Patrick Nelson's STM-01 Aims to Be a Highly-Expandable, Modular, Open Source Record Player

Software engineer and maker Patrick Nelson is working on building a fully-automatic turntable with a modular expansion system to add potential advanced features like a record-flipper or vintage computing connectivity — and is making it available as open hardware.

"This is (going to be) a fully-automatic, modular turntable, called the Statimatic STM-01," Nelson says of the project. "The built-in features of this turntable will be kept to a minimum, so that development can go more quickly. These features will be able to be expanded using the 5 expansion ports on the back of the turntable. Built-in, the plan is to have two commands: play and pause."

Those two controls are, technically, more than you need from a simple turntable: traditionally, the turntable begins turning either when specifically activated or when the tone arm, which carries the needle responsible for reading the grooves in a record and transmitting those tiny vibrations to amplifiers, is manually brought across over the surface of the record. The STM-01, though, aims for fully-automatic operation: "play" lifts the tone arm from its rest position, moves it across to the outer edge of the record, and gently lowers it to begin playback, or lifts it and returns it to the rest position if playback is already in-progress; "pause" lifts the tone-arm but leaves it hovering over the record, or gently lowers it back down if it's already lifted.

Like commercial record players, the STM-01 can only handle automatic playback if it knows how big the record is. The machine can be switched between three sizes — 7", 10", and 12" — or an "automatic" mode that uses an infrared sensors to determine where the edge of the record is. That's already going a little beyond the capabilities of a commercial player, but Nelson has more in mind: a modular expansion system that could add yet-to-be-designed additional functionality, ranging from robotic record flippers and changers to a second tone arm, an FM transmitter, alarm clock, and even a "communication adapter to your favorite vintage computer from the '70s or '80s' — some programs having been distributed as audio on records rather than the more common cassette tapes.

At the time of writing, though, Nelson had celebrated something a little more fundamental: the first successful playback of a record using the tone arm he's designed, with a commercial off-the-shelf turntable to actually rotate the record. "This thing's heart is a Teensy 4.1, which will drive two axes (elevation and azimuth, with only elevation hooked up so far)," he explains. "The elevation movement's exact position is monitored through a 10k linear potentiometer, which I'm using as an absolute encoder. It's also monitored using a wire in the tonearm lift that completes a circuit with the metal rod that pushes it up and down, so it's aware if it's currently lifted, or set down on something."

The design and testing of the tone arm is covered in the video embedded above, with more videos of the project available in Nelson's YouTube channel; currently-released design files and source code are available on GitHub under an unspecified open source license.