This article is from documentation from the 70s. The original text of A. Fanzeres was kept. In this era of “sound”, be it bizarre, incremental, modern, psychedelic sound, etc., additional circuits with the traditional linear amplifier, appear from all corners. There is a plethora of projects, and however sophisticated they are, they never quench the thirst of the experimenter or user who gets excited whenever a “new circuit” appears. Today's is an active filter, that is, it has filter performance, however unlike passive filters, which attenuate the signals and introduce losses, it invigorates the signal as well. In the filter we are presenting the frequency is 200 Hz, with a selectivity of 15 Hz, that is, 7.5 Hz for each side, the central frequency (220 Hz) and the signal is attenuated By changing the values of C3-C4 it is possible to modify the value of the central frequency of this active filter.
LIST OF MATERIALS
R1- 10 k ohms
R2 - 5 k trimmer
R3: 20k ohms
C1, C5 - 5,000 pF (4.7n)
C2, C3, C4 - 1 uF
C5: 5,000 pF
IC: uA74l
S1: 1 pole 1 position
S2: 1 pole l position
Dual 9 volts power supply
Note - capacitors are not electrolytic
