DIY Synth Takes Inspiration From Fretted Instruments

December 11, 2025 by Lewin Day 7 Comments

There are a million and one MIDI controllers and synths on the market, but sometimes it’s just more satisfying to make your own. [Turi Scandurra] very much went his own way when he put together his Diapasonix instrument.

Right away, the build is somewhat reminiscent of a stringed instrument, what with its buttons laid out in four “strings” of six “frets” each. Only, they’re not so much buttons, as individual sections of a capacitive touch controller. A Raspberry Pi Pico 2 is responsible for reading the 24 pads, with the aid of two MPR121 capacitive touch ICs.

The Diapasonix can be played as an instrument in its own right, using the AMY synthesis engine. This provides a huge range of patches from the Juno 6 and DX7 synthesizers of old. Onboard effects like delay and reverb can be used to alter the sound. Alternatively, it can be used as a MIDI controller, feeding its data to a PC attached over USB. It can be played in multiple modes, with either direct note triggers or with a “strumming” method instead.

We’ve featured a great many MIDI controllers over the years, from the artistic to the compact. Video after the break. Continue reading “DIY Synth Takes Inspiration From Fretted Instruments” →

Building A Simple Ribbon Synth

November 29, 2025 by Lewin Day 1 Comment

The usual input device for playing a synthesizer is the good old piano keyboard. However, you don’t have to stick to such pedestrian interfaces when making music. [Daisy] has a fun build that shows us how to put together a ribbon synth that makes wonderful little noises.

Naturally, the heart of the build is a ribbon potentiometer (also known as soft pots). It’s essentially a touch sensitive strip that changes in resistance depending on where you touch it. You can slide your finger up and down to vary the output continuously; in musical contexts, they can behave rather like a fretless instrument. [Daisy] employs one of these potentiometers in such a role by hooking it up to a Daisy Seed microcontroller board, which reads it with an analog-to-digital converter (ADC). The resistance values are used to vary the pitch of a dual-saw synthesizer programmed in the plugdata framework.

We’ve featured some other great ribbon synths over the years, too, like this tribute to the Eowave Persephone. They’re not the ideal choice for those that prefer their notes on pitch, but they’re beautifully fun to play with when you’re getting a little more experimental.

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Look! It’s A Knob! It’s A Jack! It’s Euroknob!

April 28, 2025 by Dan Maloney 25 Comments

Are your Eurorack modules too crowded? Sick of your patch cables making it hard to twiddle your knobs? Then you might be very interested in the new Euroknob, the knob that sports a hidden patch cable jack.

Honestly, when we first saw the Euroknob demo board, we thought [Mitxela] had gone a little off the rails. It looks like nothing more than a PCB-mount potentiometer or perhaps an encoder with a knob attached. Twist the knob and a row of LEDs on the board light up in sequence. Nice, but not exactly what we’re used to seeing from him. But then he popped the knob off the board, revealing that what we thought was the pot body is actually a 3.5-mm audio jack, and that the knob was attached to a mating plug that acts as an axle.

The kicker is that underneath the audio jack is an AS5600 magnetic encoder, and hidden in a slot milled in the tip of the audio jack is a tiny magnet. Pop the knob into the jack, give it a twist, and you’ve got manual control of your module. Take the knob out, plug in a patch cable, and you can let a control voltage from another module do the job. Genius!

To make it all work mechanically, [Mitxela] had to sandwich a spacer board on top of the main PCB. The spacer has a large cutout to make room for the sensor chip so the magnet can rotate without hitting anything. He also added a CH32V003 to run the encoder and drive the LEDs to provide feedback for the knob-jack. The video below has a brief demo.

This is just a proof of concept, to be sure, but it’s still pretty slick. Almost as slick as [Mitxela]’s recent fluid-motion simulation pendant, or his dual-wielding soldering irons.

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Designing An FM Drum Synth From Scratch

April 17, 2025 by Dan Maloney 14 Comments

How it started: a simple repair job on a Roland drum machine. How it ended: a scratch-built FM drum synth module that’s completely analog, and completely cool.

[Moritz Klein]’s journey down the analog drum machine rabbit hole started with a Roland TR-909, a hybrid drum machine from the mid-80s that combined sampled sounds with analog synthesis. The unit [Moritz] picked up was having trouble with the decay on the kick drum, so he spread out the gloriously detailed schematic and got to work. He breadboarded a few sections of the kick drum circuit to aid troubleshooting, but one thing led to another and he was soon in new territory.

The video below is on the longish side, with the first third or so dedicated to recreating the circuits used to create the 909’s iconic sound, slightly modifying some of them to simplify construction. Like the schematic that started the whole thing, this section of the video is jam-packed with goodness, too much to detail here. But a few of the gems that caught our eye were the voltage-controlled amplifier (VCA) circuit that seems to make appearances in multiple places in the circuit, and the dead-simple wave-shaper circuit, which takes some of the harmonics out of the triangle wave oscillator’s output with just a couple of diodes and some resistors.

Once the 909’s kick and toms section had been breadboarded, [Moritz] turned his attention to adding something Roland hadn’t included: frequency modulation. He did this by adding a second, lower-frequency voltage-controlled oscillator (VCO) and using that to modulate the drum section. That resulted in a weird, metallic sound that can be tuned to imitate anything from a steel drum to a bell. He also added a hi-hat and cymbal section by mixing the square wave outputs on the VCOs through a funky XOR gate made from discrete components and a high-pass filter.

There’s a lot of information packed into this video, and by breaking everything down into small, simple blocks, [Moritz] makes it easy to understand analog synths and the circuits behind them.

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70 DIY Synths On One Webpage

April 2, 2025 by Elliot Williams 12 Comments

If you want to dip your toes into the deep, deep water of synth DIY but don’t know where to start, [Atarity] has just the resource for you. He’s compiled a list of 70 wonderful DIY synth and noise-making projects and put them all in one place. And as connoisseurs of the bleepy-bloopy ourselves, we can vouch for his choices here.

The collection runs the gamut from [Ray Wilson]’s “Music From Outer Space” analog oddities, through faithful recreations like Adafruit’s XOXBOX, and on to more modern synths powered by simple microcontrollers or even entire embedded Linux devices. Alongside the links to the original projects, there is also an estimate of the difficulty level, and a handy demo video for every example we tried out.

Our only self-serving complaint is that it’s a little bit light on the Logic Noise / CMOS-abuse side of synth hacking, but there are tons of other non-traditional noisemakers, sound manglers, and a good dose of musically useful devices here. Pick one, and get to work!

Reviving A Maplin 4600 DIY Synthesizer From The 1970s

March 19, 2025 by Donald Papp 16 Comments

A piece of musical history is the Maplin 4600, a DIY electronic music synthesizer from the 1970s. The design was published in an Australian electronics magazine and sold as a DIY kit, and [LOOK MUM NO COMPUTER] got his hands on an original Maplin 4600 that he refurbishes and puts through its paces.

Inserting conductive pegs is how the operator connects different inputs and outputs.

The Maplin 4600 is a (mostly) analog device with a slightly intimidating-looking layout. It features multiple oscillators, mixers, envelope generators, filters, and a complex-looking patch bay on the right hand side that is reminiscent of a breadboard. By inserting conductive pins, one can make connections between various inputs and outputs.

Internally the different features and circuits are mostly unconnected from one another by default, so the patch board is how the instrument is “programmed” and the connections made can be quite complex. The 4600 is one of a few synthesizer designs by [Trevor Marshall], who has some additional details about on his website.

The video (embedded below) is a complete walk-through of the unit, including its history, quirks, and design features. If you’d like to skip directly to a hands-on demonstrating how it works, that begins around the 10:15 mark.

Synthesizers have a rich DIY history and it’s fascinating to see an in-depth look at this one. And hey, if you like your synths complex and intimidating, do yourself a favor and check out the Starship One.

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The Mystery Of The Messed-Up Hammond X5

December 24, 2024 by Elliot Williams 4 Comments

[Filip] got his hands on a sweet old Hammond X5 organ, but it had one crucial problem: only half of the keys worked. Each and every C#, D, D#, E, F, and F# would not play, up and down the keyboard, although the other notes in between sounded just fine.

Those of you with an esoteric knowledge of older electric organs will be saying “it’s a busted top-octave generator chip”, and you’re right. One of the TOGs worked, and the other didn’t. [Filip] rolled his own top-octave generator with a Pico, in Python no less, and the old beauty roared to life once more.

But what is a top-octave generator, you may ask? For a brief period of time in the early 70s, there were organs that ran on square waves. Because a musical octave is a doubling or halving of frequency, you can create a pitch for every key on the organ if you simply create one octave’s worth of pitches, and divide them all down using something as simple as a binary counter IC. But nobody makes top-octave chips any more.

Back in 2018, [DC Darsen] wrote in asking us if we knew about any DIY top-octave designs, and we put out an Ask Hackaday to see if you all could make a top-octave generator out of a microcontroller. We got a super-optimized code hack in response, and that’s worth checking out in its own right, but we always had the nagging suspicion that a hardware solution was the best solution.

We love how [Filip]’s design leans heavily on the Pico’s programmable input/output hardware modules to get the job done with essentially zero CPU load, allowing him to write in Python and entirely bypassing the cycle-counting and assembly language trickery. The voltage shifters and the switchable jumpers to swap between different top-octave chip types are a nice touch as well. If you have an organ that needs a top-octave chip in 2024, this is the way we’d do it. (And it sounds fantastic.)

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