This circuit is designed as a pocket sized high performance audio oscillator. This circuit can operated using battery operated version was possible and could be made at very low cost as well by using one quad op-amp to provide the entire active circuitry. This is the complete figure for design circuit.
In the figure, there are only two control pots (RV1 and RV2) and two DPDT switches. The output level pot includes an on-off switch and is of logarithmic taper to allow easier setting at low (i.e. millivolt) levels. This pot is directly coupled to A4's output to minimize response errors, provided that the load impedance is constant or quite high compared to the output impedance provided by Miniosc. The frequency sweep control (RV1A/B) has a range of about 24:1 and in combination with the High-Low range switch having a 18:1 ratio, the audio band is covered (with the exception of the lowest octave) in two overlapping ranges. The possibility of a single sweep of the audio band without the range switch was tried out and later dropped in preference to the present design.
Types like the TL074, TL084, LF347 and LF444 and other quad op-amps with compatible pin outs are not recommended for use due to both the increased battery drain and reduced margin of minimum operating voltage. The TL064 is alone in having operation specified down to a plus and minus 3 volt supply. [Schematic’s circuit source: Phill Allison Notes].
