Signal processor for audio reproduction, e.g. for CD player - has detector to identify pre-emphasis based on 4 bit code to control de-emphasiser coupled to amplifier gain control

摘要

The audio processor has a variable gain amplifier (1) that is adjusted dependent upon the input from a CD player. The amplifier acts as a compressor for the output stage. The input signal is received by a de-emphasiser stage (3) in the form of a filter that attenuates the signal above a cut-off frequency. An emphasis detector (5) receives a 4 bit input (Q) that indicates whether pre-emphasis is applied to either 2 or 4 channel signals. When emphasis is present the de-emphasiser generates an output to an input signal level detector (4), to control the amplifier gain. USE/ADVANTAGE - Car radio, tape player, radio etc. Amplifies quiet music sections without affecting louder ones.