Macumbista Soundbox (2022)

My build of the Macumbista Soundbox, a contact mic-based resonant feedback instrument.

My version has two additions (thanks to Chester W. for guidance):

• Output jack: connect a 10k/1k voltage divider before the internal speaker for line level, then connect to output jack.
• Noise reduction: connect pin 7 of the LM386 to a 10uF capacitor, then to ground. This reduces hum when connected to an amp.

The schematic specifies a 1-20W speaker and 50k potentiometer, but I used 0.5W and 100k, which I had on hand, and it seems to work.

To build the contact mic, follow basic mic building instructions in e.g. Handmade Electronic Music, then solder a metal coil to the brass part of the piezo. Clip or rest an additional metal coil to the built-in one to add more complex beating patterns and modulations.