[bojan]

Audio adapters arrived today - Fake SJ588 (blue transparent case), 4 pieces.
Because it is better to use two adapters of different varieties (so the w' doesn't confuse AR and DEC), I ordered additional 4 (grey cases).
Tomorrow I'lll have a look at waveforms.. however Maciel told me the common is actually at 2.5V respective to PC ground, so it will not be a problem to design the electronics for NJM3771 (full wave rectifier (for input voltage to NNJ3771) with OPAMPs and comparator ( to generate Phase direction signal for NJM3771).
The concept schematic is attached, however there is some work to be done in relation to output level shift and components values need to be finalised.
When I am finished with this, I will post the final schematic.