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I'm looking for a commercial source of compact underwater recorder with inputs for at least two hydrophones. Ocean Instruments is not currently marketing their Soundtrap 440 or 640 recorders, so there appears to be a gap in the market. Alternatively, does anyone know of a compact, low-power, stereo circuit board capable of recording to SD cards at a minimum of 256 kHz? [I'm thinking that a circuit board could be mounted in a commercial underwater housing.]

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Jay,

no idea about commercial source of complete stereo underwater recorder.

The board used in Loggerhead Instruments LS family uses internal stereo ADC. So, that could be an option, but 256 kHz is challenging for the selected ADC/Codec.

Alternatively, a custom development could be feasible

  • use a MCU based development board (I use PJRC's Teensy 4.1)
  • build an audioboard (I use two TLV320ADC6140, totalling 8channels at 192, 4 channels at 384, or 2 channels at 768 kHz; standard schematic)
  • software is straight forward; also, PJRC has a great forum with lot of data acquisition examples)
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  • $\begingroup$ The form-factor for the Teensy 4.1 is great for an underwater housing (long and skinny). However, building an audioboard for it would be beyond my capabilities. I see that Jay Shoe designed a 4-channel audio board for it (forum.pjrc.com/threads/…), but his kickstarter failed to generate enough interest. Maybe we could generate additional interest here. $\endgroup$
    – Jay
    Nov 17, 2022 at 18:13
  • $\begingroup$ Alternatively, would you be willing to market your audioboard design? 4 channels at 384kHz would be great for a tetrahedral hydrophone array. Can the SD writer on the Teensy maintain that data rate? $\endgroup$
    – Jay
    Nov 17, 2022 at 18:13
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the two multi-channel ARUs I'm familiar with are the 2-ch Wildlife Acoustics SM4M - discontinued now but the integrated SM4BAT recorder unit is still available in its in-air mic-input form, which i'm sure could be modified for hydrophone inputs (max SR of 512 kHz, 16 bit). And the 5-ch (SR 384 kHz, 16 bit) ORCA from Turbulent Research / RS Aqua in the UK - definitely not compact, but I noticed Turbulent do an OEM version of the card inside their 1-ch (24-bit) Porpoise recorder so, they might be worth contacting. They did used to offer a compact 5-ch version of the ORCA called the ACE, but i haven't heard much about that one for some time now. RTSYS also make a multi-channel recorder - the 4-ch RESEA. Their 1-ch recorder, Sylence-LP (512 kHz, 24 bit), is dinky; i haven't used the RESEA but it looks a fair bit larger.

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  • $\begingroup$ Many thanks, Chris. The 2-channel version SM4 you mentioned (like the SM4M) can only do 48kHz. The SM4Bat has only one channel (although the board may have two inputs, it cannot record them both at 256kHz according to the spec sheets). I'll follow up on the other two leads. Jay $\endgroup$
    – Jay
    Dec 1, 2022 at 19:52

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