Help with stereo noise

[John S]

Ok, I've got a problem and I was hoping that there is a bona fide car stereo expert lurking around that offer some advice.



I've got a real bad (loud) hum/popping sound in my system. With the Key in ACC it sounds great, very clean no electrical noise. If I turn the key to on I get an initial high pitched squeal that dies down into a low popping sound then stops, when I start the engine hum/popping starts up. It's not ignition noise and it does not vary with RPM. And only happens when the cars electronics are on. The electronics consists of:
FAST XFI ecu
MSD 6a
MSD blaster coil
Aeromotive A1000 electric fuel pump with the pump controller.
MSD one wire alternator

I've checked all the grounds and power leads, disconnected the RCA leads from the stereo to the amps and even swapped them out, I even installed the ground loop isolators in the RCA outputs from the stereo.

I run 3 amps in the car, I do not get any noise at all from my sub amp, but I do get it from the 4ch amps controlling my rear speakers and the 4ch amp on my front speakers. All three amps are grounded to the chassis with a 4awg ground and the power to the amps is from a 2AWG lead connected directly to the battery (engine comp)

Although loud the level remains constant and I can drown it out with the volume control.

Since it only happens when the key is ON or the engine running I though it might be related to the MSD or pump but I dont know of any way to bypass them and test it out.
I dont know where to look next.... any advice sure would be appreciated!

[formula]

how are your wires run? Power anywhere near speakers? Sounds like you might be bleeding EMF over from your juice lines to the speaker lines...

[all wired]

its sounds like the problem is coming from something that powers with ignition. MSD boxes and fuel pumps can definitely create noise. I would recommend turning the ignition on (so that the noise is present), then disconnect the MSD, see if there is change. If not, disconnect the fuel pump, etc.

Once you isolate where the noise is coming from, now you can take steps to eliminate it. If is the fuel pump, make sure the fuel pump power wire isn't running with the RCAs, etc.

[IMPALAMAN1]

msd sells a capacitor.... i had the same problem.....

ran my wires ... reran..... reran again.... msd is the monkey wrench. added the cap to the power into the 6a.... no more noise....

i believe the new one is blue.

http://static.summitracing.com/globa...e/msd-8830.jpg

[class67]

Install a capacitor and seperate your power wires and speaker wires. Run them on opposite sides of the car.

[redfire69]

battery is grounded to chassis/body as well?

[audioman]

Noise can come from different things. Power,EMI and or ground loops. The first test I would do is take a ground wire from the radio and attach on your amp. If that didn't work putting a cap in the system is reducing the voltage spikes in your car and filters the voltage so that could be a case and I've seen in the past if you have an older and or inexpensive amp, noise could be radiated from the power supply. I'm not knocking your equipment but you didn't tell us what you where running. Even if it's good equipment, things can go weird.
You might even have a bad cell in your main battery.

It's not easy removing noise and sometimes you just have to try different things to get the noise to stop.

I have 3400 watts of power in my system and every time I get a noise I know my voltage between my two batteries are freaking out. That's the price I pay for the system.

3400 watts=(if real watts) 283 amps of draw at full tilt at 12 volts.
Not magic it's ohm's law like mother nature: can't be fooled.

[IMPALAMAN1]

AH YES GOOD POINT. the power supplys in the old fosgate bd series were infamous for creating ripple.... and a funny humming noise it was usually the power supply solder joints to the board.... i even had one of my linear power 2.2's give me some grief from the power supply but it went away with a clean 12 volts.... the wonderful world of electronics.

let us know whice one works for you.