How to do IM distortion measurements? - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

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 28th May 2007, 05:33 PM   #1
diyAudio Member
 
Join Date: Mar 2007
Location: Canandaigua, NY USA
Default How to do IM distortion measurements?

Can anyone give me an overview of making IM distortion measurements to a very low level? I understand the principal, but have no idea what's commercially available, or if there's a good DIY project available. I don't have an SA, other than a sound card, and really prefer old fashioned dedicated hardware based instruments.

Regards,
Conrad
  Reply With Quote
Old 28th May 2007, 06:09 PM   #2
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
some soundcards are pretty good, Lynx Studio products are excellent but pricey

being cheap I use the US$130 Juli@ (google juli@ rmaa for IMD plots)

for higher res with a soundcard there are 2 issues that can be easily improved for simple 2 tone IMD tests

DAC/analog output inherent nonlinearity causing IMD in the test signal

you could use separate channels to create the hi/low sines and separately buffer and add them in a resistor or inverting opamp summer, any nonlinearity should just give harmonics of the sines up to the point the signals combine


ADC/input amp nonlinearity

hi pass filter could remove most of the low frequency sine, passing the hi + IMD products, reducing the low sine amplitude before going into the ADC reduces production of IMD by any nonlinearity inherent in the input


I am currently trying to push measurement resolution with the Juli@ where I'm limited by on board crosstalk - shouldn't be an issue with IMD measurement though - I'm using a US$150 Universal player to serve as source with 192/24 DVD-A test files and just using the Juli@ for ADC
  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
Alpha15a distortion measurements log cuibono Multi-Way 24 14th January 2014 02:54 AM
Geddes on distortion measurements MBK Solid State 257 19th July 2012 05:15 AM
Distortion measurements Vg Multi-Way 5 13th August 2004 11:32 AM


New To Site? Need Help?

All times are GMT. The time now is 05:03 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