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Showing posts from February, 2023

Eurorack VCO Module - AS3340 v2.1

The journey to a reliable VCO based on the AS3340 has taken a lot of testing and three board revisions.  The post about v1 and a bunch of the testing is here . Below are some lists of things I modified or completely changed on the PCB. If you're looking for a schematic jump to the bottom and use v2.1 so far it's passed all my tests. Note v2.0 had mistakes and v1.0 isn't worth using. On the first version I noted several changes to make: Schematic Changes v1 to v2: Change R10 to 47kΩ Change R9 to 0Ω New C1 100pF across R10 and R9 New C15 10uF polarized cap from -5 to GND.  R6 DNU R21 & R23 changed to 5.1kΩ RZ1 changed to 18kΩ R26 changed to 100kΩ and new R31 is 100kΩ. New  R32 for 'hysteresis' between PWM and Pulse. Separated grounds on Linear FM and Scale Adj. circuits for clarity. Added another TL072 (U6) and supporting circuits. This is intended to supply two reference voltages from the 5V source. The idea is to provide Soft Sync (pin 9) with a stable voltage o