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Project Notes

#434 krell

Building the Boldport Krell - a handheld DSP synthesiser built around a Microchip dsPIC and a design from madlab.


Here’s a quick demo..



Krell is a handheld DSP synthesiser. Buttons and potentiometers dial up a range of sounds. The Boldport project is a remix of a soldering project by James Hutchby of MadLab.

At the core of the circuit is a Microchip dsPIC33EP128MC202-I/SP. It’s an interesting choice - a digital signal controller that is really designed for precision motor control, now put in service of creating music (or at least weird sounds).


Qty Description
x1 dsPIC microntroller, Microchip dsPIC33EP128MC202-I/SP
x1 3.3V Regulator, TI LP2950-33LPRE3
x1 NPN bipolar transistor, ON BC547CTFR
x1 220μF electrolytic capacitor, Multicomp MCUMR6V3227M6.3X5
x2 10μF electrolytic capacitor, Multicomp MCUMR16V106M4X5
x1 10μF tantalum capacitor, Suntan TS19001C100MSB0A0R
x3 100nF capacitor, Suntan TS170R1H104MSBFB0R
x6 47KΩ trimmer, Piher PT10MV10473A2020-I-PM-S
x6 Black thumbwheel, Piher 5034
x4 White LED, Valcon VDIFFLED-3mm-W
x2 100Ω resistor, Multicomp MCF 0.25W 100R
x1 1KΩ resistor, Multicomp MCF 0.25W 1K
x6 10KΩ resistor, Multicomp MCF 0.25W 10K
x1 Battery holder, TruPower BH 431-1P
x1 3.5mm stereo jack socket, TruConnect 20-0137
x1 28-pin DIP socket, TruConnect 22-0114
x1 DPDT slide switch, C&K JS202011SCQN
x1 Button sheet, Snaptron Peel-N-Place™
x1 PCB

kit_parts kit_pcb_back kit_pcb_front


My quick re-draw of the circuit..



It’s a nice simple build this time for just an iron and my favourite 2% Ag solder.

The Snaptron buttons are an interesting construction variation: they come preset with clear adhesive strip. With careful alignment, all buttons stick in place with no soldering required. I can see this being super efficient for small batch assembly.




The finished noise maker..


Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.