Something like that it seems. Would be interesting to know roughly what the quantization Noise Transfer Function (NTF) is (or the equivalent to whatevs his deal is) as that determines to some extent the level of out of band quantizaiton noise filtering needed. That's quite a large oversampling rate also. So is he interpolating the imput signal to the (maybe) delta sigma? If so, using what type of filter? WTA? Maybe that's why he needs a lot of taps. Because running the delta sigma that fast might require a fairly large interpolation filter before actually hitting the delta sigma (or PDM, or PA, or WMD).