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PCM2912A: Question of PCM2912A Noise Floor

Wayne Chen (Audio AE)
Genius 15950 points
Part Number: PCM2912A

Hi Sirs,

Would you pls advise if the noise floor measurement in line with the PCM2912A's specification? I added AES127 software filter and 10kOhm load impedance

Played 0dB FS, 1kHz sinewave with maximum volume, Got 685.8mV rms (-3.275dBV) as full scale output voltage.

Play silence file, Got 42.76uV (-87.867dBV) as PCM2912AEVM's noise floor. The noise level is audible -> Was it in line with PCM2912A's specification?


Stop playing media file, Got 24.07uV (-93.836dBV) as PCM2912A EVM's shutdown mode.



Thank you and Best regards,

Wayne Chen
09/11/2017

  • 0
    TI__Guru 57800 points

    Hi, Wayne,

    The value obtained is close to the expected performance of the device, there are a couple points to consider with this measurement:

    • Have you tried using a different audio player?, It seems the digital signal provided is very close to the full-scale voltage output (expected to be 0.7Vrms) with the used player.
    • Could you please confirm that an A-weighted filter is also used for the measurement?. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    TI__Genius 15950 points
    Hello Diego,

    Thank you for your concern. I used Windows Media Player. I did not use an A-weighting filter. We found minor audible noise when playing silence tone from EVM's line-out path thus we are trying to quantize the noise floor on the EVM.

    We have one question, does USB audio driver shutdown the PCM2912A when not playing media file, since we found different noise floor when playing silence tone and stop.

    Thank you and Best regards,

    Wayne Chen
    09/12/2017
  • 0 in reply to Wayne Chen (Audio AE)
    TI__Guru 57800 points

    Hi, Wayne,

    I think that whenever Windows stops playing audio, the USB bus becomes idle, so the PCM2912A shuts-down the output stage.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer