Musical Instrument Automatic Selector Switch

Model AS-3

View of the assembled board with wired jacks.
View of the wiring for the battery box, wall adaptor jack, and output jack.
View of the assembled board up close.

Instead of electrolytic capacitors, I use solid tantalum capacitors. Tantalum capacitors are more expensive than electrolytic capacitors, but have better stability and reliability. The ceramic capacitors are of the higher quality monolithic type.

When I layed out the board I was using JFET transistors in the TO-18 package. Now I am using JFETS in the TO-92 package which were easier to obtain for a while. Looks like the TO-92 package will be going away leaving the TO-18 as the only choice for this part number.

Note that I found that we really don't need the sensitivity adjustment potentiometers since the musician overrides that with the controls on the instruments. So capacitors C12, C9, C14 and the pots R20,R19,R21 can be eliminated and bypassed with a jumper wire as shown in the picture. And R10, R13, R16, R23 becomes 100K instead of 68K.