I don't know where the **** to get the speaker input for my subwoofer.. I have a new amp, but it only has one lead (either speakers or a subwoofer) and I have this retarded stock audi amplifier.. How can I wire this, what did you guys do? I have an aftermarket stereo but I have the RCAs leading to the rear (useless) amp.

use y connectors or take the "useless" amp out

Im planning on doing this, but whats the easiest way?

Y connectors is easier But if you have an aftermarket deck and an amp why are you using the stock Audi amp?

Because it has only one output, so I can't connect both sub and speakers

If your amp has "high level inputs", you can tap into the speaker outputs of the stock rear amp. Otherwise, you can tap into the inputs from the headunit to the rear amp. This is what I did. I have a 4 channel amp so I removed the stock amp all together. I found the left and right signal wires and soldered RCA cables to them to plug into my amp.

Here is a DIY I did a while back. Ask away if you have any questions after the read. Good luck.

Doug

I posted this at Audi World but I think it will help you out.

"As far as adding a sub, I couldn't handle not having one after picking up my A4 at the end of 2009. After much research and looking through the tech article found here AudiWorld Tech Articles, there is an easy way to get line-out to your sub amp and it's right at the driver's side rear speaker. This is taken from the tech article which I have added and taken out less important info.

First things first. This worked for me but do this at your own risk. I will not be held responsible if you screw something up. If you don't understand something, then ask before you start snipping wires. This installation does not require you to cut any of your car's wiring so please don't. Tapping means stripping a section of insulation off of the wiring leaving the bare copper wire showing at which point you can solder another wire to it and wrap your work with electrician's tape.

These wire colors worked for me but you may want to verify that they are the same before starting by looking at the back of your wiring harness off the stereo. My OEM stereo had a diagram stuck to it with the wiring diagram.

The rear amp is a smallish thing, normally attached to the rear left speaker in the rear deck plate. There is a connector plugged into the side of the speaker when you drop your drivers side rear seat down.

The brackets represent the slots that slid into the male harness end. The side with the outward piece is the piece I chose as the "top".

________[ ]________
(1) (2)
(3)
(4) (5)
(6)
(7) (8)
________[ ]________

1: White- Switch
2: Red-Blue lead to Right speaker
3: Brown-Red lead Right speaker
4: Red-Blue (thicker): 12v
5: Blue-Green Right pre-amp from head unit.
6: Red-Green Left pre-amp from head unit
7: Brown (thicker) Ground
8: 2 Brown-black Grounds for pre-amp leads.

In order to get line out, you just tap into the pre existing wiring using Scotch locks or stripping the wiring insulation and soldering the connection. These instructions will assume you are soldering the connections.

1. Take a set of RCA cables and cut one set of ends off making sure there is enough length to reach the amp.

2. Strip the end exposing about an inch of both the inner core and ground (outer metal sheathing). Do this for both ends then twist the grounds together from the left and right channel.

3. Strip the insulation off of the Blue/Green, Red/Green, and 1 of the Brown/Black wiring from the connector leading to the rear speaker using a razor knife. Do not cut the wires.

4. While you're under there, go ahead and strip the white wire on the connector for the amp's remote turn on.

5. Get a length of small gauge wire for your remote turn on and strip one end.

6. Get your connections ready for soldering by twisting the right RCA's inner core to the Blue/Green wire's stripped section. Then twist the left RCA's inner core to the Red/Green. Then the RCA's twisted ground from the left and right channel to Brown/Black. Finally twist the remote wire to the white wire.

7. Solder and tape up your work.

In order to get power to the amp, I ran a heavy gauge wire from the battery to the trunk. I ran ground to one of the bolts underneath the rear seat."

You could tap into the 12v at the connector plug but I don't know if it can handle a sub amp's current draw. Judging by it's small gauge, I wouldn't think so but it's up to you. You will soon find out when the fuse keeps popping when the bass hits. If it does, do not increase the fuse size in the panel as this will start fires. The best way is to run a heavier gauge wire directly from the battery with an in line fuse as close to the battery as possible. Good luck.