Re: 99 Passat premium radio - what is this? (sequel95)
sequel95,
Welcome to VWVortex!
If your radio looks like this, you have what is known as a VW Premium IV head unit:
http://www.doki-doki.net/~lamune/gti/98radio.gif
It is not a Monsoon head unit. You can tell that it is not Monsoon, because it has only bass and treble tone controls, whereas the Monsoon head unit has a midrange tone control in addition to the bass and treble. Also, if you look at the "roof" of the trunk, forward of the trunk opening, you will not see a Monsoon amp, which (if you had it) would be suspended from the roof of the trunk in a metal cage (similar to how it is in a '00 Jetta).
So, assuming you do not have Monsoon, you want to add a sub. No problem. The way I added a sub to my Premium IV head unit is as follows:
I bought a Blaupunkt F00E500014 output adapter:
http://www.continentalimports.com/f00e500014.html
This plugs into the back of the Premium IV head unit. See the following diagram. The yellow adapter plugs into pins 1 - 6:
http://www.doki-doki.net/~lamune/gti/Late98radio.jpg
What you get with this arrangement is two pairs of pre-amp outputs which can be controlled by the head unit's fader and balance controls, plus a remote turn-on lead (to automatically switch your external amp on and off when you turn your head unit on and off).
You can then run RCA patch cords to an external amplifier. I hooked mine to a 4-channel JL Audio 300/4 amp and ran my front door speakers off the front channels and bridged the rear two channels to mono for my sub (the bridging was done using a switch on the amp). My rear door speakers continue to be powered by the head unit (for fill). I control my sub volume by using the fader control. If you choose to only add a sub to your stock system, you could just hook up the rear two channels from the head unit and leave the front two channels for future use (I think you will find that the sub will be louder than the rear speakers, so doing this should not pull your sound stage too far aft).
This only addresses how to get the signal to the sub. Other aspects, such as routing a power line and grounding the amp, or different types of subs, can be easily found elsewhere, such as this helpful site:
http://erikorton.home.attbi.com/monsoon.html
Hope this helps,
Brian
p.s., the head unit is made by Panasonic. Also, If you want to add a CD changer later on, here's a good one to get (note: you will need one of the adapters listed on this page):
http://store.yahoo.com/logjam/pancx.html
