The volume control on a Blues Harp Mic is pretty simple. The potentiometer should be about 500k ohms or larger and it works best if it is an Audio or Log taper pot. Linear taper pots work quite well, but there is less fine control of the volume.

In high impedance mics hooked to guitar amps the resistance of the pot should be high, although over a meg there is not appreciable difference. 100K will work fine, but expect a slight loss of bass. 500K is the best compromise between cost, availability and sound.

In low impedance wiring the pot should be about the same resistance as the impedance of the element. (Impedance and Resistance are two similar animals, but they are measured differently. Resistance as measured by a Ohm Meter is not even close to the Impedance.)

The wiring is simple. The element may (or may not) have one side labeled with a + sign. It doesn’t matter that much, really, but purists like to have the “push” and the “pull” of the mic coordinated to the amps speaker. Human ears cannot tell the difference, I think. The plus side goes to the right side of the pot on a standard pot with tabs or the right side looking from the bottom on military small pots.

Here is a wiring diagram: