Re: [Cin] OT: when you try to record dolphin, but result is mostly radio interference

The radio signals which are interfering could be shortwave. I would recommend using ferrite clamps on the cables which do not carry digital signals, especially those in the most sensitive area, like from the hydrophone and pre-amp. Also the pre-amp power cable, if it is not battery powered. And screen the pre-amp, if it is not in a metal box. The pre-amp itself ought to have provisions for preventing this, like a low-pass filter at the input. MatN