Spice simulation

[Edmond Stuart]

.......................
Yes, I water cool my amps. No, I'm not willing to go cryogenic on my phono stage just to lower the noise...
...wait a minute...
Just kidding. It'd be a pain in the butt.
Still, I'd like to pick their brains over a beer. Better yet, single malt Scotch or a good wine.

Grey

Hi Grey,

As far as I can remember, Marcel van de Gevel has built a 'cryogenic' phono stage and published it in EW, some 9 years ago. Of course he didn't use liquid He, rather a negative resistance. As he is a diyaudio member, you can easily find his e-mail address and ask him for more info.

Cheers,

 

[Edmond Stuart]

............Unfortunately, I have a MAC, not a PC, ..........

Bonsai, I have BSpice on the computer in front of me. I prefer MICROCAP which is Spiced based. ................

So you prefer an early MAC version of Micro-Cap. These stone age versions were released between 1981 and 1987. For today's standards rather obsolete I think.

Cheers,

PS: Micro-Cap 9 supports: the Philips Mextram bipolar model. This is a vertical NPN or PNP bipolar model that describes velocity saturation, base widening, Kirk effect, impact ionization, and self heating effects.

 

[GK]

So you prefer an early MAC version of Micro-Cap. These stone age versions were released between 1981 and 1987. For today's standards rather obsolete I think.

Cheers,

PS: Micro-Cap 9 supports: the Philips Mextram bipolar model. This is a vertical NPN or PNP bipolar model that describes velocity saturation, base widening, Kirk effect, impact ionization, and self heating effects.

I've got the old DOS PC version of Micro-Cap and I use it a lot. Only for passive stuff though. It's a little gem and is fantastic for quickly double checking pasive filter/matching networks for RF stuff. Draws really nice and clear full screen graphs, which puts some of the modern fancy packages to shame, in this regard.

Cheers,
Glen

 

[Edmond Stuart]

I've got the old DOS PC version of Micro-Cap and I use it a lot. Only for passive stuff though. It's a little gem and is fantastic for quickly double checking pasive filter/matching networks for RF stuff. Draws really nice and clear full screen graphs, which puts some of the modern fancy packages to shame, in this regard.

Cheers,
Glen

Hi Glen,

I'm using version 8. Graphs are now almost full screen and still pretty nice. Why not using the free demo of version 9? Probably much easier than switching to DOS, unless your version runs in a DOS-box.

Cheers,

 

[ingrast]

I used Microcap for several years before finding LTSpice when joining DIY. Since I am not a sophisticated Spice user I cannot really make a comparative evaluation. Being simulators just that, I use to do a quick check for design ideas and explore alternatives before commiting to hardware.

OrCad comes to mind, and it was my staple schematics capture tool in the DOS days, played a little with the integrated capture-simulation-layout version later but found it not very friendly for casual use.

Rodolfo

 

[Bob Cordell]

I once witnessed an argument between a friend of mine who was a chemist and another chemist. It was one of those red-in-the-face, spittle-flying arguments that went nowhere once the two sides defined their positions. One of my degrees is in geology and they pump you full of chemistry along the way. I could somewhat follow the lines of the argument, and from what I knew it seemed that my friend had the upper hand, in large part because he had more hands-on experience. The other fellow was arguing from a completely theoretical viewpoint, which was fine as far as it went, but he wasn't including some things that my friend said were relevant. (It's been twenty years or more--I don't remember the finer points of the argument--something about solute deposition from an aqueous solution. Temperature was involved. Something about iron ions. I don't remember the rest.)
As for what you've designed...unless it's high end audio, I don't care. John Curl has earned my respect in this manner. Ditto for Nelson Pass and Charles Hansen. Electronics is a vast field. To assume that ability--even perhaps expertise--in another portion of electronics does not ipso facto grant you expertise in audio. There are too many quirky, weird things in audio.
Peufeu's memory distortion concept is one example. Simple, elegant, and quite reasonable, even from a theoretical point of view; doesn't require much, if any, hand-waving to see how it could apply. But does it show up in simulations? That's another matter entirely. I have no doubt that code can be written and spliced into simulation programs to cover this idea, but it hasn't happened yet.
Sooner or later simulators will address the things that matter in audio, but at this time it's still in the future.
Arrogant? No, just truthful.
It's all in attention to details. To take the superficial view that all that matters is reliability when thermal criteria are on the table is not at all helpful.

Grey

Hi Grey,

You are so very right about experience, and how it matters in a discussion or argument. What I have often seen is that the two participants have experience, but they have DIFFERENT experience. Some on this thread have a lot of audio experience, both professional and on the side, but they don't have a lot of experience with SPICE. There are others who have the SPICE experience and have little practical experience. Herein often lies the rub. Of course, there are also those who have experience in both domains, and that is very helpful.

The key thing about SPICE is that it is an extremely valuable tool, but it certainly does not do everything. But because it does not do thermal analysis and some of the more subtle things that may come up in audio certainly does not mean that it is not highly useful in audio design.

Cheers,
Bob

 

[GRollins]

Bob,
Isaac Asimov (I believe) once wrote a story about a bunch of armchair scientists who theorized and argued and wrangled and contrived towering reputations based on an incestuous system wherein they analyzed each others' learned papers.
The whole wobbling edifice came crashing down when one maverick decided to go out in the field and do original research.
In essence, the story is a subtle re-telling of The Emperor's New Clothes.
From my point of view, The Emperor's New Clothes stops just as the plot begins to thicken. What happened to the child who pointed out that the Emperor actually had no clothes? Do you really believe the story had a happy ending? My personal experience from when I was young, coupled with later book learning, agree that adults do not look kindly on children (or adults, for that matter) who deconstruct their world views. Children rebound nicely from finding out the truth about Santa Claus. Adults get nasty.
I well understand the attraction of simulations. I used to use them, myself. Then, as now, people were claiming, "Oh, sure, simulations used to be flawed...but now we've got [insert flavor of the month] and we're golden." Then, as now, there were glaring gaps and inaccuracies. Yet every month or two the cry would go out, "If you haven't tried Version XX, all your criticisms are invalid, because now we've got [you guessed it...the new flavor of the month]."
Well, no, the criticisms aren't invalid and there are quite a few of them. I hope that someday the list gets whittled down to nothing, but I'm not going to wait. I've got far too many hastily scribbled notes I need to try out.
Your point about people who simulate, people who build, and people who do both is valid within limits. One thing that disturbs me is simulator/builders who count their experience simulating as though it were experience building. "Oooh, look at me! I spent one hour building and seven hours simulating this week, so I have eight hours of experience." The not-so-subtle implication is that he is better than the fellow who spent a mere five hours building.
To put this in perspective, ask yourself this question the next time you take a seat in an airplane: Would you rather have a pilot who has 1000 hours actual flying time and 4000 hours in a flight simulator or a pilot who has 5000 hours experience actually flying?
To me the choice is clear.

Grey

 

[GRollins]

Hi Grey,

As far as I can remember, Marcel van de Gevel has built a 'cryogenic' phono stage and published it in EW, some 9 years ago. Of course he didn't use liquid He, rather a negative resistance. As he is a diyaudio member, you can easily find his e-mail address and ask him for more info.

Cheers,

You're evil. The worst possible thing you can do when I come up with one of these goofy ideas is encourage me.
I haven't taken time to think this through in detail, but I was thinking something less drastic than liquid helium. Dry ice (frozen carbon dioxide) came to mind, but that would be a logistical nuisance, so I had gotten as far as tanks of gas. That's going to be a problem, too, at least around here. (I live out in the boondocks.)
Do you happen to know Marcel van de Gevel's user name here?

Grey

 

[Edmond Stuart]

You're evil. The worst possible thing you can do when I come up with one of these goofy ideas is encourage me.
I haven't taken time to think this through in detail, but I was thinking something less drastic than liquid helium. Dry ice (frozen carbon dioxide) came to mind, but that would be a logistical nuisance, so I had gotten as far as tanks of gas. That's going to be a problem, too, at least around here. (I live out in the boondocks.)
Do you happen to know Marcel van de Gevel's user name here?
Grey

Hi Grey,

You're really lazy, aren't you. Never mind, his nick is MarcelvdG, or look at:
http://www.diyaudio.com/forums/member.php?s=&action=getinfo&userid=5881

Regarding simulator version xx.01 vs xx.02 etc., you probably missed my point. If we are dicussing the merits and flaws of simulators, it's not unreasonable to suppose that we mean today's simulators. So, if someone is complaining about missing features of a 25 years old version or so, that is totally irrelevant IMHO.



Cheers,

 

[rdf]

Could much of the difference in value perception relate to topology? Though nowhere near as experienced with Spice as most here I do use it regularly for sanity checks on simple tube circuits. In that application, generally low or no feedback, the topology can't compensate for inaccuracies in device models and 'calc errors' come shining through. The modeled distortion spectra ususally bears little resemblance to measurements, not urprising since the same device from different manufacturers rarely measure the same either. I would imagine though a high GNFB topology would swamp minor deviations from reality in device models. In that application Spice would be a much more powerful tool.

 

[Bob Cordell]

Actually it isn't "mine" ; the idea to apply this to audio comes from Gérard Perrot of Lavardin.

And it does not show up in simulations since the SPICE Gummel-Poon models don't handle non-constant temperature. You can add a function voltage source in the emitter and a RC circuit to model thermal inertia, but hFE and other stuff will not move, so it's really partial.

Still, self-heating of the output transistors is a clean and simple explanation of why amplifiers sound better with higher biasing while theory (and testing with sinewaves of constant amplitude) would predict optimal biasing at a much lower current that what your ears like.

output transistors heat -> Vbe multiplier compensates -> output transistors cool -> you now run in underbiased class B.

See Cordell's paper, for instance, he plots bias versus time after exercising the output stage a bit.

Oh yeah : http://ngspice.sourceforge.net/

Yes, the bias swings in the output stage with program changes have always been a concern to me. I never thought of it this way, but I guess you're saying that this is a good example of memory distortion.

Cheers,
Bob

 

[Bob Cordell]

Hi Bob,

The short answer would be yes, but I don't really feel like one, more of a systems/design engineer. My emphasis in school was analog design, RF and microwave design, then got pushed into digital on the job, which lead to computer architecture and custom processors.

I did a lot of board level design, then started chip design in the 90s, mostly VHDL and to gates through synthesis. If people don't believe in simulation what will they think of synthesis?

How about you?

Pete B.

I did linear ICs at Bell Labs, then research on high-speed CMOS SONET and Video ICs at Bellcore in the 80's and early '90's, then did research on linear optoelectronic IC's in Indium Phosphide after that. Now I'm a user of IC's in 10 Gbps optical fiber systems. I managed a group doing synthesis of HDTV chips for awhile, and the success rate using synthesis and Verilog simulation and test-benches was remarkably high, but at times it was a little scary having to put so much trust into the synthesizer, and I never did think that they produced circuits that were as compact and as fast as the technology could provide ... but there was just no other way when deling with such big chips. At Bellcore we were running 0.6-micron CMOS chips at 622 Mbps with custom circuit design and layout, but they were less than 50K transistors.

Cheers,
Bob

 

[jan.didden]

[snip].
To put this in perspective, ask yourself this question the next time you take a seat in an airplane: Would you rather have a pilot who has 1000 hours actual flying time and 4000 hours in a flight simulator or a pilot who has 5000 hours experience actually flying?
To me the choice is clear.

Grey

Grey,

I'm with you. I also wouldn't trust a pilot who had never done sim time to learn to react to situations he hadn't met yet.

Jan Didden

 

[Bob Cordell]

Bob,
Isaac Asimov (I believe) once wrote a story about a bunch of armchair scientists who theorized and argued and wrangled and contrived towering reputations based on an incestuous system wherein they analyzed each others' learned papers.
The whole wobbling edifice came crashing down when one maverick decided to go out in the field and do original research.
In essence, the story is a subtle re-telling of The Emperor's New Clothes.
From my point of view, The Emperor's New Clothes stops just as the plot begins to thicken. What happened to the child who pointed out that the Emperor actually had no clothes? Do you really believe the story had a happy ending? My personal experience from when I was young, coupled with later book learning, agree that adults do not look kindly on children (or adults, for that matter) who deconstruct their world views. Children rebound nicely from finding out the truth about Santa Claus. Adults get nasty.
I well understand the attraction of simulations. I used to use them, myself. Then, as now, people were claiming, "Oh, sure, simulations used to be flawed...but now we've got [insert flavor of the month] and we're golden." Then, as now, there were glaring gaps and inaccuracies. Yet every month or two the cry would go out, "If you haven't tried Version XX, all your criticisms are invalid, because now we've got [you guessed it...the new flavor of the month]."
Well, no, the criticisms aren't invalid and there are quite a few of them. I hope that someday the list gets whittled down to nothing, but I'm not going to wait. I've got far too many hastily scribbled notes I need to try out.
Your point about people who simulate, people who build, and people who do both is valid within limits. One thing that disturbs me is simulator/builders who count their experience simulating as though it were experience building. "Oooh, look at me! I spent one hour building and seven hours simulating this week, so I have eight hours of experience." The not-so-subtle implication is that he is better than the fellow who spent a mere five hours building.
To put this in perspective, ask yourself this question the next time you take a seat in an airplane: Would you rather have a pilot who has 1000 hours actual flying time and 4000 hours in a flight simulator or a pilot who has 5000 hours experience actually flying?
To me the choice is clear.

Grey

Actually, to me the very clear answer is neither. I'll take the pilot who has 1000 hours on the simulator and 4000 hours in the air.

Cheers,
Bob

 

[jan.didden]

Split second posting ....

 

[Bob Cordell]

2SC3264-2SA1295 SPICE Models

Does anybody here have SPICE models for the Sanken LAPT 2SC3264 and 2SA1295 power output devices? If so, I would deeply appreciate it if you would mail them to me at bob@cordellaudio.com.

Thanks,
Bob

 

[john curl]

Do you mean to tell me that there are no commonly available spice models for these devices?

 

[andy_c]

Do you mean to tell me that there are no commonly available spice models for these devices?

I looked for them and couldn't find them either. What's worse, vendors will sometimes supply models that are totally wrong. Examples of this are the OnSemi MJL3281A/1302A. I've documented the problems with these and fit new models to the datasheet parameters on one of my web pages.

 

[john curl]

Well, I hope this gets me off the hook! I didn't want to 'Spice' the design anyway. It already works.

 

[andy_c]

LOL! You weren't thinking of becoming one of "The SPICE Guys" were you?