Autowah without tears

S. N. Goodwin

      The main disadvantage of a simple wah-wah circuit is that it requires a manual trigger for the effect, usually provided by a foot-pedal. which needs solid, (and often expensive) mechanical construction and also prevents the guitarist from moving freely about the stage.
      After a couple of hand-made pedal systems collapsed in use, the standard wah-wah circuit was modified as follows:
      A light dependent resistor was mounted on the soundboard of the guitar about 2 cms from the highest string, pointing out about 1 cm from the front of the instrument. The shadow of the players hand moving across the.guitar triggers the effect — the more light
    shining on the LDR, the higher the frequency-range boosted by the circuit.
It is tolerant of quite a wide range of light levels and if the range is found to be incorrect this can be rectified in two ways. Lenses or filters can be put across the LDR, or resistors can be connected in series/parallel with it.		    Fluorescent lights could give problems with mains hum, but, under normal incandescent lighting, none were experienced. The wire to the LDR should ideally be screened, but over short distances this is not vital. Avoid bending its leads close to the body. as they can be snapped off very easily.