How to calculate intermodulation distortion ratio ?
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 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
 21st August 2011, 08:11 PM #1 pawelpl   diyAudio Member   Join Date: Jun 2011 How to calculate intermodulation distortion ratio ? As I understand IMD is measured by feeding two sine waves, f1 and f2, at different frequencies into the amplifier. On the output of the amplifier we have signal with spectrum that contain peaks on n*f1+m*f2 frequences. So, my question is how does formula to calculate IMD look like ? And how much peaks we should take into account ?
 27th August 2011, 08:23 PM #2 sycorax   diyAudio Member     Join Date: Sep 2006 Location: The North of The Netherlands I assume you are using an audio spectrum analyzer to see the spectrum. You then simply take the difference between the wanted signal and the highest peak in the unwanted signal. When you measure voltages and like to have the result in dB you use the formula: Uwanted / Uunwanted * LOG10. If you turn up the signal 1 dB and the peak you are measuring is going up 1 dB also the peak is second order distortion. If the peak is going up by 2 dB you are looking at third order distortion. __________________ DIY CD2M-PRO -> AKM4397 DAC -> Aikido pre -> GM70PP mono -> Martin Logan Vantage ESL -> Me!
 30th August 2011, 01:19 PM #3 pawelpl   diyAudio Member   Join Date: Jun 2011 Sycorax, thanks for reply. I do calculate IMD by formula below, but not sure if it is correct. IMD = sqrt( ... + AmplitudeOf(8000Hz)^2 + AmplitudeOf(9000Hz)^2 + AmplitudeOf(12000Hz)^2 + AmplitudeOf(13000Hz)^2 + ...) / sqrt(AmplitudeOf(10000Hz)^2 + AmplitudeOf(11000Hz)^2) In this example f1=10000Hz, f2=11000Hz.
 26th September 2011, 12:29 PM #4 ingenieus   diyAudio Member   Join Date: Apr 2011 Location: Pretoria Thanks. I've been looking for this answer myself. I assume that the value for "AmplitudeOf()" is in Volt.

 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 Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Aussie Amplifiers         CSS         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post halcyon Digital Line Level 70 2nd September 2017 10:03 PM tiefbassuebertr Solid State 28 30th May 2011 12:20 PM synthius Chip Amps 3 28th April 2008 05:39 AM davy_shi Power Supplies 5 20th May 2005 10:59 AM Diogo Solid State 13 4th September 2002 01:29 PM

 New To Site? Need Help?

All times are GMT. The time now is 10:32 AM.