ok so i have bravo 1.8 with alternator noise now i know that types of alternators on these cars have a habit of producing noise my brothers 146 and dads 155 did it same car electrics to a point and with the free engines very similar alternators but i figured modern sound equipment would be able to cope as my head unit was fine

ao anyway recently i have replaced everything with blaupunkt


head unit is
http://www.bluespot.co.uk/stock/queens.asp

speakers are all from there

57cm
130cm
and 5 by 7 all from th seriese

but i doubt there to blaim

and it all worked fine had absolutely no noise and sounded fantastic

i also got an active sub small one to hide in the car
http://www.bluespot.co.uk/stock/spkr0_2.asp

now this is connected to the main power in on the fuse box the other side of the dash and earthed to a bolt on the chassis all connections are soldered

now as soon as the amp comes on it seems to feed the noise from alternator back to the head unit and out all the speakers except for the sub speaker that obviously wouldn't play this high pitched wine

now if i disconnect the subs power it goes and works fine if i disconnect the rca's it goes well actually the apm turns it's self on and off with audio signal from these but for the 60 seconds that it remains on with these unplugged it's gone

if i simply touch one of the rcas earth to earth without connecting the centre pin it's back again

now the sub is wired to the head unit with
http://www.bluespot.co.uk/stock/preamp.asp
this

and
http://www.bluespot.co.uk/stock/rca.asp
this

as recomended in the instructions for both active sub and head unit

i'm going out to the car to reroute some cables and see if i can isolate the noise but i dont have much hope

any suggestions for how i can get rid of it

maybe an inline choke on the power

or i also found this
http://www.m-99.co.uk/Car_Audio/Noise_Suppressor/noise_suppressor.html

anyone think it would work in isolating the amp from the head unit or is it just worthless tat

thankyou all

edit: oh an i also noticed the noise is not affected buy altering the subs volume nor the head unit volume as such i can droun it out this may help in isolating were it's getting in you know kind of post amp in the head unit

The RCAs ground track at the head unit may be damaged. Take a piece of speaker cable and use it to ground the outer part of the RCAs, preferably at the headunit end. See if that helps.

are you sure the alternator is working properly could just not be kicking out enough power

You have noise from the grounding it is the alternator whine that you here, try putting the ground for the active sub somewhere further back, as close to the sub as poss. In the spare wheel bay is best.

ah well that's the thing i have the sub in the front of the car it's earthed on a bolt near the fuse box were i powered it i will try moving it to something more substantial (asive a masive bolt on the chasis isnt) but taking it thurther back towards the back of the car is out of the question i'm afraid

i have tested the phono end to end there goo i even tried another one i had

i know the alternator is fine as i said this noise is common on the free engine alternators even on standard fit stuff just not as loud

obviously with an amp it will be amplified

i was wondering if maybe the chasis of both components need earthing together the head unit and sub as neither is earthed to any part of the car

maybe a link wire between the earth strap on the back of the head unit

then again does the outer on the rca's not perform this task(i may be wrong) worth a try or earth both to the car

I would say that earthing properly will do the trick, and i mean the earth to the amplifier not the RCA's i would imagine you would get more noise if you did that but anyway why cant you earth directly to the chassis going to a point on the Fuse block is not idea.

no i didnt make myself clear sorry my earth is on a bolt securing a metal dash suport on that side to the shell but when the weathers good i'll try moving it it's pretty heafty so on such a small amp should be fine

littlepip17 said:

no i didnt make myself clear sorry my earth is on a bolt securing a metal dash suport on that side to the shell but when the weathers good i'll try moving it it's pretty heafty so on such a small amp should be fine

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Clearly not otherwise you wouldnt get earthing noise. I have found through the years that if you use anything other than a new earthing point then you get all sorts of problems from ground loop to completely blowing the amp.

Having it on one of the cars original bolting point may not be a good earth and will cause problems. My advice is to find a good point that is clear of electronics and bolts then Rub down the area and bolt the earth to it sealing with vaseline or silicon.

Its funny that you are geting these problems when you havnt done things the conventional way so it is a process of elimination get things done properly then if the problem persists will we have to start looking at alternatives.

i can see your point about unconventional ways and the close proximity to other electronics but i have checked the bolt as it's internal it's clean and free from any corosion ass is the metal surface it fixes to the car it's not like i've just randomly bolted it to anything that i can undo

i have said i'll try moving it to something else maybe the air bag ecu earth in the centre console i was weary of messing with that as i dont want to damage the ecu i'm not to woried about causing faults i can easily clear them at work

anyway i have bought one of them rec isolator things and i'm quite hapy with the integrity of my powers and earths not nessesarily the positions but anyway i will post back with the results waeather it's worthless tat or actually produses good results

my aim basically as it standas now is to reduce the noise as much as posible simply buy playing with what i have along with everyones sugestions and see how i get on then try the rcs thing

if all fails i'll have to start again back to basics and see how it goes it's the best way at the end of the day

littlepip17 said:

i can see your point about unconventinal ways and the close proximity to other electronics but i have checked the bolt as it's internal it'#s clean and free from any corosion ass is the metal surface it fixes to the car it's not like i've just randomly bolted it to anything that i can undoo

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Ahh but how do you know it is a good point to earth the amp, just because it go's to ground doesnt mean that it does it efficiently.
I have just had a thought is the sub in the front if so why if not then the earth should be in the back with it.

volxstu said:

Ahh but how do you know it is a good point to earth the amp, just because it go's to ground doesnt mean that it does it efficiently.
I have just had a thought is the sub in the front if so why if not then the earth should be in the back with it.

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yea sub is in the front cos i put it there up in the pasengers foot well out of sight

too big to go under the seats and i don't want anything in the boot i regularly use the boot with seats down

I had a similar problem due to a faulty RCA lead. If you have a spare one to hand its worth trying it. It can be an earth fault, but it is not always caused by this.

mirafioriman said:

I had a similar problem due to a faulty RCA lead. If you have a spare one to hand its worth trying it. It can be an earth fault, but it is not always caused by this.

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yea i thought that too i tested it with a metre and even changed it for another so tried that but thanks

littlepip17 said:

yea i thought that too i tested it with a metre and even changed it for another so tried that but thanks

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ok so my rca isolator arived today and it works perfectly does exactly what it says on the box very good prodyct

althou just cos that fact the noise is there i am still tempted to fit a choke on the power to the amp aswell just cos i want it perfect

thanks everyone for your help

i'd love a wiring diagram for the thing i got but from what i can gather it's simply a choke on the earth path of the rcas

also does not affect the sound down to the sub atall

Nice one there are people that believe that they do not work you have just proved otherwise.

volxstu said:

Nice one there are people that believe that they do not work you have just proved otherwise.

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i was one of them first time i saw one i thought that will do nothing

but amazingly i'm quite wrong and for an average of about 5 to 10 quid on ebay you can't go wrong

i been reading the box and it seems it has something to do with differing potential difference on the rca ground path

my idea of grounding the cases directly to each other may have had a similar effect who knows