Skip to main content


Showing posts from July, 2022

Eurorack Noise Generator v1

When I bought the AS3310 chips from Electric Druid for the polyphonic envelope I also bought a few other chips to experiment with. One that I expected to be a pretty straight forward project to set up for a module was the Noise2 .   The chip is just an 8 pin PIC preprogrammed to output white and pink noise. There's a thorough writeup on the development of the firmware here . Only 4 pins on the Noise2 are used and it's all 0 to 5V so interfacing is pretty easy. I wanted both filtered and unfiltered white noise and a pink noise output all buffered to prevent undo current draw on the Noise2 chip and amplified to 0 to 10V in my setup which required 3 op-amps. That left one op-amp available so I also have an inverted filtered white noise. With 4 outputs the jacks on the module could be on top and bottom and support the PCB properly. The filter in this case is a simple RC low pass filter straight off the data sheet. I went about simulating the circuit and then breadboarding it to con

Eurorack Level Display v2

 A quick update now that I've received version 2 of the Level PCB. ( For more info see v1 details here. ) The PCB with LEDs is virtually identical to the v1 version. The only real difference was that I panelized the design to get more of them for v2.    On the PCB that handles signals and power, a lot of changes were made. Used different footprint for resistors. Used wider footprints for caps I have that are 5mm pitch. Avoided collisions between the arduino header footprint and other components. Moved the 20pin header to allow for less depth overall. Used more consistent trace sizes. Added a path between the two potential inputs that can be jumpered so that the two inputs are multipled together. In using the module I find two inputs unhelpful typically. When the jumper is bridged, R20, R21, R22 and C2 aren't required. Removed a log of capacitors. Removed the 5V regulator, and rely on the arduino pro mini's regulator. Removed power LED. Removed mounting holes. All of that al

Eurorack Polyphonic Envelope Generator v1

This post is about a DIY design of a polyphonic envelope eurorack module. The idea for this module started after I bought a second hand Roland System-8 and started to understand the polyphonic features better. I had already built several oscilators from a few DIY kit providers and was running into the issue of not having enough envelopes for them all. So decided to try and build a polyphonic envelope. I jumped right into this design with a chip selection, I went over to Electric Druid and grabbed a few AS3310 ADSR chips to experiment with. I didn't have any modules that used this chip but while breadboarding a design I came across a useful reference on Eddy Bergman's site . Ultimately my goals of a polyphonic version complicated the design a bit. One thing to note on the AS3310 is that is has some odd control voltages, particularly the Attack, Decay and Release CVs are 0 to -5V instead of 0 to +5V like the Sustain CV. I wanted 0 to 10V tolerant CV inputs and potentiometers too