"Father Haskell"

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.


** Lemme guess - you have the IC in a plastic box with no shielding of any
kind ?

Ideally, there needs to be a metal box that is connected to the negative
supply, pin 4 of the IC plus the metal parts of any pots. Alternatively,
connect the metal fames of each pot to the negative rail ( pin 4) and add a
cap of about 2200pF across pins 2 and 4 to bypass radio frequency energy.

The volume pot wiper needs to be de-coupled from pin 2 by a series
combination of a 4.7 kohm resistor and a cap of about 0.1 uF. This stops DC
voltage from pin 2 appearing on the pot and helps with RF suppression.


http://www.national.com/ds/LM/LM386.pdf



..... Phil