microphone choice for EVAL AD1940-MINIBZ ADC input

Hi,

I'm trying to use a microphone in order to take sound for processing, but a normal computer mic did not work when i connect it to the adc input of the evaluation board. Should I use a preamp ?  What kind of a mic would be better ?

Waiting for answer

RIDVAN

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  • 0
    •  Analog Employees 
    on Jul 4, 2012 12:23 AM

    A stand-alone plug-in PC microphone needs a bias voltage to be provided from the preamp circuit; this bias is not available on the AD1940 mini board. In order to use a mic like this, a bias voltage should be provided through a 2k resistor on the microphone signal line. You can see a simple schematic of a microphone input on this page (see the figure labeled "Sound Blaster Microphone Input"): http://www.epanorama.net/circuits/microphone_powering.html. Here, you can see the bias supplied through the resistor to the jack ring, which is shorted to the tip.

    In order to use a mic like this with the AD1940 mini board, you will need a preamp that can bias the mic and probably provide some signal amplification. You could use a part like the SSM2167 to do this. There is an evaluation board for this microphone preamp that should allow you to plug your microphone directly in on one side, and output the signal to the AD1940 board.

    If you want to use a different microphone, you could use one of our analog MEMS microphones, which do not use the bias voltage but instead have a separate pin for the supply voltage (1.5 to 3.3 V). If you have a voltage supply to provide to the MEMS mic's VDD pin, then its output could be connected directly to the AD1940 mini board's input. Note that this solution doesn't have any gain between the microphone and ADC, though, like the SSM2167 would have.

Reply
  • 0
    •  Analog Employees 
    on Jul 4, 2012 12:23 AM

    A stand-alone plug-in PC microphone needs a bias voltage to be provided from the preamp circuit; this bias is not available on the AD1940 mini board. In order to use a mic like this, a bias voltage should be provided through a 2k resistor on the microphone signal line. You can see a simple schematic of a microphone input on this page (see the figure labeled "Sound Blaster Microphone Input"): http://www.epanorama.net/circuits/microphone_powering.html. Here, you can see the bias supplied through the resistor to the jack ring, which is shorted to the tip.

    In order to use a mic like this with the AD1940 mini board, you will need a preamp that can bias the mic and probably provide some signal amplification. You could use a part like the SSM2167 to do this. There is an evaluation board for this microphone preamp that should allow you to plug your microphone directly in on one side, and output the signal to the AD1940 board.

    If you want to use a different microphone, you could use one of our analog MEMS microphones, which do not use the bias voltage but instead have a separate pin for the supply voltage (1.5 to 3.3 V). If you have a voltage supply to provide to the MEMS mic's VDD pin, then its output could be connected directly to the AD1940 mini board's input. Note that this solution doesn't have any gain between the microphone and ADC, though, like the SSM2167 would have.

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