Due to the internal circuitry of the MAX1300, the source impedance driving the MAX1300 analog input should not be too large in order to minimize crosstalk between channels. To reduce the source impedance as much as possible, we recommend connecting the low pass filter before the buffer input, and the buffer output directly to the MAX1300 input. The internal switch will switch from one channel to another as conversion for the channel completes, and if source impedance for the channels are low, the signal should not be affected by the input from the previous channel.