Dual LPG - NLC build notes

This is a  Nonlinear circuit eurorack module. It's DIY.
Andrew describes this as based on the buchla 292 except it uses the "black box vactrol method" seen in the Shat-noir Phaser and Noiro-ze VCF/VCA.
This involves making a light proof box. .... basically you will build your own vactrol using some light sensitive resistors and diodes.

The term "Low Pass Gate" was created by Don Buchla and stands for a module that can be switched between a gentle low pass filter (6db/oct) and a VCA.  (basically they are a VCFA). It's most famous implimentation is in the Buchla 292.

The control (manually and via external CV) is responsible for frequency in the low pass mode and for loudness in the VCA mode. Additionally a combined mode LP+VCA is available. In this mode the sound becomes more dull as the loudness decreases.

The old West Coast style Buchla 292 uses vactrols(VTL5C). It has an extremely organic response to control signals.

Your choice of resistor/ vactrol greatly influences how this circuit will behave.
Since we are building this in a non perfect light proof box, and your position of the diode, its brightness,  etc etc... there is a lot of variation.... ripe for experiment. Of course if you wanted reproducibility you could just use a factory vactrol, but that would be boring. :-)

DG analogue switches are used for changing between filter and gate modes.... so we have voltage control over the different modes which is nice. It would be nice to have a combo as well... LPF/Gate/Combo.
Maybe Andrew will add this in a future module ???

Clone #042 ???

Links:
https://www.nonlinearcircuits.com/modules/p/dual-lpg
BOM

+ Original LPG 
+ LPG - Jondent 

The virgin PCBs

Choosing the diode size

Op-amps & resistors first

fOR  REVERSE protection

bUILDING THE LIGHT proof box

LED - long lead into square hole.

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DG202 or DG212 - these are quad SPST CMOS analog switches.
What doe the DG stand for???

Double Gate CMOS  (DG)
 Traditional CMOS technology is approaching physicial limitations was we approach the nanoscale regime.
One such solution is the double gate transistor, proposed in the 1980s.
"Multigate transistors are one of the several strategies being developed by CMOS semiconductor manufacturers to create ever-smaller microprocessors and memory cells, colloquially referred to as extending Moore's law.^" 

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You can find more NLC builds here.

http://djjondent.blogspot.com.au/2015/03/non-linear-circuits-ncl-index.html

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