I think I have researched this enough to intelligently ask a question without saying "I have a whine in my audio system, what do I do?"

I recently bought a 03 coupe that has a JL system in it. 300/4 amp and a e1200 amp for the sub box. Anyway the system has a bad alternator whine (goes up and down with acceleration). It also has a decent amount of noise when the system volume is all the way down or off. I turned the gain or sensitivity down a little and that has helped the 2nd issue some. it was nearly all the way up. Anyway, I noticed the amps are grounded seperately. One is mounted in the common spot behind the rear seat and grounded just below that area. The 300/4 is where the bose amp was and is grounded to the trunk area there. Both grounds are drilled. The preouts are used to connect the rear speaker audio signal to the 300/4 from the e1200. When they are disconnected, the noise goes away. So here's the question. Should I consider grounding both to the same location even though it might mean longer runs? Or should I consider a groung loop isolator? I don't have much experiance with amps. Maybe there is something else to consider? Rcas are not touching the frame anywhere.

I've done plenty of head unit swaps, but amps are new to me. I did find the RCAs zip tied to the power cables and bass boost control and corrected that. The the sound is still there, but a little better.

Also, I've ordered a siruis receiver and it appears the stock area will be tight with the big amp there. any better location? Maybe the other side where the spare tire tool kit is? I haven't looked under there yet. Maybe up in the dash somewhere?

Anyway. Thanks for any suggestions. I'm trying to aviod getting ripped off at a car stero place.

 

A big cause for that is RCAs and power wires run together but you said you've fixed that.

Are the grounds the same or greater gauge as the power going to the amps? 18" or shorter in length?

I grounded my 300/4 and 500/1 to the same spot and have zero whine.

 

The grounds are the same gauge as power and are relatively short. Probably less than 18". If I grounded to the same spot, one would have to be considerablely longer. Maybe another 24 inches.

 

Ground to the same spot even if the cable needs to be longer.

 

After listening more now that the RCAs have been moved away from the power the sound is much lower. It no longer can be heard when playing music. If the audio is off though, there is still an audible whine that would be pretty annoying. I think I'll try the same groud as Gilley has suggested. Thanks for the replies.

 

I have installed mobile electronics for a long time now and was a dealer of JL. The things you can do are to make sure you are using high quality rca's, run your power wires down the totally opposite side of the car then the rca's, and try a ground loop isolator. also, the amps dont necessarily need to be grounded in the same spot, just make sure both are good grounds with good metal on metal (not metal on paint) contact, and if possible, ground to a seat belt bolt.
i hope this helps

 

If you are going to extend one of the amp grounds to ground them together I would keep the short one on the 300/4 and extend the sub amp ground. The last 4 channel that I installed with the stock deck on a G35 had noise that I just couldn't get rid of no matter what I tried. I always use the ground loop isolator as a last resort, but in this case it was the only thing that worked.

 

Hmmm. I haven't done anything else yet as the sound is much less noticible. I received my SAT radio and installed it this week. I wasn't prewired so it took a little time with the dash teardown. I put the antenna under the deck lid as I like the clean look and will deal with a little dropout if needed. The factory sirius antenna is huge. So far it's been very good in that location though. I also put the SAT receiver on the tool kit side since the 300/4 was on the left+ crossovers. That factory harness doesn't leave much room for interpretation in terms of length. It was close.

Since I had good luck with the cable seperating, maybe better RCA's is an good option. This is a noob question but the RCAs to the e1200 Amp are kinda close to the power wires when coming through the back seat panel and to the amp. Is there a minimum distance that is industry standard? It's tough to run them completely away from power and keep them under the amp for asthetics.

You guys have helped a lot though to narrow solutions down.

1. better grounds and/or ground to same location
2. better RCAs and further away from power
3. last resort, ground loop isolator

I think I'm still going to start with #1 and ground to the same spot, although Jtrain has me wondering if that will have any benefit. One set of RCA's is rather crappy, but I trouble shot with a decent home audio set from one amp to another and there was no improvement.

 

If you tried a different set of RCA cables and there was no improvement, I would focus on grounds first. There are times when you can't avoid running RCA cables next to power wires once everything gets close to the amp and it usually doesn't cause any problems. especially if the cheap RCA's are going to the bass amp, as woofers rarely create the noise.

 

Well I beleive it's fixed.

I tried a new ground wire to the single ground location and there was no improvement. So I cleaned up all the wires again and made sure to cross any RCAs perpendicular. I also routed lots of speaker wire for crossovers away from or perpendicular to power. What I think was the cause was a power cable was running next to the factory harness in the trunk that used to connect to the Bose amp. I thought I had read that the RCAs picked up this sound but that the factory harness should not. Well either way that or something else I moved has fixed the problem. I'm back to the original grounds and it's nice and quiet.

With what little I know about the cars former owner I would expect this was a professional install. With that in mind it amazes me that so many basic mistakes were made. At least I have learned about the system setup and a good bit about wiring amps through this process.

Now finally my neighbors will stop teasing me for hanging out of the trunk every other day.

Hmmm, now I need a new project.