Car audio guru's, please help (1 Viewer)

[Mark Paquette]

Hopefully someone who is familiar with car audio can help me with this annoying problem. I have a totally stock stereo in a 2003 Passat and it works great. I purchased and installed from VW a Phatbox MP3 player that connects to the factory installed CD changer connector in the trunk. Phatbox works as advertised except I get a high pitched squeal/hum/whine that is very noticeable. The noise does not seem to change with changes in engine RPM or (heat, a/c) fan speed. I hear no hum when listening to a single CD in the head unit. I only get the hum when using the Phatbox. Could the Phatbox itself be faulty? Or possibly the factory installed CD changer wiring has some sort of issue?

 

[Jeffrey Noel]

Since the hum/whine doesn't change with the RPM, I'm stumped. I definitley shoot an e-mail or call VW. I'd say it's something wrong with the MP3 player.

 

[Aaron_Morris]

Yeah, that almost has to be an issue with the MP3 player. See if they will let you switch it out for a new unit.

 

[Ted Lee]

what's a phatbox?

first thought was a ground loop, but i'm thinking no since it's not affected by rpm's.

does all power and audio signal route via a single connection of some sort? is the connection loose or damage in any way you can tell?

are you sure your mp3 files are clean recording?

man, i'm just throwing stuff out...i'd just take it back and let them hammer it out.

 

[Mark Paquette]

what's a phatbox?

Check it out here: http://www.phatnoise.com/

My mp3's are clean and they sound fine through my Audiotron on my HT setup. Everything routes through a single cable made up of 6-8 wires with connector on the end. The cable, at least the part I can see, looks fine.

Upon further inspection the hum does slightly change with the engine RPM's. It's more of a hum with some static on top. Anyway, the Phatbox is made of metal, the brackets are made of metal and I had it mounted to the metal of the rear dash. I decided to unmount it and just leave it on the trunk floor. That pretty much eliminated the hum. The volume has to be turned up all the way to hear any kind of hum and even with the volume all the way up the hum is very faint. So is this what is referred to as a ground loop? I suppose I need to find a different way/place to mount this thing.

 

[Scott L]

Interesting. So the signal coming out of the Phatbox pretty much has to be modulated to an RF station to receive it on your head unit? There's no direct connection via RCA connectors or otherwise?

Also how does it handle VBR mp3s?

 

[Mark Paquette]

So the signal coming out of the Phatbox pretty much has to be modulated to an RF station to receive it on your head unit?

Maybe for some models of the Phatbox, but not mine. The one I have is specifically made for VW and Audi head units. It connects directly to the CD changer connection in the trunk. My head unit thinks the Phatbox is a cd changer, no RF modulation required. The Phatbox software uses software from AT&T that speaks the artist and alblum title through the cars speakers. It's a pretty slick setup.

All of my mp3's are VBR encoded and the Phatbox has no trouble playing them. It is supposed to play mp3's (vbr or cbr) and wma's.

 

[Reginald Trent]

Do you get this hum playing it with the engine off?

 

[Mark Paquette]

Nope, it's quiet as a tomb with the engine off.

 

[Diallo B]

First I would take the unit back to the dealer to let them try to hammer out the issue. If that is unsuccessful then I would try the following option.

I would not mount the unit directly to a metal surface. If you can, find some plastic or rubber to put between the unit and the mounting surface and make sure that the metal screws are also isolated from the the actual unit.

Many car amplifier companies use plastic or metal feet to mount the amplifiers into a car. They do this to avoid creating a ground loop hum and other various 'noise' problems. On my cd changer in my car plastic feet are also used to help avoid noise problems.

Hope this helps,

djb

 

[Ted Lee]

>Upon further inspection the hum does slightly change with the engine RPM's.

>I decided to unmount it and just leave it on the trunk floor. That pretty much eliminated the hum.

>Nope, it's quiet as a tomb with the engine off.

hmm...that sounds more like it. i would say (almost for sure) that this is a ground loop.

like already stated, if possible, try to use some plastic mounting brackets. or, try to eliminate any sort of metal-to-metal contact. even if you use rubber insulation, if the metal screw touches the unit and phatbox in any way, you'll still have a path for the ground - i'm thinking washers and/or grommets for the screws.

finally, i think there is some sort of in-line filter you can buy that is designed to eliminate this problem.

did we already mention the dealer? since they did the install you can make them do all the work - it's just a hassle having to take it in to them.

 

[Mark Paquette]

Thanks for all the tips. I'll be modifying my installation this weekend to eliminate any metal to metal contact. I did the original installation, not the dealer. I only take my car to the dealer when absolutely necessary and so far it hasn't been necessary

 

[Ted Lee]

hey mark -

you may wanna see if something like this will help:

http://www.crutchfield.com/cgi-bin/S...=0&cc=01&avf=N

http://www.radioshack.com/product.as...5Fid=270%2D054

i think the one from crutchfield may be more of what you need. the one from rat-shack looks like it's geared more for an amp setup.