To start off, I have the "basic" audio system in my car, the non-bose symphony with the rear amp connected to the back of therear driver-sidespeaker.

I looked everywhere when I couldn't figure out how to install my sub+amp on my "new" '00 a4 1.8t. It took WAY MORE effort to actually figure it out (i.e. tearing my trunk and interior apart), so I figured I would help out all the people like me (broke college kid) that are forced to keep the stock head unit (for now), but need a little more bass in the trunk. It turned out to be so simple. Here is the step by step:

1. Run 12v power, with fuse ideally less than 12" from battery, THROUGH the nipple where the hood latch cable is located (driver's side far corner). I just cut the whole nipple off, squeezed the length of the cable through, and luckily it just popped through behind the fuse panel inside the car. Easier than drilling the firewall.
From there, I unscrewed the plastic piece covering the hood latch inside the car, popped all the floor trim up, and ran the 12v all the way back underneath the trim, under the front corner of the back seat, and through to the amp which I mounted on the back of the rear seat. Now, snap in the trim and go back and put a heavy bead of silicon onwhere the nipple wascut off, so no water finds its way in there.
P.S. Don't hook up power until the end. Duh.

2. The middle section of this install is simple. Mount new amp wherever. Mine only fit on the back seat. Ground the new amp somewhere, run speaker wire to sub. The next part is the part that got me.

3. My amp has RCA jacks, which obviously don't connect to the stock rear amp, which is typical cheap speaker wire. Go to Crutchfield.com, Best Buy or whatever, buy a Scosche SLC4 converter, and use this converter to go from RCA to the stock speaker wire. The inputs for the stock amp can be spliced into for the inputs on the aftermarket amp. Basically, you'll have to splice into each of the necessary wires to get the right connection. I know it looks confusing, but if you pull off the plug for the rear amp, this will give you a good idea what's what. Wiring diagram is as follows:

AB
C
DE
F
GH

A=White wire. Remote. Connect this wire directly to the remote input on the new amp.
B=Blue-Red. Right Speaker. Connect this wire to the SLC4 input side. Output side will obviously be the RCA's going to the input on amp.
C=Brown-Red. Left Speaker. Don't touch.
D=Thicker Blue-Red. 12v. Don't touch (Already ran power from battery).
E=Blue-Green. Right Pre-Amp. Don't touch.
F=Green-Red. Don't touch.
G=Thick Brown. Ground. Not necessary to use this ground, as the ground wire should be as short as possible.
H=2 Brown wires. Pre-Amp grounds. Don't touch.

So, we really only need the remote line and radio signal from the rear amp. Basically, the setup is exactly the same as in any car, but the Scosche converter is between the rear amp and new amp for 2 of the connections.

That's it...

The SLC4 Converter needs to be grounded as well, and another tip: Keep the 12v line and the RCA jacks as FAR away from each other as possible. The way it's set up in my trunk, I have the sub on the passenger side of the car because the 12v is along the driver's side.

So, this worked for me and now I have a totally stock system (which sucks, but upgraded speakers and a bigger amp for the whole system is in the future) with a 760w JL audio amp and 12" JL sub.

 

Nice info a few pic would have been nice

 

this deserves to be on the diy glory section. i did mine and mine was an amped bose. my harness for the stock amp was much bigger than that lol. i can see the converter really makes a huge difference as i had to cut and splice a billion wires lol. and ya a few pix would help too for the pix people like me lol

 

mine was a lil different, for the same car.

how to install An amp and sub on a 2000 A4 with symphany stereo system.
I completly removed the rear amp, remove the upper lid to have more work space with the wires and remove the protective tape thats around the wires, what you need to do is get a volt meter analog/digital doesnt matter, i use an analog volt meter, find your power wire, keep the car off pull out the volt meter and find out which is power, write it down, then turn on the car and turn on your stereo, find the remote line, to make sure, the remote will not have power if car is off.
i cut my connector to the stock amp after finding the remote and power lines about 1'-1.5' so i could reuse it if i decided too but stepped on it after installing everything lol.
tap off your power line saftly so it doesnt short anything out.
to find what speakers wires go where, you need a spare speaker, garbage or not it will do the job. i used one from an old computer. turn the car on and put some music on, now to find out if negative or positive, the sound will sound different if you connect them wrong, if connected wrong they will sound a little echo or faint. then find left and right and just by the tune to the left rear and see which wire goes where and same for right.
My speaker wiring for my 2000 1.8T A4 with the syphany system goes as
White=Remote
Red/Blue=Power
Blue/Green= + Left
Blue/Red=+Right
Yellow/red=Negative
Yellow/Red=Negative

 

Now how would I go about getting a signal to my amp if I have the standard sound system? The speakers have only got one signal wire, with the other being ground? I want to keep the stock stereo in my '97, but just want to install an amp and sub.

If anyone has done this, it would be sweet.

Thanks,

Cory

 

okay so im curious how well this method with work for my 00 S4 with BOSE symphony. i already have a BLITZ Mlink for an ipod or iphone attacehd to the head unit.. whats the best way to get RCA and remote to my shiny new JL 500/1 slash?

 

You can just splice into the stock amp wires, that's what I did. I used the amp remote wire, ground and 2 line-level inputs right at the connector in the trunk so no need for a converter or running anything but +12v through the cabin. No permanent damage to the stock wiring either, which is always a plus. And unless the non-bose amp is different, this is by far the best solution since you won't be going from line to speaker and back to line level. Also used this method for a friend's E39, works on any car with an external amp.

 

I totally agree. No need for a line converter since the low level signal wire is already right at your fingertips at the rear speaker. Just splice in the +ve wire of a set of RCA cables to each +ve signal wire and connect both RCA grounds together to the common ground from the connector.

Doug

 

Duh.. I forgot to splice the. Common.. Total brain fart.

 

ok good thread...but

why run the extra +12V for the external amps? unless youve a huge sub amp can just get the +12 from the OEM drivers side powered speaker.

has anyone hooked too much load to this and seen it droop or pop a fuse??