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Linux/PCM2912A: Set the input PGA with Alsamixer

Harald Schuster
Prodigy 10 points
Part Number: PCM2912A

Tool/software: Linux

Hi

I am using the pcm2912a chip and I have to set the value for the input PGA for the MIC input. This value can be set between -12 and 30 dB. But Alsamixer don't show me this parameter with the default driver. Is there any other possibility to set the value?

best regards

Harald

  • 0
    TI__Mastermind 30120 points
    Harald,

    It is definitely possible to set the value, but if Alsamixer doesn't provide this default, it would need to be added.

    See page 21 of the datasheet. (section 9.5.1.2) This describes Interface #0, and it lists input PGA under unit ID#8
    are you able to modify the driver?

    We don't have our linux support team anymore, so I only have limited insight into this. But you should be able to change this value, we are certainly able to use windows to change the microphone gain (see PCM2912EVM user guide for reference).

    best regards,
    -Steve Wilson
  • 0
    TI__Guru 57800 points

    Hi, Harald,

    Welcome to E2E, Thanks for your interest in our products!.

    As you mention, this device has an adjustable PGA gain, which can be updated by the host device and it depends on the OS to change the PGA volume level. The part gain change should be implemented in ALSA by the amixer command, Once amixer is executed in the shell, it should show the microphone PGA; if it does not show it, the PCM2912A will not support mic PGA changes in ALSA. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer