Most makers only intend for their project designs to be produced in very small quantities — often just as a one-off device. For that reason, they usually aren’t designed with scalability in mind. After all, per unit cost isn’t that important when you don’t plan to manufacture your design. But this year’s Hackaday Prize is all about designing a potential product that is scalable. That’s why Kenneth Marut’s KELPIE synthesizer module project can be manufactured affordably in large numbers.
KELPIE is a monophonic and polyphonic digital synthesizer that’s intended to be used with MIDI controllers, and MIDI keyboards in particular. Unlike some other synthesizers, KELPIE can’t really be used on its own. Instead, it follows an approach that is common among professional synthesizers, where it’s assumed that the musician will be using a MIDI keyboard. That keeps the KELPIE device small, simple, and portable. It also ensures that the device can be mass-produced at a low cost using common components and manufacturing methods.
One area where that is particularly obvious is the enclosure. Many makers fall into the mistake of designing enclosures for 3D printing, which often results in geometry that isn’t practical to manufacture with injection molding. Marut has designed KELPIE’s enclosure to be printable on FFF (Fused-Filament Fabrication) and SLA (Stereolithography) 3D printers, as well as easy to manufacture with typical two-part injection molds.
That philosophy also carries over to the electronics. KELPIE’s brain is an NXP MK20D microcontroller, which is used in the Teensy 3.2 board. The DAC (Digital-to-Analog Converter) is an SGTL5000 that is found in the Teensy Audio Shield. Those chips, as well as the supporting components and input controls, are all readily-available. The device’s two PCBs can be fabricated and populated using conventional techniques. Marut estimates that the electronics would only cost $25 to manufacture in reasonable quantities, which is quite affordable considering how great KELPIE sounds.