# QA45x **URL:** https://forum.quantasylum.com/c/qa45x/8.md [Latest](https://forum.quantasylum.com/latest.md) · [Categories](https://forum.quantasylum.com/categories.md) --- ## [About the QA45x category](https://forum.quantasylum.com/t/about-the-qa45x-category/17)
**Author:** [@matt](https://forum.quantasylum.com/u/matt)\ **Replies:** 0
Discussion related to the QA450 and QA451 Programmable Load. --- ## [QA451 replacement model... ETA?](https://forum.quantasylum.com/t/qa451-replacement-model-eta/2294)
**Author:** [@Queequeg](https://forum.quantasylum.com/u/Queequeg)\ **Replies:** 1\ **Last updated:** [June 5, 2026, 12:58pm UTC](https://forum.quantasylum.com/t/qa451-replacement-model-eta/2294 "2026-06-05T12:58:02Z")
Hello QA team! Is there any update on the replacement/successor for the QA451? Many thanks! --- ## [QA451B issue with external loads](https://forum.quantasylum.com/t/qa451b-issue-with-external-loads/2171)
**Author:** [@Mudjock](https://forum.quantasylum.com/u/Mudjock)\ **Replies:** 20\ **Last updated:** [February 26, 2026, 10:41pm UTC](https://forum.quantasylum.com/t/qa451b-issue-with-external-loads/2171 "2026-02-26T22:41:08Z")
I’ve used the QA403 with the QA451B for several years, measuring a wide range of receivers, amplifiers, and amplifier boards including car/mobile audio, home audio, diy, vintage, etc… and have generally found the capabil… --- ## [Feature request - Switching out 12dB attenuation](https://forum.quantasylum.com/t/feature-request-switching-out-12db-attenuation/2042)
**Author:** [@rmod](https://forum.quantasylum.com/u/rmod)\ **Replies:** 1\ **Last updated:** [September 15, 2025, 9:52pm UTC](https://forum.quantasylum.com/t/feature-request-switching-out-12db-attenuation/2042 "2025-09-15T21:52:36Z")
Just noticed that you are making the QA451 end-of-life. If you do introduce an updated version, I would like to suggest adding the ability to turn off the 12 dB attenuation so that the unit is unity gain or as close to t… --- ## [Received QA451B today and V1.44 wants to downgrade the firmware](https://forum.quantasylum.com/t/received-qa451b-today-and-v1-44-wants-to-downgrade-the-firmware/1783)
**Author:** [@jaymz168](https://forum.quantasylum.com/u/jaymz168)\ **Replies:** 1\ **Last updated:** [March 28, 2025, 8:37pm UTC](https://forum.quantasylum.com/t/received-qa451b-today-and-v1-44-wants-to-downgrade-the-firmware/1783 "2025-03-28T20:37:37Z")
Hi, glad to see that the 451B is back in production and in stock. I just received mine from Saelig and it seems that the 1.44 software wants to downgrade the firmware. The popup says that the current firmware is 39 and… --- ## [QA451 not recognized anymore after initial starting](https://forum.quantasylum.com/t/qa451-not-recognized-anymore-after-initial-starting/1221)
**Author:** [@WinneProAudio](https://forum.quantasylum.com/u/WinneProAudio)\ **Replies:** 13\ **Last updated:** [January 17, 2025, 1:29am UTC](https://forum.quantasylum.com/t/qa451-not-recognized-anymore-after-initial-starting/1221 "2025-01-17T01:29:09Z")
I checked out our new and first QA System. After a lot of succesfully tests with the 403 I decided to check the 451 as well. The first startup shows a firmware update needed and I startetd it. After that a short message,… --- ## [Help with special dummy load from the 70's to work with QA products](https://forum.quantasylum.com/t/help-with-special-dummy-load-from-the-70s-to-work-with-qa-products/1656)
**Author:** [@TouchSpark](https://forum.quantasylum.com/u/TouchSpark)\ **Replies:** 7\ **Last updated:** [December 21, 2024, 1:15am UTC](https://forum.quantasylum.com/t/help-with-special-dummy-load-from-the-70s-to-work-with-qa-products/1656 "2024-12-21T01:15:51Z")
Hello all I am new to the forum and am going to be joining the QA family soon but I wanted to see if some of the super smart folks here can help me with a “Dummy Load” question, Yes I know not another dummy load question… --- ## [QA450 - "box must be reset?"](https://forum.quantasylum.com/t/qa450-box-must-be-reset/1492)
**Author:** [@Paul](https://forum.quantasylum.com/u/Paul)\ **Replies:** 3\ **Last updated:** [July 24, 2024, 1:46am UTC](https://forum.quantasylum.com/t/qa450-box-must-be-reset/1492 "2024-07-24T01:46:07Z")
Hi, I finally got around to trying out my QA450 that I bought in 2020. I’ve been using the QA401 and it is great, but this was my first time taking the QA450 out of the box. I hooked it up to everything, and was runni… --- ## [QA451 causing incorrect THD measurement](https://forum.quantasylum.com/t/qa451-causing-incorrect-thd-measurement/1236)
**Author:** [@Bartosz](https://forum.quantasylum.com/u/Bartosz)\ **Replies:** 6\ **Last updated:** [February 13, 2024, 5:22pm UTC](https://forum.quantasylum.com/t/qa451-causing-incorrect-thd-measurement/1236 "2024-02-13T17:22:40Z")
Dear @matt and anyone else who is able to assist. I have previously posted in this forum asking questions about the QA403. I am currently using the QA403 and QA451B to measure an amplifier I am building. My setup is sh… --- ## [Introducing the QA451](https://forum.quantasylum.com/t/introducing-the-qa451/139)
**Author:** [@matt](https://forum.quantasylum.com/u/matt)\ **Replies:** 1\ **Last updated:** [May 12, 2023, 6:18pm UTC](https://forum.quantasylum.com/t/introducing-the-qa451/139 "2023-05-12T18:18:13Z")
--- ## [QA450 U3/U4 BoM](https://forum.quantasylum.com/t/qa450-u3-u4-bom/238)
**Author:** [@SABristol](https://forum.quantasylum.com/u/SABristol)\ **Replies:** 6\ **Last updated:** [January 25, 2021, 2:23pm UTC](https://forum.quantasylum.com/t/qa450-u3-u4-bom/238 "2021-01-25T14:23:32Z")
On my QA450 (pcb RevI) I’ve blown and needed to replace one of the power resistors on a couple of occasions. I’ll quite happily take some advice on best FFT / sample rate to avoid this when running the THD v.s. Output P… --- ## [Lower than expected amplifier power measurements?](https://forum.quantasylum.com/t/lower-than-expected-amplifier-power-measurements/172)
**Author:** [@rasykora](https://forum.quantasylum.com/u/rasykora)\ **Replies:** 5\ **Last updated:** [October 2, 2020, 11:51pm UTC](https://forum.quantasylum.com/t/lower-than-expected-amplifier-power-measurements/172 "2020-10-02T23:51:58Z")
Using my new QA401/QA451 to measure THD+N vs Power for several amplifiers. The results have all shown much lower power than expected for the rated amplifier’s output. Have measured 2 Class D and 2 Class AB amplifiers. … --- ## [QA450 Frequency Response](https://forum.quantasylum.com/t/qa450-frequency-response/72)
**Author:** [@SimonA](https://forum.quantasylum.com/u/SimonA)\ **Replies:** 4\ **Last updated:** [May 4, 2020, 6:54pm UTC](https://forum.quantasylum.com/t/qa450-frequency-response/72 "2020-05-04T18:54:07Z")
Hi, I’m using the QA450 with a QA401 analyser to test an A/B power amplifier and the frequency response is down around 1.5dB at 20kHz. I’ve been assuming it’s the amp but I just ran the same test replacing the 450 with …