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Amp/Stereo Interfearance ?

778 views 18 replies 4 participants last post by  wallopsri 
#1 ·
Last weekend I transferred the stereo (big amp, 7x10s, front comps, headunit, digital eg, cd changer) from my s/charged cav to my cav t, its been installed & wired in exactly the same way & was fine prior to removal.

I now get quite a loud crackling through all speakers when the engines running, its fine with the engine off or just the ignition on.

I`ve checked the obvious (rcas etc) but it hasn`t helped.

Anyone got an ideas as to a cause ?


Cheers

Rich
 
#3 ·
I made a fresh earth to clean bare metal on the chassis, I`ll check its tight though.
 
#4 · (Edited)
i would check;
speaker wires---ensure none are trapped or been trapped and shorted to ground. also check speaker terminals are not in contact with the door skins.

you don't mention if interference is present in all ch's inc the sub, or limited to a particular set.

try holding the outer rca plug sleeves,(the earth),in one hand, and the amp chassis in the other, does this affect the interference in any way?

do the same again but instead of using the amp chassis, use the amps earthing point in the boot, again any change?

try holding the headunits chassis and the rca earth sleeves, any change?

now again holding the headunits chassis and touching a decent chassis earth?

for the above tests you may find it easier to simply connect a spare length of wire to the cars batt -ve terminal, then bare the end and hold that between finger and thumb.

i assume you have already checked all the earths under the bonnet,(batt to chassis & engine/gearbox to chassis).

when you fitted your new power cable, did you ADD another batt to chassis earth to match the new power cable?

you say you earthed the amp to the chassis of the car, in what location, boot floor?

EDIT; have a read of this mate, it may help you trace your problem.
http://www.talkaudio.co.uk/vbb/showthread.php?t=164566
 
#5 ·
The noise is through both channels (front/rear, no sub fitted), I`ve checked everything amp end. I`ll check everything behind the centre console tomorrow (theres a lot of wiring in behind the two head units, I guess something could be loose back there).

The amps earthed to the rear bulkhead of the car, I`ve checked this with my power probe & its earthing fine. I`ve not added another earth battery end but nor did I in the previous cav the system was in.

Thanks for the help :beer:
 
#6 ·
I had a chance to check everything behind the dash today, nothing wrong there..

I can only guess theres something under the bonnet causing interfearance with the power lead as it only happens with the engine running, I`m thinking maybe the wiring for the chargecooler/water inj pumps or HID`s maybe causing this.

I`ll investigate further at the w/end but anyone else got any ideas in the meantime ?

Cheers

Rich
 
#8 ·
i would suggest you relocate your earth to the boot floor,(if available you could try earthing the amp direct to the battery using 4awg cable), if the noise stops you know then it is an earth problem.

try switching the system on with no rca leads connected to the amp and engine running;

if noise is still present its a fault associated to either the amp or its wiring.

if no noise then the fault is associated with the source,(rca leads, headunit, or headunits wiring).

again if noise is present with rca leads disconnected you should check all speaker connections, also check the speaker wires are in good condition,(not trapped or chaffed where they enter the doors), you should also check that no speaker terminals are in contact with any metal surface.

you could try disconnecting all speakers one at a time to see if noise is being introduced through one channel into all the rest.

with regard power cable suffering interference from a seperate power source under the bonnet, i doubt it, my power cable runs past my coil, and i have no interference issues.

i have heard however that aftermarket HIDS can cause noise issues when poorly wired,(ensure all wiring & connections associated with these are adequate and in good condition).

did you need to modify your door speaker mounting points to accomodate the aftermarket mids, because i've come across one or two that have enlarged the hole to accomodate larger baskets, but haven't enlarged them enough which has lead to the speaker terminals grounding to the door skin,(system plays fine until engine started, then rather than alt whine you get a crackling sound).
 
#9 ·
I`ve re-earthed to amp to the boot, no difference (I`ve since put it back to the bulkhead). I`ve re-earthed the head unit & equalizer no difference, I`ve checked the front speakers & wiring & re-checked all other wiring & all is in order.

The noise does go when the all rca`s are unplugged, maybe these are at fault but why are they fine when the engines not running ?

As for the HID`s they are wired in fine & the noise is there whether the lights are on or off.


Starting to get really annoying now, from memory to replace 2 x 5 metre quality rca`s will be pricey so I`d like to rule everything else out before chuck money at it in hope of fixing it.


Thanks for the help :beer:

Rich
 
#10 ·
ok, now try it with the rca's plugged into the amp, but not plugged into the headunit,(again unplug the rca's with the system off), if noise is not present with rca's plugged into the amp whilst engine running then its a headunit or headunits wiring fault.

EDIT; your not using a pioneer headunit are you????
 
#11 ·
I`ll try removing the rca`s from the eq tomorrow, its a Kenwood headunit but only really acts as a slave unit, I`ve got a spare Alpine competion spec h/unit, if all else fails I`ll sling it in to see if it helps.
 
#12 ·
I`ve done as suggested, not a blind bit of difference, I tried a high quality Soundlab RCA (worked fine with the old Alpine setup) across each channel & no difference, that has to rule the rca`s out.

I`ve rerouted the power lead to bypass most under bonnet electrical gubbins (as a result it runs next to the chargecooler which probably wont help), I`ll see if that helps tomorrow, I doubt it.

I`m tempted to try & run the amp from another battery (I`ve got a spare) by earthing it in the boot & running the power direct to the amp, at least that may rule out any probs with the power cable.


:confused: :confused:
 
#13 ·
if it was the power cable it would be present with the rca's removed, it isn't so the fault must be before the rca's.

remove the rca's from the eq outputs, no noise means its before those. replace these but remove the inputs from the eq, if no noise the fault is before the eq. reconnect eq and move to the headunit.

remove rca's from headunits outputs, no noise implies the fault lies with the headunit or its wiring.

i believe the headunit has a faulty earth track or simply a poor earth, causing it to earth via the rca's and through the amp.

would suggest you avoid using the cars audio loom earth, instead fit a new 4awg earth to the bulkhead or some other place on the cars chassis,(ensure you clean the area back to bare metal), now earth all your audio units up front here via a distribution block. would advise you fit secondary earths to both headunits chassis.

you say you are using multiple units as source drives, how do these units recieve power?

like i mentioned before, before you go any further i would disconnect all speakers from the amp and test each ch by connecting a spare speaker up to each one in turn with the engine running, if all ch's display the noise then carry on with the above, if only one ch displays the noise, then you have either a faulty speaker or a short to ground.
 
#14 ·
I had previuosly earthed the head unit & eq independantly from the cars original loom, didn`t help, I`ve also run a earth lead from the amps earth terminal to the head unit & this hasn`t made any differance.

The EQ receives its power from the headunit & is wired in the exact way it was in its previous home (my other cav).

I`ve tried bypassing the EQ & run the rca`s direct to the head unit & the problem still persists, if I get time tonight I`ll put the old Apline head unit back in to see if this helps.
 
#15 ·
Sorta sorted it, I`ve put 2 ground loop isolator in line to the amp, no crackling anymore, not the ideal solution but its worked. I did try the old apline head unit, various rewiring, suppressors, earthing rca`s with no luck.

Cheers for all the tips :beer:
 
#19 ·
so it is an earthing issue then;)


sometimes if you run the wires to close to existing loom or dont cross parralell they interfer
in 95% of cases this can be dismissed as an old wives tale.

on numerous occasions i have deliberately wired full systems down just one side, with no issues yet.

if you ensure you earth each item correctly, you will have no bother,(but, i must say, i always use triple shielded rca's and ofc speaker wire).
 
#16 ·
did you try wiring a spare speaker to each ch in turn to check if noise was present in all or just one channel.

the next step would have been swapping the alt for another from a scrappies,(sounds like possible supressor failure or some other alt fault).

but doesn't matter now if your happy.
 
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