Alternator noise from volume control for tower speakers.

[vortech347]

This season I added tower speakers to my stereo.

To be able to control the volume I installed a PAC LC1 rca level volume control.

Since then I have been chasing a bad alternator whine when the engine is running in the tower speakers. The subwoofer and back speakers that are driven off a separate 4 channel amp from the tower speakers do not have this noise.

I tried different rca cables where I just plugged them in ran across the middle of the boat to see if it was coming from the installed cables. No luck.

I bought a new deck (Sony with iPod control) after reading about Pioneer decks being notorious for their rca's introducing noise. I wanted a newer deck with real iPod control anyway and my Pioneer's aux input stopped working.

Still no luck.

So as a last resort I bypassed the volume control to the tower and the noise is gone. The volume control is installed under the dash and is nowhere near a power wire that could introduce the noise.

Now while I'm doing this testing I turned the volume up and down on the PAC remote and noticed something. When the volume is at less than full using the dial on the PAC I get noise. If I turn the tower speakers all the way up using it I get zero noise. I confirmed it wasn't just being drowned out by the extra volume by restarting the song so the first few seconds are quiet.

So the PAC LC1 is instroducing noise into my rca's when it's at anything less than full volume.

ARGHHH! Are there other volume controls that don't bleed this noise through?

[Cam003]

RE: Alternator noise from volume control for tower speakers.

depending on the amount of different components you a running in you system i.e. amps crossovers eq you may just need to adjust your gains until the wine stops. chassing noise is no fun, but can be solved with some simple tweaking and take my advice you need to people to do this. dont run your amps at full gain.

[AuMDLST]

RE: Alternator noise from volume control for tower speakers.

Check your grounds.

[TravisFling]

RE: Alternator noise from volume control for tower speakers.

I run a pac LC1 on mine and have no problems, but I was having problems before with the same setup with two amps. I doubt it's the pac, it's probably just that you notice it when the pac is in use. It's just a line level controller and there's no power/ground to it, so it seems odd that you'd get a noise loop from a unpowered source, eh? I would check and make sure both amps are grounded in the same spot. I had a noise loop problem and I replaced the amp with a high quality amp and no problems whatsoever! What kind of amp is it?

Travis

[vortech347]

My setup is the following.

Sony CDX-GT820ip
Front rca and sub rca are run using a Monster 300X 4 channel cable to an Alpine MRV-F545 amp. The front side of the amp drives 2 speakers in the rear of the boat and the back side is bridged driving an Infinity 12" Perfect 12 VQ.

The rear rca out from the deck has a 3' Dynex patch cable into the PAC LC1. From the PAC LC1 to the second amp is a Radio Shack Gold RCA cable. Both cables are pretty good quality although they are not twisted pair.

The amp powering the tower speakers is a Phoenix Gold Tantrum 300.2.

The original 4 in boat speakers are running off deck power right now.

So I have a total of 6 in boat speakers, 1 sub and 2 tower speakers.

Power and ground to the amps are run from the battery to distribution blocks. From the battery to the blocks is 4 gauge and then from the blocks to the amps is 8 gauge.

The amps are under the passenger seat and with the battery up front in my boat the 4 gauge run is only about 4' for each and from the distribution blocks to the amps is 1' or less.

The gains on the Alpine amp are set pretty much middle of the road as it's a very powerful amp. It's birth sheet shows 172 w/channel x 4 at 14.4v and it's rating is 125x4. So I have the front side turned down a lot so the back speakers it drives do not overpower the rest of the deck powered in boat speakers. The rear section bridged 4 ohms is rated at 500 w rms and I have the gain set about 1/2 way. The sub can handle it fine but I don't have a big charging system so I have it set conservatively.

The PG amp gain is set to about 75% of the dial as my tower speakers call for 150w rms/channel and that's basically the power rating for the amp.

Believe me I thought it was very weird but when the PAC is turn all the way down or all the way up I get no noise. Any where in between I get a lot of alternator noise.

I even went as far as buying another twisted pair 3' cable from the deck to the PAC and I already have a twisted pair 17' patch cable as well. I tried it with them plugged in and the cable just laid across the middle of the boat to the amp and I still had noise only when the PAC is at partial volume.

As soon as I took the PAC out of the of the picture by going from the back of the deck straight to the amp the noise was gone. Add the PAC back in and partial volume with it and again I have the noise.

I know stereo's pretty well but have never had to chase noise to often because I always made sure my grounds were good.

The only ground I have not changed is the receiver's which is still grounded to the dash's factory ground.

I appreciate the info and keep it coming.

[Mikeski]

Replace the PAC with something else, try this, it's cheap:

http://cgi.ebay.com/SCOSCHE-EFX-CAR-...QQcmdZViewItem

[TravisFling]

I would also try to ground the reciever to the distro block and see if that does anything. You can also get a pac in line noise filter, which is a band aid, but makes the lake more enjoyable until you get it found. My problem was in the amp for the highs, and when I swapped that out everything worked great. I wonder why the pac would do that... is it located under the dash and drilled through to the front of the dash?