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TAS2505: Some Questions About Soft-Stepping and Audio Gain

Jiahe Liu
Prodigy 110 points
Part Number: TAS2505

Tool/software:

Hello,

I have some questions about the soft-stepping mechanism and audio gain settings in TAS2505:

1. According to TAS2505 reference guide, some waiting time for the soft-stepping needs to be set, but what I didn't understand was why the time should be inserted before the DAC gain and the output driver gain are set. Shouldn't we wait after the gain values are written through I2C so as to allow for time to let the gain reach the desired level? 

2. I was wondering if the soft-stepping feature is only useful when we're playing continuous music and want to adjust the volume mid-way. If we set up the gain beforehand and then play the music, do we still need the soft-stepping to avoid pop sounds? 

3. I am only using speakers in my application and not using AINL/R. There are three places where I can set the gain to adjust the audio volume: DAC digital gain, speaker attenuation gain, and speaker driver gain. I was wondering what these three do respectively, and which ones I should set to increase/decrease volume for least sound distortion.

All the best,

Jiahe Liu

  • 0
    TI__Genius 11655 points

    Hi Jiahe,

    Thanks for reaching out. Please allow me some time to look into the questions. Appreciate your patience! 

    Regards,
    Sydney Northcutt 

  • 0 in reply to Sydney Northcutt
    TI__Genius 11655 points

    Hi Jiahe,

    It seems the ordering here is slightly incorrect. There are two different soft-stepping processes that happen. One for the analog gain and one for the DAC digital gain. The instructions are referring to the analog gain as you must wait for the allotted time. Step 6 should actually come before step 4 in the screen shot you shared. Powering the DAC is still the last step. 

    DAC soft stepping comes into operation during: 
       a. power-up, when the volume control soft-steps from –63.5dB to programmed gain value,
       b. volume change by user when DAC is powered up, and
       c. power-down, when the volume control block soft-steps to –63.5dB before powering down the channel

    Typically the speaker driver gain is set to the max value needed and kept there during operation. This is mainly because it goes from 6 dB to 24 dB with 6 dB steps. The DAC digital gain and speaker attenuation gain have much smaller steps of 0.5 dB, so either of these can be used for volume adjust. They have slightly different ranges. 

    Regards,
    Sydney Northcutt