Music Easel Adaptation - Envelope Generator

Revision 1

Original circuit by Don Buchla (used with his kind permission); adapted by Aaron Lanterman

This is based on the envelope generator circuit of Board 3 of the Music Easel. You should spend some time studying the original schematics.


Schematic & layouts

Complete PCB layout
PCB, silkscreen
PCB, top copper layer
PCB, bottom copper layer



Front panel connections usually have a square and round pad together in a white box. The round pad is the signal, and the square pad provides a convenient ground.

ATIN, DURIN, DECIN - attack, duration, and decay CV inputs; influence is controlled by ATCV, DURCV, and DECCV settings, respectively

PIN - pulse input

B3P6 - corresponds to original Easel Board 3, Pin 6

TRAN, SUS - connect TRANS and SUS to the extremes of a single-pole on-none-on switch, and connect B3P6 to the common terminal of this switch. This lets the user switch been "transient" and "sustained" modes. (Note I only tested the transient functionality.)

POUT - pulse output

ENVOUT - envelope output

LED - on the Easel schematics, this is actually called "LAMP" and is shown going through a lamp-looking symbol to a +12 V supply. I haven't tried doing anything with this, since it's a low priority for me, but if someone can get something to light up I'd love to hear about it.

+13.5 V - a supply created using a buffer op amp (most users will not need this)


ATOS, DUROS, DECOS - attack, duration, and decay offsets

ATCV, DURCV, DECCV - attack, duration, and decay CV controls; control influence of ATIN, DURIN, and DECIN inputs, respectively


These should be considered advanced projects, and should only be attempted by people with extensive knowledge and experience in electronics, particularly in terms of practical construction and debugging techniques. The boards are dense and the documentation is sparse. If you are just getting started with Synth DIY, we recommend starting with kits by Blacet Research or PAiA, or boards by Music from Outer Space. (There are numerous other kit and PCB manufacturers, but those are relatively newbie-friendly.)

If you try to build one of these projects, you must assume that you will be on your own, and be confident enough to tackle the project under those circumstances. I am interested in learning about people's experiences in building the boards, and will try to answer questions over e-mail, but I don't have time to do any hand holding.

Any PCBs made available to the public are provided as-is, with no guarantees or warranties whatsoever. Similarly, no guarantees or warranties are made about the correctness or usefulness of the information on these webpages.

Any electronic project may present a risk of injury or death, particularly when dealing with mains voltages. It is important to follow appropriate safety practices. The author of these pages, Aaron Lanterman, disclaims any liability for injury, death, or other damage caused in using the PCBs or any of the information contained on these webpages.