It’s been a year since I’ve last worked on the Magnetic Cello’s electrical guts. This week, with fresh eyes and a deeper understanding of op amps and phasors, I started again throwing capacitors and resistors at a breadboard.
So far, I have worked on three regions:
- Tone Filter: I added in a more sophisticated filter that generates the four basic waveforms of analog synthesis: Square, Saw, Triangle, and Square. I will need to fine tune some values later, but I am already happy with the sound I’m getting.
- Resistive Ribbon: I tweaked how the circuitboard turns a linear increase in resistance into an exponential increase in frequency. After a more rigorous analysis of the circuit, I realized that a few resistors were not really needed. I simplified the design of this part of the circuitboard, and made the space between notes feel just a little bit more natural.
- Precision Tuners: Reworking the ribbon circuit also allowed me to change what type of tuners can be used to adjust the frequency of each string. By replacing the single turn tuners with the larger range and more precise 15 turn tuners, it will now be possible to tune each string to any frequency, from around C2 to E5. This means that the instrument can be tuned up to the range of a violin, and the intervals between each string can be customized without needed to open up the instrument.
These are just a few incremental improvements, but it’s quite a bit of progress for few days of work. With a deeper understanding of electronics and a solid design to work off of, I’ve been able to approach these circuits with a fresh pair of eyes and make improvements that were not obvious before.
I’ll next be working on the magnetic coil parts of the circuit next. Hopefully, I can make some improvements there too.