Hello!<p>I would like to know what the color codes are. I If you can assist me, please send me what you can. I have checked the archives, but I'm not coming up with anything substantial. Perhaps I'm not typing in the correct keyword?<p>Also, can anyone supply me with the color codes, and location of, the amp wires that are supposedly in the trunk? <p>Would it be O.K. to use a "level adjuster" to allow me to install an amp onto the factory concert head unit?

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The archives do address this issue. According to prior posts, the concert radio already has "low-level" outs for direct input into an amp without the use of a line level adjuster.<p>I suggest that you use search words such as "low level" "line level" "rca" , etc. As I recall, that worked for me when I did the search for my own install.<p>Hope this helps.

The head unit outputs are speaker-level for the front speakers and you must use a converter to bring them down to line level. For the rear speakers, Audi uses a non-shielded pair of wires with a very low level output. These are run to AMPLIFIED rear speakers for the stock Concert system. You really shouldn't consider them line level, because they are unshielded. If you amplify them with a high-gain amp, you will quite likely introduce noise into the system.<p>The workaround is to use only the front speaker outputs to both the front and rear amps. You'll lose the fader function on the head unit, but can easily balance the speaker output at the amplifier.<p>This is exactly what I did, and the sound (at least from the CD changer) is fabulous through MB Quart speakers. Used a moderate power 4x30 watt amp with subwoofer outputs in case I should decide to add a sub later. Don't think I'll need to though--those 6-1/2" MB Quarts really pump out the bass!<p>John

Actually there are 2 sets of line level outputs on the concert stereo. And they are real line level outputs, except that they utilize a common ground. The front set is not wired to anything, i.e. the pins on the deck aren't connected to anything. The second set as you said runs to the rear amp through unshielded wire. The best way to add an amp is to splice a set of RCAs to the line level outputs directly at the rear of the deck and then run a shielded RCA cable to the amplifier(s). Alot better than using speaker level to line level convertors.

Very interesting. I had no idea what that extra set of pins was. Should be an easy matter to pull the head unit and splice the RCA's to them.<p>Although, I must say, the sound through the Monster Cable converters is entirely satisfactory to my ears even so!

Just buy an amp that takes line level inputs as well as low level. That way it's your option and you can skip the line level thingies.

I too went with the Monster Cable converter prior to "checking the archives." As usual, there is always someone who has already tried to do something you (in the figurative sense) are trying to accomplish with the A4.<p>I have had "high end" systems in other cars and have never really been with line level converters. However, because I had the trip computer which integrates the factory head unit with the computer display, I thought I had no choice. With the use of the line level converter (even the Monster Cable model), the sound wasn't as clean as I had hoped. Needless to say, I did the RCA conversion and the sound improved greatly.<p>I cannot stress enough, check the archives. They are nothing short of a gold mine.