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Re: Kinect tear down

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  • dan michaels
    ... I understand foldback and aliasing, but don t quite see why it s much of an issue with speech or even music when sampling at 44-Ksps, as there is
    Message 1 of 126 , Dec 5, 2010
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      --- In SeattleRobotics@yahoogroups.com, "Peter Balch" <peterbalch@...> wrote:
      >
      > Dan
      >
      > > Another difference is that I wanted to be able to display data
      > > at as high a fequency as I could, whereas with something like
      > > speech+music 98% [whatever] of the energy is well below the
      > > maximum sampleable nyquist frequency.
      >
      > True but those high freqs are very important. Look at the difference between > Kar and Tar or Sar and SHar. Most therapy seems to be with children and they > have significant energy above 10kHz. Therapists often concentrate on those > kinds of phonemes.
      >
      > 44100 sounds generous but turns out not to be. We reckon a sharp cutoff at > 20kHz is just about tolerable. (As I'm sure you know, if we don't filter > before the ADC then the very high frequecies of speech "fold back" over the > spectrum and mess it up.)
      >



      I understand foldback and aliasing, but don't quite see why
      it's much of an issue with speech or even music when sampling at
      44-Ksps, as there is essentially no energy near or above 20-Hz
      for those signals. I suppose you can tell the difference by
      ear.


      >
      > > > TACQ which is (according to which part of the doc you read)
      > > > either 100nS, 7.67uS or 11uS.
      >
      > What do you think it actually is?
      >
      > > I assume the "F" series
      > > went to 120-pF from 51-pF on the "C" series because they wanted a
      > > little better noise filtering for 10-bit res,
      >
      > Interesting. where did you get those figures? There must be a doc I haven't > read.
      >
      > Peter
      >


      The holding capacitor values come straight out of the Microchip
      datasheets. For the PIC16F87X, d/s DS39582B, the cap is shown
      in figure 11-2, and TACQ is also on that page. The "C" series
      cap value also came out of the d/s.

      I notice some of d/s for later parts don't show these values.

      Looking at the formula, the TACQ value is obviously based upon
      a 1st-order capacitor charging ckt, and is linearly related to
      both the value CHOLD and also the impedance of the external
      voltage source, RS.

      Equation 11-2.
      ================
      TACQ = Amplifier Settling Time + Hold Capacitor Charging Time
      + Temperature Coefficient
      = TAMP + TC + TCOFF

      TC = 2 ìs + TC + [(Temperature – 25°C)(0.05 ìs/°C)]
      = CHOLD (RIC + RSS + RS) In(1/2047)
      = - 120 pF (1 kÙ + 7 kÙ + 10 kÙ) In(0.0004885)
      = 16.47 ìs

      TACQ = 2 ìs + 16.47 ìs + [(50°C – 25°C)(0.05 ìs/°C)
      = 19.72 ìs

      TACQ is dependent directly upon RS. The other R values in the
      formula are internal components. If RS is close to zero, then
      TACQ will be about 10-usec, so it varies dependent upon the
      external ckt. CHOLD is 51-pF in the "C" series, so TACQ will be
      less than 1/2 of the value shown here.
    • David Buckley
      You mean the SPO256 by GI, 28pin DIL ? They also had a 40 pin DIL CTS256A-AL2 text to speech for spo256 I have use the SPO256 back in the 80s and also last
      Message 126 of 126 , Dec 12, 2010
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        You mean the SPO256 by GI, 28pin DIL ?
        They also had a 40 pin DIL CTS256A-AL2 text to speech for spo256
         
        I have use the SPO256 back in the 80s and also last month but never got around to using the latter, I do have the Tandy data that came with them (somewhere I hope).
         
        David - robots42
         
         
        ----- Original Message -----
        Sent: Sunday, December 12, 2010 11:26 PM
        Subject: Re: [SeattleRobotics] Re: Speech and frequency vs time

         

        A long time ago, when Radio Shack still sold IC's, I got a speech
        synthesizer set, but I never did anything with it. Has anyone used them?

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