I have FL MCA and DAB installed in my preFL Mk4. I know people have problems with DAB volume when CD multichanger is connected.
So i tried myself - and it is true - it sounds awful!
Big drop in volume and sound quality decreases a lot - almost like high pass Filter, very dull sound.
Someone i know has tried to switch L+/R+ only with relay but unless you disconnect L-/R- as well the problem remains.
Anyone worked out a fix for this? I suspect impedance mismatch but not sure.
I know of fix using 4 pole relay to disconnect audio, controlled by CD motor - but this is a poor solution and should not be needed!