Send me your Synth Pro and I will install an SPFX1 and upgrade the resistors in the unit to improve the decay and release slopes. This modification is to correct the voltages going to the main VCA. If you have a recent synth pro then you probably have the correct resistors already.

You can choose to have 10k/470ohm resistors as recommended by MFB, or 4.7k/220ohm resistors which further improve the slopes but slightly reduce output volume.

Price does not include shipping costs.