R17 and R18 are 4.7k resistors. + If you plan on using I2C with an ER-301, Ansible or TXo, (ie I2C "MASTER" mode) you should populate the 4.7K resistors. + If you plan on using I2C with a monome Teletype, do not populate these resistors - it may well cause problems.
........................ I'll leave these off for the moment... see how it goes
If you are familar with modular synthesizers, you will probably be aware of logic gates. But did you know of their connection to the Apollo mission to the moon? It's nearly 50 years since those heady days. Apollo changed our lives in so many ways & the technology used then, permeates our society to this day.
Above is a pic of the AGC - The Apollo guidance computer. (The original uploader was Grabert at German Wikipedia. [Public domain]) This was the computer that took those 3 men to the moon and back. In addition, it was one of the first computers to use integrated circuits (ICs). The AGC was in fact the world's first "embedded system".
Today ICs are everywhere. But back in the late 1960's they were a revolution NASA's goal was to use components that were low weight, had low volume & operated on low power. Coupled with this, they had to be extremely reliable. With these goals in mind they decided to use a single simple integrated circuit for all logic functions.
Since just one chip was used, NASA could really test it under whatever extreme conditions it liked.... to make sure that it could survive everything which space travel could throw at it.
AGC dual 3-input NOR gate
This single chip contained a three input NOR Gate. It's incredible to think that it's possible to carry out all logic functions to take men to the moon with just a NOR gate.
This gate gives a positive output only when both inputs are negative.
The beauty of the NOR gate, is that it is what is known as a universal gate. In other words, it can be combined with itself to make any other kind of logic gate
For example a NOT gate can be made by joining the inputs of the NOR gate.
The OR gate can be made by inverting the output of a NOR gate.
The AND gate is made by inverting the inputs of a NOR gate.
We can go on and on, but I think you get the idea.
The AGC dual 3-input NOR gate schematic
NASA used about 5,600 in total for the later AGC versions.
The Serge TWS and WM are classic waveshaping modules.
Wave shaping is one of the fundamental parts of oscillator designs as well as being one way to achieve distortion and design new waveforms from existing waveforms. When building a oscillator core, often waveshapers are used to derive additional waveforms from a single saw or triangle core. + Oscillator cores & Exponential Converters
The timbre circuit from the Buchla 259 is another example of the early use of waveshapers.
I understand that Don's Harmonic Oscillator from the Buchla 100 series used waveshapers to add harmonics to the core oscillator.
There are lots of modern manufacturers of waveshaping modules in many formats. To be continued ............