Over sensitive Cortado MkII kit

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  • This topic has 3 replies, 2 voices, and was last updated 1 year ago by brach.
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  • #33318 Reply
    DrM
    Participant

    I have built the kit and find that it works well, too well actually. I’ve turned down the bias setting as far as the
    POT would allow, and still this thing seems to be oversensitive. I’m feeding the mic into a ZOOM F4, and I have to
    leave it at it’s lowest gain setting. I’ve even tried using 24V instead of 48V for the phantom power. Is it possible to
    desensitize this circuit further? Perhaps increasing/decreasing the value of R8?

    Also, does anyone know what the output impedance is for this mic? And what the frequency response is?

    Daniel

    #33349 Reply
    brach
    Moderator

    I’m sorry about your Cortado’s sensitivity issues…It is a sensitive piece of equipment. The easiest solution is to use mechanical dampening to reduce the sensor’s ability to detect vibration. Try wrapping it in cloth or high density foam or potting it with hot glue or something to stifle the vibrations that get to the disc.
    The MkIII does have a pad, if you are interested in that.
    Please don’t confuse “sensitivity” with “head room.” By turning the pot all the way down you are reducing the bias voltage on the FETs causing them to loose a lot of headroom. Reducing the phantom power voltage will only reduce the headroom too…it will still be just as sensitive, but it can’t pick up as large of signals without distorting.
    I can’t remember what the frequency response is off the top of my head. The output impedance is a few thousand ohms…I’m sorry, I don’t remember specifics.
    -Brach

    #33526 Reply
    DrM
    Participant

    Thanks for the info.

    Could I use or make an attenuation pad, such as a balanced U or O design? I found a site with a lot of good info about
    building attenuators.

    Is it also possible that you could look up the output impedance, or give a good guess? The input impedance for my Zoom
    H4 on the XLR inputs is 2k Ohm.

    Daniel

    #33559 Reply
    brach
    Moderator

    Either of those types of pads would probably work. Feel free to experiment.
    The output impedance is around 6K ohms.
    Good luck.
    -Brach

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