Using LTSpice for learning about amp circuits?

Discussion in 'The Workbench' started by What?, Nov 22, 2020.

  1. What?

    What? Well-Known Member

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    I have a few tube amp books which I have read from here and there, but what they seem to be sorely missing is active involvement, i.e., all theory, no doing. I'm looking at the book by Richard Kuhnel titled, Guitar Amplifier Electronics Circuit Simulation, which uses LTSpice. I have one of Kuhnel's other books titled, Guitar Amplifier Electronics Basic Theory, which I have read on here and there. Two problems that I have with that book are:

    1) Instead of starting top down with a less detailed overview of amps and gradually filling in more details as needed, it is all about details every step of the way, which makes for losing the forest for the trees and weeds and is very dry and boring to read.

    2) It involves no real hands on projects, which I think is a big part of learning about anything technical.

    I'm thinking that Circuit Simulation book might be a good way to go in conjunction with continued reading at Rob Robinette's site and elsewhere. What do you think about using LTSPice as something of a n00b tool for learning about amp circuits before getting into actually building something? Of course a simulation is going to ignore lots of real world practical issues, but I'm thinking that it might be a good way for actively getting a hold on concepts before getting into real world issues.
     
    Last edited: Nov 22, 2020
  2. What?

    What? Well-Known Member

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    Think I'll just go with my gut on this one and give it a shot. I'll report back when I have had a chance to get some stuff knocked up in LTSpice.
     
  3. What?

    What? Well-Known Member

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    Not wanting to wait around on the book to arrive, I have a downloaded champ schematic running in LTSpice. Pretty neat stuff, just changing values here and there and probing around to see how the voltages and currents change. I'm guessing that there probably is a way to pass audio files through a schematic, but I don't know what sort of issues that might bring up, such as aliasing. Not that I think it would provide audio output very similar to what would be heard from a real circuit, but maybe it could be useful for getting some rough idea of what circuit changes might sound like. It would be neat as hell to have something like LTSpice as an audio plugin.
     
  4. What?

    What? Well-Known Member

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    Yep, it is possible to input and output .wav files.

     
  5. jchrisf

    jchrisf Well-Known Member

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    Is it free? I might have to give it a try while I am teaching myself about tube amps and circuits.
     
  6. What?

    What? Well-Known Member

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    Yep. I'm running it in Linux under Wine, so it appears to be available on all major desktop platforms too.
     
  7. What?

    What? Well-Known Member

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  8. What?

    What? Well-Known Member

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    I'll be damned. https://livespice.org/

    Apparently that does trade off more complex models for simpler ones for gaining realtime capability (accuracy traded off for speed). It might be worth checking out though.
     
    Last edited: Nov 22, 2020
  9. What?

    What? Well-Known Member

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    And this seems to be falling into the realm of JohnH's DIY Attenuator: https://hackaday.com/2018/11/20/simulating-a-speaker/

    JohnH's stuff is why I originally installed LTSpice in the first place. But I had things come up and got distracted away from tinkering with it.
     
    Last edited: Nov 22, 2020
  10. What?

    What? Well-Known Member

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    I wonder if there are good resources out there for waveshape signatures to do with guitar amps, such as specific compression and clipping patterns.
     
  11. What?

    What? Well-Known Member

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    It might be interesting here to simulate a preamp, pass some audio through it to a file, and send the output into an effects loop return of a real amp to see how close or far away it sounds to the real deal. That might help in getting a realistic grounding for expectations and limitations. If it were in the ballpark, it might be a reasonable means for estimating component value changes before actually modifying an amp.
     
  12. What?

    What? Well-Known Member

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    That was quick. The book already showed up. In the meantime, I had found some decent resources to get going with for creating components for a pot and a transformer (not included in LTSPice by default), as well as some for getting more accurate simulations. If any of you are thinking about using LTSpice for playing around with amp circuits, I would just see what a'la carte resources you can pull together first to get going with and start knocking some stuff up. This book looks like it gets pretty deep into each aspect of simulation, one at a time in lengthy fashion, and it just may end up being like the Basic Electronics book by the same author, examining each tree in depth and losing the forest. These books are written more like long instruction manuals where you're trying to memorize lots of things along the way rather than being more like a series of conversations with a knowledgeable friend where light bulbs are going off and you're seeing where to do the work along the way. So I suppose I might use it as a reference along the way of using other resources that I have found, going into depth from the book as needed.
     

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