Audio Inputs – Impedance and Time Precision

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  • 21st October 2015 at 16:44 #26540
    Prof . Gerhard Gruhler
    Participant

    I want to use the uTrack24 as a mobile Multichannel-Recorder for acoustical measurements in car cabin. My two questions are:
    1) What is the input impedance of the analog inputs? I need it for designing the microphone amplifiers.
    2) Is there exact sampling of all 24 channels at the same sample time or have I to expect delays in between the channels?
    What about the time jitter of the sampling?
    (Remark: We had experiences with our old recording system which was also based on CIRRUS ICs, that we needed to install an additional reference impuls for exact timing in between the 24 channels)

    Thanks for any helpful support

    21st October 2015 at 17:09 #26541
    Chetan
    Participant

    Hi Gruhler

    1) What is the input impedance of the analog inputs? I need it for designing the microphone amplifiers.
    Differential inputs with 10 kOhm each to GND.

    2) Is there exact sampling of all 24 channels at the same sample time or have I to expect delays in between the channels?
    All channels are exactly the same, except CH7/8, 15/16 and 23/24 which have a few samples more latency.

    What about the time jitter of the sampling?
    DCO-based clock recovery based on crystal oscillator –jitter is not zero but should definitely not be an issue.

    25th October 2015 at 23:16 #26547
    Seneca St James
    Participant

    [quote=”digichetan” post=974]Hi Gruhler
    2) Is there exact sampling of all 24 channels at the same sample time or have I to expect delays in between the channels?
    All channels are exactly the same, except CH7/8, 15/16 and 23/24 which have a few samples more latency.
    [/quote]

    Curious for reasoning behind this?

    26th October 2015 at 13:05 #26549
    Chetan
    Participant

    [quote=”hoserama” post=980]
    Curious for reasoning behind this?[/quote]

    The analog ports are in groups of 8 channels. The Cirrus ADC converter has only 6 inputs. The other 2 inputs are handled with another ADC. Each of the 3 groups of 8 channels have been designed in the same way.

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