Hi,
Noise, a neverending story...
I just installed my empeg along with a Helix HXA-40X for front and rear systems, a Helix HXA-20X for subwoofer and a SONY XEC-505 activ-crossover in a BMW 318ti.
I've done nearly everything described in the FAQ and the BBS-threads dealing with this problem to avoid any noise from the beginning, e.g. I didn't place the audio cables next to the power wires, good mass connections and so on.
The result is quite good, but a silent alternator noise remains. Unplugging the RCA jacks from the Amp results in perfect silence, so the noise comes along with the audio cables. I've tried to use a high quality noise de-coupler (galvanic). The result was, that I could hear almost everything - turning the lights on/off, the airing, a very loud alternator noise...
QUESTION: How is this possible?
Thanks in advance

Thorsten

You're running a multi-amp system, right? On my system, changing the way my two amplifiers were connected altered the ground loop and prevented noise. Maybe try messing with that?

Yep, two amps...
Both connect to the same ground point.
What do you mean by 'the way they're connected.'?

I mean changing the RCA ins and outs as to whether the amps connect to each other or both the the head unit or whatever, as illustrated here.

The amps don't connect to each other, they are totally separated. Nevertheless, I've already tried to let the HX40 amp the sub and the HX20 the rear or front. It was always the same.
Anything about the De-Coupler paradoxon?

Another problem could be that you ground is not secured properly (ie the surface could have paint or some other form of debrie allowing an improper ground to your amp) another could be if you are running a single loop setup ( all negitive leads going back to the negitive post on the battery or one location for all grounds on the chassy of the vehicle ) not a good idea ensure all grounds are seperate. To fix this ......if you have already tried a noise filter......is to run a stiffening capacitor, now i know these are for easing the jolted loads on the battery but they also work very well to get rid of noise from the alternator......a good rule of thumb for this is 1000 micro ferods per watt of you system at about 16 to 20 volts

in a BMW 318ti.

Is it just my imagination, or do the BMWs, particularly the three-series, have more alternator noise problems than all the rest of the cars we discuss in this bbs? Combined?

tanstaafl.

Another possibility is the routing (and quality) of your RCA cables. They can pick up the noises you described along the path between the Empeg output and your amp inputs.

One experiment you can try is to temporarily bypass your current RCA cables with a new pair that stays way clear of any other car wiring. If this eliminates the whine and switching noises, it's almost surely a coupling problem with your current RCA cable routing. If this is the case, rerouting away from other wiring and using higher quality (stronger shielding) cables should fix this problem.

Good luck

Amps/caps/etc should be grounded at different points to prevent that kind of ground feedback..

My 3 series (325e) had a bad alternator whine with a cheap amp, but when I borrowed a friend's older not-too-bad amp, the problem just went away altogether. Don't know if the problem was due to just the amp or both the amp and the car, but more fuel for the fire....

ya its jsut the gear..my lexus has a decent amount of altwhine.. but im just too lazy to fix it iknow exactly what it is

I am fine sure that I've secured the ground properly...
Maybe I'll give the capacitor a try, but That would be quite expensive, especially the ones with electronic protection...

Yeah, they seem to produce a LOT of electronic smog...
I went to a local installer asking him how to eliminate the noise and he just said: 'oh, it's a 3 series BMW, I think you've gotta get along with some noise...'

I should give it a try, but I have to buy some then... And high quality cables have high quality prices...

The amps aren't cheap (at least in my opinion) ;-))
Audiotec Fischer, Helix HXA40-X....
But maybe there is a problem with those amps and BMW's...

Routing path and high quality cables are not mutually exclusive. They both can help if it's an inductive pick-up issue. By far the most effective solution is likely to be the cable routing. So you should be able to get away with a cheap RCA cable. For the "experiment" I'd buy a long one that you can run at least a foot away from any current-carrying wires.

If it's easy, you can also try repositioning your current RCA cable while the engine is running to see where it may be picking up noise. A fraction of an inch or a few degrees of rotation can have a big effect.

Is it just my imagination, or do the BMWs, particularly the three-series, have more alternator noise problems than all the rest of the cars we discuss in this bbs? Combined?

hmmm...i think the 3-series has competition from the boxster.

--dan.

Yes, you have very high quality amps. It could be your amps, or it could be your signal cable. I have a 1995 BMW M3 and had noise until I switched my amps from Phoenix Gold to Xtant. I also changed my signal cable to Monster Cable XLN-Pro, the best on the market.

First, you can't just unplug the RCA at the amp to see if the amp is the culprit. You have to then plug in muting plugs to the amp (shorted out RCA's). If you still hear noise at the amp, your amp is bringing in noise. If you don't hear noise, plug in the same muting plugs to the RCA's (with adaptors) in front. If you get noise there, your cables are introducing the noise. If not, you have to pull the Empeg out and run RCA's outside the car to the amp. If you are still getting noise, it's the power going to your Empeg that's giving you noise.

If the signal cables are bringing in noise, call David Navone (car audio god...see http://www.davidnavone.com for number) and beg and plead for a set of XLN Pro cables. I got mine for $50 and they list for about $250, so try him first. These are the BEST cables on the market and there is a petent pending on the "Delta Factor" technology. It basically keeps the signal wires a certain distance from anything it's routed by (chassis, other cables, etc.) to reduce noise.

The BMW's are particularly noisy because of the placement of the battery in the trunk.

I'm assuming you routed your signal wires down the middle?

Good luck!!!
Wes
'95 M3

I always thought the "short the cables at the amp" was a bogus diagnostic step. Because if the source of the problem is a ground loop, then disconnecting the RCA cables between the amp and the headunit will rid you of the noise even if the cables are perfectly good.

Thanks alot, I'll try everything you've mentioned as soon as possible.

BTW.:
My BMW has it's battery right next to the engine. Only the BMW's with little space in the engine bonnet have the battery in the trunk.

Yes, that step will not do anything if the problem is a ground loop. But, it will work if there is induced noise going into the speaker cables, RCA cables, or the amp.

Wes

My point is that the step is often described as being a way to detect inductive noise. But if done the way it was described in this thread, it would not be able to diagnose the difference between ground loop noise and inductive noise.