note some of the variations you are calling flutter are actually "Quantization noise" and can never be eliminated from the adc process,
the best adc result is always +-1 count. at the expense of some resolution[level bandwidth etc] you can filter it out "mostly" people with "hifi" ears reckon they can hear it on the best of cd recoding's , yet scratched vinyl records are pure, go figure. as a true cloth eared pariah i call wtf