The Synth Kit: Under the Hood

By Emily Tuteur

Music, like making, is universal. No matter how far you travel, either in distance or time, you’ll find people creating, and whether it’s things or sound, the act of creating is a constant that connects us all. With that, we are extremely excited to announce the littleBits Synth Kit . Developed with Korg, the world-renowned electronic instrument company, we have successfully combined music and making to provide an experience that has never been seen before. Taking our goal of making an electronic design platform accessible for all, now anyone can dream up new sounds or songs and make them a reality as fast as their mind will allow. We think this could be the start of a new chapter in the history of music technology and we hope you’ll join us for the ride.

-Paul Rothman, Product Development

Developed in partnership with Korg, a pioneer of electronic musical equipment, the littleBits Synth Kit is designed for musicians, hobbyists, and music lovers with an interest in making exciting new sounds and building their own infinitely customizable and expandable analog modular instrument.

The littleBits Synth Kit includes an assortment of 12 electronic Bits modules that instantly snap together with magnets to create circuits like those used in Korg’s famous analog synthesizers (like the MS-20). The Synth Kit also includes a project booklet outlining step-by-step instructions for 10 projects.


Box Closed-4(no background)LR


booklet 2LR

The Synth Kit was developed over the course of 9 months and is a collaboration between two seemingly different companies that share very similar ideals and principles. We embarked on creating a kit that would behave as a modular analog synthesizer but was accessible to anyone with an interest in sound. We started by ideating the different modules that might be possible and picked the ones that would offer the most complete and varied experience.

After several modules for the kit were selected, a MAX/MSP patch was created to simulate the behavior between them. This simulation informed a lot of the features and interactions the modules now possess.


When thinking about the hardware layouts, the original sketches included trim pots for controls. This ensured the modules would remain small and there was no current precedent for a module to contain more than one potentiometer. After some reflection, it was realized that creating an instrument that required a screwdriver to adjust the controls would not be useful in a performance setting. We then decided to take the step to replace the trim pots with potentiometers, breaking a current convention but making the kit much more playable.

 synth Bits Patches

Each module has a story. Here are brief descriptions of how the modules came to be:




In the first incarnation of the oscillator module, the circuit was digital and was built around a microcontroller. This gave us the ability to include a waveshaping function that allowed the sawtooth waveform to morph into a triangle waveform and the square wave become a pulse wave with variable duty cycles. It also enabled the oscillator to have a much wider pitch range that went into deep low frequency oscillator (LFO) territory. Ultimately, the sound quality of the digital oscillator was too tiny and noisy to be usable in the kit. By switching to an analog circuit, we had to sacrifice the waveshaping and extended frequency range but came away with a much richer sounding oscillator. In the future, the digital oscillator design could be resurrected for use as a dedicated LFO. The i31 oscillator in the Synth Kit goes into the LFO range but a dedicated LFO could provide much lower frequency and with various waveforms.


The keyboard module had several design decisions involving ergonomics. To date, the keyboard is the longest module in the library. We needed to keep it playable but not too long. We did tests with various tactile switches that required different actuation force as well as sizes, heights, and actuator lengths. The spacing of the keys was also tested in different configurations to ensure playability in the most compact size. The module ended up being long enough that it warranted the addition of legs to the bottom of the PCB to ensure physical stability. The addition of the mode switch was a result of playing the MAX/MSP simulator and not wanting to need to keep holding a button to complete an envelope cycle, which makes playing melodies easier. The octave dial was a later addition as it was originally a range control. Jumping from octave to octave was deemed a better solution than sweeping through all pitches.

 keyboard switches LR

Micro Sequencer

With the micro sequencer, we had to make another decision about module size. A typical analog synthesizer sequencer is eight or 16 steps. For the Synth Kit, these numbers of steps would make for an extremely long module. Because of this, we opted to go with a four-step sequencer. A four-step sequence is still musically useful and by using additional modules, a user can chain multiple micro sequencers together to create longer sequences of notes. We felt this was a good compromise between functionality and keeping true to the littleBits design aesthetic. The addition of the clock mode ensured that multiple sequencers could be synchronized and the trigger output provides a clock pulse to send to additional modules.


With the filter, we all agreed that we wanted to use the MS-20 circuitry. The MS-20 is a highly regarded filter sound and a classic Korg design. We originally attempted to use the 1978 version of the filter without the OTA but ultimately ended up using the later design and implemented a 13700 OTA to have better DC response. We think it retains all the classic character of the original design.


During the development process, we had a moment when we were trying to decide between including a looper module or a delay module in the kit. Ultimately, we decided that a delay would be easier to use out of the box for most people and would be useful in a wide number of configurations. In addition, the delay is capable of very primitive looping by way of turning the feedback up high.

The design itself is based on the same delay IC used on Korg’s Monotron Delay synth. The circuit itself is different but shares some qualities in sound, being that it has similar characteristics to a “bucket brigade” analog delay.


The first configuration of the Synth Kit was conceived to have an ADSR envelope as well as a VCA. The idea was put forward that the VCA could be included in the envelope to reduce the number of modules in the kit and make creating circuits easier. At first it seemed to be a strange concept when thinking of traditional synthesizers but after some thinking and creating sample circuits, it appeared to be a good path forward. As for the envelope controls, we decided that having full ADSR would double the size of the module and possibly be overkill given the small nature of the keyboard. There is still potential for an ADSR module to come along in the future but the more simple attack and decay circuit does a great job at creating envelopes within the system.


The random module serves the purpose of an all-in-one sample and hold module in a traditional modular analog synthesizer. It contains a white noise generator (that would usually seed the sample circuit) as well as a random voltage generator that emulates a sample and hold circuit. An interesting thing to try is to place a filter after the random module set to random voltage mode. You can create slewed random voltages instead of the standard stepped voltages.


The split module takes the place of a branch or fork module and a pair of wire modules. In the context of the Synth Kit it’s extremely useful but we also anticipate it being used in a lot of littleBits circuits, especially logic.


The ability to mix multiple audio signals was always an important feature to have in the Synth Kit. Mixing two oscillators together expands the sonic possibilities by allowing the user to set intervals between them, achieving different “feelings”. Setting the oscillators at unison, fifths, octaves, etc. all have unique characteristics. The mixer can also be used to mix control voltages which enable the user to mix control voltages which make it possible to use the keyboard and microsequencer at the same time.

Synth Speaker

The synth speaker was an exercise in standing up for quality. The speaker enclosure used is a full range speaker complete with rear port for bass frequencies. It was a debate as to whether we would use such a high quality speaker as many times products ship with a speaker that is just good enough to give a sense of the audio capabilities before plugging it into a real amplifier. We wanted the Synth kit to stand up on its own and not require external amplification to experience it. While there is no substitution for a large amplifier or PA, the synth speaker is great quality for its size.

So there you have it. A brief overview of how the Synth Kit came about. We hope you’ve enjoyed these insights into our process and that you’re inspired to make something that makes music!



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