Multi-Ouptut Sustainer Guitar
Multi-Output Sustainer Guitar
This sustainer guitar is essentially 6 eBows built into a guitar. The control plate features a 3 way switch for each string to allow the user to select between Sustain, Harmonic Sustain, or Off. There are 7 output jacks - one per string and one master output.
I executed this project using SLA 3D printing, laser cutting, PCB milling, CNC routing, and traditional Lutherie.
The final guitar with embedded sustainer circuitry
Video Demos:
Photo Gallery:
Custom 6-channel pickup coils
At the heart of this project is the pickup assembly. The base is laser cut acrylic, the bobbins are 3D printed, and the coils were wound on my mini-lathe. There is one pickup for each string on the guitar.
Custom 6-channel driver coils:
This assembly is where the amplified signals are pumped back into the strings to sustain them indefinitely.
Wax potting the coils:
Dipping the pickup and driver coils in melted wax fills in the air gaps between the winds in the copper. Filling this space fights against microphonics and unwanted feedback.
6-channel sustainer circuit board:
Signals from each string are routed to this custom circuitboard where each string’s note is amplified and sent to the driver coils. The circuit board was designed in Eagle and fabricated by JLCPCB. Surface mount components made the board small enough to fit inside of the guitar.
Early Prototyping:
The sustainer circuit started out on a breadboard. I used the “fetzer/ruby” design commonly found online for eBow replicas.
The coil making process started out with sewing bobbins. I used my mini lathe to wind 42 AWG enameled copper wire thousands of times around each bobbin. I tested with these crude coils before eventually trying a couple other ways to make the bobbins look neater and more uniform.
Rather than make a multi-breadboard setup, I etched the circuit into copper blanks on a desktop CNC machine. The circuit board layout was designed in Eagle PCB and milled on a Nomad Pro CNC. Here you can see the circuitboard in the middle of the milling process.
Each milled board supported two sustainer channels. 3 were daisy-chained together to prototype a full 6 string guitar.
Before 3D printing the final versions of the bobbins, I tried to laser cut the 6 coil assemblies. They worked electrically, but I needed a higher level of adjustement on a string by string basis.
Before miniaturizing the circuit and building a custom guitar body, the guitar looked a lot more like this ratsnest on my workbench
Future Improvements:
Although it was incredibly exciting to get this working, there are some fundamental issues with this method of sustaining. eBows work well because their pickup and driver coils are a few millimeters apart. Since my coils were several inches apart, as you fret up the guitar you will notice better and worse responses from the strings as you adjust the nodes and antinodes of the string vibrations. Sometimes an upper harmonic is accidentally accentuated, and sometimes the feedback just isn’t enough to keep the string vibrating indefinitely.
I have no plans to improve this exact guitar, but I have continued to work on sustainer circuitry and embed sustainers in guitars.
Check out two of my newer projects using sustainer technology to learn more: