View tda7439 datasheet:

TDA7439 ? THREE BANDS DIGITALLY CONTROLLED AUDIO PROCESSOR INPUT MULTIPLEXER - 4 STEREO INPUTS - SELECTABLE INPUT GAIN FOR OPTIMAL ADAPTATION TO DIFFERENT SOURCES ONE STEREO OUTPUT SDIP30 DIP28 TREBLE, MIDDLE AND BASS CONTROL IN 2.0dB STEPS VOLUME CONTROL IN 1.0dB STEPS TWO SPEAKER ATTENUATORS: SO28 - TWO INDEPENDENT SPEAKER CONTROL IN 1.0dB STEPS FOR BALANCE FACILITY - INDEPENDENT MUTE FUNCTION ORDERING NUMBERS: TDA7439 (SDIP30) ALL FUNCTION ARE PROGRAMMABLE VIA TDA7439B (DIP28) TDA7439D (SO28) SERIAL BUS DESCRIPTION The AC signal setting is obtained by resistor net- works and switches combined with operational The TDA7439 is a volume tone (bass, middle and amplifiers. treble) balance (Left/Right) processor for quality audio applicationsin car-radio and Hi-Fi