AI003 Looping ADSR Envelope generator

Rated 5.00 out of 5 based on 2 customer ratings
(2 customer reviews)


An easy to build looping ADSR module. the build guide is located here.

The manual is located here.

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The AI003 Looping ADSR Envelope Generator DIY Kit is a looping ADSR Envelope Generator. It can be manually triggered via Momentary Push Button, Gated via the Gate Signal, Triggered or re-triggered by a Trigger input, or set into a loop mode via a toggle switch. An LED shows the status of the output.

This Looping ADSR Envelope Generator DIY Kit circuit was derived (with permission) from the great and simple circuit (only 2 ICs!) from Nicolas on the forums. With some help from the great Dave Brown, the circuit was updated to provide additional voltage protection, more uniform looping and gate behavior, more precise LED monitoring, and some nice user experience updates.

In Gate or Trigger mode, the envelope can be used as a traditional ADSR envelope generator. In loop mode, the output sends a variable exponential waveshape between Ramp, Triangle, and Sawtooth LFO with control over the attack and decay of the LFO shape.

The modes are dependent on whether or not the gate jack is inserted, and for triggers, the Sustain level – see the chart below. We will be releasing a more traditional ADSR with “normal” gating functions shortly (but with twice the part count and no AD loop).

Mode Plug in Gate Jack Sustain Level Output
Loop True 0 AD Loop when Gated
Loop FALSE 0< AD Loop
Loop TRUE 0< AD Loop when Gated
Loop FALSE 0 AD Loop
ADSR TRUE 0 ADSR – no trigger
ADSR FALSE 0< Trigger Mode but will "hang" on sustain
ADSR TRUE 0< ADSR – no trigger

Minimum Gate/Trigger Signal: 2V
Attack Time: 20ms – 14 seconds
Decay Time: 10ms – 20 seconds
Release Time: 100ms – 7 seconds
Max Voltage (when run off +/- 12V): 7.5V

All jacks, knobs, and other components are soldered directly to the PCB. There is no wiring, making this kit ideal for those who know how to solder, but are still starting out in their DIY Synthesis journey.

We recommend this kit as the third module you build. It is easy, has only two ICs, and can be built in a single sitting. If it works, you are ready to build other modules.

The Build Guide is here

The Eurorack Kit Contains everything you need to build your first DIY Analog Synth Module:

  • High Quality 3.5 mm Jacks
  • A PCB
  • A Eurorack Panel
  • High quality Alpha Potentiometers
  • All components required to build the AI003 Looping ADSR Envelope Generator.

Additional information

Weight N/A
Product Type

Built and Tested, Full Kit, PCB, PCB and Panel

-V mA


+V mA


2 reviews for AI003 Looping ADSR Envelope generator

  1. Rated 5 out of 5

    This is a really great, simple ADSR envelop generator. I built this as my 6th module and did it short of 2 hours. Super nice PCB layout and had ample room when soldering components. The envelop itself performs really well! I wasn’t sure about the lack of low, medium, and high range selection but the circuit is designed to not need that. It’s a very wide range on each parameter. Would have liked an additional EG out or an inverted envelop but for the price, it’s an exceptional performer! If you’re new to DIY but have built at least one other module, this one would be great next.

  2. Rated 5 out of 5

    (verified owner)

    Very clear and easy to understand guide. It was also easy to source parts from Tayda to save a little ~money~ along the way. I built it in a few hours and have been very happy with its performance. It does exactly what it promises and was a very inexpensive and fun build.

    I’ll definitely be keeping my eye out for more AI Synthesis stuff!

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