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Thread: New Teensy 4.1 DIY Synthesizer

  1. #76
    Member fdaniels's Avatar
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    Besides the fact that S/N ratio isnt not really an important parameter to a Synth (at least i didt care for it, "musicallity" or usabliity are magnitudes of more importance) - does it make sense to measure on a breadboarded Circuit since it can be totaly different on a PCB? Just asking....

  2. #77
    Senior Member Rolfdegen's Avatar
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    Hi Mark
    Thanks for your analysis. I made a new measurement (Balckman-Harris 1024 point) with the same audio file.
    The 1st picture shows only the noise without sound. The 2nd picture shows the complete audio file.





    Greetings. Rolf


  3. #78
    Senior Member Rolfdegen's Avatar
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    Quote Originally Posted by fdaniels View Post
    Besides the fact that S/N ratio isnt not really an important parameter to a Synth (at least i didt care for it, "musicallity" or usabliity are magnitudes of more importance) - does it make sense to measure on a breadboarded Circuit since it can be totaly different on a PCB? Just asking....
    I think S/N ratio will get a little better with a PCB board. Usability is also very important in my development

    I want to build a small synth with good usability (e.g. Shruthi).



    Greetings. Rolf

  4. #79
    Senior Member Rolfdegen's Avatar
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    Hello ..


    Today the ordered components came. The relay for the audio on circuit is really small and sweet


    The relay then hardly takes up any space on the circuit board. I save on a control line on the Teensy and switch the relay via a transistor with a delay time.


  5. #80
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    Quote Originally Posted by fdaniels View Post
    Besides the fact that S/N ratio isnt not really an important parameter to a Synth (at least i didt care for it, "musicallity" or usabliity are magnitudes of more importance) - does it make sense to measure on a breadboarded Circuit since it can be totaly different on a PCB? Just asking....
    I'm just trying to correct the common misconception about noise-floor measurements using the FFT - its very
    rarely appreciated that noise isn't measured the same as a single tone. Noise is measured per hertz, and thus
    the width of an FFT bin determines how much noise it sees. Using an FFT to measure noise involves corrections
    for the bin width and for the window used (its noise bandwidth).

    And of course there's the constant confusion about interference v. true noise

    [ And don't get me started on the poor performance of the Hann window function for measurements - all
    commercial spectrum analyzers use a flattop window to be able to take accurate measurements. ]

  6. #81
    Senior Member Rolfdegen's Avatar
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    Thanks for your good explanation.

  7. #82
    Senior Member Rolfdegen's Avatar
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    Hallo..

    AntiPop circuit without relay..

    IC5 LM317 slowly increases the operating voltage for the audio amplifier.



    Audio file: First sound with anti pop and second without

    Link: https://drive.google.com/file/d/1BYZ...ew?usp=sharing

    Greetings Rolf

  8. #83
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    Quote Originally Posted by Rolfdegen View Post
    Thanks for your good explanation.
    If you want to find out more, this is the paper that inspired me: https://holometer.fnal.gov/GH_FFT.pdf

  9. #84
    Senior Member+ Frank B's Avatar
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    Oh man... why does everything have to be in English. Why are papers by Germans published exclusively in English, and then have to be translated back by other German readers... grrr
    We pay taxes... I see it coming..in 30 years everything will be in Chinese. Fortunately, I won't be very interested in it then.
    Last edited by Frank B; 01-16-2021 at 02:17 PM.

  10. #85
    Senior Member Rolfdegen's Avatar
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    @Frank
    My Teensy Synth blog in deutsch: https://www.sequencer.de/synthesizer....87599/page-22

  11. #86
    Senior Member+ Frank B's Avatar
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    Danke
    Hab grade die ersten Beiträge überflogen. Also der Teensy 4.x kann ganz sicher eine sehr hohe zweistellige Anzahl von Stimmen
    Irgendwer schrieb mal er würde 15 samples aus externem Flash gleichzeitig abspielen. Das war auf einem Teensy 3.2 (<100MHz)

  12. #87
    Senior Member Rolfdegen's Avatar
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    I still want to save processor power for future functions

  13. #88
    Senior Member Rolfdegen's Avatar
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    Sorry.. Its IC6 LM317

  14. #89
    Senior Member Rolfdegen's Avatar
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    Hallo again..

    Voltage output on the LM317. Since the LM317 cannot regulate its output to 0 volts because of its internal Uref of 1.25V,
    With its voltage drop, the LED ensures that the output voltage begins to rise at 0 volts.
    The voltage drop at the LED also has the disadvantage that the maximum supply voltage at the output amplifier sings a bit.


    without AntiPop



    with AntiPop


    Greetings from germany. Rolf
    Last edited by Rolfdegen; 01-16-2021 at 05:41 PM.

  15. #90
    Senior Member Rolfdegen's Avatar
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    Hello again..

    I exchanged the LED for two 1N4148 diodes. This reduces the voltage drop behind the LM317.



    Greetings Rolf

  16. #91
    Senior Member Rolfdegen's Avatar
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    Hello again..


    It is progressing. I am currently programming the filter page and
    to display the filter fade from LowPass to HighPass.




    Greetings Rolf

  17. #92
    Senior Member Rolfdegen's Avatar
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    The filter page

    The sound interference comes from rendering with MP4 in Video Deluxe.

    Video: https://youtu.be/2QipRkolZk0



    Greetings. Rolf

  18. #93
    Member fdaniels's Avatar
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    Are you left-handed? Because you put the Encoder to the left of the Display. Since most people (86/87) are Right handed placing it to the right would be much better, since you are hiding the Display when operating the Encoder with your right hand.....

  19. #94
    Senior Member Rolfdegen's Avatar
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    Hi Frank

    Thanks for your tip. It's a prototype. The layout isn't final yet. Some buttons, joystick, volume control and LEDs are added.

  20. #95
    Senior Member Rolfdegen's Avatar
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    Hello again..

    My next step is to implement the Filter Envelope and Amp Envelope



    A better video of envelopes and filters is coming. Best Greetings from wuppertal in germany. Rolf
    Last edited by Rolfdegen; 01-28-2021 at 11:47 AM.

  21. #96
    Senior Member Rolfdegen's Avatar
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    Small update ..


    The envelopes also get a delay and hold parameter. These two parameters will be added to the graphic later.
    In addition, there is a peak meter in the header for checking the output level on the DAC.





    Greetings from germany. Rolf
    Last edited by Rolfdegen; 01-28-2021 at 07:24 PM.

  22. #97
    Senior Member Rolfdegen's Avatar
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    Hello friends..

    I adjusted the envelope Attack time from 1ms to 0.25ms . That makes more punch with percussion sounds.



    1ms



    0.25ms


    Greetings Rolf

  23. #98
    Member fdaniels's Avatar
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    You really want to have an exponential release phase.....

  24. #99
    Senior Member Rolfdegen's Avatar
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    Yes that would be good. The envelope code would have to be changed for this

  25. #100
    Member fdaniels's Avatar
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    Quote Originally Posted by Rolfdegen View Post
    Yes that would be good. The envelope code would have to be changed for this
    You could do your own. If so, why not implement something more interesting than an ADSR?

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