LTSpice - tremolo effect simulation

Discussion in 'General Electronics Chat' started by Bonapetro, Jan 16, 2019.

  1. Bonapetro

    Thread Starter New Member

    Jan 16, 2019
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    This is my first post on this forum, so hello everyone! I hope you're doing fine!

    I am writing because of the issue I have during simulating of Tremolo effect in LTSpice software.
    My schematic that I use shows picture below:

    LTSPice_scheme.png

    The problem is the fact that LTSpice does not simulate this effect at all. It is so strange, because I have built a physical effect based on this schematic and everything works good. I investigated effect on oscilloscope too and the output signal looks as it should.
    Furthermore I have created a potentiometer model (LTSpice does not have its own in libraries) based on one of the YouTube tutorial and only one of them works properly (VOLUME, near C5 capacitor). Changing values of the other has no effect in output signal.. Here is potentiometer model:

    potencjometr_LTSpice.png

    Can you explain me what is wrong with this schematic that it does not simulate? Input and output signals have shown below:

    LTSPice_tremolo.png

    Thank you in advance for any help!
     
  2. Alec_t

    Expert

    Sep 17, 2013
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    Welcome to AAC!
    It would be helpful if you post your asc file.
    You have a signal-in source in your schematic, but I see no low frequency source to produce the tremolo effect.
     
  3. Bonapetro

    Thread Starter New Member

    Jan 16, 2019
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    Thank you for response!
    How can I add frequency source? And in which place should I put it?
    ASC file was attached.
     
  4. bertus

    Administrator

    Apr 5, 2008
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  5. Bonapetro

    Thread Starter New Member

    Jan 16, 2019
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    After studied this and the other websites involve phase shift, I still don't really know how can I implementate it in schematic.
    The idea with frequency source sounds fine. I read that to use this source, we need to use 'modulator' model in LTSpice. Unfortunately I can't find any informations about parameters I should write inside the model.
     
  6. Alec_t

    Expert

    Sep 17, 2013
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    If you want to continue using a phase-shift oscillator as in the asc file, reduce the 100uF cap to 1uF and run the sim for at least 10 secs to allow oscillations time to build up.
    If you want to use the Modulate device (from the Special Functions folder), here's an example of its use to generate a 1kHz signal amplitude modulated at 25Hz:-
    Modulate.PNG
    The mark and space values are set by right-clicking on the device symbol.
     
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  7. Bonapetro

    Thread Starter New Member

    Jan 16, 2019
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    Could you please send a picture of modulator's Component Attribute Editor? I don't know what parameters I should type in Value, SpiceLine, etc.
     
  8. Bonapetro

    Thread Starter New Member

    Jan 16, 2019
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    Ok, I think I got it but the potentiometers still do not work I guess. Do you suspect any reason of this? And the output signal looks a little bit weird to me, doesn't it?
     
  9. Alec_t

    Expert

    Sep 17, 2013
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    I don't see any definition of parameters R and Val.
    The output looks weird because J2 gate is overdriven and not biased correctly.
     
  10. Bonapetro

    Thread Starter New Member

    Jan 16, 2019
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    Actually they are, but because of small font you can't to see them:
    upload_2019-1-17_11-46-34.png

    You are right. After changing transistor to the other, the output signal looks much better! Thanks.
     
  11. Bordodynov

    Well-Known Member

    May 20, 2015
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    See
    2019-01-17_14-56-38.png
     
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  12. Bonapetro

    Thread Starter New Member

    Jan 16, 2019
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    It seems like it works properly using standard sinus input signal. Thanks a lot! Where did you find the issue?
     
  13. Bordodynov

    Well-Known Member

    May 20, 2015
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    See
    2019-01-17_16-16-37.png
     
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  14. Bonapetro

    Thread Starter New Member

    Jan 16, 2019
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    Looks amazing! :) Do you know why can I set Rtot and wiper only for volume pot? For the others I can not open parameters window.
     
  15. Bonapetro

    Thread Starter New Member

    Jan 16, 2019
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    Additional amplitude of my output signal is about 0.2V instead of 0.8V.. All parameters are enable in potentiometers. I'm going daffy..
     
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