I'd like to eliminate the 60 Hz noise on the DC power supply coming into my laptop as it leaks into my data acquisition. I know this is the source because if I unplug the transformer from the laptop so that the laptop is running on the battery alone most of the 60 Hz noise goes away. There is, parenthetically, no chance of a ground loop, I made sure of that. Running the laptop unplugged is an option for short periods of time, but the equipment supposed to be idiot-proof. In the end I would like to keep the laptop plugged in while making the measurements in question.
Obviously the main offender would the transformer brick, but the ripple from the wall source ground before it gets there might be a factor too. Is there a preferred way to eliminate the ripple after the transformer to get a nice clean DC signal into my laptop? Should I just build a connection box with a passive low-pass filter, or is there some better way? I'm sure this issue comes up in audio equipment (which I know nothing about) since 60 Hz noise can be heard, and is ever present.