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AM3030 - Prophet 5 Rev 2 VCO
Overview This is VCO is based around the classic SSM2030 chip that was used in the original Prophet 5's (Rev 1 and 2). The SSM2030 was the first non-proprietary VCO chip ever
produced, Dave Rossum created it in 1977. The chip was the basis for a number of custom E-mu Systems synthesizers, as well as the original Prophet 5 and 10. This is a good VCO design which has HF trimming, and the relatively similar
performance of each chip within a batch enabled polyphonic designs. However its performance has been exceeded by more recent discrete designs.
Original Circuit
The original design is very simple, with basic square, triangle and sawtooth waveforms being created from the VCO core. This is exactly out of the datasheet, and as used in the Prophet 5 Rev 2.
An external tempco resistor is
required (1K 3600ppm) and some simple CV and modulation summing Op Amps.
AM Circuit The Analog Metropolis circuit is based on the original but with some additional features:
- LFO mode
- Soft and Hard sync options
The VCO PCB outputs three waveforms; triangle, pulse and triangle. These waveforms are
mixed together on a second set of PCB's into both inverted and non-inverted outputs. This second set of PCB's also holds a set of 4 momentary push buttons that control high quality analog switches (DG202's) via simple CMOS flip-flops. This
replicates the look of the Prophet 5 control panel and makes for more interesting ergonomics.
The switch PCB's are generic and can be used to control any analog synth module. More details on Push Button Sub Module (PBSM) are here. more »
Panel The front panel is a high density AM design, 90mm wide and 4U high, with black lettering. Controls knobs are standard Eµ Modular designs.
Build History
The schematic was transferred into Eagle CAD in July 2005, and prototype boards were sucessfully tested in November 2005.
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Site Options
Resources
* SSM2030 Datasheet 
* Typical SSM2030 VCO 
* AM3030 PCB layout