The TTSH needs Gate AND Trigger signals with 10/11Volts, otherwise it wont work as designed in usage of the AR/ADSR.
here the simple Solution:
i offer the Gatebooster bare pcb for 8€ (shipping 1,50€)
assembled for 20€ (shipping 4€)
add 2,20€ if needed as registered shipping.
in case of the version with midi implant connector run a 1M resistor from ground to Pin3 of TL072 fix the issue.
preferred Solution: connect the gatebooster input with a cable from the GATE Input jack from the ttsh. (its needed to cut the trace from the S/H/Gate switch)
( ignore the boost trig out pointer on the picture - use the TRIG instead of GND 
for Rev.1 use the speaker holes to mount a bracket
for rev.2 :
drill 2 holes in the pcb and mount brackets with woodscrews, cut the TIP/HOT traces for 3 jacks on pcb, use one ground (you dont need 3 grounds) run wires from gatebooster to the tip of the jacks
use power from a module section (there are 6 solderholes, 2x3 rows - test with a voltmeter the voltage output/polarity) run powercable to the gatebooster.
Theory:
