Music Easel Adaptation - Pulser & Inverter

Version 0

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

This is based on the pulser & inverter circuits on Board 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


The schematic and PCBs linked above contain some significant errors, most of which must be corrected during construction.



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.

PIC, PIO, FB - Pulse Input Common, Pulse Input One-Shot, and Feedback. You want to try to find a single-pole on-off-(on) switch, where the (on) indicates momentary operation. Hook PIC to the common switch terminal, hook PIO to the (on) terminal, and hook FB to the regular on terminal. This will let you do just one "pulse," or if you switch to the feedback mode quickly after doing one pulse, the pulser will drive itself and you will get repeated pulses. The middle position turns off the pulsing. If need be, you could just use a regular on-off-on switch here.

PCVA, PCVB - Pulser CV outputs A and B. A is active when AEN is set high; B is active when BEN is set high.

PPA, PPB - Pulser pulse outputs A and B. A is active when AEN is set high; B is active when BEN is set high.

Y1, Y2 - terminal of an electronic switch; connection made when BEN is set high (untested)

Z1, Z2 - terminals of an electronic switch; connection made when BEN is set high

ANOT, BNOT - logical "not" of AEN and BEN

AEN, BEN - A and B enables; see other connection instructions for details of what they enable. I plan to connect these to a switch that will let be switch between automatically-on (connect to +15 V) and connect to an external input. Most users will probably just want to tie AEN to +15 so the A outputs are always enabled. Some users may want to just ignore the B outputs entirely. Some might want to only use the "B" part of the circuit to control the Z1,Z2 and Y1,Y2 electronic sswitches, and ignore the pulser B outputs. Do whatever makes you happy.

INVI, INVO - inverter input and output; takes 0-10 V CV and outputs 10-0 V CV. The inverter is independent of the rest of the pulser, so you can invert whatever CV signals you want.

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.


LOS - Level (pulser rate) Offset (Easel schematics and this version of the PCB say 50K, but I recommend 10K linear)

LCV - Level (pulser rate) CV; controls amount of influence of the LIN input (Easel schematics and this version of the PCB say 50K, but I recommend 10K linear)

TRIM - Trims the pulser rate - set to personal taste


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.