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Thread: Hydrophone for Teensy

  1. #1
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    Hydrophone for Teensy

    Good Morning! I am studying the properties of Teensy audio and the Audio Shield. I also have a piece of Sparkfun TRRS Breakout (https://www.sparkfun.com/products/11570) to use with a hydrophone (it works like a microphone, but it's for recording sounds in aquatic environments).

    The idea would be to connect the TRRS with the Audio Shield board to record sounds, store them on a microSD card and then use the Audio Shield to play them.

    If someone can tell me which pines are those found in the Audio Shield and the TRRS, I would appreciate it a lot.

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  2. #2
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    Missing from here is the pinout of your hydrophone - the sparkfun board just takes a generic four pin connector and breaks out the pins, which would be ground,audio left,audio right and mic for the mobile phone headsets commonly using this style of plug. Since I would expect a hydrophone to have no stereo speakers that pinout would be wrong, and my guess would be that there is a powersupply to a preamp involved in some way. Getting this wrong has a high probability of damaging something so only guess if you can afford to replace every part involved or have the equipment to probe the thing very carefully.

    If you can identify the signal pin/s you can probably connect them to one or both of the audio shield line in pins, assuming it really is line level
    https://en.wikipedia.org/wiki/Line_level
    Again, this will require either finding documentation or using test equipment to verify what is coming out of those pins before connecting them to the teensy.

  3. #3
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    Thank you very much for the information. Yes, I have a preamplifier, or at least I think it can work. It also belongs to SparkFun, so I guess it will be possible to use it with the hydrophone.

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  4. #4
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    Can you please explain or sketch your planned layout of parts? At the moment your original question is very opaque, since it appears to be asking how to connect a four conductor tip/ring/ring/shield connecter to the audio board, but your second post shows a nothing with that would need that - in which case it might just be as simple as running from your out+ and out- to the line in left/right and gnd pins on the audio board Edit - do not do this - if that board is what it looks like on the sparkfun site it will blow things up - see note at end

    This will most likely not work that well due to input impedance differences
    https://en.wikipedia.org/wiki/Input_impedance
    and because that preamp looks like it is balanced and the audio board is unbalanced
    https://en.wikipedia.org/wiki/Balanced_line

    Can I suggest backing things up a bit and that your actual question is probably how to connect the Hydrophone to the audioboard? Depending on the Hydrophone and what you need quality wise using the audio board mic inputs and the inbuilt preamp may be all you need to get close enough quick enough. Working that out means knowing more about the hydrophone and what sort it is and what form it's output takes.

    Edit - if that sparkfun board is https://www.sparkfun.com/products/11044 that is not a a high quality audio/instrument preamp suitable for boosting small signals from hydrophones up to usable levels. It is a amp intended to boost line level audio to drive a speaker using a class D Amp https://en.wikipedia.org/wiki/Class-D_amplifier generally not what you want in any high quality audio path. It will work if you are after a low fidelity output to drive a small to medium speaker on the output end of the Audio board though.
    Last edited by GremlinWrangler; 10-31-2018 at 02:39 PM. Reason: Found the break out

  5. #5
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    Quote Originally Posted by nestor26 View Post
    to use with a hydrophone
    Tell us which hydrophone!

  6. #6
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    Good Morning. I attached a picture of the scheme with the desired idea. My question would be about how, in some way, to connect the hydrophone to the audio shield plate or to the Teensy. Through the hydrophone, it would record sounds that would be stored in an audio file (.WAV or any other acceptable format) on the SD card and then play that file and be heard from the headphones (in this part it would not be a problem, since I dominate the issue of reproduction, my problem is how to connect the hardware elements)

    On the other hand: how do I include the audio amplifier in this scheme and in the final design?

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  7. #7
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    I forgot it: the hydrophone I'm using is Aquarian H2A

  8. #8
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    Link to the actual product page
    http://www.aquarianaudio.com/h2a-hydrophone.html
    Reading the manual it appears to be a stereo device that needs bias power to work and also a preamp.

    The simple test may be to connect the shield part of the plug to the teensy audio shield mic ground and the tip to the mic input and load the pass through example to see if anything useful is heard. This will only be mono so if you want to use the stero capabilities of the unit you will need a stereo preamp that provides bias power as described on the linked product page. This will involve either doing the research to make one or buying one. The stereo line out of the preamp then go to the line in pins on the audio board.

    A commercial stereo recorder may also solve the problem in a neater package.

  9. #9
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    Quote Originally Posted by nestor26 View Post
    I forgot it: the hydrophone I'm using is Aquarian H2A
    Do you have more information coming with hydrophone than published on web? schematic etc?
    to me it seems that the same piezo is either presented as two single ended or as differential signal.
    what are they saying, the bias voltage should be? (6V?)

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