Problem with head unit swop - any ideas?

GeneralWest

GeneralWest

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I've just fitted my Alpine ida-X305 head unit into my 2001 S3. The car has Bose and had the Symphony head unit. The Alpine powers up and works fine, all the speakers are working and I'm pretty sure the tupperware sub is as well.

However, I get a really loud THUD through all the speakers when I either turn the volume down to 0 or change source on the head unit. It doesn't seem to happen at any other time.

I'm using the same Autoleads adaptors that I used to install the Alpine in my pre-facelift S3 which was non-BOSE, could this be the problem?

Any help would be appreciated, I don't want to keep trying things because I'm sure the thudding won't do the speakers any good.
 
Standard feature of the Bose system I'm afraid. The Alpine grounds the RCA's when doing electrically noisy stuff, this discharges the capacitor array on the input stage of the Bose amp which gives you the loud pop.
4 ways round it:
1. Use the speaker input adapter PC9-408, this cures the popping but gives you a dirty signal to the Bose amp, and is prone to buzzing/hissing and interference
2. Change the Bose amp to something decent
3. Solder capacitors inline with the signal lead on all the RCA's as per this thread:
http://www.audi-sport.net/vb/showthread.php?26307-A6-BOSE-System-With-Sony-headunit-Problem
4. Swap the Alpine HU for a Becker GP which is Bose friendly
 
That sucks! Cheers for the advice Andy, you've saved me a lot of stress trying to find the problem. I have got an Alpine V12 and a couple of Pioneer amps sitting around gathering dust, I wasn't sure whether to put them in the S3 but it looks like I've got no choice.
 
You'll need to change the sub too as that will still pop and it has its own amp inside the tupperware enclosure.
 
Thanks mate, I didn't realise it had it's own amp in there. I've got two Pioneer subs, one 10" and one 12". I'm going to install all 3 amps at the weekend (in for a penny in for a pound). I'll run the front and rear speakers off the head unit. But for the time being I'll just hook the 10" up to one of the Pioneer amps and leave the other two disconnected. If it sounds good I'll leave it at that.

I had a silly idea about hooking the tupperware up to the Alpine V12, would this be a complete waste of time? Or should I just wait untill I can afford one of your stealth subs, which are brilliant bit of design btw.
 
Unfortunately you can't hook the Bose speakers up to the HU. They are very low impedance (about 1.5ohms) and will fry the HU's internal amp. You need to drive them off a V12 or similar which should be 2 ohm stable. Personally I would swap the speakers while your at it as they rarely sound good with anything other than the Bose amp. No idea what the Bose sub would sound like hanging off a decent amp, can't sound any worse, but again the drivers are low impedance, so either wire them in series from a bridged output or drive them from separate channels. Sorry, nothing is simple with Audi or Bose.
 
Lol, I was pleased that my new car had Bose but it's rapidly becoming a pain in the butt. It's gone from a simple headunit change to a full-on system install. All I really want is to operate my iPod through the head unit. Maybe a denison ice link or similar would be easier but I really like the Alpine HU. I wasn't intending to change the speakers because I hate messing around with interior trims, but I might have to bite the bullet and ditch the Bose altogether. :think:
 
Hmmm, I've been considering my options. The Becker GP does look a bit plain jane but I'm sure it looks ok once in the car.

I've decided to stick with the Alpine and change the Bose speakers. I'll start scouring the interweb for some replacements. I'm guessing there's not a set available that will fit straight in without adaptor rings etc.
 
I've changed my mind again. I've now decided to buy a PC9408 so I can hook the Alpine up to the Bose speakers. I know that the sound quality won't be brilliant but it's just a temporary fix until I change the speakers a later date.

This means I can spend this weekend getting the head unit, amps and sub(s) nicely installed. Once again, thanks for your advice Andy, much appreciated.
 
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