hooked up 4 channel amp in boot now have engine noise??

[drizzt_stylez]

Yep, my system (the one DeeCee mentioned spending many hours on ) wasn't a cheap system. Verrrrry frustrating problem indeed.

As DeeCee said, its a process of elimination. Check/replace/sand (etc) your grounds, tidy your cabling up, swap in other gear one at a time to see if that eliminates the noise. DeeCee found that it was my Headunit causing the noise (after spending a hell of a lot of time trying every other method to fix it ) when he swapped mine out for his and the noise stopped.

[astrae]

I had this problem for a while in my Levin. I had my hand in the dash moving the rca's around the noise got dramatically worse the closer i got to metal.

Basically the professional looking Rca cables I got off trademe were crap... had no insulation at all. basically looked like alarm cable...

Unsoldered the plugs off them, went down to DSE and bought some insulated audio cable and soldered the plugs back on. problem solved and made to length...

[igor]

*believes Matt*

You've got a changing current which is a changing magnetic field, the magnitude of the change (rather than the direction) dictates the field. If we needed AC to induce a current then ignition coils wouldn't work...

There is a big difference between the magnetic field generated by an ignition coil, and the magnetic field generated by a DC power cable. For one, the ignition coil using the flux generated by a collapsing magnetic field to create the high-voltage ignition spark. You hardly get that much variation in magnetic field off an amp cable.

If you are getting alternator noise through you system, then the chances are that the high-frequency filter on the alternator is $&#$%, you just didn't notice it until you installed your audio incorrectly.

[RevolutionStarlet89]

I have the same problem, have tried seperating cables, made sure the ground isnt looping and problem hasnt dissapeared, if i "wriggle" the rca cords around you can get risd of the sound for a short time but no more that 15 secs.
Would lyk sum light to be shone on the matter.......

[sergei]

I was talking not about NOISE SUPRESSOR but LINE TRANSFORMERS.
You have to understand where the noise coming from.
Nose supressors are desinged to remove noise from power supply/charging system. But the problem with audio is that noise is supressed really well on power side of the things, while the signal side of of the amp is not, because of its nature the amp has a quiet high gain and the loop created by extra ground wire acts as a radio, amplifying all that wine. if you will hook up the speaker to battery thru transformer (to eliminate DC component) while the car is running, you will probably hear very little noise.
This ground loop eliminator box is connected to RCA cables just before amp, what basically inside is a transformer (1 to 1).

Have you heard of balanced, or twisted pair?
The reason behind that twisted pair performs better (SNR and bandwidth) then a good shielded coax, is that the external noise is canceld out in twisted pair (due to nature of it). Balanced XLR is like a twisted pair (but slightly different) vs RCA (wich is like a COAX, and basically is a low quality COAX).

Most of the alternator whine noise is coming from shielding on RCA cables. (due to ground loops mentioned above).

I agree noise supressors are waste of time and money, while groun loop isolation is not.

Have tried to insert RCAs half way (as outer contact - shielding, not touching the amp) you will see that noise wilh reduce alot.

[sergei]

oh, and there is no high frequency filter on alternator, the unit is a 3 phase generator with a diode bridge + voltage regulator. All that noise is coming from harmonics from sharp dips where the 3 phases overlap after rectifying. an there is no reasonble filter wich could filter that in that ammount of current sometimes alternetor has to supply, hence all that unilftered harmonics are picked up by ground loops, and thats why noise supressors don't really work as most of the amps and head units will have a good filter inside (usually large coil + large capacitor) and incase of amps they have switching power supplies anyway wich operate at much higher frequency (~40Khz 50Volts), and higher frequencies once rectified are very easily filtered...

[RevolutionStarlet89]

I would advise anyone with this problem to check their headunit is not faulty, i recently found this out which was a big relif, so much for noise suppressors etc.....