The Plasma Synthesiser

In its initial incarnation, Plasma was a two-voice Virtual Analogue monophonic synthesiser with an integrated sequencer. Later incarnations added CEM-based analogue filters and envelope generators although this was at a time when Curtis chips were in very short supply so adding these components was not deemed a sensible long term strategy.

Initially, the oscillators were the instrument's weakest link. Aliasing was a serious problem. Later experiments with Karplus-Strong and PolyBLEP oscillators helped to improve the sound but the correct solution - band limited oscillators - were still a way off.

Current Status:

• Last updated : 02-Feb-23
• Two voice architecture with digital filter and EG's working
• Hardware checks out and working as it should
• Midi-In fast and responsive. Pitch bend not working. Modulation wheel only partially working.
• Envelope generators imprecise
• Effects - delay working, reverb sounds crude and metallic
• Sequencer - single channel record and playback working

Next steps:

• 1. Figure out how to develop the front panel controls so that they match up with the capabilities of the Teensy audio library
• 2. Design the new audio path using the Teensy audio tool
• 3. Port Teensy Midi-over-USB protocol
• 4. Design a new CPU card around a Teensy 3.5
• 5. Solve the LCD mounting issue
• 6. Design an enclosure for the rack-mounting version
• 7. Don't forget to add a volume knob on the output (ahem...)