On Tue, 30 Apr 2024 12:16:57 +0300 Andrew Randrianasulu <[email protected]> wrote:
*I think* preamp in this case is battery-powered.
By ferrite rings you mean like those?
Yes, those ferrite clamps; an nearby electronics shop or ham might be of assistance. They are also used to prevent computer signals _causing_ RFI, e.g. on VGA cables. It is often difficult to determine where the RFI (radio frequency interference) is picked up. If the hydrophone cable is differential (two opposite signals, with a separate shield) usually via a XLR connector, then _in theory_ that cable should be less suspectable for RFI. The pre-amp still might be, if it's common mode signal rejection for high frequencies is not good. It can even be caused by badly configured XLR connectors/plugs, but I don't have those details anymore; it has something to do with grounding of microphone cable shield and signal ground. As a quick test wrap any item which processes the still analog signal into aluminium foil, to determine which item picks up the RFI. Some readings (search for "EMI/RFI XLR", or "EMI/RFI audio" if not XLR): https://service.shure.com/s/article/radio-interference-on-a-microphone-cable... MatN