Alternator interference...??

[onebar]

Just looking for a bit of help with regards to alternator interference. have a 2800w monoblock and a 400w amp in the boot but getting a whistling interference from the 400w amp. Im pretty sure is the alternator and i think i need some kind of inline suppressor. have found this but not sure if its the right thing as i would of thought it would have gone inline on the 12v feed to the amp??

http://www.halfords.com/webapp/wcs/..._productId_189944_langId_-1_categoryId_165626

also found this but spoke to a dude at halfrauds who after trying to tell me it was exactly what i needed quickly backtracked after i showed him the size of the power cable.

http://www.halfords.com/webapp/wcs/..._productId_209859_langId_-1_categoryId_165626

any help at all would be greatly appreciated.

i really need to lose the stupid whistling!!!

 

[AlexG]

Where are you earthing your amps too?

If its not the earths it will be the RCA leads dude. What ones are you using cheapo ones from a wiring kit? I had them before and i used to get a whine, in my new car i have just put in some audison sheilded 4 way RCAs £45 worth! You can also get a bit of interferance of you run the two sets of rcas together i think so try and seperate them a wee bit.

 

[Struggler]

i had this kinda interferance,

turned out to be shitty RCA cables,

audioleads ones worked perfectly, sell em in halfords for £10

 

[onebar]

iv had the problem before and thats exactly what i thought because last time it was the rcas. so i tried the rca's from the monoblock amp which were working fine and very high quality and i still get the interference?? everybody ive spoken to seems to think alternator?? im determined to get this sorted today lol!!!

 

[onebar]

oh and BOTH amps are earthed to the rear headlight...... its been suggested that i earth them seperately? Only thing is i dont see this making a difference as the earth shouldnt have any current through it anyway u either have a good earth or a bad earth and the fact that the 2800w amp works absolutely perfect would indicate that it is a good earth??

 

[alsh]

have you routed the power lead for the amp near to the rca?? if so.. thats why you will hear a whining noise.

 

[onebar]

no mate all power and signal are kept completely seperate rcas are down the driver side and remote and power down the passenger side. Also checked the remote incase it was snagged and even replaced the remote just to be super safe lol.

 

[wallop]

Morning mate....

Will post a guide to locate the source of your fault shortly....

Should only take a few minutes to read but I type with one finger, so it will take a while to type....

 

[wallop]

System Switched OFF

remove RCA leads from affected amplifier....

Switch system ON and play as normal

Noise still present indicates fault lies in the boot, (99% amplifier earth location)....

Noise no longer present indicates fault lies before the affected amp....

System Switched OFF

Replace RCA leads into affected amplifier....

Pop head unit out and remove the RCA leads that feed the affected amp....

Switch System ON and play as normal....

Noise still present indicates faulty RCA leads...

Noise not present indicates fault with head unit or associated loom....

Let me know how you get on....

 

[onebar]

your a legend! im going to go do all that now and i will let u know how i get on. really appreciate the help!

 

[onebar]

still getting the same interference. the subs work fine from both pre outs so i cant see it being the headunit or loom. the headunit works perfectly in a different car with no interference at all, by the sounds of it its going to be the alternator.....???

 

[onebar]

i have a feeling its going to be the earths!! have just spoken to an ICE company who say 99% is earth. only thing is when i take the rca's out the noise stops....??

 

[wallop]

Just a few more questions then;

1, Is the noise present when system is playing but engine is OFF???

2, Is head unit a Pioneer???

3, You have tried the head unit in another car this morning???

Poor amplifier earthing causes a 'ground loop' which basically means the amp is earthing through two or more different sites causing feed back to occur....The amplifier could be earthing through the head unit via the RCA leads....

 

[AlexG]

Connect your earths to the Isofix bar. There are two bolts holding it in one on either side of the boot at the bottom of the rear seats.

Running mulitiple rca leads can give you interferance. you said that the rca for your monoblock are good quality but your rcas for your components are not. Id say switch them rcas for some better quality ones.

 

[onebar]

have switched the rca's and subs are still fine but still getting interference through 6x9's. have also now connected both earths to isofix bar, also bought a splitter box for the power and fitted that as before it was just bridged between the amps. Iv changed the rcas to the amp with interference to a different channel on the headunit and still getting the same problem??

 

[AlexG]

No body has mentioned the big three yet?

How about earthing your headunit directly to the chasis?

 

[onebar]

its earthed directly to a cleaned bit on the isobar on the back seat.

 

[wallop]

have switched the rca's and subs are still fine but still getting interference through 6x9's. have also now connected both earths to isofix bar, also bought a splitter box for the power and fitted that as before it was just bridged between the amps. Iv changed the rcas to the amp with interference to a different channel on the headunit and still getting the same problem??

Please answer my earlier questions in post 13.....

1, Is the noise present when system is playing but engine is OFF???

2, Is head unit a Pioneer???

3, You have tried the head unit in another car this morning???

Along with....

4, Does interference change in pitch when you rev the engine???

5, Does interference change in volume when you turn stereo up/down???

 

[matt|H]

2, Is head unit a Pioneer???

Bloody Pioneer nothing but trouble lol.

 

[onebar]

when the engine is off there is still interference, and when i start the engine it whistles, the pitch increases with the rpm. Havent tried another headunit but have tried a different pre-out on the back of the head unit and still get the same problem. Will try another headunit some point but i had 2 amps running from it before with the same kind of set up and no problems at all.

 

[onebar]

and its a sony headunit

 

[AlexG]

What gauge cable have you got going from the negative on the battery to the engine and chasis?

 

[onebar]

not sure m8 i havent looked to be honest, somebody did mention earthin everything to the battery though??

 

[wallop]

OK, to recap & confirm symptoms;

1, Interference present whether engine running or not...
2, RCA leads removed from amp, No interference...
3, RCA leads removed from head unit, but fitted in amp??? Can't locate an answer...

If you try running the system with the RCA leads removed from the head unit but fitted in the amp and get no interference then that indicates head unit earth track issues or associated loom issues.....

If you do get interference, (which I think you will), then I would replace the RCA leads, (sounds like the shielding inside the leads has failed)....

What gauge cable have you got going from the negative on the battery to the engine and chasis?

With regards^^this^^....If interference was only present whilst the engine was running then this could have an effect, but interference whilst engine not running indicates a faulty item rather than a resistance induced ground loop....

Ah crap!!! I'm supplying reasons again

 

[onebar]

haha after replacing everything bar the amp i think im gona possibly try replacing it. where can i get a cheap little 400 watt amp?? I cant say iv tried with the rcas in the amp but not the headunit il check that out tomorrow at some point. if i do get interference il try with a different headunit and see how that goes. only thing i dont understand is how it worked with the same set up before....only difference now is the amp??

 

[AlexG]

sony headunit?

Did you say you have tried another headunit?
I had one in my last install and it was s**t imo. lots of clipping.

 

[wallop]

haha after replacing everything bar the amp i think im gona possibly try replacing it. where can i get a cheap little 400 watt amp?? I cant say iv tried with the rcas in the amp but not the headunit il check that out tomorrow at some point. if i do get interference il try with a different headunit and see how that goes. only thing i dont understand is how it worked with the same set up before....only difference now is the amp??

With regards highlighted sentences;
This would indicate faulty RCA leads, not a faulty head unit

 

[onebar]

as before m8 have tried my sub rca's which are high quality and still getting the same problem. I have a preout on my main amp could i try running a signal from that output to the input on the smaller amp?