The power supply for this 1972 circuit must be symmetrical and the BC549 transistors. Care with the layout is important to avoid capturing tinnitus.
This interesting bandpass filter using an operational amplifier 741 has its cutoff frequency...
January 2017 - Mouser Electronics is announcing the availability of the new OptoMOS® CPC1010N...
This circuit was obtained in the Audio Handbook of the National Semiconductor of 1977. The...