MiniADSR

Introduction

This is my take on RenĂ© Schmitz' Fastest Envelope in the West. It’s a four parameter envelope generator. Attack, decay, and release times can range from 200ms to 16s.

A front view of MiniADSR v1.0

The final build is in a standard 4HP Eurorack panel.

My layout for MiniADSR v1.0

Build

Bill of Materials

Applicable for v1.0.1 PCB. Here’s a list of what I used. All resistors are 1/4W, electrolytics are 5mm diameter at most, box type caps are 5.00mm pitch.

Passives

Transistors and ICs

Hardware

Schematics

Version 1.0.x has the bare minimum controls for an ADSR. Four knobs, one input, and one output.

Please don’t mind the weird connector pins. This was done to accommodate the multi-board setup. If you are building it on perfboard/breadboard, just connect matching numbers (eg. A1-B1 will be a point of connection).

PCB

PCB shops use Gerber files for etching copper traces, printing labels, drilling holes, and other manufacturing steps. You can download my zipped Gerber files for a version you like and upload those into their website.

My PCBs in this series were sponsored by PCBWay – a great option for prototyping. Use their Quick-order PCB tool to get an instant quotation on the files.

Check out the PCBWay community page to order the PCBs directly from them:

This build requires three PCBs: Main, Control, and Front. Make sure to print all three of them!

Versions

1.0.1. Minor fixes

Addresses issues present in v1.0.

TitleFilename
SchematicsMiniADSR 1.0.1.pdf
Gerber FilesMiniADSR 1.0.1 - Main.zip
MiniADSR 1.0.1 - Control.zip
MiniADSR 1.0.1 - Front.zip
1.0. Initial Design

This has some issues that require bodging.

MiniADSR v1.0 fixes. Cut through the red lines, add a wire on the green.

Some build notes

Connections between panels

The front panel and the control board are held together by the 3.5mm audio jacks. The control board and the main board are coupled at two points: the 12mm M3 brass standoff and the 16-pin headers.

The 12mm M3 brass standoff I used to connect the control and main boards

The pins also carry power and audio signals between the two boards.

The photo shows a bit of space between the pin socket and the board. I tried to use a 11mm M3 brass standoff but it seemed too short. I recommend installing the standoff before soldering to ensure that the boards end up parallel to each other.

Power options

I provided two possible options for powering these boards:

  1. The first one is a standard 2x8 IDC connector found in most Eurorack modules. This is the one I’d recommend if you already have a Eurorack system.
  2. The second one is a 6-pin JST header which I use for all my modules. I find the more compact and easier to buy where I’m from.

You’ll only have to pick one to use on your board.

Custom KiCad footprints

I made my own footprint for the RV09-type potentiometers as well as some guide lines for the panels. Download and install it if you wan’t to modify the PCB. You can find my KiCad footprint libraries on Github.

Tests

Test setup

The range of attack, decay, and release times are dictated by C3. I ran a couple of tests with my oscilloscope to help you decide on the value to use. I recorded the output at different knob positions (minimum, 9 o’clock, 12 o’clock, 3 o’clock, and maximum).

A screenshot from my oscilloscope with yellow as the gate input and blue as the MiniADSR's output.

Results

Attack duration tests were done with the decay and knobs at minimum and sustain knob at max. Decay and release duration tests were done with sustain at max.

I found that the lower values were useful for short generative bleep-bloops, while the higher values were useful for long swells especially when performing with a keyboard.

My plans for v1.1 will include a range switch that would add a capacitor in parallel to make both short and long range options available in one module.

Demos

You can watch my demo and build video of my PCB version on Youtube.

I also built this module on perfboard last year. You can find a demo in my ADSR Envelope Generatorpost or on Youtube channel:

Conclusion

I’m pretty happy with how this module turned out. I’m working on a more full featured version of this and looking into a range switch and a manual trigger button.

Follow me on Youtube and Instagram for updates!