Two new CMOS IC's had been developed to realize a car radio audio system based upon digital signal processing techniques. The first chip is doing source switching. A/D and D/A conversion, stereo decoding. ARI decoding and analog volume control. The second is a masc progammed version of a general purpose signalprocessor. This IC realizes audio features like stereo matrix, deemphasis, tone control, ambience enhancement as well as non audio functions like PLL, noise reduction systems, ARI etc. Both chips can be controlled by any microcomputer by means of a slow serial bus.