MOTM

For quite some time I've been contemplating a couple of enhancements to the 
800 ADSR generator.  The obvious "wants" are a manual gate switch (to 
audition that portion of a patch), either a "gate on" LED or a gate output 
LED (that tracks voltage level via intensity), and an adjustable gate delay.

The gate LED has already been done (http://www.hotrodmotm.com/800_mods.htm) 
and a manual gate switch is pretty much cake, but the delay option is a 
little more involved.  Am looking for opinions on the viability of this idea: 
Add the activity LED like Moe did, add a manual gate switch as has been 
suggested by many, and turn the SUSTAIN pot into a dual-use mode: 
SUSTAIN/DELAY.  I envision that a multifunction piggyback board be added to 
the 800.  The manual gate switch (an NKK switch to match other MOTM modules) 
is used to trigger a gate on-demand.  But this added NKK switch would have a 
center-off, and momentary On/On capability.  When the NKK switch is lifted, a 
manual gate is created and the 800 module works as if a gate-in has been 
received.  Let go of the added NKK switch and all is normal (gate goes away). 
 But, press down on the added NKK switch and you have selected the 
"delay-time-set mode".  Using the existing SUSTAIN pot, adjust for the 
desired DELAY time wanted (1 millisecond to 10 seconds, log curve).  Release 
the added NKK switch and the module works as normal except that the added 
piggyback circuit "remembers" the selected delay time and delays each 
incoming gate by the user-selected amount.  (Of course the SUSTAIN pot will 
have to be adjusted back to where it was before you adjusted the delay time.) 
 By again lifting the added NKK switch, one can audition the delay time just 
added.

Getting this to work is not difficult.  But would this be a workable user 
interface?  (Yes, the SUSTAIN pot is linear... the conversion to a log-taper 
for time-delay adjustments would be handled by circuits on the piggyback 
board using a PIC processor, a couple of opamps, and some passives.  And yes, 
just like a dedicated pot, the piggyback circuit would remember delay 
settings even after the synth is powered down.  This circuit is designed, but 
not yet prototyped.)

Lastly, I would sacrifice the -ENV output in favor of a voltage control input 
for the delay time.  That way, delay times could be made to vary by note, 
random event, or anything else one could dream up.  This modification would 
certainly require some hacks to the existing 800 module, but should be 
minimal in severity and number.  The changes would be reversible.  I would 
suggest that a pair of MTA-156 connectors be added to the piggyback board and 
use a short (3") MTA-to-MTA cable to supply power to the 800 board to 
preserve use of the existing cable.

In conclusion, one would end up with an 800 that has a manual gate switch, 
gate activity LED, an adjustable gate-delay over a wide range of times, and a 
gate-delay voltage-controlled input.  That, while adding only 2 small holes 
in the front panel of the MOTM 800 (LED and NKK switch).

Comments?

Cheers!
Tom Farrand