Yamaha DTXpress/DTXplorer/DTXtreme

Hello there,
I want to plug two tp 65 on the 9/10 trigger. I bought an Y splitter 
with one stereo male jack on one side and two mono female jack on the 
other.
I plug the two tp 65 five on the Y splitter and  plug the splitter in 
the 9/10 trigger. I only get one sound from both (it's the trigger nine 
for both).
If I use the mono jack from kp 65 (kick) and I plug it into 9/10,  I 
get the two correct sounds.

What's wrong with the Y splitter ?

Another thing, did someone built the keith's circuit, the one that gave 
the same thing than the 9/10 trigger on the other trigger. If yes, is 
it possible to someone to build a couple of them for me, i buy them of 
course.

Thank in advance
Vincent