# QA450 U3/U4 BoM **URL:** \ **Category:** QA45x\ **Created:** [January 19, 2021, 10:58pm UTC](https://forum.quantasylum.com/t/qa450-u3-u4-bom/238 "2021-01-19T22:58:10Z")\ **Posts on this page:** 1\ **Showing post:** 4
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\ **Post date:** [January 20, 2021, 4:41pm UTC](https://forum.quantasylum.com/t/qa450-u3-u4-bom/238/4 "2021-01-20T16:41:00Z")
Hi @SABristol, yes, as long as your power is under 200W, you can trip the QA450 as much as you like it should fully self protect no matter how long the FFTs are. Are you saying that at 80W you experienced a burned up load resistor? The link below looks at FFT size versus THD. Take a look at the video at the end of the post to see the fast testing–55 points in 6 seconds. > [@FFT Sizes with the QA401 & QA450](https://forum.quantasylum.com/t/fft-sizes-with-the-qa401-qa450/124): > > The QA450 is designed for really fast burst testing of amplifiers. Because of its size, the QA450 can handle an average power of 5-10 watts, and a peak power of 200W or so. The QA450 is NOT the tool you want if your aim is a load that can soak up lots of power while you tune in real time. The manual goes into a lot of detail on the power levels and time durations for testing. A lot of engineers like to use really long FFTs for their measurements. But beyond a certain point, there’s not much to … --- _[View the full topic](https://forum.quantasylum.com/t/qa450-u3-u4-bom/238)._