# Improving AMP THD vs Frequency automated test results **URL:** \ **Category:** QA40x\ **Created:** [May 4, 2022, 10:16pm UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682 "2022-05-04T22:16:03Z")\ **Posts on this page:** 10\ **Page:** 2

**Author:** ![VAR](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/var/32/959_2.png) [@VAR](https://forum.quantasylum.com/u/VAR)\ **Post date:** [May 9, 2022, 4:06am UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682/22 "2022-05-09T04:06:03Z")

Thanks! I found the post and I hate to admit it, but I have never used any of the Measurements Buttons. I just select what I want with the Add measurements window. So I set it up to go from 20Hz to 40kHz with the THD measurement button, set the XLOG to the same and then ran the automated test from 20-40kHz with the THD+N box unchecked and (imaginary drum roll) it gave me the range I wanted- here is the plot: ![Douk NS-01G Prothd vs fri 5w](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/2X/9/9fdb9386256eefb13cef3e9584ec97eced22a952.jpeg) It is for a different amp, but looks fine. I also plotted the THD/SNR at 20kHz and it gave a power reading that was reasonable (forgot to see what it said the THD was though 😲). So maybe not setting the range using the THD measurement button was the problem ??? ---

**Author:** ![Moto](https://avatars.discourse-cdn.com/v4/letter/m/2bfe46/32.png) [@Moto](https://forum.quantasylum.com/u/Moto)\ **Post date:** [May 9, 2022, 3:47pm UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682/23 "2022-05-09T15:47:54Z")

Yes. The thd button menu sets the range in the input signal over which distortion is measured and the automated test menu sets the range over which the generator will generate a signal. At least that’s the way I think it works! Glad you got the results you needed. ---

**Author:** ![VAR](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/var/32/959_2.png) [@VAR](https://forum.quantasylum.com/u/VAR)\ **Post date:** [May 9, 2022, 5:01pm UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682/24 "2022-05-09T17:01:00Z")

🙂 Will see how my measurements go later today using a 4ohm load- I will pay attention to the “manual” measurement THD at 20k this time… ---

**Author:** ![VAR](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/var/32/959_2.png) [@VAR](https://forum.quantasylum.com/u/VAR)\ **Post date:** [May 11, 2022, 7:17pm UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682/25 "2022-05-11T19:17:32Z")

It’s me again. I couldn’t resist hooking the Yamaha back up and ran the THD % with all settings set from 10hz-45khz and got this plot: ![THD 20k Hann dB 10to45k by 5 span](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/2X/6/6de306f4a3a2ae207ceb22f9a307195356a4a5b2.jpeg) It looks pretty darn good compared to the \<0.01% spec! I also measured the THD at 20kHz under the same conditions and got this, which compares very close to the plot above. I found that I had to extend to 45kHz to get the %THD to be non-zero : ![THD 20k Hann dB 10to45k span](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/2X/f/f8ca4d03cbf6c0ab92ec51825b580bc5c3305713.jpeg) ---

**Author:** ![Moto](https://avatars.discourse-cdn.com/v4/letter/m/2bfe46/32.png) [@Moto](https://forum.quantasylum.com/u/Moto)\ **Post date:** [May 11, 2022, 9:26pm UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682/26 "2022-05-11T21:26:00Z")

Well you would only have one harmonic there at 40kHz. So not much to measure ---

**Author:** ![VAR](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/var/32/959_2.png) [@VAR](https://forum.quantasylum.com/u/VAR)\ **Post date:** [May 12, 2022, 2:10am UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682/27 "2022-05-12T02:10:58Z")

Indeed, but at least things are kinda what I expected- I appreciate you taking an interest! ---

**Author:** ![Moto](https://avatars.discourse-cdn.com/v4/letter/m/2bfe46/32.png) [@Moto](https://forum.quantasylum.com/u/Moto)\ **Post date:** [May 12, 2022, 3:13pm UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682/28 "2022-05-12T15:13:49Z")

Out of curiosity, what is your load resistor setup? ---

**Author:** ![VAR](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/var/32/959_2.png) [@VAR](https://forum.quantasylum.com/u/VAR)\ **Post date:** [May 12, 2022, 4:13pm UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682/29 "2022-05-12T16:13:44Z")

I would love to. I was planning on showing them in an upcoming video I was planning to do for my (small) youtube channel when I talk about using the QA402 (don’t laugh too hard 🤣). They are not “pretty” and I learned from making the 8ohm loads when I made my 4ohm loads, but I can “shoot” the load part and use it later and just post it to my cloud drive for now. Later today or tomorrow most likely. ---

**Author:** ![VAR](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/var/32/959_2.png) [@VAR](https://forum.quantasylum.com/u/VAR)\ **Post date:** [October 6, 2022, 4:20am UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682/31 "2022-10-06T04:20:44Z")

I made a new pair of loads and a new video showing one of them (they are almost identical): > **[DummyLoad.mp4](https://drive.google.com/file/d/1AUVOt3V0BjDT5sPjGki2I9H4LuAb2bg2/view?usp=sharing)** > > Google Drive file. ---

**Author:** ![RobbN](https://avatars.discourse-cdn.com/v4/letter/r/b77776/32.png) [@RobbN](https://forum.quantasylum.com/u/RobbN)\ **Post date:** [October 6, 2022, 6:01pm UTC](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682/32 "2022-10-06T18:01:29Z")

Forgive me if I’m jumping in without being fully informed here. I’m new with this software and have not fully digested all of this post. But I just wanted to note that I have run into issues with this test when averaging is turned on in the main window of the app. [Previous page](https://forum.quantasylum.com/t/improving-amp-thd-vs-frequency-automated-test-results/682.md?page=1)