Guys, after 14 horus of meticulous work - I'm done!

I ended up being very creative with some Dynamat and I got the door speaks taken care of NO PROBLEMO! :)

It sounds great, with one exception!When I start the car I've got the sounds of a ground loop... Oddly enough it only does it when the car is running, so I assume it's "RF noise" probably due to the alternator.

Here's the kicker.... I've got two 4 guage (-) and a (+) wires coming STRAIGHT from the battery to the distro blocks... I'm power the radio, amps, (and even the REMOTE ON for troubleshooting purposes) and I'm STILL getting the "whine/hiss" when I start the car! It get's higher pitched the higher the RPM's go. I'm really at a loss here! ALL connections are good and I can't for the life of me figure out WHERE this noise is being introduced into my system! CD/FM/AM - it doesn't matter, it's STILL there! ughhh All this for nothing.. Still, no clean sound - unless the engine isn't running. Bummer. I'm in a state of dissolusion - I'm drained. Pathetic. Good night.

Please advise.

Oh, a note... I do have one amp powered up with a RCA feed to it but it's not pushing anything (my sub <JL Stealthbox> won't be here for 5 more days )
but that shouldn't be causing this noise. If it is, then it would do it with the motor on OR off... I ONLY have the hiss when the motor is running. WTF?????

Bueller? Bueller???

Anyone anyone???

 

You put the Problem in your message. Its called a ground loop and its caused by having either something improperly grounded or poorly grounded. You should not ground to the battery. That's a no no. The battery doesn't give you power, the alternator does. Ground directly to the frame as close to the amps as possible. This will likely solve or minimize the noise. I have mine to the frame behind the back wheel. If this doesn't help, post again and we'll take stronger measures.
92TripleBlack :cheers:

 

i agree with triple black.........no no on the battery grounding.......direct ground to the frame is the only way.

 

Make sure you sand the area you are grounding to so you have a good clean ground. I use 100 grit sand paper.
92TripleBlack :cheers:

 

To cure a ground loop problem, you must first identify what path is being used to inject noise into the system. Typically, the low level audio connection between the HU and an external power amp is weak link in a system. In systems without an external power amp, then high levels of noise from the alternator and ignition system fed up the power cable would be the source.

Noise can be picked up in a system many ways. The direct path is by leakage currents flowing through the various conductors in a system. Radiation is also a large problem. When a plug fires or a distributor rotates, an RF signal is radiated. Both the AM radio in a system and a low level audio input will pick up this noise impulse. When you place two wires next to each, they will have capacitive and inductive coupling between them. You never want to route low level audio signal with power cables. The noise currents flowing up and down the power cable will couple into the audio cables.

There are many sources for noise in a system with an external power amp. First is the alternator itself. It is a big noise generator due to it's internal brushes. If the noise suppression capacitors in the alternator are bad, the noise will be worse than normal. Next is the cars ignition system. Having a distributor and coil producing sparks is not good for low noise. Finally the DC to DC power supply in the power amp can also be a large noise generator. All these noise sources have one thing in common. They cause noise currents to flow in ALL wires in a system. These noise currents will follow every path possible from the source of the noise through the audio system and then back to the noise source. Think of it as having many wires of various resistance running from one point to another. The noise will be divided up between all the wires before returning back to the source. The goal is to minimize the amount of noise in a power cable that will return through an audio cable. You cannot eliminate this noise, only minimize it. How you hook up the power to a stereo system is critical.

One quick check for ground loops would be unplug the HU pre-amp outputs. If the noise dissapears, then short the center to the shield on all cables with a bare piece of wire. Connect the big shorted mess to the HU RCA pre-amp outputs shield only. If the noise comes back, then the noise currents are coming down the shields of the low level audio cables. You need to then stop power amp supply current from sending leakage current down the audio returns. If the noise dissapears, then the noise is actually riding on the audio signal. You need to look at the HU power feed to find out the problem. Many aftermarket HU's have poor power feed noise rejection compared to a stock HU.
he power amp input cables together where they would connect to the HU.connect the

 

Gentleman,

Thanks for your responses!

I'm not trying to argue, I'm JUST CURIOUS so I'll ask this..

Since I'm connected DIRECTLY to the battery < 4 guage hot and 4 guage cold> doesn't that mean that's OK to ground at the battery since that's where power is orginating? If not, I'll find a new ground!

The preamp RCA are next to the main 4 guage power wire for about 2 inches RIGHT next to the amp. Could this be a source of noise?

I have eliminated the headunit as I ran power DIRECTLY to the 4 guage feed AND the 4 guage ground to the Head unit. Man, this is really bugging me. This car has some SERIOUS show stopping sound, but then I start the car and there is that little whine... ughhh Thanks for your help and recommendations. I'm going to try all of it!

 

2 things:

1) NEVER, EVER run ground back to the battery :eek:. Ground your amps as close as possible to where they are mounted, directly on the chassis (try to ground them at the same point if possible).

2) NEVER, EVER run your RCA and your positive cable right next to each other :eek: :eek:. The electromagnetic field created by the positive wire will induce interference into the RCA cables. This is because the high voltage (12-14 volts) of the power will cause interference w/ the low voltage of the RCAs (2-9 volts, depending on the head unit). Run those RCAs at least a foot or two apart from the power.

These two techniques, I can almost guarantee (given your head unit is not messed up), will solve your alternator whine problem. :yesnod:

Good luck... Show us some pics when you can! :cheers:

 

I agree with dtorc4....


You might want to run the audio up the center of the car next to the passenger seat and the poewr down the side of the car... thats how I did it.... on a buddies FRC... which would seem to work with a Z06....

On my car... I still have the stock HU and I did the same thing... but I ran the audio down the driver side and power down the passenger side.... by a rule... most audio guys keep at least 1 ft between the wire... since our cars are fiberglass...we have a lower chance of interferance from the cars body... :cool: :cool: :cool: :cool:

 

First we need to put some facts up here.

1. In "plastic" cars like a C5 with poor chassis grounds and cheap thin guage wiring throughout, you cannot always rely on "local" grounds in the rear where you may mount the amp. Running two large guage wires to the battery + and - is sometimes a necessity. The noise at the battery is also lower than on the back of the alternator. If your power amp is huge, then you must provide a low impedance + and - path to the battery or the amp could oscillate. The resistance AND inductance of the wiring to the battery is important to the power amp.

2. The noise in a system has ZERO to do with the fact that the power cable has 12-14 volts on it and the low level audio cables have 2-9 volts on them. The alternator, ignition and power amp internal DC-DC converter generate HUGE noise spikes and leakage current induced voltages are many many times higher than 12 volts. If you keep power and signal cables seperated from each other, the biggest problem is usually stopping these leakage currents from running up and down the low level audio shields.

Finally the description of how the system is wired is very poor. I cannot figure out how you have your HU and amp wired. They should NEVER be fed by the same power cable. The power amp DC-DC converter puts way too much reflected ripple and noise back onto it's power cable.

 

Gentleman, and 99HT,

Thank you! I figured it out <with your help!!> It was, now get this, the fact that the RCA pre-amp was NEXT the GROUND!!! Of all things! When I moved them about 3 inches apart it COMPLETELY subsided! THANK GOD! :)

99HT,
I think you may believe my system is wired poorly because of the troubleshooting description I gave above. If you go back and read it from TOP to BOTTOM you will see that I rewired it out of desperation trying to eliminate the noise. After unsuccessful attemps I changed back to the way it should be.
I can assure you my system is wired MOST professionally with NO expense spared in this system!

I did run the preamps down the center console and the power down the passenger side <under door rail>. The problem was when I brought them under the pass seat and connected them to the amp. The path's were crossing and that's where the interference was originating! Fixed it, thank God! :)
About the pictures... I've got a couple of shots that a buddy took yesterday when he stopped by. I had JUST finished replacing the head unit, running 2/3's of the wires, and installing the new speaks. Since I went for the hidden look you can't see ANYTHING (amps are under pass seat) other than the HU and the sub <when it gets in... still a week away>!
I will snap some pics of the finished product! It is VERY very professional/sharp. I took it by two buddy's houses today and they said, "I can't believe YOU did this! It looks factory, but only better!" :) (You should have seen there expressions when they heard it cranked!

The sound is PHENOMENAL! The mids and hi's are CRISP, SHARP, and LOUD! :) I can't wait to get a sub in there to take care of the lows <we're talking audiophile quality!>!! :)

Thanks for all of your help! It's GREATLY appreciated! :) I'm ROCK'n NOW!