Disco sound limiter

1 The environmental nuisance value of discos is in direct proportion to their sound level. The circuit proposed here cannot be disabled by the disc jockey, since it is built into the output amplifiers used in the disco. Its oper- ation is amazingly effective: if the preset sound level is exceeded, the input of the amplifier is short- circuited for a few seconds. Any disc jockey whom that has happened to a couple of times soon gives up trying to break the sound barrier. The power amplifier output is con- nected to the metering input of the present circuit (C1). This signal is ap- plied to low-pass filter R4-C2 via Pi (which sets the maximum volume) and buffer IC1. In case of line inputs, this opamp can be given a gain of 20 dB by the omission of the wire link across R2. The signal from the low-pass filter is rectified (half wave) by IC2 and IC3. The resulting direct voltage is ap- plied to Al and A2 which compare it with two reference voltages derived 2 disco sound limiter 101 EE J...