This circuit was found in a 1966 EEE. The circuit uses transistors from the time but can be made with modern equivalents. The operating frequency ranges from 0.1 to 1 kHz.
Circuits like this one, using the LM386 audio amplifier, are available from other sources in this...
This bass and treble control only attenuates the corresponding signals, requiring further...
Using a large inductance, this circuit was found in a Popular Electronics from the 90s. The...