This chip is a comprehensive upgrade of the previous generation of Electric Druid voltage controlled envelope generator chips, the VCADSR 7B and LOOPENV 1B. The VCADSR had both GATE and TRIGGER inputs, and the LOOPENV featured a MODE CV that allows selection of normal ADSR, Gated looping, or full LFO-style Looping modes. This chip combines the features of both onto a single chip, and removes the need for a crystal and reconstruction filter. It also improves the output sample rate to 31.25KHz, improves the envelope table resolution, and uses a multiplying DAC for the output, which allows full analog Level CV control without any loss of resolution or calculation errors.
The ENVGEN8C chip keeps the other features of the originals, like full voltage control over all parameters (Attack, Decay, Sustain, and Release)l, and the TIME CV which shortens the overall time of the whole envelope. The TIME CV makes an excellent modulation input for either envelope modulation or LFO frequency modulation. It also adds a PUNCH input which holds the maximum level for a few milliseconds before starting the Decay stage. This is very useful for adding extra punch to short percussive envelopes.
The datasheet includes example circuit diagrams, example waveforms, and the chip pinout diagram.
If you’d like to program your own chip for personal use, code and further details are available over on the original article about the new Druid chips.
Modular Synth Envelope Generator design
Here’s an additional schematic showing one way the chip could be used for a modular synth envelope generator. This includes input/output protection and CV inputs for various parameters. Hopefully you will find it inspiring!