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TAS2505: Great Sound Quality except for Low Volume Noise on Output

DuncanM24
Prodigy 20 points
Part Number: TAS2505

Tool/software:

Hello TI,

I have been working on integrating the TAS2505 into our products, and we are pleased with the results however there is low volume noise that can be heard during quiet audio playback.

I have tried a number of combinations of clock dividers, NDAC/MDAC, DOSR, but the noise still persists, I don't think it is the audio file since the noise was not heard on a previously used audio amp and the raw audio files do not exhibit the noise.

I am using I2s, 16 bit word, BLCK is 352.8 kHz, audio is sampled at 11.025kHz. Looking at the documentation the minimum input is 512kHz, however other than the noise on the output while playing audio I haven't had any issues with it.

Of the combinations, one that seems to work well enough is this, although in my experience the lower the DOSR value the better, I've had popping sounds at higher DOSR values

P = 1
R = 3
J = 32
D = 0
NDAC = 2
MDAC = 3
DOSR = 128

[352.8*10^3*((3*32)/1)]/[2*3*128] = 44100

Putting that through the equation gives 44100 Hz which is 4x the frequency of the audio, but the quality is much better and less noisy than when the equation is modified to output 11.025kHz.

I have adjusted the processing blocks, but they haven't made an audible difference, the same for PTM.

Speaker amp is set to 6dB, and volume of different audio files is controlled with the DAC Channel Digital Volume Control Register.

Thank you,
Duncan

  • 0
    TI__Genius 11655 points

    Hi Duncan,

    Is this for all audio signals? Or just one? If you provide me the audio file I can try it out on my end. 

    Are you having an issue using 44.1kHz? Are you hearing popping sounds?

    Regards,
    Sydney Northcutt 

  • +1 in reply to Sydney Northcutt
    Prodigy 20 points

    Hi Sydney,

    I was able to fix this by reducing the speaker volume control register(0x2e) and upping the dac digital volume control register(0x41).
    There was a bunch of noise that was being amplified by the speaker, but making those changes fixed it.

    To answer your question, I haven't had popping sounds since I made the changes I described above at 44.1kHz.

    Thank you for reaching out, it is greatly appreciated!

    ~Duncan