Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Vacuum Tube SPICE Models
Vacuum Tube SPICE Models
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 7th March 2018, 08:37 PM   #1631
Ray Waters is offline Ray Waters  United States
diyAudio Member
 
Join Date: Nov 2010
Location: Kansas
As long as one realizes that real devices have specification tolerances that are not captured in a SPICE model, my experience is that simulation results are reasonably accurate compared to an actual circuit. Of course, datasheets suffer from the same limitation as SPICE models, in that they represent a "typical" device that may not be a perfect representation of the tube you have in front of you.

When it comes to modeling a circuit's frequency response, particularly for frequency shaping circuits like phono preamps and tone controls, I have found that different models will give different results more often than not. These difference are generally insignificant (fractions of a dB) but are noticeable nonetheless. I usually run simulations using several models if I can, and if there is general agreement among them then I consider that good enough. Occasionally I'll find that a particular model has convergence problems in a given circuit, but having other models to choose from gets around that issue most of the time.

I should probably add that I mostly design using mainstream tubes that are still in production, so the number of models I really need in my custom library is relatively small. This practice also makes it easier to keep multiple models on hand because there are lots of 12AX7 models out there, for example.

SPICE is a great tool if you understand both its limitations as well as its capabilities.
  Reply With Quote
Old 8th March 2018, 02:32 AM   #1632
khutch04 is offline khutch04
diyAudio Member
 
Join Date: Oct 2016
Thanks Ray. Your experience matches what I hoped to hear but with only the ability to compare results from published schematics to the specs of the original amps so far I was not certain what to expect. I do simulations all the time at work using LTSpice some, but generally much higher priced tools (well I guess everything is much higher priced than LTSpice since it is free, eh?!) and special purpose tools too. When I was doing semiconductor designs the process variation was built into the process model so we would do designs using the nominal models and then run a "corners" analysis and tweak the design when necessary. Some things like absolute resistor values were so variable that you used circuit tricks like building circuits that depended on resistor ratios rather than resistor values to achieve the specs. And of course if a dozen transistors could do a job 7% better than one you might well consider that to be an acceptable tradeoff!

It is a far different world when you design with tubes and I do expect that the models will vary more from real world results using these models compared to the multi-million dollar model packages I had the luxury of using and depending on back then. If the results you typically get are in the right ballpark when compared to a real circuit I have the confidence I need to proceed.

Thanks again.
  Reply With Quote
Old 8th March 2018, 03:08 AM   #1633
Ray Waters is offline Ray Waters  United States
diyAudio Member
 
Join Date: Nov 2010
Location: Kansas
Glad to be of help. BTW, I too am a degreed electrical engineer from the old days, when vacuum tube circuits were still being taught in the electronics curriculum. I sure wish that tools like SPICE had been available back then! But in retrospect, I think I'm better off having learned circuit design the hard way, since I now have an appreciation for what the tool is doing "under the hood" instead of just blindly accepting whatever output the tool creates. I still start most designs with old fashioned load line analysis before ever getting into simulation. But I can get to the finish line much quicker now than in the old days.
  Reply With Quote
Old 8th March 2018, 11:41 AM   #1634
mr2racer is offline mr2racer  United States
diyAudio Member
 
mr2racer's Avatar
 
Join Date: Jul 2009
It seems Spice has difficulties modeling transformers as well. Is that what other's have found?
__________________
Artificial intelligence is no match for natural stupidity- Red Green
  Reply With Quote
Old 9th March 2018, 03:26 PM   #1635
Ray Waters is offline Ray Waters  United States
diyAudio Member
 
Join Date: Nov 2010
Location: Kansas
I don't think LTspice has "difficulties" modeling transformers. LTspice actually makes it relatively easy to include parasitic elements (resistance and capacitance) in the inductor model. As is the case with other device models, the accuracy of the model depends on how close the model parameters are to real-world devices.

There are a lot of good tutorials on the Internet for how to model transformers; here is just one:

Transformer Model in LTSpice – Step by Step Guide

If you are looking for models of output transformers, Robert McLean produced a library that can serve as a good starting point. Here is his post containing the models:

SPICE Transformer Model Spreadsheet

And here is where he posted some transformer symbols that can be used with his models:

SPICE Transformer Model Spreadsheet

This should get you started.
  Reply With Quote
Old 9th March 2018, 10:44 PM   #1636
mr2racer is offline mr2racer  United States
diyAudio Member
 
mr2racer's Avatar
 
Join Date: Jul 2009
Thanks Ray
__________________
Artificial intelligence is no match for natural stupidity- Red Green
  Reply With Quote
Old 12th March 2018, 02:34 AM   #1637
rsheptak is offline rsheptak  United States
diyAudio Member
 
Join Date: Feb 2015
Location: Pinole, CA
Vacuum Tube SPICE Models
Default 6T9 LTSpice tube model and curves?

I have used google to look for a 6T9 LTSpice model, or barring that, curves without luck. Anyone have either?

The 6T9 is a compactron having a triode said to be a 6AV6, and a pentode identical to a 6AQ5A with a lower plate dissipation of 12 Watts. Can I use their models? or their curves? to approximate models for the triode and pentode sections of the 6T9. Assuming the curves, how do I do that?

I've found both Norman Koren's matlab tools and Teodoro Marinucci's Excel spreadsheet both of which generate LTSpice model files, but never used either before. Koren's script seems to generate a partial model to which you must hand add other parts.

Thanks for any suggestions.

rus
  Reply With Quote
Old 13th March 2018, 04:33 PM   #1638
jazbo8 is offline jazbo8
diyAudio Moderator
 
jazbo8's Avatar
 
Join Date: Jan 2011
Location: In Transient
Vacuum Tube SPICE Models
Quote:
Originally Posted by rsheptak View Post
The 6T9 is a compactron having a triode said to be a 6AV6, and a pentode identical to a 6AQ5A with a lower plate dissipation of 12 Watts. Can I use their models? or their curves?
Yes, they should be good enough.
  Reply With Quote
Old 14th March 2018, 07:56 PM   #1639
rsheptak is offline rsheptak  United States
diyAudio Member
 
Join Date: Feb 2015
Location: Pinole, CA
Vacuum Tube SPICE Models
Thanks Jazbo8!

rus
  Reply With Quote
Old 24th March 2018, 09:08 AM   #1640
kokoriantz is offline kokoriantz  Lebanon
diyAudio Member
 
Join Date: Dec 2015
Location: south east asia
Is there any spice model for 6AR8 or 6LE8?
  Reply With Quote

Reply


Vacuum Tube SPICE ModelsHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Vacuum tubes SPICE models, another way Dominique_free Software Tools 2 12th November 2013 06:26 PM
Tube spice models nhuwar Tubes / Valves 45 25th November 2011 08:47 AM
Computer program for tube curves and Spice models Jim Tonne Software Tools 9 21st November 2010 10:10 AM
Got my tube spice models, and tubed CD player page back on the air wa2ise Tubes / Valves 2 20th April 2008 11:07 PM


New To Site? Need Help?

All times are GMT. The time now is 07:07 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki