I noticed there was a lack of Audio related info on Audizine so I decided to compile some of my knowledge and some of the knowledge I was able to find on here. As far as I know all information applies to B6 and B7 A4s and S4s unless I note otherwise. I take no credit for any of the information provided and assume no liability for anything you do to your car. If you find that something is wrong, outdated, find a broken link or have something that you like to add, please let me know by a PM. Enjoy!
Q: What’s the difference between the Bose system and the Non-Bose system?
A: The headunits are the same with different coding which can be changed by using a Vag-Com. Both systems have the same amount of speakers. On the Bose system, the headunit provides line outs to the Bose amp which powers all of the speakers. The amp has a dedicated output for the center speaker. On the Non-Bose system, the headunit powers the front speakers while the external amp powers the rears and sub. The center speaker is spliced together from both of the front speakers. On the 2004.5 A4s (not sure about the S4s) Audi changed the Bose amp and added the Bose Audiopilot feature. This is similar to the previous GALA feature, which raises the volume as your speed (or cabin noise) increases.
Q: Where can I learn more about car electronics/audio?
A: I recommend this site.
Symphony II Diagram:
Q: Can I upgrade to the Symphony II+ headunit?
A: Yes you can. See this thread.
Q: How do I disable the internal equalization/compression in the headunit?
A: Please see this thread by TJHUB in the B7 section.
Q: Is it possible to enable the line outs on my headunit?
A: This can be done by using an adapter made by TeddyBGame (or your own custom one) to give you RCA outs. You then need to ground the “Bose Pin” to enable the line outs (see the thread in the previous question).
Bose Amp Diagram:
Q: How can I disable the Bose Audiopilot?
A: See this thread where you can either do it yourself or find the TSB information for your dealer.
Q: How do I retain my steering wheel controls?
A: You need the SWI-Can from PAC (Pacific Accessory Corporation), available at Enfig Car Stereo. You also need the SWI-Jack or SWI-PS depending upon your headunit.
Q: Where do I find the speed sensor wire?
A: The site that had this information originally (here) is dead. Behind the driver’s side kick panel there should be a group of connectors. On the black connector your want to tap the blue/white wire (pin 13).
Q: Where do I find the reverse light wire?
A: On the same connecter in the above answer: the blue/red wire (pin 15).
Q: Where do I find the illumination wire?
A: Remove the headlight switch by pushing in and turning clockwise. You want to tap the gray/blue wire.
Q: Can I use the OEM “Sharkfin” GPS antenna?
Q: Can I use the OEM “Sharkfin” Satellite radio antenna?
Q: What dash kit do I use for a double din radio?
A: This one. You have to cut out the bar in the center with a dremal.
Q: What do I need to mount the Pioneer Avic D3 in my dash?
A: See the above question. You also need the ADT-VA133 or a D2 mounting bracket.
This is it for tonight. I plan to add more.