microcompressor

7-92 — elektor juiy/august 1981 microcompressor Dynamic range compressors can be used in any device that requires a constant audio output level. The first example that comes to mind is the automatic record level control in cassette recorders. The compressor can also be employed, however, in such items as amateur radio equipment, discotheques, babyphones and intercom systems to ensure optimum intelligibility and to prevent any damage to amplifiers and loudspeakers. When used in combination with a microphone, compressors give amazingly good results as both quiet and loud decay time ss 100 mum speech passages are equally intelligible. The circuit itself is designed around the TDA 1054 multi-Purpose opamp from SGS-Ates. This IC contains four separate elements, each of which performs its own particular task. Ida is a pre- amplifier which is used to boost the input signal to about 50 x (1 + R5/R4I. Opamp IC1b is also used as a preamplifier, but this has a gain of 400 x (1 + R11/R10). ...