down to see if it helps.
Thanx

 

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13.65@102mph. 2800 hi-Stall.
230RWKW@5250 rpm. 625NM.

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 Post subject: Re: interference of engine noise thru stereo
Posted: Thu Aug 09, 2012 4:33 pm 
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Also, if the RCA cables need to cross the power cable, cross them as close as possible to right angles. That should help reduce any interference through RCA/Power cable interchange.

 

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 Post subject: Re: interference of engine noise thru stereo
Posted: Thu Aug 09, 2012 4:46 pm 
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Hi Benny : Just read back through what I wrote and seem to have come across as dismissing what Phongus said re seperating power and signal wires . Phongus is totally right in so far as power and signal wires should be totally seperated due to induced current . Given todays modern cable insulation and the fact that most RCA leads are shielded it is a low percentage chance this is what is causing your problem but try it first as it is a free easy fix . Sorry Phongus

P.S. Bite the bullet and buy the best RCA cables and power cables you can . I use Jaycar as they have good quality stuff at very reasonable prices .

RCA 's - http://www.jaycar.com.au/productView.as ... TID=1030#4

Power cable - http://www.jaycar.com.au/productView.asp?ID=WH3092 ( Available in other gauges aswell , just used this for illustrative purposes )
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 Post subject: Re: interference of engine noise thru stereo
Posted: Thu Aug 09, 2012 5:32 pm 
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wrongwaynorris wrote:
Hi Benny : Just read back through what I wrote and seem to have come across as dismissing what Phongus said re seperating power and signal wires . Phongus is totally right in so far as power and signal wires should be totally seperated due to induced current . Given todays modern cable insulation and the fact that most RCA leads are shielded it is a low percentage chance this is what is causing your problem but try it first as it is a free easy fix . Sorry Phongus

P.S. Bite the bullet and buy the best RCA cables and power cables you can . I use Jaycar as they have good quality stuff at very reasonable prices .

RCA 's - http://www.jaycar.com.au/productView.as ... TID=1030#4

Power cable - http://www.jaycar.com.au/productView.asp?ID=WH3092 ( Available in other gauges aswell , just used this for illustrative purposes )


No need for apologies :). Everyone out to help and happy to be proven wrong.

 

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EL XR6 motor, EL ECU + J3 chip, WADE 1673 Camshaft, 3" S/S intake, Pacy 4480, 2.5" Hi flow cat, 2.5" Lukey exhaust.
Max Power = 144.6 rwkw (03/05/2008)

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 Post subject: Re: interference of engine noise thru stereo
Posted: Thu Aug 09, 2012 8:04 pm 
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wrongwaynorris wrote:
" Hmm.. Its a sony head unit.
What would be the best way to remedy this ground loop?
Seems impracticle to send ground wire either from the amp in the boot to the HU or vice versa.."

Hi Benny : It may be impractical but it will solve your problem instantly and permanently . Are either the head unit or amp ' s earthed directly to the cars bodywork ? If so remove the earth cable and sand / file the paint off till you have bare clean metal and try reearthing via this new earting point . If that doesn't work its back to a common earthing point . If you do go down this route use a good quality oxygen free copper lead as it has zero line impedence .


Or when people upgrade the power cable, they almost always forget to upgrade the body-battery earth cable.

Upgrade that to at least the same size as the power cable you use (I usually go a size bigger again).

e.g. in my LTD, I've got a 4GA positive run from battery to the boot. and replaced the little 12GA factory earth (from the overflow tank mount, to the batter), with a short 2GA run. I've got zero noise. By doing this, you help reduce the discrepancy between various earth points, hopefully eliminating ground loops without have to run a long ground cable to the boot.

 

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