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Thread: Teensy 3.6 + PT8211 DAC : pitched sound when recording analog signal

  1. #1
    Junior Member
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    Teensy 3.6 + PT8211 DAC : pitched sound when recording analog signal

    Hi,

    I have a Teensy 3.6 and a PT8211 DAC.

    I uploaded the PT8211Sine sketch and outputted the sound directly to my amplified speakers. The sound is nice and clean, no problem.

    Then I connected the audio jack from the DAC to one of the input of my audio interface (Behringer UMC204HD). The input allows to choose between "LINE" or "INSTRUMENT". With LINE selected the signal level is to small but it is good with INSTRUMENT so I selected INSTRUMENT.

    Then I recorded the sound with Audacity. This time the sound is not nice and clean at all, it is like pitched. I tried selecting LINE but I get the same pitched sound. I tried recording with Ableton but I get the same pitched sound.

    Do you know what can cause this ? I thought maybe it is because the DAC is 44.1KHz and my Audio Interface is 192K but I don't really think so. I tried with all the possible preference settings from Audacity but I always get this pitched sine wave.

  2. #2
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    What does the waveform look like in Audacity, and what should it look like ?

  3. #3
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    The waveform looks like a 440Hz sine wave with harmonics/noise. It should look like 440Hz sine wave without harmonics/noise.
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  4. #4
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    I connected the Teensy to the line input of my laptop and I get a clean sinewave in Audacity. So this is my audio interface causing the problem.

  5. #5
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    Found the problem, haha... A male TRS jack in a female XLR input won't work properly... Now I'm using a male XLR cable jack, problem solved. Shame on me... So the problem was not the teensy or the DAC or my audio interface but the cable.

  6. #6
    Senior Member PaulStoffregen's Avatar
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    Wow, would not have suspected the cable. Normally we hear about bad (power only) cables with USB.

  7. #7
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    The problem was more me not knowing a TRS audio jack is not intended to be put in an XLR connector. First time using the inputs of an audio interface.

  8. #8
    Senior Member
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    Some audio devices use TRS as balanced mono signal, using T and R as the hot/cold signals.
    Sometimes TRS is used as stereo though, so it can get confusing.

    There are combined XLR/TRS connectors out there, its definitely a thing. I'd expect such a connector used
    as an input would accept a mono jack and work fine, as this puts ground on the ring.

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