Monotron Gets All the Mods

[Harry Axten] turned the diminutive Korg Monotron into a playable analog synthesizer, complete with a full-sized keyboard spanning two octaves and a MIDI interface.

Korg Introduced the Monotron analog mini-synthesizer back in 2010. They also dropped the schematics for the synth. Hackers wasted no time modifying and improving the Monotron. [Harry] incorporated several of these changes into his build. The Low-Frequency Oscillator (LFO) has been changed over to an envelope generator. The ribbon controller is gone, replaced with a CV/gate interface to sound notes.

The CV/gate interface, in turn, is connected to an ATMega328P which converts it to MIDI. MIDI data comes from one of two sources: A two-octave full-sized keyboard pulled from a scrapped MIDI controller or a MIDI connector at the back.

The user interface doesn’t stop with the keyboard. The low-cost pots on the original Monotron have been replaced with much higher quality parts on the front panel. The tuning pot is a 10-turn device, which allows for precision tuning. All the mods are mounted on a single board, which is connected to the original Monotron board.

The fruit of all hard work is an instrument that is a heck of a lot of fun to play. Check it out in the video below. Want more? You can read all about hacking about the Monotron’s bigger brother, the Monotribe.

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MIDI to CV/Gate The Easy Way

Let’s say you’ve got a modular synthesizer. You’re probably a pretty cool person. But all your cool laptop DJ friends keep showing off their MIDI-controlled hardware, and you’re getting jealous. Well, [little-scale] has the build for you.

The Teensy 3.6 is the current top-of-the-line Teensy from PJRC, and it’s [little-scale]’s weapon of choice here. With USB-MIDI and two 12-bit DACs on board, it’s made creating an interface between the worlds of analog and digital music into a remarkably simple job. Control voltages for pitch and velocity are pushed out over the analog pins, while pin 29 is used for gate signals.

It’s a testament to the amount of development that has gone into the Teensy platform that such projects can be built with virtually no off-board components. The build is a further step forward in simplicity from [little-scale]’s previous work, using a Teensy 2 with an offboard DAC to generate the output voltages.

Here at Hackaday, we’ve always been big fans of adding computer control to analog hardware. This CNC mod to a guitar pickup winding machine is a great example.

Hackaday Links: September 17, 2017


Mergers and acquisitions? Not this time. Lattice Semiconductor would have been bought by Canyon Bridge — a private equity firm backed by the Chinese government — for $1.3B. This deal was shut down by the US government because of national security concerns.

[Jan] is the Internet’s expert in doing synths on single chips, and now he has something pretty cool. It’s a breadboard synth with MIDI and CV input. Basically, what we’re looking at is [Jan]’s CVS-01 chip for a DCO, DCF, and DCA), a KL5 chip for an LFO, and an envelope chip. Tie everything together with a two-octave captouch keyboard, and you have a complete synthesizer on a breadboard.

As an aside relating to the above, does anyone know what the cool kids are using for a CV/Gate keyboard controller these days? Modular synths are making a comeback, but it looks like everyone is running a MIDI keyboard into a MIDI-CV converter. It seems like there should be a –simple, cheap– controller with quarter-inch jacks labeled CV and Gate. Any suggestions?

World leaders are tweeting. The Canadian PM is awesome and likes Dark Castle.

Way back in July, Square, the ‘POS terminal on an iPad’ company posted some data on Twitter. Apparently, fidget spinner sales peaked during the last week of May, and were declining through the first few weeks of summer. Is this proof the fidget spinner fad was dead by August? I have an alternate hypothesis: fidget spinner sales are tied to middle schoolers, and sales started dropping at the beginning of summer vacation. We need more data, so if some of you could retweet this, that would be awesome.

Remember [Peter Sripol], the guy building an ultralight in his basement? This is going to be a five- or six-part video build log, and part three came out this week. This video features the installation of the control surfaces, the application of turnbuckles, and hardware that is far too expensive for what it actually is.