"Sound surge / thump"(?) when using USB / Ipod A4 Bose

[fattiereturns]

Hi folks

Have recently fitted a KDC BT-8141UY to my A4. Previously had Chorus with full Bose speaker system.

I've plugged in an adaptor for the speaker wires. It allows me to plug in the speakers to the pre-outs on the head unit using RCA plugs. The adaptor also has a blue wire, which powers the amplifiers within the bose speakers(?). I've connected this to the P.Out on the stereo. Works fine. The P.Out is also connected to the blue wire which powers a separate antenna adaptor, which I understand is needed to boost the ariel signal. So, both of these items are being powered by the P.Out from the head unit.

On the other connector, the the red and yellow bullet plugs were swapped over to allow the head unit to be powered from the permanent live. (I'm told that the switching off and on of the original head unit is actioned by means of a signal, rather than the Ignition feed simply being cut). This means I have to manually turn the unit on and off which I can just about live with...

So, the stero works, I've got the bluetooth working with my phone, the sound from unit and the bose system is fantastic, and my milk-white gloomy scottish face has almost broken into a small un-sustained smile.

HOWEVER: When I connect a USB device to the flying USB female lead, or when I change track, or even when the track is changed normally by the head unit, there is a "click" and "thump" noise from the speakers. It's bloomin loud, irrespective of how loud the volume happens to be. It's the kind of noise you might hear when turing on or off a stereo or an amplifier, or the initial noise when you connect speaker wires that are live.

In my debateable wisdom, I put diodes in line with both the amp and ariel adaptor supply lines, thinking they may not have liked sharing a supply, but this made no difference whatsoever so I took 'em out.

The set up is close to perfect, but something about the power to the amp or the speakers, or the way the head unit handles silence between USB or iPod track is ruining my one shot at auto-audio happiness...

I've looked on other sites for adaptors for Audi and they all seem to recommend different things, so an idiot like me is proper good and stuck, unless I want to spend £100 trying them all! Some are simple connector and wiring adaptors, some seem to be active and stuff... or maybe it isn't the wiring?

HELP!

(Thanks for reading)

[ini]

Your aftermarket HU is muting the signal on the RCA output to the Bose amp during volume/track change etc

The Bose amp already has a capicitor array to deal with this, as in the standard setup the headunit does not deal with the noise, the amp does.

When the HU grounds/mutes the RCA, it is discharging the capacitors in the Bose amp causing the loud pop's.

Here are some solutions:

http://www.audi-sport.net/vb/showthread.php?t=43956

http://www.audi-sport.net/vb/showthread.php?t=26307

[fattiereturns]

Your aftermarket HU is muting the signal on the RCA output to the Bose amp during volume/track change etc

The Bose amp already has a capicitor array to deal with this, as in the standard setup the headunit does not deal with the noise, the amp does.

When the HU grounds/mutes the RCA, it is discharging the capacitors in the Bose amp causing the loud pop's.

Here are some solutions:

http://www.audi-sport.net/vb/showthread.php?t=43956

http://www.audi-sport.net/vb/showthread.php?t=26307

Thanks for taking the time to reply buddy, I'll have a look at these shortly...!

[fattiereturns]

OK, have read the article, and putting capacitors in-line with the RCA outputs sounds like the one for me. The guy originally posted pictures of this set up but his photobucket account has been closed due to inactivity....

Quote from him "you just need to know how to solder on phono plugs and sockets to screened cables and put capacitors in line in the plugs."

I'm competent with circuit and wiring diagrams, and am quite good at burning myself with soldering irons, so if anyone has info on exactly how this is achieved I'd love to see it...

It sounded ok till he mentioned using screened cable, I was just gonna use crimps and heatshrink....

Oh, and it's definitely more of a "thump" sound than a "pop"....