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TAS6424E-Q1: Digital gain

Peter Xu
Expert 5155 points
Part Number: TAS6424E-Q1

Tool/software:

Hi team,

Can customer change digital gain when in play mode?

Customer heard pop noise when they changed digital gain.

Regards,

Peter

  • 0
    TI__Mastermind 40685 points

    Hi Peter,

    Yes, to customer is allowed to change the gain in play mode.  A pop might be heard if they change the gain by large values. This can be reduced by changing the volume rate in I2C register 0x01, bits 2 and 3.  Change them to 1 step per 8 FSYNCs to slow the volume change by 8x.

    Regards,
    Gregg Scott

  • 0 in reply to Gregg Scott
    TI__Expert 5155 points

    Hi Scott,

    They set the register according to your advice and they found the noise still exists.

    Do you have any other solutions?

    Regards,

    Peter

  • 0 in reply to Peter Xu
    TI__Mastermind 40685 points

    HI Peter,

    Can you please share the test and measurement process your customer is using, so we can reproduce this in our lab?  We do not hear a pop in the speakers when the digital gain is changed when listening to music.

    Regards,
    Gregg Scott

  • 0 in reply to Gregg Scott
    TI__Expert 5155 points

    Hi Gregg,

    The test procedure is as follows:
    Adjust the power supply to 13V (since the CLIP logic is triggered only below 14V), and power on the head unit. Play a 100Hz audio from the media source and turn the volume to the maximum to cause clipping and trigger the CLIP logic (the MCU will repeatedly adjust the amplifier gain via I2C). At this point, the speaker will produce a fluctuating 100Hz audio accompanied by "pop, pop, pop" noise.

    Regards,

    Peter

  • 0 in reply to Peter Xu
    TI__Mastermind 41700 points

    Hi Peter

      If testing like this, the pop noise would not able to fully removed by the device.

      This device doesn't' have internal DSP, the digital gain is generated by the circuit with fixed step 0.5dB. At close to max output level, 0.5dB change is also quite large step.

      Customer could use their MCU to change the input signal level, make the change more slower. MCU calculation could realize very small step change.