Aftermarket stereo engine noise problem! (Pro's PLEASE help)

[wally91vhevrolet]

I thought I knew everything there was to know. Well here we go. I've got a 91 Silverado and I have BAD engine noise on my subs and my tweeters. I have an Audiobahn A8000T amp hooked up to my subs and an Audiobahn A6004T 4 channel amp on 4 tweeters. I regrounded all my grounds in new places and was SURE to make a solid connection. I also purchased some Rockford Fosgate signal cables for both amps. I thought for sure this would eliminate the engine noise. But its still there. Before I start the truck up, everything is chrystal clear. When I start the truck the subs rumble really low and the tweeters make a high pich buzz noise. Ive tried messing with all my settings and nothing changes it. Adjusting the level only makes it louder or softer. What can I get to eliminate this engine noise or what can I do? I've got my power wire that runs from my battery, through the firewall, down the passengers side of my truck back to my amps. The wire is 4GA from the battery to a splitter in the truck and then the wires split to two 8GA wires. One of those runs directly to my A6004T amp and the other runs to an Audiobahn capacitor and my A8000T amp. Each ground is in a separate place on the frame of the truck and are 8 GA wires. My signal cables are only 6.6ft and run from my CD player down the middle of the truck to the amps. The CD player is a Pioneer DEH-P9600MP and is only 6 months old. I may also point out that before I had the A6004T amp, I had a Sony 4 channel amp and there was LITTLE engine noise. None on the subs. Now that I put in this new amp, Its gotten way worse. All help is appreciated.

[superchuckles]

ok, first off, the big mistake you're making is seperate ground points. in a perfect world, or where you have enough wire & distances aren't too far, the ideal way to do ANY stereo system you want to keep noise out of is to ALWAYS ground EVERYTHING at the same point if at all possible. the reason you want to do this is, since your low level imputs on the amplifier are such minute voltages, any difference in ground potential between any two devices on the system get translated into motor noise (alternator and distributor) in proportion to the distance between ground points. also, the same thing applies on the other side..... i.e. when possible, connect all BATT constant hots to the same power connection - same reason behind it. doing just these two things eliminates 95% of the problems in installs (in the last 15 years, this is all i've had to do to eliminate any motor noise problems..... & i've done a lot of custom systems). maybe another 2% of it can be eliminated by running your RCA cables in a route that is as short as practical, but either at right angles to, or as far away from as possible in relation to your power cables. "filters" of the $10-$20 variety that consist of a small capacitor & maybe even a choke are a waste of your time & money, since the choke will only lower voltage to your system & thereby add distortion too). large caps are ok for getting rid of some of it, but by your description, i would unhook all those seperate grounds (god that was like the very opposite of what you should have done.... i can feel the other installers out there cringing at the thought) and find one very good point to ground them to. when you're done with all that, turn down the gains on your amps as far as possible. by that i mean the ideal setting on your gains should be where to hit your max volume, your stereos volume control would be set to about 3/4 of the way up. if turning your stereo volume up to only 1/3 or 1/2 the way up is blasting you out, you have your gains WAY too high- turn them down!

[wally91vhevrolet]

the ONLY reason i grounded it in seaparate spots is because one ground on my 4 channel amp would need to be extremely long to reach the ground for my cap and sub amp... i HAD it like this and STILL had motor noise... that is why i changed it... i made the grounds MUCH shorter and grounded all 3 directly on the frame (2 on one side and 1 on the other) it didnt change anything and i know i dont know a WHOLE lot, but if it was a bad thing the noise would have been worse this way.. also my signal cables run down the center of my truck not crossing any power wires.. the only place it comes CLOSE to a power wire is when it connects to the amp.. also where i had everything grounded to the same part on my frame, the metal actually changed colors a bit.. this is also another reason that led me to changing the grounds.. another question.. if it had anything to do with the grounds on my amps wouldnt the noise still occur with no signal cables connected to my amps (with my amps still on) because when i disconnect my signal cables it goes away COMPLETELY.. even when i disconnect them from my CD player it goes away COMPLETELY.. so I'm believing the noise is being picked up through my CD player some how other wise it would still be there when i disconnect the signal cables?

[wally91vhevrolet]

OK heres an update of everthing new i've tried. I emailed pioneer and cardomain and tried these things they recomended.
-Ran a return ground from the amps to the cd player (noise still there)
-Moved my RCA cables around to see if there was any change in the noise (no change)
-Checked to see if noise was present when key is in "ign" position and motor is NOT on (noise was present but not as loud. It is deffinately louder when the motor IS running)
-While in the "ign" position without motor running i pulled some fuses (A/C, lights, ect...) (no change in sound)
-Unhooked alternator with motor running to check for change in sound (slightly softer)
I'm led to believe this is a mix between alternator noise, distributor noise, and some type of electric interference. Please help me out im at the edge of just giving up because I have COMPLETELY run out of ideas.

[superchuckles]

ok, the reason i say use one ground is like i said, using different ground points will increase resistance between the different units (say stereo is grounded within 6 to 10 inches of stereo, but amp in trunk is grounded 6 inches from amp - so you're looking at about 7 feet of steel between the two. if either one of those grounds loses even the tinest bit of its integrety, you're looking at massive amounts of noise that will be created. if all units share the same ground point, chances of that happening are reduced by a large factor. anyhow, when it's not practical, you don't HAVE to do it that way. i've got a couple of questions... do you have any electronic crossovers, or equalizers, or anything between your head unit & amp? if so, when you unplug the head units rca's from the crossover/equalizer, does the noise go completely away like it does when you unplug the rca's from the amp(s)? it should be clear that the noise is obviously coming from before the amp, and i can tell you why. amplifiers get their power from an isolated source - they use a switching power supply similar to an AC inverter, that converts 12vdc into AC, which in turn is rectified & regulated & filtered somewhere between 36 & 80 volts DC (combined - almost all amps use a center tapped dc output, the tap being the divider between the left & right channels). this is why amps that have such high sensitivity & power can have no noise like you said, when unplugged from the stereo. unfortunately, until recently, almost nobody has made head units or any other support gear that uses switching power supplies to isolate their power too. apparently your stereos low level output is such a low voltage that the amount of noise getting past the charging system that isn't filtered out, is being amplified as a differential voltage. you can try putting capacitors on this, but the thing is, the waveform that's getting past the battery that's causing this noise is so small, that it would take probably a 2farad or more capacitor to cut it down by a noticeable amount..... but it will be an exponential increment you'll need to increase the cap size for each factor you're trying to filter out. there have been two extreme cases i had in very exotic systems i've done where i completely removed 100% of the motor noise - but it takes an unusual solution to do it. first thing i did was get an AC inverter & hooked it up to a relay thats switch to turn on was from the key, but the relays output was tapped straight from the battery. then i plugged in an AT computer power supply to the inverter, since it uses a very stable filtered switching power supply, that has enough 12v+ current output to run 10 stereos. mind you, the computer power supply runs everything EXCEPT the amp. it powers stereo (cd or tape player, or just head unit), disc changers, displays, electronic crossovers, spectrum analyzers, any of the audio equipment that you are running except for the amp, which gets its power straight from the battery, since it has its own switching power supply & doesn't need to be filtered. you must connect the computer power supplys ground output (the black wires) to the cars chassis for this setup to work, and don't use any of the other output voltages from said power supply unless you're using for some other project. this setup may seem strange, but with it, you can start the car, & remove the battery and you will hear NO motor noise in the stereo (just so long as you keep the motor running at enough RPMs to keep voltage high enough to keep the car running while powering stereo that is). extreme needs can inspire exotic answers ..... if you need help with making something like this, leave another note & i'll tell you how to get hold of me

[wally91vhevrolet]

ok, with Cardomain.com's help and other idividual help, we've determined that the cause if a defect in my CD player. We determined this by touching a short wire to the shield of the RCA cable conneced to the head unit and touching the other end to the head unit casing itself and the noise STOPPED COMPLETELY. I was told there was some type of short in the headunit and i'm sending it in to be repaired or replaced under waranty. Thank's for everyones help.

[lilrogue78]

Originally Posted by superchuckles

ok, the reason i say use one ground is like i said, using different ground points will increase resistance between the different units (say stereo is grounded within 6 to 10 inches of stereo, but amp in trunk is grounded 6 inches from amp - so you're looking at about 7 feet of steel between the two. if either one of those grounds loses even the tinest bit of its integrety, you're looking at massive amounts of noise that will be created. if all units share the same ground point, chances of that happening are reduced by a large factor. anyhow, when it's not practical, you don't HAVE to do it that way. i've got a couple of questions... do you have any electronic crossovers, or equalizers, or anything between your head unit & amp? if so, when you unplug the head units rca's from the crossover/equalizer, does the noise go completely away like it does when you unplug the rca's from the amp(s)? it should be clear that the noise is obviously coming from before the amp, and i can tell you why. amplifiers get their power from an isolated source - they use a switching power supply similar to an AC inverter, that converts 12vdc into AC, which in turn is rectified & regulated & filtered somewhere between 36 & 80 volts DC (combined - almost all amps use a center tapped dc output, the tap being the divider between the left & right channels). this is why amps that have such high sensitivity & power can have no noise like you said, when unplugged from the stereo. unfortunately, until recently, almost nobody has made head units or any other support gear that uses switching power supplies to isolate their power too. apparently your stereos low level output is such a low voltage that the amount of noise getting past the charging system that isn't filtered out, is being amplified as a differential voltage. you can try putting capacitors on this, but the thing is, the waveform that's getting past the battery that's causing this noise is so small, that it would take probably a 2farad or more capacitor to cut it down by a noticeable amount..... but it will be an exponential increment you'll need to increase the cap size for each factor you're trying to filter out. there have been two extreme cases i had in very exotic systems i've done where i completely removed 100% of the motor noise - but it takes an unusual solution to do it. first thing i did was get an AC inverter & hooked it up to a relay thats switch to turn on was from the key, but the relays output was tapped straight from the battery. then i plugged in an AT computer power supply to the inverter, since it uses a very stable filtered switching power supply, that has enough 12v+ current output to run 10 stereos. mind you, the computer power supply runs everything EXCEPT the amp. it powers stereo (cd or tape player, or just head unit), disc changers, displays, electronic crossovers, spectrum analyzers, any of the audio equipment that you are running except for the amp, which gets its power straight from the battery, since it has its own switching power supply & doesn't need to be filtered. you must connect the computer power supplys ground output (the black wires) to the cars chassis for this setup to work, and don't use any of the other output voltages from said power supply unless you're using for some other project. this setup may seem strange, but with it, you can start the car, & remove the battery and you will hear NO motor noise in the stereo (just so long as you keep the motor running at enough RPMs to keep voltage high enough to keep the car running while powering stereo that is). extreme needs can inspire exotic answers ..... if you need help with making something like this, leave another note & i'll tell you how to get hold of me

Jezus dude thats insane I have built computers for some years and have built car stereos into them and amps and all sorts fo shit Hell even a bad ass car radio with a LCD display and have NEVER had any noise in my system and i have had a couple system in cars that i have played hell with trying to get noise out of and if i would have EVER thought of a design like that man i woulda done it! that is so awesome i praise you for that idea its EXTREME