justjed:
More questions about that. The input side looks like a 1st order high-pass filter with a cutoff freq. of 11MHz. So it seems like there won't be much signal left under 10kHz. Maybe a bandpass filter would be better there?
On my first glance at the Maxim application note I thought the noise spectrum went down to low frequencies (fig 2). Now I'm not so sure about the scale on that graph. The input impedance of that amplifier chip is low: the data sheet implies 50 ohm, which would give a corner frequency of 6.8MHz on the input stage.
Since we're looking for much lower frequencies, a high input-impedance amplifier would be preferred.