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.