XSeries-forum

Hi Guys,

I have just installed a Denon 6 channel amp that plays through a old skool Alpine DSP Eq after modding the BM54 for a line out through RCA connections.

I now have the alternator whine coming through and also when I start the car all the speakers make a popping like noise.

Anyone have any ideas how to eliminate this??

I used the BM54 body as the earth for the lineout jacks.
Also in the pinout diagrams it shows line out level output, could I have picked up a lineout signal from these pins?

Thanks in advance for any advice

Sorry forgot to add that I have taken the live for the amp from a spare location in the big fuse box that the battery cable goes into and earthed it at the earth point just behind the spare wheel.
The permanent live for the Eq has been taken from the tow plug.

Earth loop feedback me thinks...
You can try removing the shield from the plugs at either end (Pull out until the outer connection breaks but leaves the inner connected)

Or ensure you have a good earth at all points leading to a common point..

You can get an earth loop isolator but that is covering the issue rather than sorting the problem

Ref the popping, perhaps a timer on the supply (or outputs) until engine running ?

Thanks Steamrotter

Have tried the ground loop isolator but didnt make a difference and also tried earthing the headunit case with a fresh earth straight to the casing as I have done the line out rca conversion on the BM54.

I have to admit i have the same whine from mine.
However from different cause..

I have the Business RDS cassette jobby no BM54.
I fitted speaker to line out convertor and 2 amps (4chan & 2chan)

Get the whine from that lot but probably due to the second battery causing a capacitive load..

My solution to the whine..
Turn it up..
1300W soon drowns that out!!!

the whine is definitely earth looping. few things to try:
1. first and foremost give a super solid earth connection to the amp. when the earth isn't strong enough the amp draws earth from the line in. this causes earth loop.
2. disconnect the earth side of the line in entirely, leaving only the positive of the line in connected, on the amp's line-in, earth the outer to the car (this will overcome the prob by giving a solid earth through line-in but its a roundabout, 1 above is the solution)
3. earth loop isolators - i think u've already tried this.

the pop (or thump) - u can build something like this.. or fix something like this.. tbh even i have this, didn't bother to address this, now u've got me thinkin :-[

The speaker pop is a very high energy spike and has been known in some (worst) cases to push the voice coil out of the magnet. Seen it done on a 15" stack and it was quite impressive, if not expensive!!!

Continuation of this could weaken the surround and adhesive..

Jayana the amp at the moment is earthed to a earthing point on the chassis just behind the spare wheel straight to the body. I will have a go at earthing straight to the amp casing and see if it makes a difference.
I have heard you can fit a resistor to a point between the alternator and the distribution point that helps but not quite sure where or which resistor.

A resistor will drop the voltage which you may not want to do.  Do you mean a suppressor, in which case that is a capacitor to kill the whine caused by AC ripple from the alternator (hence the whine) on the DC feed?

Richard

Richard you may well be right. Any ideas which one and where to fit it??
Its been a few months now and the misses getting well p#@sed off now and trying to get me to put everything back to standard  :'( :'(

Usually there should be one on the alternator itself.  It's years since I fitted them but I seem to remember them being between the alternator case and one of the positive leads.

You need to kill the sine wave at the 'generator' end.  The alternative would be between the case of the amp and the power feed in.

Have a web search for fitting suppressors and see if that helps.  BMW do fit several for the OEM ICE kit and I believe they are at the rear somewhere.

Richard

'pop' is normally caused when the amp turns on before the source.

have you got the 'remote on' taken from the HU so that it turns on after the HU?

as for the whine.. advice given sounds about right, it will prob be a poor earth. try earthing direct to the battery terminal. with the correct gauge wire for the amp.

Thanks Richard I will try and do something with it on the weekend.
Redz I have taken the remote on for the Eq and the Amp from pin 16 on the radio which is suppose to be the Acc Remote.