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PCM1865EVM: Gain Change Loud Click Issue

Part Number: PCM1865EVM
Other Parts Discussed in Thread: PCM1865

Hello,

When I write I2C PGA gain change commands to the PCM1865 I get very loud clicks in the audio output. So much so, that the DAW I'm testing with (REAPER) automatically mutes the output every time I change the gain - very distracting. I've tried enabling soft-ramp and filtering the DC with no luck. I have the 4 PGAs ganged. Is this a known issue or is there a work-around?

Thanks,

Colin

  • Hi, Colin,

    The click issue described could be related to the PGA behavior, it is recommended to make the changes of PGA level in small steps to avoid these kind of issues. Do you have Smooth PGA change enabled?, could you try changing the PGA gain in 0.5dB steps and see if the behavior is the same?

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer 

  • I am already making the changes in 0.5dB steps with smooth PGA enabled.

    Any other register settings I should look at?
  • Colin,

    Thanks for the feedback, could you please let us know the exact steps and configuration used to reproduce the issue?, I performed some tests in the EVM by changing the PGA gain while recording, if Smooth PGA is disabled, I am able to listen to the clip (is not very loud), with smooth PGA enabled, there is no clip. Also, clip can be heard when changing the digital mixers whether smooth PGA is enabled or not.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • Thank you for your reply Diego. I disconnected the I2C lines from my micro-controller and tested the PCM1865 by connecting the EVM to Purepath Console. I did not notice the gain change problem to be as bad when changing the gain using the TI GUI. I then noticed that even-though my I2C lines had been disconnected, when pressing the buttons I have setup for gain change to my micro, the pop/click happens. Of course the gain doesn't change, because I2C isn't hooked up. It's odd because these buttons just go straight to a port on the micro controller. When probing the connections between the two boards (power, ground and I2S), the only ones that seem to be showing the problem are DOUT1 and DOUT2. Any thoughts?

    Thank you very much for your time.

    Regards,

    Colin