# Latest **URL:** https://forum.quantasylum.com/latest.md?page=2 [Latest](https://forum.quantasylum.com/latest.md) · [Categories](https://forum.quantasylum.com/categories.md) **Page:** 3 --- ## [Input bandwidth and display settings](https://forum.quantasylum.com/t/input-bandwidth-and-display-settings/2241)
**Author:** [@ruffrecords](https://forum.quantasylum.com/u/ruffrecords)\ **Replies:** 3\ **Last updated:** [March 11, 2026, 12:13pm UTC](https://forum.quantasylum.com/t/input-bandwidth-and-display-settings/2241 "2026-03-11T12:13:03Z")
I am considering buying a QA403 but I have a couple of questions I cannot seem to find an answer to. First does the input bandwidth follow the sample rate. In other words at 192KHz sample rate can I measure signal up to… --- ## [Testing an audio compressor](https://forum.quantasylum.com/t/testing-an-audio-compressor/2231)
**Author:** [@skipburrows](https://forum.quantasylum.com/u/skipburrows)\ **Replies:** 3\ **Last updated:** [March 7, 2026, 3:33pm UTC](https://forum.quantasylum.com/t/testing-an-audio-compressor/2231 "2026-03-07T15:33:12Z")
Hey all… I’m currently in development of a new audio compressor. I’ve been tuning the attack and release time mostly by ear. However now that I think it’s sounding nice I’d really like to dig in and try and get the actu… --- ## [QA403 Availability](https://forum.quantasylum.com/t/qa403-availability/2235)
**Author:** [@ReALab](https://forum.quantasylum.com/u/ReALab)\ **Replies:** 1\ **Last updated:** [March 5, 2026, 11:46pm UTC](https://forum.quantasylum.com/t/qa403-availability/2235 "2026-03-05T23:46:33Z")
When can we expect to find the QA403 or its replacement available? --- ## [My custom Q403 case](https://forum.quantasylum.com/t/my-custom-q403-case/2232)
**Author:** [@skipburrows](https://forum.quantasylum.com/u/skipburrows)\ **Replies:** 4\ **Last updated:** [March 5, 2026, 4:32pm UTC](https://forum.quantasylum.com/t/my-custom-q403-case/2232 "2026-03-05T16:32:37Z")
Hey all. I finished my custom Q403 case. I have 2 outputs and inputs per channel for added flexibility. I also took the +side of each input and “Y’ed” to b&c connectors so you can put a scope from the DUT. Works well. … --- ## [BUG on QA403x Release 1.222](https://forum.quantasylum.com/t/bug-on-qa403x-release-1-222/2213)
**Author:** [@YvesLegault](https://forum.quantasylum.com/u/YvesLegault)\ **Replies:** 5\ **Last updated:** [March 4, 2026, 1:31pm UTC](https://forum.quantasylum.com/t/bug-on-qa403x-release-1-222/2213 "2026-03-04T13:31:36Z")
In the “dBV” menu, “External Gain” section… The two “ZERO” buttons and the “+6 dB” button are inserting a “.” instead of a “,” as a decimal separator when used, causing a red error message to display. I am running the … --- ## [Adding a switch to the 403](https://forum.quantasylum.com/t/adding-a-switch-to-the-403/2227)
**Author:** [@peppermint](https://forum.quantasylum.com/u/peppermint)\ **Replies:** 13\ **Last updated:** [March 3, 2026, 1:20am UTC](https://forum.quantasylum.com/t/adding-a-switch-to-the-403/2227 "2026-03-03T01:20:43Z")
It drives me absolutely crazy that I have to plug and unplug the USB cable every time I need to use the 403. Quite frankly, adding a simple switch would cost next to nothing. It could even be at the back of the unit, nex… --- ## [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… --- ## [Verifying Calibration Automatically](https://forum.quantasylum.com/t/verifying-calibration-automatically/2153)
**Author:** [@matt](https://forum.quantasylum.com/u/matt)\ **Replies:** 9\ **Last updated:** [February 26, 2026, 10:06pm UTC](https://forum.quantasylum.com/t/verifying-calibration-automatically/2153 "2026-02-26T22:06:14Z")
Release 1.221 is up HERE This release has a new feature that is discussed HERE This allows you to generate a calibration report for your QA40x hardware if you have a recently calibration 6.5 digit DVM. You really do ne… --- ## [Measuring noise](https://forum.quantasylum.com/t/measuring-noise/53)
**Author:** [@handsome](https://forum.quantasylum.com/u/handsome)\ **Replies:** 7\ **Last updated:** [February 21, 2026, 9:48am UTC](https://forum.quantasylum.com/t/measuring-noise/53 "2026-02-21T09:48:27Z")
HI there, I am thoroughly enjoying using my QA401 - great hardware! I would like to know what are the best parameters for measuring/quantifying amplifier noise? I prefer unweighted measurements and use a 20-20 000Hz b… --- ## [1.920 THD is \> THD+N](https://forum.quantasylum.com/t/1-920-thd-is-thd-n/550)
**Author:** [@mhuth1776](https://forum.quantasylum.com/u/mhuth1776)\ **Replies:** 24\ **Last updated:** [February 21, 2026, 3:28am UTC](https://forum.quantasylum.com/t/1-920-thd-is-thd-n/550 "2026-02-21T03:28:19Z")
Notice that the THD is shown as -89.8 dB while the THD+N is shown as -91.9 dB. When the frequency is raised a bit, then the anomaly goes away. --- ## [What is maximum frequenz range for a frequency response measurement with the QA403](https://forum.quantasylum.com/t/what-is-maximum-frequenz-range-for-a-frequency-response-measurement-with-the-qa403/2225)
**Author:** [@Diskus](https://forum.quantasylum.com/u/Diskus)\ **Replies:** 2\ **Last updated:** [February 20, 2026, 11:26am UTC](https://forum.quantasylum.com/t/what-is-maximum-frequenz-range-for-a-frequency-response-measurement-with-the-qa403/2225 "2026-02-20T11:26:04Z")
Good morning, What is the limit for a correct measurement? Is it correct by 200 kHz? Greetings from Germany --- ## [Question regarding measuring filterless class D amp](https://forum.quantasylum.com/t/question-regarding-measuring-filterless-class-d-amp/2203)
**Author:** [@Gruesome](https://forum.quantasylum.com/u/Gruesome)\ **Replies:** 28\ **Last updated:** [February 18, 2026, 7:41pm UTC](https://forum.quantasylum.com/t/question-regarding-measuring-filterless-class-d-amp/2203 "2026-02-18T19:41:21Z")
I’m just getting started using the QA403. After getting some pretty bad (multi-%) intermodulation results measuring a tube amp that otherwise seems not so bad, I thought I measure my ‘good amp’ for reference, a Loxjie A3… --- ## [Issues with high frequency measurements](https://forum.quantasylum.com/t/issues-with-high-frequency-measurements/2056)
**Author:** [@skipburrows](https://forum.quantasylum.com/u/skipburrows)\ **Replies:** 3\ **Last updated:** [February 18, 2026, 6:01am UTC](https://forum.quantasylum.com/t/issues-with-high-frequency-measurements/2056 "2026-02-18T06:01:03Z")
Hi all… Been awhile.. As TSA just dropped my Audio precision for the 2nd time!! I’m really trying to use my Q403 for travel analytics. Having an issue with higher frequency measurements. As shown in fig 1 you can see … --- ## [Two question about 403](https://forum.quantasylum.com/t/two-question-about-403/2216)
**Author:** [@walge](https://forum.quantasylum.com/u/walge)\ **Replies:** 0\ **Last updated:** [February 17, 2026, 4:36pm UTC](https://forum.quantasylum.com/t/two-question-about-403/2216 "2026-02-17T16:36:03Z")
HI with 403x sw is it possible to do a plot, p.e. of frequency , and then do another plot leaving the previous one on screen? Same as AP do. Second question, there is a trick to undertstand if one value of Vin on 403 i… --- ## [Help with 60hz noise](https://forum.quantasylum.com/t/help-with-60hz-noise/2108)
**Author:** [@skipburrows](https://forum.quantasylum.com/u/skipburrows)\ **Replies:** 30\ **Last updated:** [February 16, 2026, 4:13pm UTC](https://forum.quantasylum.com/t/help-with-60hz-noise/2108 "2026-02-16T16:13:58Z")
Hey all… As I’m really really trying to use the 403 in place of my old Audio precision however I’m having an issue.. See fig 1.this is the 403 balanced with outputs to inputs. Notice 60hz at -80. This is with the lapto… --- ## [Windows Computer needs - Memory, etc](https://forum.quantasylum.com/t/windows-computer-needs-memory-etc/2212)
**Author:** [@Aleph5](https://forum.quantasylum.com/u/Aleph5)\ **Replies:** 11\ **Last updated:** [February 12, 2026, 8:24pm UTC](https://forum.quantasylum.com/t/windows-computer-needs-memory-etc/2212 "2026-02-12T20:24:34Z")
As a non-PC person (Mac), it looks like the best bet to get my QA403 properly running is to buy a Windows laptop. A refurb such as one from Dell can cost under $200, but is there anything I would want in terms of memory,… --- ## [Frequency Response issues in a QA403. (edit: Be careful to turn off Weighting)](https://forum.quantasylum.com/t/frequency-response-issues-in-a-qa403-edit-be-careful-to-turn-off-weighting/2129)
**Author:** [@squasher](https://forum.quantasylum.com/u/squasher)\ **Replies:** 10\ **Last updated:** [February 12, 2026, 8:03pm UTC](https://forum.quantasylum.com/t/frequency-response-issues-in-a-qa403-edit-be-careful-to-turn-off-weighting/2129 "2026-02-12T20:03:28Z")
I’m trying to measure the Frequency Response (FR) of a moving coil SUT (step-up transformer) and think I’m hitting some limitations in the QA40x app’s Frequency Response tool. Even though I’ve attempted to extend the ap… --- ## [Shipping costs to germany/europe?](https://forum.quantasylum.com/t/shipping-costs-to-germany-europe/2143)
**Author:** [@Calvin](https://forum.quantasylum.com/u/Calvin)\ **Replies:** 12\ **Last updated:** [February 8, 2026, 4:43pm UTC](https://forum.quantasylum.com/t/shipping-costs-to-germany-europe/2143 "2026-02-08T16:43:15Z")
Hi, I assume that the total costs of a QA403 will be 599$ plus shipping fee plus taxes. Can anyone estimate how much the shipping plus taxes, resp. the overall sum will be? Can I get a invoice stating the correct sum … --- ## [QA40x Plot: linear graphic?](https://forum.quantasylum.com/t/qa40x-plot-linear-graphic/2204)
**Author:** [@Alfredo1958](https://forum.quantasylum.com/u/Alfredo1958)\ **Replies:** 4\ **Last updated:** [February 6, 2026, 8:25pm UTC](https://forum.quantasylum.com/t/qa40x-plot-linear-graphic/2204 "2026-02-06T20:25:04Z")
Hello everyone. My name is Alfredo Di Pietro and I’m an Italian audio reviewer. I own a Quantasylum QA403, I’m very happy with it, and I use it with both QA40x and QA40x Plot software. Regarding the latter, I’m very sorr… --- ## [QA40x software question: plotting individual harmonics](https://forum.quantasylum.com/t/qa40x-software-question-plotting-individual-harmonics/2196)
**Author:** [@Gruesome](https://forum.quantasylum.com/u/Gruesome)\ **Replies:** 3\ **Last updated:** [February 6, 2026, 12:33am UTC](https://forum.quantasylum.com/t/qa40x-software-question-plotting-individual-harmonics/2196 "2026-02-06T00:33:52Z")
I’m just getting started with using the QA403 and associated software. In QA40xPlot it is pretty straightforward to select which harmonics to plot in a distortion versus frequency graph. I’ve looked through the QA40x ma… --- ## [QA403 user manual](https://forum.quantasylum.com/t/qa403-user-manual/2200)
**Author:** [@Ecul](https://forum.quantasylum.com/u/Ecul)\ **Replies:** 1\ **Last updated:** [February 5, 2026, 4:28am UTC](https://forum.quantasylum.com/t/qa403-user-manual/2200 "2026-02-05T04:28:08Z")
Is there a formal user manual for QA403? I see the getting started guide but I dont see a formal manual. I am new at this I would like to better understand how to use this tool at the maximum potential. E --- ## [Weighting for wow and flutter](https://forum.quantasylum.com/t/weighting-for-wow-and-flutter/1536)
**Author:** [@tomatillo](https://forum.quantasylum.com/u/tomatillo)\ **Replies:** 2\ **Last updated:** [February 4, 2026, 7:19pm UTC](https://forum.quantasylum.com/t/weighting-for-wow-and-flutter/1536 "2026-02-04T19:19:22Z")
Im new to using the Qa403 for testing amps. I saw it has a visualizer for wow and flutter. I was wondering how to set it up for NAB, JIS, CCIR, or DIN weighting? It would be cool if there could someday be a checkbox to s… --- ## [Need help with geophones and qa472](https://forum.quantasylum.com/t/need-help-with-geophones-and-qa472/2149)
**Author:** [@Nash](https://forum.quantasylum.com/u/Nash)\ **Replies:** 1\ **Last updated:** [February 3, 2026, 4:52pm UTC](https://forum.quantasylum.com/t/need-help-with-geophones-and-qa472/2149 "2026-02-03T16:52:51Z")
Hi, I know nothing about audio or electronics and have been one of those people relying on chatgpt to try to do something above their pay grade. Tldr: Can a two-lead geophone work with pre2 of the qa472 preamp at all? I… --- ## [RIAAA test with 403](https://forum.quantasylum.com/t/riaaa-test-with-403/2176)
**Author:** [@walge](https://forum.quantasylum.com/u/walge)\ **Replies:** 14\ **Last updated:** [February 2, 2026, 10:27pm UTC](https://forum.quantasylum.com/t/riaaa-test-with-403/2176 "2026-02-02T22:27:15Z")
Hi I ma byìuying a 403 stuff. There is a way to have a file with a RIAA file? With the right curve? I have a AP with a file that is a perfect RIAA curve. Thanks WAlter --- ## [Mirror the input to pc](https://forum.quantasylum.com/t/mirror-the-input-to-pc/1816)
**Author:** [@skipburrows](https://forum.quantasylum.com/u/skipburrows)\ **Replies:** 3\ **Last updated:** [February 2, 2026, 8:45am UTC](https://forum.quantasylum.com/t/mirror-the-input-to-pc/1816 "2026-02-02T08:45:06Z")
Good day all… I was wondering if anyone has figured out a way to get to input of the 403 to be mirrored on the pc speakers? I’m so used to the audio precision and have really gotten used to the audio cue for bench work.… --- ## [What is wrong with the THD calculation with ext. Generator](https://forum.quantasylum.com/t/what-is-wrong-with-the-thd-calculation-with-ext-generator/2174)
**Author:** [@Sven](https://forum.quantasylum.com/u/Sven)\ **Replies:** 15\ **Last updated:** [January 30, 2026, 2:28pm UTC](https://forum.quantasylum.com/t/what-is-wrong-with-the-thd-calculation-with-ext-generator/2174 "2026-01-30T14:28:51Z")
Attached a screenshot with questionable THD calculation when using an external generator. Software Version 1.220 --- ## [Automated test AMP THD versus frequency](https://forum.quantasylum.com/t/automated-test-amp-thd-versus-frequency/2125)
**Author:** [@Gerrittube](https://forum.quantasylum.com/u/Gerrittube)\ **Replies:** 3\ **Last updated:** [January 30, 2026, 12:38pm UTC](https://forum.quantasylum.com/t/automated-test-amp-thd-versus-frequency/2125 "2026-01-30T12:38:48Z")
With it’s default setting I get this error. What’s happening here, what should I do? --- ## [Has the QA403 output out-of-band residual signals?](https://forum.quantasylum.com/t/has-the-qa403-output-out-of-band-residual-signals/1785)
**Author:** [@Sven](https://forum.quantasylum.com/u/Sven)\ **Replies:** 44\ **Last updated:** [January 29, 2026, 3:02pm UTC](https://forum.quantasylum.com/t/has-the-qa403-output-out-of-band-residual-signals/1785 "2026-01-29T15:02:55Z")
Found that my soundcards Creative E-MU 0204 and Tracker Pre emit residual waves in a out-of-band frequency region, around 100 kHz and higher. Since I work also with analog measurement instruments which go up to 1 MHz ban… --- ## [Is my QA403 Broken?](https://forum.quantasylum.com/t/is-my-qa403-broken/2181)
**Author:** [@Bimmer](https://forum.quantasylum.com/u/Bimmer)\ **Replies:** 3\ **Last updated:** [January 29, 2026, 2:39pm UTC](https://forum.quantasylum.com/t/is-my-qa403-broken/2181 "2026-01-29T14:39:16Z")
Hello Forum Last week, during the regular day work, something happend to the QA403. Looks like the inputs and outputs are disconnected and the hardware is generating 150Hz signal and mearusing itself only on right chann… --- ## [Measure frequency response of digital stethoscopes](https://forum.quantasylum.com/t/measure-frequency-response-of-digital-stethoscopes/1437)
**Author:** [@dangieschen](https://forum.quantasylum.com/u/dangieschen)\ **Replies:** 5\ **Last updated:** [January 29, 2026, 2:15pm UTC](https://forum.quantasylum.com/t/measure-frequency-response-of-digital-stethoscopes/1437 "2026-01-29T14:15:53Z")
Hi, I’m a partner in a Telehealth startup and we’re working on some patents and grants and I need to get the IR of our digital stethoscope (I think!). I want to remove the characteristics of the hardware from the body so… [Previous page](https://forum.quantasylum.com/latest.md?page=1) [Next page](https://forum.quantasylum.com/latest.md?page=3)