1. A digital signal processing device comprising: supply means for supplying a sequence of code word signals; coefficient storage means for storing predetermined weighting coefficients; multiplying means for multiplying ones of said code word signals by ones of said weighting coefficients and producing a sequence of output signals; and first combination means for combining two sequences of signals from said multiplying means, and producing an output signal; feedback means for feeding back a quantized representation of said output signals to said supply means, comprising a quantizer having a first and second input, and an output connected to said supply means, and second combination means for combining said output signal of said digital multiplier with a sequence of code word signals from said supply means, and producing an output signal for controlling said quantizer.