I got my mids and highs installed this weekend with my JL e2150. I'm getting alternator whine, but I had the RCA's tapped in at the head unit, front and rears (rears running my sub). Sounds really good, but I can't figure out this whine problem other than a GLI slightly softens it. Turning down my gain works too but its just not loud enough. I also checked to make sure it wasn't the air bag ECU. Any ideas??? OH yeah, whine occurs when the head unit is on ( amp also) but not when off. Thanks

 

Make sure the ground is clean for the amp. Does it look like it's grounded to some clean unpainted metal?

 

Here's my 0.02 (oh, and thanks for doing those tests first and reporting the problem very clearly - sounds like it's NOT the passive xovers)):

First off, I'm surprised, since I don't have this with my JL 300/4. I'm glad everything else worked good...

*temporarily* turn the F gain down all the way to minimum. Then test for noise. I suspect you have none.

If that's the case, then you can try taking the HU ground (or the ground wire for the amp, which I expect are the same electrically) and temporarily extend it back to the ground of the amp. That *might* do it.

Is the GLI up front or in back? If it's up front try moving it to the back just to see.

But what took care of this in joerockt's car (he had a little whine with his Kicker with the gain raised, and wanted more volume) was an RCA line driver. This allowed him to bury the gain on the amp and drive it hard on the input. If I were adding one of these I would put it where the OEM amp was, if it fits.

AudioControl, PG, Visonik, and some others make these. So do Boss, PAC, and Audiobahn, but don't do that...

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I currrently don't have a line on line drivers (argh) but I am working on it. Zapco used to make a sweet one but I don't see any on ebay...

 

Thanks for the help guys, I'm still working on it...Is it possible the spliced RCA's are picking up noise in the console somewhere?? although I'm sure they aren't getting any from the Airbag ECU becuase I tried wiggling the wires toward it and it didn't affect the noise either way. Thinking a line drive might be my only option but thats another 50 or 100 bucks so Id rather solve the noise issue if possible. I'm going to go back to the shop and see what they think, but he did say "just turn the gain down" so who knows what they are willing to do.

 

The strange thing about this is when you raise the gain then the noise appears... if I raise it on the JL, it appears, and when I lower it, it goes away. So if dropping the gain temporarily solves the issue, IMO it's not radiated noise onto the RCA splices.

So if you need more volume than that amp can give you at minimum gain, I suspect you might be right about needing the line driver. I would ping joerocket and ask him, he added that after the original install... : )

If the

 

I picked up a PAC Turbo1 line driver for $30 shipped.

http://www.audiooutfitter.com/store/TURBO-1.html

I think that's a good recommendation by Eld.

 

So that will bring up head unit output up to 4.2 Volts max. Is that enough?? What is the head unit at now approximately? Just want to know if how much I will gain

 

I believe that it's at 2.2 volts right now. Eld should be able to confirm this when he gets back on Monday. This will allow you to turn down the gain on your amp allowing you to hear less ground noise.

 

I've not run a 0dB reference sine wave through the HU to see the max voltage.

I know that the Alpine HU that measured exactly the same as the TSX HU was considered a "2V" HU back before 4V HU's came out, but this was not the spec, just word-of-mouth. I've got a 0dB reference track disc now and maybe I can run it thru this week.

But the issue as I understand it, apart from any numbers, is this: With your gain on the floor you have no noise, but noise appears as you lift the gain off of the floor.

So a line driver allows you to leave the amp gain on the floor and still get more volume.

 

I picked up the PAC line driver. Hope it helps. The instructions say it only needs a power wire and not a ground "unless there is no sound." Kind of strange...TSX536, Let me know your experience with it and how much it improved your sound and reduced noise...thanks

 

It will ground through the RCA audio shield ground if it doesn't have a ground wire.

 

I had noise too, but I picked-up a GLI from RadioShack and it solved the problem. It easy to find a good spot for it too, all you have to do is move it around in the cavity until you no longer recieve interference.