dimo

I have a 98 A4 and i just recently installed an aftermarket alpine cda 9855 head unit in my car. I previously had the delta head unit and it was a piece of crap. Anyway, i follwed the wiring instructions that are in the manual for the alpine. I have sound and it sounds perfect, the only problem is when i change the radio station of turn on the car, or turn off the car or change the track number on the cd. The problem is there is a loud POPing noise that occurs everytime i do one of the above things. I have no idea what can be causing this. Did i forget to connect a wire somewhere?? Any help will be greatly appreciated.

MacSub

via the rear RCA's. Just simply run some speaker wire all the way to the rears from the Alpine rear speaker output and disconnect the crappy matchbox sized rear amp that's bolted to the left rear speaker.
This will get rid of the popping and give you much more power as the rear amp is only 2 x 20w.
The popping by the way is cause by a wierd capacitor setup on the input stage to the amp. All decent HU's ground the RCA's when doing anything electrically noisy like changing source or CD etc. This discharges the capacitors in the rear amp very quickly thus the pop.

dimo

Both the fronts and rears had to get hooked up to rca line levels in order to get sound so all the door speakers and rear deck speakers are powered by the amp in the back under the rear deck. If i just ran speaker wire to the rear speakers, that won't solve the popping sound in the front speakers. Not only that but won't running the bose speakers from my head unit fry out the headunit because of the speaker impediance? Some people have suggested that it may be a ground loop causing the popping sound, but everything is grounded fine. There was a "security anit theft" wire plugged on the rear of the stock stereo (brown clip??), does that have to be grounded also?

MacSub

As already stated the popping is caused by the Alpine RCA's being directly connected to the Audi amp. Yes you're right you can't connect the HU speaker outs to the 2 ohm Bose speakers, so the only other way other than replacing the speakers is to use a line out converter on the speaker outs and feed this to the Bose amp. Most car audio places sell 2 types of adapter. The one you currently have (RCA input) and a more expensive one (speaker input) which uses a Hi to lo converter to take the speaker outputs back down to pre-out level, but gets rid of the popping as the LOC cannot ground the RCA's when changing CD.

Ashleey

I got my Alpine HU to work with a Bose setup by using the Autoleads PC9 408 and which effectively uses the ISO speaker outs of the HU rather than the RCA outs.