There are Sigma Delta ADCs, which sample quantised to one bit at a higher frequency. They need to do some processing in the analogue domain though. IIRC you nee

There are Sigma Delta ADCs, which sample quantised to one bit at a higher frequency. They need to do some processing in the analogue domain though. IIRC you need to multiply the sample rate by 4*N to get the equivalent of an N but DAC