here's a pic of what I have used in the past which should work for you.
The stereo minijack goes in preamp trigger. The other end is cut with one lead on one pass amp trigger +ve terminal and one on -ve terminal.
The second cord is simple lamp cord that I've put crudely crimped spades on. One end is connected to the same two terminals of the 1st pass amp and the other end is connected with like terminals on the second pass amp.[IMG]
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