wah-wah box for guitars

0 wah-wah box for guitars In this day and age of electrophonics, a wah-wah box is still a popular means of animating an otherwise tired sounding guitar. Such a box, which is basically a high-Q low-pass or band- pass filter, can be designed in various ways. Early designs were invariably based on active (transistorized) double-T filters. The present circuit, using opamps and operational transconductance ampli- fiers (OTAs), is rather more complex but also more efficient and more reliable. Three pairs of opamps, each con- sisting of an OTA and a buffer ampli- fier, in conjunctions with capacitors C 2, C3, and C4, form a low-pass filter. Since the usual series resistances have been replaced by voltage- controlled current sources (OTAs), the roll-off frequency of the filter is deter- mined by the currents flowing into pin 5 of the 3080s. These currents are themselves directly proportional to the input control voltage, Uc, which has been converted in A, and T,. This voltage, which is de...