music, guitars & other obsessions

Q1 Wrap-Up

Man, time flies, three months have already gone by… This quarter was a pretty productive one – I evaluated many new design tools for tube amp design, in an effort to streamline the process, as well as improving the accuracy of the simulation. While it still has some short-comings, I have managed to narrow it down to three main tools – pctube, MathCAD and TINA.

The “front-end” is based on the great pctube program by Ayumi Nakabayashi, which is responsible for building tube models, plotting characteristic charts, and some single-stage design work. TINA handles the circuit simulations, and MathCAD is used for symbolic analysis when the time comes for really digging into the math behind the simulations.

One area that still requires more work is TINA, it just does not perform as well as SIMetrix when it comes to transient analysis, so occasionally SIMetrix is still needed to tackle those “tough” simulations. Hopefully, the new release of TINA will make it converge better.

A side benefit to all this effort was the opportunity to bone up on some of the basic math and electrical engineering subjects which I have long forgotten, wish I was twenty years younger, it was so much easier then!

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4 responses

  1. Hoang Minh Duc

    Thanks for your useful information. I’m playing with pctube from Ayumi now, but it’s really hard for me to plot a pentode’s curve. And I wonder how I can derive a pentode model for C3M tube. Can you help me?

    April 30, 2013 at 6:07 pm

    • jazzbo8

      Glad you find the information useful, generating pentode models is not as straight forward as the triode. But if you follow Ayumi’s direction and use pctube.r properly, it should be no problem. You need to use the triode-connected chart as the input for the ip.cal routine, and for pentode.chara, you need to enter the following: 150,150,0,0.055,0.0125,250e3, and of course all the capacitance. Hope this helps, let me know if it works for you (or not).

      May 3, 2013 at 4:40 pm

      • Hoang Minh Duc

        Thanks, jazzbo8. I’ve made it. But when I tried the pentode model in Multisim 12, the convergence problem showed up, even with other pentode models in Ayumi’s folder . I still haven’t got time to find the cause. Have you tried his pentode models in Tina, LTspice..?

        May 11, 2013 at 12:46 am

      • jazzbo8

        Sorry to hear it did not work for you. So far, all the Ayumi’s pentode models including the C3M worked in TINA and SIMetrix. It might just be a syntax thing with Multisim. If you can send me a picture of the circuit you are trying to sim, I can try it on TINA and see if it will converge.

        May 11, 2013 at 7:27 am

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