This low power bass booster is from the 1977 National Semiconductor Audio Handbook. The circuit is powered by 6 to 9 V voltages and the feedback determines the enhanced bass range.
This sophisticated circuit with two LF411 operational amplifiers appeared in the November 1984...
This circuit uses battery power, but it can be powered by an 80 to 200 V power supply, with no...
This interesting circuit, which can be used as an alarm, was found in a 1997 documentation. It...