WP-20 – cheap effect synth

The design has over 30 years – it was created in 80’s by company named Waveform Processing. Synthesizer was sold as a kit for self-assembly . This is probably the simplest analog synthesizer, with all the basic modules, that every “adult” synthesizer has: 1x VCO , 1x VCA , 1x VCF , 1x LFO and 1x AD . VCO can be controlled via optional external input, but is not scaled in volts/octave, You can however, create melodic lines using analog sequencer.

WP-20 internals
WP-20 “final” version … the ethernal prototype

My construction is quite ugly – loaded into cartoon (very strong, but only a cartoon ). I choosed cartoon due to possibility of rapid modification – you do not need to drill – and I do not like to drill. The interior is also not very beautiful. I hope to put it in a proper plastic (or aluminium) enclosure some day.

Ugly, ugly PCB

All components cost less then 15 euro – including lion’s share for the mechnical / passive components like potentiometers, knobs and switches. The PCB was made using photochemical method, the positive comes from the original operating manual (You can find it on excellent MFOS site). And most important – how it sounds ! Below You can hear and see small demo, sound was recorded directly from the line-out.

Sounds nice, but not amazing, but still good for a low component count effect synthesizer. Noteworthy thing is filter – very simple, and quite well sounding, especially at high resonance (design works well only with LM3900 !) . The whole synthesizer is much simpler than SoundLab Mini Synth, and the fun You get not lesser. Highly recommended !


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