Having installed a few simple systems in the days when you could disconnect the battery, run cables through convenient panel gaps and grommets without setting off warning lights willy nilly, I am now fortunate enough to have an 09 Elegence 2.0 TDI with 8 speakers to play with. I have replaced fronts with some old Infinity components that are in their third vehicle and the rears with fairly basic Alpine coax and now need an amp to improve sound quality, give a little more volume and to drive an old Shadow Works 12" sub in un-ported enclosure. So looking at a 5 way Alpine or Hertz amp under passenger seat. The Columbus can be tweaked with VCDS to give line (pre out) level but I think this is an on or off setting and cannot be applied just to the front output. So first question is - is this the best approach or should I use speaker level outputs into appropriate amp to preserve fader function which I think is lost when setting to line level? I do not want to cut into the harness so will use connectors to convert the 8 pin speaker output on the back of the Columbus to 4 RCAs into the amp and then speaker feed back to the original connector, not sure if I can mention supplier here. Second question - is this feasible or is there a simpler way? I do not see the point of using LOCs. Third question - how to use a power on cable with Columbus, route power feed from battery and where to earth? Lastly will any of this invalidate the warranty?

I know this is a lot to ask but any pointers would be appreciated and thanks in advance.

I'm not an expert at all but I recently retrofited the Sound System,so I'll try to answer as good as I can.

Firstly,I think you should do the connections to keep the fader because it's very useful on better speakers/loud volumes.As you said,you can either set the entire Columbus for amp or no-amp,you can't do it only for front speakers.I would connect each Columbus output(rear left/rear right/front left/front right doors) to a amp channel.

For the second question,I don't see a better way than the one you said,but keep in mind that you have almost no space behind the Columbus.

For the third one,I don't think you can run a power on cable to Columbus because it uses CAN BUS to communicate with the amplifier.I'm not an electrician,but you could try the glovebox bulb,in my Superb it stays on until I lock the car.You can run the power cable to the back of the interior fuse box,just don't forget to put a 30A fuse(it should be enough I think).You can wire the ground to the lower left/right A-pillar,right under the hood release lever there is a 10mm hex nut.

I'm not an expert at all but I recently retrofited the Sound System,so I'll try to answer as good as I can.

Firstly,I think you should do the connections to keep the fader because it's very useful on better speakers/loud volumes.As you said,you can either set the entire Columbus for amp or no-amp,you can't do it only for front speakers.I would connect each Columbus output(rear left/rear right/front left/front right doors) to a amp channel.

For the second question,I don't see a better way than the one you said,but keep in mind that you have almost no space behind the Columbus.

For the third one,I don't think you can run a power on cable to Columbus because it uses CAN BUS to communicate with the amplifier.I'm not an electrician,but you could try the glovebox bulb,in my Superb it stays on until I lock the car.You can run the power cable to the back of the interior fuse box,just don't forget to put a 30A fuse(it should be enough I think).You can wire the ground to the lower left/right A-pillar,right under the hood release lever there is a 10mm hex nut.

Shame, I do not think the glove box power supply will be up to the job but good to get confirmation that it is all or nothing on the Columbus line out front! What amp did you use for you set up?

Long time ago I used a relay and the glove box bulb to wire a radar detector,that's why I thought it would work.I used a VW Scirocco Dynaudio amp,I had to order some Bose connectors from Audi...it was pretty hard to make it work with the Columbus,but in the end I did it and it sounds wonderful,much better than the Sound System in my opinion.Also,as an advice,put some dampening materials on the doors.For all 4 doors(door cards,interior/exterior metal part of the door) it costed me about 35 pounds(17 sheets @ 2 pounds each).I ordered them from UK,they were cheap but very efficient.No more rattles,tyres noise was reduced and the doors feel very solid when you close them

Long time ago I used a relay and the glove box bulb to wire a radar detector,that's why I thought it would work.I used a VW Scirocco Dynaudio amp,I had to order some Bose connectors from Audi...it was pretty hard to make it work with the Columbus,but in the end I did it and it sounds wonderful,much better than the Sound System in my opinion.Also,as an advice,put some dampening materials on the doors.For all 4 doors(door cards,interior/exterior metal part of the door) it costed me about 35 pounds(17 sheets @ 2 pounds each).I ordered them from UK,they were cheap but very efficient.No more rattles,tyres noise was reduced and the doors feel very solid when you close them

Cheers, I may be better off with a pro install as they can deal with any canbus issues and good advice about the doors.