The Music Thing Modular Turing Machine is as ubiquitous in generative Eurorack patches as houseplants are in modular Youtube videos.
I bought the TM and the Pulses expander as kits from Thonk – a quick guesstimate at the pricing meant there really wasn’t much to be gained by sourcing the parts directly.
The Vactrol Mix expander kit was out of stock, so I went with the PCB, but the BOM is all standard stuff & the only thing I didn’t have on hand were the vactrols. These are VTL53Cs – which no-one seems to have in stock. VTL5C1s seem to be twice as expensive, and have a much faster reaction time – which means they might “click” in this application.
I went with these – Silonex NSL-32SR3s. They work fine – the only thing to bear in mind is the dot on this Vactrol denotes the -ve pin of the LED.
The Turing Machine itself is all through-hole, and very straightforward. The Pulses is even simpler – it has a few SMD resistors, but don’t let that put you off if you’ve not done any surface mount boards before. They’re larger than any SMD I’ve built before – not 0805, possibly 1206? – and if you can build the TM itself, you can defintely build this.
The Vactrol Mix is a quick build too – all through hole and nothing challenging.
There are build guides on Thonk, and the Eagle files are on the Music Thing Modular github.