Measuring THD
 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

 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
 21st June 2010, 02:24 AM #1 meconlen   diyAudio Member   Join Date: Apr 2010 Location: Sarasota, Fl. Measuring THD Every definition of the measurement of THD implies a sum from 1 to infinity. Unless you count the sound floor as 0 this is immediately meaningless since such a sum won't converge. Google turns up pages of people who say things like the first three or first five harmonics only. One page even said that the subharmonics were harmonics and counted from 1 being one of the subharmonics (1k with a 7k fundamental, how he chose 1k as being the first I have no idea...). When I take the output from a HP 331A and correct for the meter rage setting and the -20 dB level for full meter indication I get something that approximates the meter's reading when measuring with a fundamental of 1k at +4 dB from a HP 625A. On the other hand when I look at the corrected numbers, they are all below the sound floor, yet I can clearly see harmonics above the sound floor in the output of the 652A. Should I be converting the sound floor and distortion measurements to voltage and summing them at each harmonic? 1) When measuring THD on a spectrum analyzer how many measurements do you take? 2) How do you handle the sound floor? Do you just not count any measurement that is the sound floor? Yes, I know that THD isn't the be all and end all of sound quality, but for my purposes right now I'm playing around with the right quiescent current levels for various topologies of differential amplifier and keeping the response flat with respect to voltage is a worthy goal. Thanks -- Mike

 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         Holton Precision Audio         CSS         Dx Classic Amplifiers         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 ygg-it Solid State 1 13th June 2010 07:54 AM okapi Everything Else 18 7th June 2010 01:08 PM form109 Solid State 4 29th March 2010 10:44 PM mgm2000ro Solid State 5 1st June 2006 12:19 AM Pierre Class D 17 7th June 2005 07:18 PM

 New To Site? Need Help?

All times are GMT. The time now is 10:27 PM.