Spice simulation - Page 5 - diyAudio
Go Back   Home > Forums > Design & Build > Software Tools

Software Tools SPICE, PCB CAD, speaker design and measurement software, calculators

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 11th May 2007, 11:26 AM   #41
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Interesting to see different John's and Bob's attitude. I am saying that it is not about age. Often we can see people 25 years old or so, with attitude of retired people
  Reply With Quote
Old 11th May 2007, 11:29 AM   #42
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Mr Walt Jung´s opinion then : ECO

(hopes the Cali Gov. is wearing a seatbelt, 60 year olds better be carefull)
__________________
The buck stops Here
  Reply With Quote
Old 11th May 2007, 11:44 AM   #43
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
A guy named Nick Carter is now designing amps for someone else......
  Reply With Quote
Old 11th May 2007, 05:29 PM   #44
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
First of all folks, I have SPICE on my computer. I have had it there for at least a decade. Before that I used an early version of MICROCAP, which I still use sometimes, when I need AC or TRANSIENT ANALYSIS.
As this power amplifier (JC-1) is the product of evolution of a circuit that I first designed 35 years ago, I am somewhat familiar with its tradeoffs, and it just isn't worth doing a SPICE simulation of it at this point. It is not a bad idea, just that I am not on someone's payroll to make the effort required.
Just this week, I spoke to Walt Jung about computer emulation. He uses LT Spice and has recommended it to me. Unfortunately, I have a MAC, not a PC, and I have yet to make this darn computer emulate the LT Spice circuit. If I show weakness here, it is in working with the computer, and making IT bark!
Anyway, Walt was telling me that the computer gave one result and the prototype gave another. Which would you choose? I was going over the hard data just last nignt which points this out, that will be published in a future issue of 'Audio Express' as a response to an LTE.
If someone out there wants to go through the time and effort to emulate the JC-1 into LT Spice and find out interesting things about it, I would be willing to send them a schematic.
Personally, I have 2 JC-1's within 2 meters of me that are not being used at the moment, that I could take to my test bench (3 meters away) and test, if I wished. I just don't wish to, in order to see if my amp can tolerate multiple ceramic caps DIRECTLY across the terminals. I don't want to drive my Porsche over a speed bump at 100 mph, either, just to see if it can do it safely. It is the same sort of reasoning.
Spice is just fine, if you are comfortable with it, but it is not the real thing, it is just an emulation. I wouldn't get too cocky about that, sonny.
  Reply With Quote
Old 11th May 2007, 05:38 PM   #45
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Absolutely. Spice is just 1st approach and prototyping is necessary. Anyway, spice saves much time!
  Reply With Quote
Old 13th May 2007, 02:35 PM   #46
andy_c is offline andy_c  United States
Banned
 
Join Date: Apr 2003
Yes, and things also became confused because there were two discussions going on before the split. Just for reference , the start of this particular one was Glen's post 1457 on this page of the thread. Strangely, if I try to link to the post directly, it goes to the wrong place - probably due to the split.

Anyway, as I mentioned earlier to Glen, I tried to connect fT to the hybrid-pi parameters, and then to the SPICE parameters that relate to it in equation 11 on this page. This was for a more complete fix of bad MJL3281A/MJL1302A models from an earlier thread that I remember you were a part of.
  Reply With Quote
Old 14th May 2007, 05:45 PM   #47
diyAudio Member
 
Join Date: Sep 2006
Quote:
Originally posted by john curl
First of all folks, I have SPICE on my computer. I have had it there for at least a decade. Before that I used an early version of MICROCAP, which I still use sometimes, when I need AC or TRANSIENT ANALYSIS.
As this power amplifier (JC-1) is the product of evolution of a circuit that I first designed 35 years ago, I am somewhat familiar with its tradeoffs, and it just isn't worth doing a SPICE simulation of it at this point. It is not a bad idea, just that I am not on someone's payroll to make the effort required.
Just this week, I spoke to Walt Jung about computer emulation. He uses LT Spice and has recommended it to me. Unfortunately, I have a MAC, not a PC, and I have yet to make this darn computer emulate the LT Spice circuit. If I show weakness here, it is in working with the computer, and making IT bark!
Anyway, Walt was telling me that the computer gave one result and the prototype gave another. Which would you choose? I was going over the hard data just last nignt which points this out, that will be published in a future issue of 'Audio Express' as a response to an LTE.
If someone out there wants to go through the time and effort to emulate the JC-1 into LT Spice and find out interesting things about it, I would be willing to send them a schematic.
Personally, I have 2 JC-1's within 2 meters of me that are not being used at the moment, that I could take to my test bench (3 meters away) and test, if I wished. I just don't wish to, in order to see if my amp can tolerate multiple ceramic caps DIRECTLY across the terminals. I don't want to drive my Porsche over a speed bump at 100 mph, either, just to see if it can do it safely. It is the same sort of reasoning.
Spice is just fine, if you are comfortable with it, but it is not the real thing, it is just an emulation. I wouldn't get too cocky about that, sonny.

Nobody's disagreeing with you, John, except where you tend to put SPICE down because you have made a reasonable choice not to use it for yourself.

You're preaching to the choir; most of "you folks" here are intelligent enough not to believe every single thing they get from a SPICE simulation. Even apart from the limitations of what is only an approximation of the real world, we still have the garbage-in, garbage out problem.

SPICE is only one of many tools, but don't put down those who use it to advantage as being too lazy or inept to protoype their design. By the same token, we will not put you down for choosing not to use it in light of your experience over the years.

Based on some of the very reasonable points you have brought up about output coils, some good SPICE experiments might show that output coils are needed less than many of us think.

Bob
  Reply With Quote
Old 14th May 2007, 06:25 PM   #48
nikwal is offline nikwal  Sweden
diyAudio Member
 
Join Date: Aug 2005
I've been using spice in different forms for many years too, from textfile dos version at school and amispice on amiga and then multisim on windows , but only as a hobby..
My experiences with spice is, sure it does'nt react exactly as in real life but often you can develop some kind of feeling that the circuit is wrong when the simulator behaves badly. And also the later multisim's are ridiculously fast to work with.
MY point was: If you've been playing with it for this long it's impossible to take it seriously, you will know how it works by feel.. and what spice's weird errors and stuff ACtually means..
My work I do to make money in this world is circuitboard repars, most often for trains, sometimes digital and sometimes analog circuits.
Sometimes I stumble upon a design that I feel is just -wrong- , I say to myself, SURE this works in therory but what a fool to acually DO it..
I visited my friend that's in some kind of high school (whatever it's called there) anyhow they were making a robot that played soccer with very advanced camera image recognition and shitloads of stuff i didn't understand, BUT then i looked at their stepper motor driver and just said, you've been having problems with the stepper driver right?? without hesitation. He was a bit surprised and said , yeah a bit , how the hell did you see that..I said naeeh I just a feeling I got when looking at thoose circuits.. hmm my point again is you got to have a sense for feeling..
  Reply With Quote
Old 15th May 2007, 02:32 PM   #49
PB2 is offline PB2  United States
diyAudio Member
 
PB2's Avatar
 
Join Date: Sep 2004
Location: North East
Blog Entries: 1
Quote:
Originally posted by john curl
Bark, Bark! SPICE is OK, but you should know its limitations and that it can sometimes be misleading.
When I was young, SPICE was only a concept, but we had specific electronic analysis programs that worked on mainframe computers, mechanical calculators, and slide rules. When we wanted to evaluate a design, we built it. I used to build them for others, at first, then I finally got to build my own designs. This was the way of the engineer of 35 years ago and more. Like the proverbial: "When I was young, I had to walk to school." often said by parents to childern, when I was young we had to actually build our own circuits in order to see how well they work, and we got used to it.
You, newbe engineers, are taught in school how to use Spice, and you can't see a world without it. You also tend to rely on it, perhaps more than is completely wise in all situations, but there is nothing wrong with using it, if you wish.
This question came up when Bob Cordell apparently was surprised that I had not made a SPICE emulation of the JC-1 power amp. I told him (in so many words) that it was not really necessary, since Parasound did it the hard way, we built it and tested it.
The SPICE scare stories are to point out that no emulation is perfect, and to keep that in mind when designing.

John,

I have done both, worked for small companies where we did a design and just built it, and large companies where major simulation efforts were done.

I'm curious, you say Parasound just builds it, which is fine many companies do this, however I'm wondering do they run the prototypes in an environmental chamber to verify/test over the intended temperature range, or beyond for life testing? Also, do they do this over the allowable line voltage range?

This is a required verification step for many military designs.

Pete B.
  Reply With Quote
Old 15th May 2007, 04:29 PM   #50
peufeu is offline peufeu  France
diyAudio Member
 
Join Date: Mar 2001
Location: Lyon, France
You know, in EE school we had a class called "Numerical analysis" which covers computer simulation of pretty much anything.

The first thing that they teach you is that you should know HOW your simulator works, so that you know WHAT you are simulating, and how much you can trust the results.

Simulations are just a way to solve equations which represent an arbitrarily chosen part of reality. And reality is always right.

Drawing a circuit in Spice and then pressing a button to get a nice curve, means nothing.

If the effects you are interested in are well represented by the models your simulator uses, and are not swamped in reality by stuff that the simulator doesn't model, then you'll get something usable. When you know what you're doing, that tends to be the case.

However, when the things you try to study are not in your models, "knowing what you're doing" can mean many things, like not running the simulation at all since you know it will be useless, or hacking subcircuits from measurements to get a better model, or running it anyway, and comparing with real measurements, and studying the interesting differences.

But don't spit on simulations. Without them, you wouldn't be sitting in front of your computer, because it could never have been designed.

Stuff that SPICE lacks :

- thermal effects (self-heating, thermal inertia, thermal runaway, influence of temperature on transistor hFE isn't well modelled)
- Gummel-Poon is full of holes, like Cbc variation with Vce, etc
- Some transistor models are really suspicious
- Doesn't model layout, ground loops, etc (Protel does signal integrity and crosstalk modelling though)
- MOSFETs and JFETs aren't very realistic
- all transistors are perfectly matched (in real life, you'll get offsets)
- etc
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Need help with Spice simulation overmind Everything Else 4 23rd December 2002 04:58 PM


New To Site? Need Help?

All times are GMT. The time now is 08:48 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2