I have Canton sound system in my Enyaq coupe rs 2023. I would like to change Canton sound system amplifier to DSP amplifier.
How to code the device to output speaker signal from the head unit?

I am in the same situation.
I had a quadlock harness from my old Octavia that i thought would work. So i pulled all the trim and ran all the cables, only to realize that the speakers werent connected at the headunit. But at the amplifier in the right side of the trunk.

So to get the highlevel signal, current best option is this cable https://www.audiotec-fischer.de/en/match/adaptors-harnesses/pp-uni-2-38

Then I would need a rather expensive DSP like https://www.audiotec-fischer.de/en/helix/processors/dsp-pro-mk3

I am not certain, i havent had time to measure, but i think that one needs to get 8 highlevel signal into the DSP to get the entire frequency range. Since the front tweeters, mids, woofers and the subwoofer in the trunk all get discrete signals from the Canton Amp.

For the time being i attached a high-low level converter to the connector for the stock subwoofer. And fed that signal into the amp for my own sub.
It works, but when the headunit is turned to around 60% the signal to my amp goes silent, until i turn down the headunit under 60% again