Diy Modular Synth – Part 0

Beginnings

One year ago, I knew nothing about synthesizers, nothing about circuit board design, and had never even heard of Eurorack. Over the last year I have been learning my fair share of electronics, and just a couple of months ago Ericasynths released a DIY kit to create your own Eurorack modules with excellent guides not just to follow along with, but to actually learn from. I am going to be working through all eight modules, and documenting my experience putting them together.

Step 0

I did not order the DIY Kit. I will order it if for no other reason than to support Ericasynths for putting together something so awesome, but I wanted to look for parts myself. I placed a Digikey order for parts enough for all eight modules, and it will be here on Friday.

However, I am going to start each module by reading through the booklet, and creating the modules in a circuit simulator first. I have, in the past, used Falstad to create simulated circuits. I love Falstad, but I know it has its problems. I’ve wanted to learn spice for a while, and this seems to be a great opportunity to do so.

I typically like having a lot of work being done on a cloud server, with end-clients connected to it. I am going to attempt to set up a workspace for ngspice such that I can write code in VSCode on the server.

I am back after a few days of trying to get something like this working. I was able to use ngspice on my cloud server and get ascii plots, and even able to generate pngs that I could load. However, I realized that my knowledge of electronics is a barrier when trying to work with it. I think with some more knowledge in addition to talking with people about some sort of “standard library” of components (something as simple as an op-amp has to be written using subcircuits)– something like that has to exist, but I’m just not finding it.

I could use ltspice, but ltspice is just free as in beer, and I was really hoping for a workflow that was as much true libre as possible.

In the end, to move forward, I did end up using Falstad to get an understanding of using a hex-schmitt trigger with a diode-interrupted feedback to simulate oscillation, an op-amp buffer to read this oscillation and then a cap to AC couple this buffer.

…Unfortunately, my saved Falstad file did not load when trying to take a video of it, and also to share here. -_-

Next Steps

As of this morning, December 16th, I have gotten a big Digikey box with the components I need at least to Breadboard a few of these modules out. I also have access to an Othermill, to create single-sided or double-sided boards to prototype with. I will be attempting to get the entire VCO working on a breadboard next.