Posted by & filed under Envelope Generators, Projects, Synth DIY.

This project is a development of my earlier VCADSR envelope generator. Whilst that chip had both GATE and TRIGGER inputs, this chip replaces the TRIGGER input with a MODE CV that allows selection of normal ADSR, Gated looping, or full LFO-style Looping modes.

LoopEnvADSRMode
Standard ADSR mode generates the shape you expect, and allows CV control of envelope depth and overall time.
LoopEnvGateMode
Gated looping mode loops while the Gate is high. When the Gate goes low, the envelope goes to the Release stage.
LoopEnvLFOMode
LFO Looping mode loops all the time, acting like a highly versatile LFO.

The LOOPENV chip keeps the other features of the original VCADSR, like the LEVEL CV which controls the output level and can act as an ‘envelope depth’ control, 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.

Full details are in the datasheet below, but the envelope times range from 1mS through to 10Secs, in 4 even decades, and all control voltages run from 0-5V.

There is also a digital input which selects either a ‘traditional’ exponential envelope shape, or a early-digital-era linear envelope.

Pinout Diagram

LOOPENVPinout

Version 1B – a bug fix

After publishing this code, a small bug was discovered whereby the Gated Loop mode wouldn’t exit to the release stage correctly. Version 1B corrects this.

More details

Looping Envelope elsewhere on the web

Rick Holt of Frequency Central has developed a DIY PCB and panel in Eurorack format for this project, described on the Frequency Central Loop/Env generator DIY page.

Additionally, Rick also builds and sells completed modules based on my chips. You can find these on his Frequency Central LoopEnv page.

    Related Products

  • LOOPENV 1B Envelope Generator

    This chip is a development of my earlier VCADSR envelope generator. Whilst that chip had both GATE and TRIGGER inputs, this chip replaces the TRIGGER input with a MODE CV that allows selection of normal ADSR, Gated looping, or full LFO-style Looping modes. The LOOPENV chip keeps the other features of the original VCADSR, like the LEVEL CV which controls the output level and can act as an ‘envelope depth’ control, and the TIME CV which shortens the overall time... Read more »...

    More Info Buy Now

One Response to “Voltage Controlled Looping Envelope Generator”

  1. Colin Croy

    Hey Tom, another chip to get really excited about for me! I just wanted to get a little bit of clarification. I want to use this chip in a guitar context to use the envelope to control the “mix” knob between a guitars dry signal and an effects loop and the way I envision it is that I could use it as a standard envelope follower, but also with a momentary footswitched gate —— ie. attack is triggered by the switch press and the release is triggered by the switch release. I’m also curious about the looping envelope mode and what that sounds like…

    Thanks!!

    Reply

Leave a Reply

Your email address will not be published. Required fields are marked *