Hydrophone frequency response
I've tested the frequency response of two hydrophones for use with an AudioMothDev. The Aquarian H2a uses plug-in power and doesn't require any modifications to be used with the AudioMothDev board. However, I found that its flat frequency response only extends to 3 kHz. Signals levels are down 20 dB by 10 kHz and were undetectable at 30 kHz. The HighTech HTI-96-min requires the addition of a resistor (10-12 kOhm) from the audio input to the ground. It also requires external power (3 v is enough from one version, but I could not use the external voltage provided by the board without adding noise). The HTI-96-min has a flat frequency response to 30 kHz and a useable frequency response up to 140 kHz.
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Hi Jay, We just purchased the Aquarian H3, which seems similar to the H2 in terms of capability. Just so I can understand your post a little better, is the audio only clear to a frequency of 3 khz when attached to the H2a? And you lose amplitude and fail to hear anything making noise above 30 khz? This is an issue, I have looked at purchasing a pre-amplifier like this one https://www.aquarianaudio.com/pa1.html, but I dont think we can get it in time. In your experience will we struggle to pick up sounds underwater with a dev attached to an aquarian hydrophone?