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Variable Sample Rate vs Constant Sample Rate

Patrick McCormick1
Prodigy 20 points

All of the ADCs and DACs seem to support specific sampling rates up to 192 kHz.

I have a question:  Is there a chip that supports variable sampling rate?  Specifically, if the analog signal varies in frequency, why don't converters vary in sampling rate to meet the optimum sampling frequency at all times?

Are there any products in the TI audio line that offer this sort of approach?

  • 0
    TI__Guru**** 189401 points

    Hi, Patrick,

    Welcome to e2e, and thanks for your interest in our products!

    Unfortunately, I don't believe anyone is doing anything like this as it would complicate the system.

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 20 points

    I think there's a golden opportunity for TI here.  For some reason, there is a popular notion that the Nyquist sampling frequency is sufficient for reproducing any waveform faithfully to the highest range of human hearing.

    The simple fact is that it cannot reproduce a square wave at 20kHz.  All the arguments for Nyquist show their proof by using higher frequency sine waves of different frequencies to show the construction of a square wave of a substantially lower frequency.  This proves nothing as music contains lots of different waveforms even in the higher registers.

    Therefor, I think there's an opportunity to develop a digital recording process that uses the rate of change of the slope of the input waveform to determine and continually vary the sampling rate.  Put another way, only store data points at those specific points in time which can reproduce the original waveform faithfully.

    I think Nyquist just confused everybody and now, we either listen to really harsh, under-sampled audio, or end up with larger than necessary files by switching to an unnecessarily high sampling rate for the entire file.

    Who can I talk to at TI about this?

  • 0 in reply to Patrick McCormick1
    TI__Guru**** 189401 points

    Hi, Patrick,

    You could contact your local TI Sales Office to discuss this in more detail.

    -d2