Help with ground loop issues

[Bun-Bun 10+ year member]

Ok so I have this whine coming from my speakers. Had alternator whine as well but fixed that mostly by going straight to the battery from the HU (was on stock wiring).

The whine starts a few seconds after turning on the system, builds up for a bit and then stays a constant but slightly wavering high pitched whine. This is present whether the ignition is on or off and with the engine running or not.

Two things make the sound stop. 1. Unplugging the RCA's from the 4 channel amp. 2. or turning off the sub amp (disconnecting the remote wire).

My system is as follows.

Alpine CDA-9887 head unit

Alpine PDX4.150 amp

Memphis MC1.1500 MClass sub amp (1100wrms x1)

Memphis MClass Components (15-MCS6 )

Memphis MClass Coaxial 6x9's

Memphis Power Reference 10" subs x 4

1/0 gauge wire running from front battery to alternator, starter, body. 4 gauge running from front battery to fuse box. 1/0 gauge (pos and neg) running from front battery to back battery underneath the car strapped to the frame. 1/0 gauge running from back battery to distribution blocks (pos and neg with pos being fused for each amp). 4 gauge running from distro blocks to amps. 8 gauge running from HU to back battery (pos and neg).

I have tried disconnecting the antennae. I have checked with a volt meter RCA shield to HU casing has continuity (less than 1 ohm). I have checked with a volt meter RCA connectors on amps to ground have no continuity (greater than 20Mohm). I have very little to no alternator whine with headlights off. I have a little bit of whine with headlights on (I suspect that is the dimmer switch wire to the HU).

I am ripping my hair out over this. And trust me... thats difficult being that I am bald! Help! TIA

Build log http://www.caraudio.com/forums/car-audio-build-logs-cars-trucks-suvs/334371-2007-grand-marquis-ultimate-build-log.html

Click to read more...

 

[Volvowith18psi 10+ year member]

Try thicker shielded and/or grounded RCAs? IDK, just a newb thought....

 

[Bun-Bun 10+ year member]

I went to a local car installer and we came to this conclusion. The sub amp is radiating EMI into my RCA's (he tells me digital amps are noisy). I had the excess length of RCA coiled up under my amp board right underneath the sub amp. So I took the back seats out and everything out and rerouted the cable so that they are as far away from the sub amp as possible and coiled the excess cable behind the back seat. The noise isn't completely gone but it has lessened... I think. the true test will be with my GF in the car.

These are the RCA's I currently have Knukonceptz product detail for KRYSTAL KABLE 2 CHANNEL 6M TWISTED PAIR RCA CABLE

Local installer is pushing these Got Wirez. RCASBK-17 He claims that they ran these next to some neon ballasts and had no noise come into the line.

My regular installer closed up shop. I don't know if I really trust this guy. Probably just trying to sell me his product. And I really do not feel like pulling those RCA's out and running new ones...

Thoughts? Anything else I can do? The 4 channel amps is close to the sub amp so the end of the RCA's is still 2" away from the sub amp.

 

[fasfocus00 5,000+ posts]

have you tried grounding the RCAs? i know a lot of ppl swear by "RCAs and power wire can't cross or touch" but i've done and seen enough installs to know that the problem is deeper than just where the wires are to cause noise through the speakers. also theres a chance it might be something in the amp.

 

[Bun-Bun 10+ year member]

Something in the sub amp you mean? With the sub amp off the sound is clear with no noise.

Try grounding at the amp end you mean? There is continuity to the head unit case and RCA ground, so they are grounded. There is 3 ohms resistance between the amp end of the RCA's and the amp ground. Should I try ground the RCA's at the amp end?

The RCA's do not touch or cross any power wires for the stereo. I ran all the power stuff on the passenger side of the car and the RCA's on the drivers side.

I do not see what those wirez RCA's would offer over my knu conceptz.

 

[Volvowith18psi 10+ year member]

Just food for thought: my kicker RCAs are wire tied praticaly (non grounded) to my 1/0 power wire. 0 noise atm...

 

[fasfocus00 5,000+ posts]

Something in the sub amp you mean? With the sub amp off the sound is clear with no noise.
Try grounding at the amp end you mean? There is continuity to the head unit case and RCA ground, so they are grounded. There is 3 ohms resistance between the amp end of the RCA's and the amp ground. Should I try ground the RCA's at the amp end?

The RCA's do not touch or cross any power wires for the stereo. I ran all the power stuff on the passenger side of the car and the RCA's on the drivers side.

I do not see what those wirez RCA's would offer over my knu conceptz.

yeah, could be something in the sub amp. probably not but I have seen it a couple time, literally twice. if you already have them grounded at the headunit than theres no need to do it as the amp. dude seems to just be selling you, i've never seen RCAs eliminate noise just reduce it. just curious but where did you ground the head unit? check the ground for your headunit. something i've tried before and it's work with fairly good success, use some good 14 gauge primary wire. run ground it in the same place your amps are and run it to the head unit ground.

 

[Louisiana_CRX 5,000+ posts]

Ground everything from one point not different areas of vehicle

 

[2RZ-FE 10+ year member]

I have 3 grounding points and no issues. Everything else in a car isn't grounded to one point so meh.

Just make sure it's a good ground. Use a DMM.

 

[Bun-Bun 10+ year member]

yeah, could be something in the sub amp. probably not but I have seen it a couple time, literally twice. if you already have them grounded at the headunit than theres no need to do it as the amp. dude seems to just be selling you, i've never seen RCAs eliminate noise just reduce it. just curious but where did you ground the head unit? check the ground for your headunit. something i've tried before and it's work with fairly good success, use some good 14 gauge primary wire. run ground it in the same place your amps are and run it to the head unit ground.

The head unit is grounded directly to the trunk battery. Everything stereo related is grounded at the trunk battery. Head unit is powered/grounded by 8 gauge wire. Battery to distro blocks is 1/0 gauage and distro blocks to amps is 4 gauge. Trunk battery to front battery is 1/0 gauge.

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He does seem like a pushy salesman. I know a good set of RCA's can reduce noise, but I already have a good set of RCA's.

Ground everything from one point not different areas of vehicle

Everything is grounded directly to the trunk battery.

I have 3 grounding points and no issues. Everything else in a car isn't grounded to one point so meh.Just make sure it's a good ground. Use a DMM.

I have read conflicting opinions on this. To my understanding of electrical theory grounding everything stereo related to the same point is the best case scenario in regards to ground loops. Which is why I wired my stereo such that everything is connected to the trunk battery for both power and ground. But now as I go deeper into reading there are installers claiming that wiring amps to the same ground point will cause noise and other issues (artefacts in tweeters on bass hits for example).

That said I know you can ground at separate points and have a clean system as well. I never had problems with alternator whine before this car and I always grounded to body/frame of the vehicle before. This was the first car I wired everything to the trunk battery and the first time I had alternator whine (though that was because I was lazy and didn't finish wiring the head unit at first and used stock wiring).

My problem now doesn't seem to be a ground loop issue but more a EFI into RCA issue coming from the sub amp. Which makes sense because I couldn't understand how I could possibly have a ground loop issue with everything powered and grounded at the trunk battery. Where is the potential for loop?

 

[fasfocus00 5,000+ posts]

solution seems too complex for me. from everything i've seen on here and from what you said, it's pretty much text book.

 

[Bun-Bun 10+ year member]

Well the noise was significantly reduced after I rerouted the RCA's away from my amp board and put the excess wire behind the back seat instead of underneath the amps. Last night I had the stereo on the entire time and my GF didn't complain once about the whine. So for the time being I am going to accept the results. The noise is still there, which still bugs me that it is but at least I can't notice it now while driving.

 

[philnutz1]

dont use the battery to ground your head unit or anything else.

 

[Bun-Bun 10+ year member]

Not even the trunk battery?

What is the rationale behind this? When I was building the system I went with mind set that if I completely separate the audio system from the car's electrical that I would eliminate and chance for a ground loop. Everything is connected at the back battery for both power and ground and then from there 1/0 running to the front connecting to the alternator.

I don't think it is a ground loop issue I am experiencing. I believe it is RFI from the sub amp.