THD vs output power in LTspice - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 1st July 2011, 07:04 PM   #1
Banned
 
Join Date: Jan 2005
Default THD vs output power in LTspice

Is it possible to do a THD vs output power graph in LTspice in any way ?

Anyone knows ?
  Reply With Quote
Old 1st July 2011, 07:45 PM   #2
diyAudio Member
 
Join Date: Oct 2004
Location: Denmark
Quote:
Originally Posted by Tekko View Post
Is it possible to do a THD vs output power graph in LTspice in any way ?

Anyone knows ?
I would like to know about that as well.
  Reply With Quote
Old 2nd July 2011, 01:09 AM   #3
djoffe is offline djoffe  United States
diyAudio Member
 
Join Date: Oct 2008
Default Not a graph, but a start

Here's a file...maybe you've already done this, in which case, my apology for the redundancy. A typical kind of amp, and I sweep the drive level. If you look in the Spice error log file (view=>spice error log), you see the output distortion.

I know you wanted a graph, but maybe this is a useful stop along the way.

unzip the model file and the .asc file into the same directory, and run the test case.
Attached Files
File Type: zip THD Measurement Sample.zip (4.9 KB, 95 views)
  Reply With Quote
Old 5th July 2011, 02:21 AM   #4
djoffe is offline djoffe  United States
diyAudio Member
 
Join Date: Oct 2008
Default Here's that Graph!

The enclosed zip file contains a pdf file that describes what's going on in the enclosed LTSpice files.

In a nutshell, it lets you make plots of THD versus input level in LTSpice.

Given this example, you could probably also do THD plots versus frequency, but I haven't tested that. I thought I'd get feedback on the original question first before continuing.

I hope this is useful, and clearly enough documented to be understandaable. Feedback is appreciated.

Dan
Attached Files
File Type: zip distortion versus level distribution.zip (281.9 KB, 113 views)
  Reply With Quote
Old 5th July 2011, 09:49 AM   #5
MiiB is offline MiiB  Denmark
diyAudio Member
 
Join Date: May 2005
Location: Denmark
nice thanks....
  Reply With Quote
Old 5th July 2011, 11:09 AM   #6
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

In bob cordell's book he specifically uses LTSpice for distortion simulations.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
  Reply With Quote
Old 5th July 2011, 11:51 AM   #7
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Albany , NY (smallbany)
Quote:
Originally Posted by djoffe View Post
The enclosed zip file contains a pdf file that describes what's going on in the enclosed LTSpice files.

In a nutshell, it lets you make plots of THD versus input level in LTSpice.

Given this example, you could probably also do THD plots versus frequency, but I haven't tested that. I thought I'd get feedback on the original question first before continuing.

I hope this is useful, and clearly enough documented to be understandaable. Feedback is appreciated.

Dan
It is understandable , but the subcircuit part of it would be problematic to implement with a much larger circuit. It is redundant. thanks for the idea ... I don't know to what level I will abuse it yet.

I have the level stepped and can see both my fourier and error log total THD , therefore I can see the data I need (below 1). It would be a lot of work just to get a handy (level vs. THD graph). It seems a shame , as I have the total THD data stepped in the log , that it could not be directly plotted out versus the stepped levels.

OS


The FFT with multiple steps shows the progression of H2 -9 as output increases , which is still quite useful.
Attached Images
File Type: gif THD.gif (42.4 KB, 233 views)
__________________
Mongrel website , always current and updated :
http://www.fidelityforce.com/ostripper
  Reply With Quote
Old 4th January 2012, 01:40 PM   #8
diyAudio Member
 
Join Date: Feb 2008
Location: Denver, CO
One more link to solution LTSPICE THD Analyzer
__________________
Audio Perfection
  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
LTSpice way too high input sine wave THD Neutrality Software Tools 8 17th May 2011 02:53 AM
LTspice model for Dynaco A470 Output Transfomer Ray Waters Tubes / Valves 5 17th February 2011 03:33 PM
THD in LTSpice ? Tekko Solid State 74 30th November 2010 01:37 PM
OT: how can I measure THD of my amplifier if my sound card is 0,02% THD ? ygg-it Solid State 1 13th June 2010 07:54 AM
LTspice tool for power amp power supply component evaluation andy_c Software Tools 2 23rd August 2009 05:10 PM


New To Site? Need Help?

All times are GMT. The time now is 12:00 PM.


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