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TAS5805M: I2S LRCK (sampling rate) of TAS5805M

Mickey Lee
Prodigy 130 points
Part Number: TAS5805M
Other Parts Discussed in Thread: TAS5805,

Hi TI Team,

We saw the default LRCK setting of TAS5805 EVB was 44.1kHz and converted the tuned data to a .h file on this EVB.

In the next step, had this .h file put into our product.

However the DSP chipset of our product was operating in 48KHz LRCK rate and it resulted in that a bit of deviation on the frequency response of AMP output compared with the EVB's

(via the Audio Precision).

 

Could we configure the LRCK sampling rate of TAS5805M as 48KHz and recheck whether the frequency response reaches the consistency with the EVB's?

Regards,

  • 0
    TI__Mastermind 31740 points

    Hi Mickey

        Yes, you can use 48KHz as the sampling rate. Actrually the device 5805 won't distinguish 48KHz and 44.1KHz, as they are very close to each other. The device will use 48KHz as the base sampling rate for the calculation even you choose 44.1KHz in the PPC3. Thank you.

  • 0 in reply to Shadow He
    Prodigy 30 points

    I think there is a misunderstanding, let me explain the issue clearly.

    Here is what I did

    Step 1

    Power on 5805EVB and load the PPC3 setting which is a simple setting that has only two filters, as below.

    now the i2s clock setting transmit to 5805EVB is LRCLK = 44.1kHz and CLK = 2.82MHz

     

    Step 2

    Do the measurement sweep sine 20Hz to 20kHz. Measure the analog output of the amp, the result is as below, the blue one.

     

    Step 3

    Change the transmit clock to LRCLK = 48kHz and CLK = 3.072MHz, keep the same GUI setting as step 1, then do the measurement sweep sine 20Hz to 20kHz again. Amp analog output is the red one. It looks like a little bit of frequency shift from the blue one.

    What is the cause of this issue? Is that any sampling rate setting wrong?

     

    thanks

  • 0 in reply to Hsiao CHE-YI
    TI__Mastermind 31740 points

    Hi Hsiao

       I understand your concern and let me explain it more specifically.

       The Equalizer/Biquad is a digital processing module in our device. Through the Digital Signal Processing theories, the sampling rate will affect the calculation of the filter parameters. That is to say, under different sample rate, if you want to realize the same filter effect, the parameter for the filter would be different and should be re-calculated. But as I said before, our device won't distinguish 48KHz and 44.1KHz sample rate, as they are very close to each other. And it will use 48KHz to calculate the filter parameters, even you use LRCLK = 44.1KHz.

       So in your test results, when you use LRCLK = 48kHz, the frequency response results are accurate. And when you use  LRCLK = 44.1KHz, the results will have some small error. And the 5805 is designed in this way, change register settings won't help it. 

       But it's OK for you to use 44.1KHz as the sample rate, apart from a little error in the Equalizer, there won't be other problems.

       Thank you.