A VCADSR with punch!

[jorgen.bergfors at idg.se]

Hi DIYers
Yesterday I completed a mod for my Doepfer PMS VCADSR module, which I have 
designed myself. 
The mod adds two features. Firstly there is adjustable trig level. With a pot I 
can set the trig level between 0,5 and 10 volts. 
The second feature is the most interesting. I call it "Punch mode". With it 
activated, the envelope goes immediately to full amplitude and stays there for 
a time set by the attack knob (or CV). Then it goes into the decay phase as 
usual. 
The punch feature is designed for really percussive sounds where you both have 
a quick attack and quick decay. A normal ADSR doesn't stay long enough at the 
maximum level to give a really powerful snap if the decay time is too short. 
With the punch feature you can set the length of the snap to suit your taste. 
Another advantage is that you are guaranteed that the attack is instanteous. 
With a normal ADSR you must charge the capacitor in the attach phase, which is 
always bound to take some time. A well known fact is that some synths don't 
have as snappy attacks as you would like. In my circuit the delay is only 
caused by a LM311 comparator, a 4001 RS-flipflop and two Tl072 opamps. There is 
no capacitors, except a 33pF that prevents the LM311 from ringing at the 
transients. 

/Jorgen