This is the schematic design of HiFi Expandor Circuit with
De-emphasis. The circuit is based NE570. The NE570 can be used to
construct a high performance compandor suitable for use with music. This
type of system can be used for noise reduction in tape recorders,
transmission systems, bucket brigade delay lines, and digital audio
systems. The circuits to be described contain features which improve
performance, but are not required for all applications.
HiFi Expandor Circuit Diagram
The
expandor to complement the compressor is shown in the above circuit.
Here an external op amp is used for high slew rate. Both the compressor
and expandor have unity gain levels of 0dB. Trim networks are shown for
distortion (THD) and DC shift. The distortion trim should be done first,
with an input of 0dB at 10kHz. The DC shift should be adjusted for
minimum envelope bounce with tone bursts. When applied to consumer tape
recorders, the subjective performance of this system is excellent.
