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CCS/ AIC3106/C6748: AIC3106 volume control pop noise

Part Number: TMDSLCDK6748

Tool/software: Code Composer Studio

I'm developing an audio program by referring to the McAsp example.

My first goal was to bypass the sound that came into Line-in.

Also receives input from the mic port to perform some calculations.

I wanted to decrease the line-in sound passing bypass according to the calculated results.

However, if you use registers 86 and 93 to turn down the sound, pop noise will occur and the sound will be too small, so I looked for another way.

The way I thought about it was to store the sound source in memory and bring it back to play.

And again this time, I tried to use registers to decrease the sound, but pop noise continued to occur.

Is there any way to reduce bypass sound?

Or is there a way to decrease sound without pop noise when playing it in the txBuf of the McAsp example?

Why pop noise occurs when you decrease the volume?

  • Hello,

    Can you please share which software package you are currently using? StarterWare, Processor SDK, MCSDK, etc?

    Have you made any clocking modifications to your board/software?

    Can you try running the example without the USB connected to see if that reduces the noise?

    Are you observing any McASP errors such as frame sync?


  • I am using McASP Starterware audio loopback example.

    Clock is the default state and operates at 300MHz.

    I'm testing with debugging with jtag. Do you mean to remove usb and test it by flashing it?

    I have not seen any McAsp errors yet.

    
    
    
    
    
    
  • Gibeom,

    Could please describe your HW setup (audio source, cables user, speaker/headphones) in detail and indicate if you are seeing this behavior with the HW out of the box with prebuilt binaries. Also,  note impact of modifying register 86 and 93 is a question for our audio converters team who support the AIC3106 codec. You can check for similar issue reported on the audio converter forums like these:

    https://e2e.ti.com/support/audio/f/6/t/296431

    https://e2e.ti.com/support/audio/f/6/t/548904

    The MCASP loop back example that we provide only sets up the clocks and the gain for the AIC3106 since C6748 MCASP provides the bit clock that is used for sampling the data on the AIC3106 (slave configuration).  The MCASP is simply looping back the data that is used on is serializers so is unlikely to be introducing any noise unless there is some issue with clocking or data corruption.

    We also request that for new development then please use MCASP LLD driver example from Processor SDK RTOS package since starterware code is obsolete. Having said that the starterware example has been used multiple times by users and known to be working without any issues.

    Regards,

    Rahul

  • Gibeom, 

    1.Registers 86 and 93 should not be used to dynamically change the volume. 

    2. The line outputs will always have a pop sound when they are powered up,  these outputs were intended to be used with external amplifiers, which would have a mute. The external amplifier would remain in mute while these outputs were powered up,  then unmuted after. 

    which bypass path are you using?

    best regards,

    -STeve Wilson