Circuit Simulation Tools?

Discussion in 'Shock Brother's DIY Amps' started by muswell_hillbilly, Apr 18, 2019.

  1. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    I apologize in advance if there are many threads that already cover this topic :(

    New to this forum and amp building, and without any hardware to play with, went searching for circuit simulation tools...

    Stumbled upon CircuitLab.com. Anyone have experience with it? Or some other recommendation?

    At first glance, it seems pretty cool! Was able to quickly kludge together a power supply circuit, with emphasis on the elevated heater reference I was reviewing on an earlier thread:


    amp.png



    ElevHtrCT.png

    Able to run time and frequency domain simulations. Doesn't have any tube models that I've found, so limited there. I used "ideal" diodes with a constant DC voltage source to simulate a 5Y3 rectifier tube. Have only messed around on the power supply side - curious to see how it might work on the input side, with regard to tone control simulation. But before I invest too much time, wondering if there is some other way to experiment that doesn't require a rack of components, soldering iron and a lot of time ;)

    Cheers...
     
  2. LudwigvonBirk

    LudwigvonBirk Tele-Holic

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    LTSpice is kind of quirky but with patience you can do a lot with it. If you google around you can find some good prior art you can examine and saw away on.

    RobRob's site (of course!) is a good starting point for LTSpice info.
     
  3. Phrygian77

    Phrygian77 Tele-Afflicted

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    LTspice is good. The problem is finding the good tube models. Then you also need some good transformer models.

    Sent from my HTC U Ultra using Tapatalk
     
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  4. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    OK then! Seems LTSpice needs a closer look! Thx!
     
  5. LudwigvonBirk

    LudwigvonBirk Tele-Holic

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    Good find, thanks for sharing. Free and nothing to install, gotta like that.
     
  6. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    Yeah - starts out that way, but then demo mode expires, and you have to sign-up for some level of membership. But I used it just enough to appreciate how simple it was and how quickly I could set up and simulate a circuit, so I shelled-out for the lowest membership so I could keep using it to better understand how the circuits are working, and how component value changes affect the behavior...
     
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  7. beninma

    beninma Tele-Afflicted Silver Supporter

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    LTSpice seems to do everything circuit lab does and a lot more but the UI is ancient and it has a pretty steep learning curve!
     
  8. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    I have memories of Spice syntax from using it forever ago, and vaguely remember it was anything but intuitive. Sounds like it hasn't changed! Maybe it will come back to me ;)
     
  9. robrob

    robrob Poster Extraordinaire Ad Free Member

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  10. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    Thx, Rob - I'll definitely check it out! And since I've got you on the line, a personal thank you for everything you've put together on your site! I wouldn't be anywhere near where I'm at without it as a resource! I'm hooked!
     
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  11. Asmith

    Asmith Friend of Leo's

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    I used to have a circuitlab subscription but cancelled it, its eady to use but limited. If you're looking to model valves its useless only good for solid state and if you check the forums it seems dead and as if there are no further development so its not something to be added later. I moved to ltspice, its free and you can find the good models for all kinds of devices including valves. It can do everything circuitlab and more but its a steeper learning curve but worthwhile.
     
  12. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    Thx, Asmith. I noticed the lack of any tube models with it, which is clearly a drawback for the circuits we like to model. Guess I got drawn in by the simplicity, but it's simple for a reason - it's limited ;) Another vote for LTSpice, from an ex-CirtuitLab user, no less. Sounds like the way to go. Thx!
     
  13. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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  14. Phrygian77

    Phrygian77 Tele-Afflicted

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    Those tube models on that site are old, and they're not the ones you want to use.

    Sent from my HTC U Ultra using Tapatalk
     
  15. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    Awesome - thanks! Sooo much information out there!
     
  16. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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    Could you please guide us to better ones?

    And out of curiosity: why don't I want to use the old ones?
     
  17. Phrygian77

    Phrygian77 Tele-Afflicted

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    It's been a long time since I did the research. The Koren models and those on the Duncan site are very old and don't have accurate curves, especially the screen grids. You can Google LTspice and tube models, and you should be able to find the good recent ones.

    Sent from my HTC U Ultra using Tapatalk
     
  18. Asmith

    Asmith Friend of Leo's

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    I've found this to be true from my experience. I designed and built a single ended valve amp, it predicted that the preamp had enough clean headroom to overdrive the power valve. The master volume proved otherwise, when edge of breakup occurs its still there with the MV turned down so its definitely coming from the preamp. Amp still sounds great but I'm going to open the amp up again to put in an extra clean gain stage just before the power amp beacuse I'm probably not even getting max clean output.

    The spice models did predict the voltages perfectly which made testing my amp a doddle, which is still a lot more than I could get from circuitlab. But I still need to update those koren tube models to something better.

    I have a pretty sweet idea for this amp which I want implement when I open this amp up anyway. I'm going to use ganged potentiometers and a switch to make a switchable tonetack/coupling cap. Amp is currently based on the vox top boost channel but in the flick of a switch it can be an orange AD15 preamp (with a cathode follower before the tone stack).

    Looks like I'll want a new cab though, i liked my previous orange amp a lot which had a pair of V30s in it.
     
  19. Phrygian77

    Phrygian77 Tele-Afflicted

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    I pretty sure you can find the good tube models on the diyaudio.com forum. I don't have time to search and post a direct link, but you should be able to easily find them.
     
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