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Thread: PT8211 Audio Kit Playback Distortion

  1. #1

    PT8211 Audio Kit Playback Distortion

    I've recently assembled the PT8211 audio kit (thanks PJRC for developing this great kit!).

    However I'm testing the playback in comparison to the SGTL5000 and I'm getting some very noticeable distortion with the PT8211 kit.

    Has anyone else experienced this issue?

    I'm using the test sine code from https://github.com/PaulStoffregen/Au...PT8211Sine.ino
    Code:
    #include <Audio.h>
    #include <Wire.h>
    #include <SPI.h>
    #include <SD.h>
    #include <SerialFlash.h>
    
    // GUItool: begin automatically generated code
    AudioSynthWaveform       waveform1;      //xy=110,75
    AudioOutputPT8211        pt8211_1;          //xy=303,78
    AudioConnection          patchCord1(waveform1, 0, pt8211_1, 0);
    AudioConnection          patchCord2(waveform1, 0, pt8211_1, 1);
    // GUItool: end automatically generated code
    
    void setup() {
      AudioMemory(15);
      waveform1.begin(WAVEFORM_SINE);
      waveform1.frequency(440);
      waveform1.amplitude(0.99);
    }
    
    void loop() {
    }
    Here's the oscilloscope reading with jagged sine waves (in light blue):
    Click image for larger version. 

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    Last edited by jdev; 07-13-2017 at 03:11 AM. Reason: used simpler code and added oscilloscope reading

  2. #2
    Senior Member+ Frank B's Avatar
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    The pt8211 works well for me. No distortions.

  3. #3
    Senior Member PaulStoffregen's Avatar
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    I tested a PT8211 board just now. Here it is on my desk:

    Click image for larger version. 

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    Here's the waveform I see on my scope when running the code you posted:

    Click image for larger version. 

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    Here's another view with the scope's FFT turned on. Looks like minor harmonics at 880, 1320, 2200 and 3080, but they're all at -50dB or less.

    Click image for larger version. 

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    I have no idea why your PT8211 board is making that terrible waveform. The sine output looks pretty good here.

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