Digital parametric filters for studio mixing desk

Design and implementation of real-time filters for digital audio require handling large words and multiplication rates over 200 000 operations/second. The present paper report on theoretical and practical work done at T. D. F. to realize a dedicated processor based on commercial slice processors and multipliers. Flexibility and power of this equipment make it a very efficient research tool since it provides in real time three second order filters on a stereophonic channel. A complete mixing desk could be made up by putting such modules together. 16 bit coefficients and 32 bit sample words have proved necessary in order to reduce the center frequency of filters to 40 Hz even with sampling frequencies as low as 32 kHz.