We’ve all had that problem. Up on stage, rocking out Jimi Hendrix-style on guitar with your band, but frustrated at having to mess around with foot pedals to control all of the effects. [Richard] solved this problem in a unique way: he put a preamp and a microcontroller in a guitar that can create some very interesting effects.
For the musically challenged, electric guitars often have several sets of electromagnetic pickups that detect vibrations in the strings at different points along the strings. Selecting different pickup combinations with a built-in switch changes the sound that the guitar makes. [Richard] wired the pickups in his Fender Stratocaster to the microcontroller and programmed it to switch the pickups according to various patterns. The effect is somewhat like a chorus pedal at times and it sounds very unique.
The volume and tone knobs on the guitar are used to select the programmed patterns to switch various pickups at varying speeds. This has the added bonus of keeping the stock look of the guitar in tact, unlike some other guitars we’ve seen before. The Anubis preamp, as it is called, is a very well polished project and the code and wiring schematic are available on the project site along with some audio samples.
[Richard] recently rediscovered some files from a hack he did back in 2004. He was experimenting with exciting piano strings via electromagnetic fields. The idea shares some elements with the self tuning piano we saw back in 2012. Piano strings, much like guitar strings, are made of steel alloys. This means they create electricity when vibrated in a magnetic field. This is the basic principle upon which electric guitar pickups are built. The idea also works in reverse. The strings will vibrate in response to a modulated electromagnetic field. Anyone who has seen an E-bow knows how this can be applied to the guitar. What about the piano?
[Richard] started with the Casio CZ-101, a classic synth in its own right. The Casio’s output was run through a Peavy 100 watt amplifier. The amplified output was then used to drive custom coils mounted on a piano. The coils had to be custom wound to ensure they would be compatible with the 4 – 8 ohm impedance expected by the amplifier. [Richard] ended up winding the coils to 28 ohms. Six of these coils in parallel put him just over the 4 ohm mark. The coils effectively turned the piano into a giant speaker for the synth. In [Richard's] write-up (word doc link) he mentions that the strings basically act as a giant comb filter, each resonating strongly in response to frequencies in its harmonic series.
The results are rather interesting. The slow attack of the magnetic fields coupled with the synth’s patch results in a surprising variety of sound. The three examples on [Richard's] blog vary from sounding like a power chord on a guitar to something we’d expect to find in an early horror movie. We would love to see this idea expanded upon. More efficient coils, and more coils in general would add to the effect. The coils on various string groups could also be switched in and out of the system using MIDI control, allowing for even more flexibility. Continue reading “Piano Repurposed as a Resonant Synth Speaker”