# QA40x **URL:** https://forum.quantasylum.com/c/qa40x/15.md [Latest](https://forum.quantasylum.com/latest.md) · [Categories](https://forum.quantasylum.com/categories.md) --- ## [About the QA40x category](https://forum.quantasylum.com/t/about-the-qa40x-category/354)
**Author:** [@matt](https://forum.quantasylum.com/u/matt)\ **Replies:** 1\ **Last updated:** [August 9, 2023, 2:45am UTC](https://forum.quantasylum.com/t/about-the-qa40x-category/354 "2023-08-09T02:45:11Z")
Discussion related to the QA402 and QA403 Audio Analyzer --- ## [QA404 and QA403 Update](https://forum.quantasylum.com/t/qa404-and-qa403-update/795)
**Author:** [@matt](https://forum.quantasylum.com/u/matt)\ **Replies:** 65\ **Last updated:** [September 23, 2026, 11:47am UTC](https://forum.quantasylum.com/t/qa404-and-qa403-update/795 "2026-09-23T11:47:16Z")
A short update on what is happening with material shortages and QA404 and QA403. First, a graph over time of the % of TI’s portfolio that Digikey has in stock. This is focused on DCDC converters because throughout the sh… --- ## [macOS ampMeasure public beta](https://forum.quantasylum.com/t/macos-ampmeasure-public-beta/2387)
**Author:** [@davorin](https://forum.quantasylum.com/u/davorin)\ **Replies:** 8\ **Last updated:** [September 17, 2026, 5:36pm UTC](https://forum.quantasylum.com/t/macos-ampmeasure-public-beta/2387 "2026-09-17T17:36:53Z")
Hi all, I’ve been building a native macOS app for the QA403 over the past weeks and it’s now feature-complete enough for a beta: ampMeasure — spectrum/THD/THD+N analysis with per-harmonic readouts, SMPTE/DIN/CCIF IMD, f… --- ## [Pink Noise User Weighting](https://forum.quantasylum.com/t/pink-noise-user-weighting/2386)
**Author:** [@Rammis](https://forum.quantasylum.com/u/Rammis)\ **Replies:** 13\ **Last updated:** [September 15, 2026, 10:00pm UTC](https://forum.quantasylum.com/t/pink-noise-user-weighting/2386 "2026-09-15T22:00:54Z")
I’ve been trying to create a user weighting filter which corrects pink noise input to read as “flat” on the spectrum analyzer (I know white noise already does). This is so I can make the QA403 read as an audio RTA when u… --- ## [ampMeasure 1.0 is now on the Mac App Store 🎉](https://forum.quantasylum.com/t/ampmeasure-1-0-is-now-on-the-mac-app-store/2396)
**Author:** [@davorin](https://forum.quantasylum.com/u/davorin)\ **Replies:** 0\ **Last updated:** [September 15, 2026, 3:24pm UTC](https://forum.quantasylum.com/t/ampmeasure-1-0-is-now-on-the-mac-app-store/2396 "2026-09-15T15:24:12Z")
Thanks to everyone who jumped on the TestFlight beta — your feedback shaped this release. For those just seeing this: ampMeasure is a native macOS app that drives the QA403 directly over USB — no Windows or virtualiza… --- ## [Driving DAC to be measured to full output](https://forum.quantasylum.com/t/driving-dac-to-be-measured-to-full-output/2394)
**Author:** [@sumitc](https://forum.quantasylum.com/u/sumitc)\ **Replies:** 3\ **Last updated:** [September 15, 2026, 2:57pm UTC](https://forum.quantasylum.com/t/driving-dac-to-be-measured-to-full-output/2394 "2026-09-15T14:57:23Z")
I am trying to measure a SMSL D400 DAC which is capable of outputting 5 Vrms. I would like to be able to drive the DAC to this max voltage and then step down from there to see the impact on SINAD. The DAC is connected … --- ## [More precision in exported CSV files?](https://forum.quantasylum.com/t/more-precision-in-exported-csv-files/2374)
**Author:** [@iainfarq](https://forum.quantasylum.com/u/iainfarq)\ **Replies:** 1\ **Last updated:** [August 18, 2026, 3:35pm UTC](https://forum.quantasylum.com/t/more-precision-in-exported-csv-files/2374 "2026-08-18T15:35:44Z")
I’m currently running version 1.223, and I’m attempting to export trace data from graphtool to use elsewhere. It seems that all CSV files (at least the ones I’ve tried) limit values to 2 decimal places. Is this an actu… --- ## [Phonalyzer for QA40x](https://forum.quantasylum.com/t/phonalyzer-for-qa40x/2343)
**Author:** [@Gerrittube](https://forum.quantasylum.com/u/Gerrittube)\ **Replies:** 17\ **Last updated:** [August 16, 2026, 6:47pm UTC](https://forum.quantasylum.com/t/phonalyzer-for-qa40x/2343 "2026-08-16T18:47:37Z")
Phonalyser is a free, open-source (AGPLv3) audio analyzer for Windows / Linux / macOS (soon), aimed at electrical audio-device measurement — no acoustic path — and specifically at the low-THD end where ordinary tools run… --- ## [Turntable cable test: cheap vs hifi](https://forum.quantasylum.com/t/turntable-cable-test-cheap-vs-hifi/2373)
**Author:** [@dlap56](https://forum.quantasylum.com/u/dlap56)\ **Replies:** 3\ **Last updated:** [August 14, 2026, 2:45am UTC](https://forum.quantasylum.com/t/turntable-cable-test-cheap-vs-hifi/2373 "2026-08-14T02:45:27Z")
What will be a simple test with q403 to compare good turntable cable vs cheap one. regards tks Dan --- ## [QA402/403 I2S expansion specifications](https://forum.quantasylum.com/t/qa402-403-i2s-expansion-specifications/612)
**Author:** [@audio-dav](https://forum.quantasylum.com/u/audio-dav)\ **Replies:** 8\ **Last updated:** [July 25, 2026, 3:59pm UTC](https://forum.quantasylum.com/t/qa402-403-i2s-expansion-specifications/612 "2026-07-25T15:59:23Z")
Hi, I have the pin-out of the expansion header, but couldn’t find the documentation for the pins in the header, i.e. max speed, io-levels etc. Also, would it be possible to add support for TDM8 and TDM16? Thx David --- ## [Revox B77 recording calibration](https://forum.quantasylum.com/t/revox-b77-recording-calibration/2338)
**Author:** [@Krypton95](https://forum.quantasylum.com/u/Krypton95)\ **Replies:** 6\ **Last updated:** [July 18, 2026, 10:56pm UTC](https://forum.quantasylum.com/t/revox-b77-recording-calibration/2338 "2026-07-18T22:56:56Z")
Hi everyone, Just sharing an interesting experience. While calibrating my Revox B77, I couldn’t find the usual bias peak, making the standard bias adjustment impossible. Instead, I monitored the frequency response in … --- ## [Continous measurements via REST API](https://forum.quantasylum.com/t/continous-measurements-via-rest-api/2342)
**Author:** [@tomiczeq](https://forum.quantasylum.com/u/tomiczeq)\ **Replies:** 0\ **Last updated:** [July 16, 2026, 10:45am UTC](https://forum.quantasylum.com/t/continous-measurements-via-rest-api/2342 "2026-07-16T10:45:43Z")
Hello. I am working with QA403 for capturing DUT output signal and using python for automated testing. I successfully used /AcquisitionAsync, /AcquisitionBusy and GET endpoints for acquiring some audio measurements. I… --- ## [QA403 Input and Output Impedance](https://forum.quantasylum.com/t/qa403-input-and-output-impedance/2340)
**Author:** [@BrandonS](https://forum.quantasylum.com/u/BrandonS)\ **Replies:** 1\ **Last updated:** [July 14, 2026, 11:53pm UTC](https://forum.quantasylum.com/t/qa403-input-and-output-impedance/2340 "2026-07-14T23:53:52Z")
I’ve been looking around, and I can’t find the spec for the QA403 Input and Output Impedance. Can someone provide it or point me in the right direction? --- ## [Interesting Problem (?) with PWR THD vs FREQ Automated Test](https://forum.quantasylum.com/t/interesting-problem-with-pwr-thd-vs-freq-automated-test/2334)
**Author:** [@VAR](https://forum.quantasylum.com/u/VAR)\ **Replies:** 8\ **Last updated:** [July 13, 2026, 2:31am UTC](https://forum.quantasylum.com/t/interesting-problem-with-pwr-thd-vs-freq-automated-test/2334 "2026-07-13T02:31:56Z")
I am doing some testing on a 1969 vintage Kenwood Receiver. Since it has pre out/main in jacks, I decided to test the amp by itself. The receiver is rated at 53w/8ohms at 0.5%THD. I was able to run a THD vs Pwr and Freq… --- ## [QA401 noise floor](https://forum.quantasylum.com/t/qa401-noise-floor/2325)
**Author:** [@BeeElectronic](https://forum.quantasylum.com/u/BeeElectronic)\ **Replies:** 6\ **Last updated:** [July 7, 2026, 10:25am UTC](https://forum.quantasylum.com/t/qa401-noise-floor/2325 "2026-07-07T10:25:09Z")
Hello, I am a little worried with my QA401 noise floor when I do mesurment from an class D amplifier. I don’t use the QA401 so often and last time it what 2 or 3 years ago for an home made class D amplifier. Back then,… --- ## [Testing amps upto 300W into 8ohms](https://forum.quantasylum.com/t/testing-amps-upto-300w-into-8ohms/2313)
**Author:** [@nick-fl](https://forum.quantasylum.com/u/nick-fl)\ **Replies:** 4\ **Last updated:** [June 18, 2026, 6:19pm UTC](https://forum.quantasylum.com/t/testing-amps-upto-300w-into-8ohms/2313 "2026-06-18T18:19:13Z")
Hi everyone, I am designing a tapped dummy load for high-power amplifier testing with my QA403. My immediate goal is to test a 200W into 8 ohms amplifier (40Vrms). Because this hits the absolute maximum input limit of … --- ## [QA403 I2S Input / Output](https://forum.quantasylum.com/t/qa403-i2s-input-output/1441)
**Author:** [@syso](https://forum.quantasylum.com/u/syso)\ **Replies:** 33\ **Last updated:** [June 17, 2026, 12:24pm UTC](https://forum.quantasylum.com/t/qa403-i2s-input-output/1441 "2026-06-17T12:24:56Z")
We’ve recently ordered a QA403 for our AD/DA testing setup. In our setup, we’ve made breakout board for the QA403 which gives us the I2S signals (out only) LVDS on a HDMI connector, so we can use a 1m cable to our DAC t… --- ## [USB: startech ST4200SUBM: USB 2.0 hub ok?](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285)
**Author:** [@mkg\_el34](https://forum.quantasylum.com/u/mkg_el34)\ **Replies:** 7\ **Last updated:** [June 6, 2026, 11:41pm UTC](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285 "2026-06-06T23:41:31Z")
I bought a startech ST4200SUBM USB hub for my QA403. I put 7 V on the external power source pins and confirmed it converts it to 5V on the USB port. Opening it I see it uses a DC-DC switching converter chip (MT3905), w… --- ## [Multiple QA403 devices](https://forum.quantasylum.com/t/multiple-qa403-devices/2292)
**Author:** [@abarbeau](https://forum.quantasylum.com/u/abarbeau)\ **Replies:** 6\ **Last updated:** [June 5, 2026, 12:55pm UTC](https://forum.quantasylum.com/t/multiple-qa403-devices/2292 "2026-06-05T12:55:32Z")
Is there a way to control more than one QA403 on a single PC other than running one on the PC and another on a VM? --- ## [First impressions](https://forum.quantasylum.com/t/first-impressions/2284)
**Author:** [@Krypton95](https://forum.quantasylum.com/u/Krypton95)\ **Replies:** 2\ **Last updated:** [May 27, 2026, 9:13pm UTC](https://forum.quantasylum.com/t/first-impressions/2284 "2026-05-27T21:13:17Z")
First impressions: fantastic! This device is very handy and simple to use. It can generate so many figures and graphs in such a short time. Of course, every parameter has to be chosen carefully to achieve the best resu… --- ## [Capture long audio input signal (above 22s~)](https://forum.quantasylum.com/t/capture-long-audio-input-signal-above-22s/2280)
**Author:** [@hubert](https://forum.quantasylum.com/u/hubert)\ **Replies:** 3\ **Last updated:** [May 27, 2026, 7:16pm UTC](https://forum.quantasylum.com/t/capture-long-audio-input-signal-above-22s/2280 "2026-05-27T19:16:43Z")
Hi! I’m working on python automated test framework, and I’m using QA403 for capturing DUT output signal. All is running on ubuntu machine. I’m using QA40x REST API /Acquisition and /Data/Time/Input which allows me to c… --- ## [QA403 availability in Eleshop](https://forum.quantasylum.com/t/qa403-availability-in-eleshop/2266)
**Author:** [@Krypton95](https://forum.quantasylum.com/u/Krypton95)\ **Replies:** 3\ **Last updated:** [May 20, 2026, 4:33pm UTC](https://forum.quantasylum.com/t/qa403-availability-in-eleshop/2266 "2026-05-20T16:33:54Z")
Hi everyone! Due to many very good reviews about the QA403 performances, I decided to order one by Eleshop on April, 5th (2026) Unfortunately, Eleshop are unable to give me a shipping date. Shipping forecast is shiftin… --- ## ["Ringing" in Freq response using Triggered Response/Expochirp with Streamer](https://forum.quantasylum.com/t/ringing-in-freq-response-using-triggered-response-expochirp-with-streamer/2279)
**Author:** [@VAR](https://forum.quantasylum.com/u/VAR)\ **Replies:** 8\ **Last updated:** [May 19, 2026, 2:13pm UTC](https://forum.quantasylum.com/t/ringing-in-freq-response-using-triggered-response-expochirp-with-streamer/2279 "2026-05-19T14:13:52Z")
I am trying to measure the frequency response of a Streamer/preamp through its line output. I generated the .wav file file using these settings: and put the file on my NAS drive for the streamer to play back. This is… --- ## [QA403 output on my oscilloscope](https://forum.quantasylum.com/t/qa403-output-on-my-oscilloscope/2272)
**Author:** [@tmccann](https://forum.quantasylum.com/u/tmccann)\ **Replies:** 5\ **Last updated:** [May 10, 2026, 6:59pm UTC](https://forum.quantasylum.com/t/qa403-output-on-my-oscilloscope/2272 "2026-05-10T18:59:38Z")
New to the QA403. I’m looking at the output of the box on my scope and I get the sine wave I expect but also a rapid flashing signal of graduated amplitude at the same time underneath the main plot. Also the VRMS of th… --- ## [QA403 ADC overflow](https://forum.quantasylum.com/t/qa403-adc-overflow/2264)
**Author:** [@tspacker](https://forum.quantasylum.com/u/tspacker)\ **Replies:** 4\ **Last updated:** [April 27, 2026, 9:45pm UTC](https://forum.quantasylum.com/t/qa403-adc-overflow/2264 "2026-04-27T21:45:29Z")
Running V1.220 on Win11 Pro. Recently I have seen a ADC overflow error and I can see the bad data in the Freq and ime display. The video shows the problem ADC over flow Frequency domain. I used 64k FFT with no averages, … --- ## [6dB gain with Differential Cables](https://forum.quantasylum.com/t/6db-gain-with-differential-cables/946)
**Author:** [@rsrecords](https://forum.quantasylum.com/u/rsrecords)\ **Replies:** 4\ **Last updated:** [April 13, 2026, 1:52pm UTC](https://forum.quantasylum.com/t/6db-gain-with-differential-cables/946 "2026-04-13T13:52:59Z")
HI, forgive me if this is obvious but should I be seeing a 6dB gain with differential cables vs single ended? I built a set of xlr to bnc cables using stereo mogami 2528. --- ## [I don't understand this 6 dB gain](https://forum.quantasylum.com/t/i-dont-understand-this-6-db-gain/1256)
**Author:** [@sten](https://forum.quantasylum.com/u/sten)\ **Replies:** 3\ **Last updated:** [April 13, 2026, 1:46pm UTC](https://forum.quantasylum.com/t/i-dont-understand-this-6-db-gain/1256 "2026-04-13T13:46:32Z")
Hi all I am running the QA40x software version 1.194 on Linux with Mono. In this self-test, I am shorting the left inputs and outputs. According to the measurements, I’m outputting a sine wave of amplitude -6 dbV, yet t… --- ## [QA403 - 1000W audio amp-speaker test issue](https://forum.quantasylum.com/t/qa403-1000w-audio-amp-speaker-test-issue/2260)
**Author:** [@AUXPhile](https://forum.quantasylum.com/u/AUXPhile)\ **Replies:** 5\ **Last updated:** [April 11, 2026, 5:31pm UTC](https://forum.quantasylum.com/t/qa403-1000w-audio-amp-speaker-test-issue/2260 "2026-04-11T17:31:38Z")
Hello folks, We are facing trouble in testing a 1000 W power amplifier with the QA403. The website directs to use a dummy load made of power resistors of 8 ohms with -14 dB attenuation, but as we are running short on ti… --- ## [Mesurment setup](https://forum.quantasylum.com/t/mesurment-setup/2247)
**Author:** [@Deadcap](https://forum.quantasylum.com/u/Deadcap)\ **Replies:** 3\ **Last updated:** [March 25, 2026, 6:11pm UTC](https://forum.quantasylum.com/t/mesurment-setup/2247 "2026-03-25T18:11:57Z")
Hi, I am working with the Q403 on testing power amps. My setup is a dummy load and Q403 and an oscilloscope connected to the amp’s output. Some amplifiers don’t like the input and output grounds connected and make oscill… --- ## [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… [Next page](https://forum.quantasylum.com/c/qa40x/15.md?page=1)