AM8069 VCF & VCA

NJM2069 chip

Overview  This module is replica of the filter used in many Korg synths and samplers around 1985/86, such as the DW6000, DSS-1, DSM-1 and Poly 800. The rich analog filter based upon a NJM2069 chip counter balanced the digital waveforms in the DW/DS range. and output VCA’s.

EuroRack Module: 14HP wide
User Manual: Download PDF

Description The AM8069 design has been kept simple and harnesses the VCF and final VCA in the NJM2069, but not the signal input VCA’s. This means it can fit into a 14HP EuroRack module. The NJM2069 chip is hard to locate, but they can be located NOS or salvaged from old Korg circuit boards.  The development of the module took many years (on and off) as I worked out the signal voltages. I eventually powered up a DW8000 voice PCB and tested the voltages and then replicated these in my design. Two audio signals are buffered and level corrected before going into the NJM2069, the filter cutoff frequency and resonance, as well as the VCA level are individually controlled by 3 buffered and level corrected CV signals.

The additional VCF signal input and Log VCA pins are not used. The filter response is switched between 2 and 4 pole by a front panel push button, that triggers a simple CMOS 4013 latch to drive a M5201 Op Amp on and off, and to switch the panel LED on and off. The wait was worth it, these are very nice sounding filters!

Module Availability A short run of 20x completed modules is expected in early 2018.

Copyright AMSynths 2017