Homemade, powered by small 13 vct transformer from an old boom box and LM317T regulator (ps seems capable of 14v clean power, easily). Sounds like it's picking up the nearest AM station, especially loud and clear when I touch the volume and gain control shafts. Touching the heat sink behind the 317 with a fingertip _quiets_ the interference, though.
Causes? Fixes? Thanks.