Thanks for your reply!
But it doesn't really tell me what signals are present on the pins of the DIN output on the echocord...
I've soldered a cable as following;
pin 1 of DIN to tip of the TRS jack
pin 2 of DIN to ring and sleeve of the TRS jack
but the signal is very distorted.
Could the output be symmetrical, where the ring would be soldered to another pin...? If so, which pin could it be?