How much distortion is too much? - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

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 2nd December 2008, 05:07 PM   #1
diyAudio Member
 
dead rat's Avatar
 
Join Date: Sep 2008
Default How much distortion is too much?

I have simulated my class d amplifier in PSPICE.

20kHz sin signal (yellow) is converted to PWM with:

Green: 400kHz triangular wave.
Red: 200kHz triangular wave.
Purple: 100kHz triangular wave.

excuse my ignorance, but how do i find out how much distortion the sine wave can take before it sounds really crappy?


I would like to know this before i spend hours bringing my amplifier into the real world.
Attached Images
File Type: jpg wave.jpg (48.1 KB, 228 views)
  Reply With Quote
Old 2nd December 2008, 05:50 PM   #2
BWRX is offline BWRX  United States
diyAudio Moderator Emeritus
 
Join Date: Jan 2005
Location: Pennsylvania
The answer to your question will depend on who you ask, but typically a good THD figure to shoot for is 0.1% or lower at reasonable power levels. How much you can tolerate depends on your ears and whether or not you're trained to listen for it. Obviously, the speaker system used will have a very large part (more so than any decent amp) in this as well.
__________________
Brian
  Reply With Quote
Old 2nd December 2008, 07:29 PM   #3
diyAudio Member
 
dead rat's Avatar
 
Join Date: Sep 2008
Is there any equation/tool i can put my faith in, to help me pick the optimal PWM frequency?

Or is this more like trial and error?
  Reply With Quote
Old 2nd December 2008, 08:09 PM   #4
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
Residual components above 20Khz are not important, they are usually ignored for THD measurement. You should focus on components below 20Khz. This requires a test frequency below 5Khz or 10Khz.
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 3rd December 2008, 08:42 AM   #5
Gyula is offline Gyula  Hungary
diyAudio Member
 
Gyula's Avatar
 
Join Date: Feb 2004
Location: Kunszentmárton, Hungary
Send a message via Yahoo to Gyula
Quote:
Residual components above 20Khz are not important, they are usually ignored for THD measurement. You should focus on components below 20Khz.
As long as your speakers are linear. But nothing is linear in reality. The sidebands around the carrier harmonics are also infinite, so they can be above the noise floor in the audible range. It depends on the carrier and the audio frequency.
  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
How to get the less distortion with BJT? dododio Solid State 24 6th September 2008 10:55 AM
Neo 8 distortion? studiotech Multi-Way 4 17th April 2005 06:22 PM
Non Linear Distortion testing - Harmonic Distortion JMB Multi-Way 0 20th July 2004 03:54 PM
op amp distortion zahlm Parts 3 15th May 2004 08:45 PM


New To Site? Need Help?

All times are GMT. The time now is 05:40 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