# Maximum THD testing frequency **URL:** \ **Category:** QA401\ **Created:** [September 21, 2020, 9:20pm UTC](https://forum.quantasylum.com/t/maximum-thd-testing-frequency/164 "2020-09-21T21:20:57Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Stuartmp74](https://avatars.discourse-cdn.com/v4/letter/s/f19dbf/32.png) [@Stuartmp74](https://forum.quantasylum.com/u/Stuartmp74)\ **Post date:** [September 21, 2020, 9:20pm UTC](https://forum.quantasylum.com/t/maximum-thd-testing-frequency/164/1 "2020-09-21T21:20:57Z")
Hi All, I was doing some distortion testing on the weekend and was only able to take measurements up to 6.5khz Is this normal and if so why is it so low? My previous testing platform which was a Scarlett 2I4 audio interface and I unsed multi instrument as the testing software. I used to test up to 16Khz as this gave me 6 harmonics out to 97Khz. ![download_20200922_071411](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/1X/50a0fe6d0a5c7e0855c605779ef93b7d66d4041e.jpeg) Also attached is a plot of multi instrument at 15.999Khz ![20200922_111653](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/1X/908523fda12c7a24ad75ce37b2c37f2063b5a95d.jpeg) ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\ **Post date:** [September 22, 2020, 6:06am UTC](https://forum.quantasylum.com/t/maximum-thd-testing-frequency/164/2 "2020-09-22T06:06:26Z")
Hi @Stuartmp74, in the THD options, you need to set the measurement stop frequency to the highest harmonic you wish to capture (keeping Nyquist in mind) ![image](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/1X/84b5020b2f40af7efc9c6219b740b8ab1a82387a.png) ---
**Author:** ![Stuartmp74](https://avatars.discourse-cdn.com/v4/letter/s/f19dbf/32.png) [@Stuartmp74](https://forum.quantasylum.com/u/Stuartmp74)\ **Post date:** [September 22, 2020, 9:53am UTC](https://forum.quantasylum.com/t/maximum-thd-testing-frequency/164/3 "2020-09-22T09:53:54Z")
Thanks, @matt its working. I hadn’t check that context menu before. ---
**Author:** ![Stuartmp74](https://avatars.discourse-cdn.com/v4/letter/s/f19dbf/32.png) [@Stuartmp74](https://forum.quantasylum.com/u/Stuartmp74)\ **Post date:** [September 22, 2020, 9:52pm UTC](https://forum.quantasylum.com/t/maximum-thd-testing-frequency/164/4 "2020-09-22T21:52:22Z")
Hi @matt, upon further investigation it appears that the AMP THD Versus Frequency dialogue box does not allow values over 20,000 hz Am I doing something wrong again? ![20200923_074654](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/1X/cb033370f6844e665b9d5cfc9b2cab01a5c6dc3b.jpeg) I was about to change it to 95999 hz in the THD context menu as discussed previously ![20200923_074524](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/1X/172ecbb2e32e4e430fa60d8119c5b8e2c6c7eac5.jpeg) It would also be great if we could have a lower minimum increment that 1 dB ![20200923_075350](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/1X/5455c5735f734f18e536d47e8419ea4e0c3c3dfd.jpeg) ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\ **Post date:** [September 23, 2020, 3:20am UTC](https://forum.quantasylum.com/t/maximum-thd-testing-frequency/164/5 "2020-09-23T03:20:26Z")
Currently, all the plugins must assume 48K sample rate. There’s no way for a plugin to query the user sample rate that has been selected. And so, there’s no way to error check. Maybe that could be changed easily, I’ll check. I’ve entered the issue on github > > > Currently, the plugins all assume a 48K sample rate, and there are limitations applied to ensure choices can't be made that...