I’m working on a piece for electronics and Javanese gamelan in slendro. As a way to coordinate acoustical events and digital ones (without having to know what those might be) I decided to build a bonang barung out of PVC parts. I wanted to create a player situation that was nearly identical to sitting and playing bonang, so I decided to build 12 instruments that were each a drum trigger and independent sound source. I ordered 6 inch cleanout caps and female fittings and found an electronic surplus selling speakers that would fit inside.
Looking around at tiny amp designs, I tried putting together a basic LM386 circuit, and found that running my Max/Msp patch through it sounded pleasantly distorted and would provide a nice contrast to the cleaner, brighter gamelan sounds. LM386 chips don’t seem to handle polyphony very well, but for a single sampled pot they sound perfect–almost like Konono No. 1, or something. My first tests with a slendro arpeggiator and a big bass speaker are here. I put together all the amplifiers in a few days, and by the last 5 I reduced the circuit to a much smaller footprint by straddling the LM386 across power and ground and then bending pins 2,4, and 6 inward to their respective rails. Similarly, I found putting the big capacitor close to the LM386 allowed me to bend the excess wire sideways and solder it to the chip.
I spent a day filing off all the plastic burs and stamping on the PVC. I even filed down the square edges to round them off a little– they looked too militant or something at first. I then painted the pots matte black, only to discover I needed paint for plastic (it has a solvent in it and was really nasty). I sanded and repainted the pots shiny black and the playing surfaces shiny gold. They will look pretty impressive up on a bonang rack under stage lights.
To mount the speakers inside the pots, I glued lengths of extension cord that I had from building relay circuits that make up another part of the piece. I found that by cutting the cord so that it was barely larger that the inside circumference of the pots, I could hold the weight of a speaker with tension alone. After gluing them in, the mounting surfaces are totally solid.