I just bought it too. Now hope to know when I will have it
Hi @Matt. It would be a good thing if it was possible to set the display to either light color scheme or dark color scheme. The light color scheme is very useful when you need to make prints so you donāt have to consume large amounts of ink with printer. I donāt know if it is possible to do this. Thanks
Btw, where is the QA403 manual located? I only found a qa401 manual dated May 2020ā¦. Scratch that, I see from GitHub that it is installed with the software.
Butā¦. Wouldnāt it be much easier to just have a link in the Downloads section of your website? Documentation seldom needs constant revisions as bug fixes, and having it on the website imho would also make prospective buyers more interested in the devices you sell, reading a manual is the best way to learn about the product and - incidentally- allow me to read it on a tablet or iPad, which I cannot do since I canāt install the sw on iOSā¦.
Minor gripe I know but still!
On the other hand a more serious question on the availability of the QA451, when is that slated for purchase?
Hello I just buy one also (was looking since mounths for qa40x availlability back).
Hope the order will be proceed as I live en French.
Iām a newbie in audio analysis (I build a hifi power amplifier on my free time for now) so I have somes questions; maybe itās not the right place to do in such case can you send me in rigth forum section?
My question is about noise generator, what the purpose of that for audio measurements ?
Hi @Joop99, good point! Itās been clarified (I hope)
Hi @Claudio, 100% agree and itās coming.
Hi @pizzigri, a very good point. I just added a link to the latest manual on the QA403 product page. The QA402 and QA403 share the same manual. The QA451 is all kitted and ready to go, but itās being held as some parts used in the QA451 might be pulled and used to make more QA403. There is a particular part called the SN6505B from TI that is extremely scarce right now and unfortunately itās used in most every product we make. Normally, this part is about $1.20 from TI when you buy in thousands. Right now, the parts brokers in Asia have this part listed for $137 each quantity 1k parts. Pretty unreal. And delivery from TI, if you order today, is 85 weeks.
Hi @Briks, I donāt often use the noise generator, but itās a great way to sanity check what you are seeing because thereās not really any fancy signal processing involved. You just squirt noise into the DUT, and measure the energy in each FFT bin, and then with some averaging applied you can clearly see the frequency response of the DUT. Other techniques such as chirps can give a much clearer response, BUT they can be susceptible to errors due to long path delays you might encounter in certain devices that have lots of processing.
Ok thatās relative to frequency response measurement, I understand how a set of noise measure with averagin can be less dependant to internal processing compared to a chirp.
Many thanks for your answer! In a more general way is there somewhere a guide about basic audio measurements fondamental ?
Hi @Matt. I downloaded version 1.135 while waiting for my ordered QA403 to arrive. I noticed that āAutomated Testsā is dimmed and not working. Is this perhaps due to the fact that the QA403 is not connected? Or is there some other reason? Thanks
Hi@Claudio, you are correct, when connected AND the run button isnāt pressed you can pick Automated Tests. In release 1.140 there was a fix made where if the IDLE button was active, then the automated test would fail (because the ADC/DAC was busy). So, now if IDLE is active and you try to open Automated Tests youāll get a message asking you to first turn off IDLE.
Hello, I need a QA403 to especielly test noise and THD of my audio amp. So waiting for a QA403 I try some stuff āpoors man way styleā for noise estimation.
I use a low cost headset with high sensibility JVC-HA-S660 given for an extravagant 102dB/mW.
I connect it directly on the speaker output of my amp and try to listen for noise. I heard nothing but my 40 old ear are low sensitivity 
then I try with my daughters (8 and 10 yeard old) they heard nothing despite my digital volume pushed to max. So I try other things: test with a a 1KHz sine wave to be sure about the sensitivity of headset:
I feed my amp with the smallest signal upon I heard it via USB (my design embed a DAC). For now I use arta software as sin generator, I ask for a 1Khz sine wave with a volume set to -100dB (Level dBFS, the min arta can generate). My amp digital volume is set to max (0dB) and then I start using windows volume to lower down up to I heard nothing. I stop with windows control volume set to 10%, at 12% I can heard the signal. Then is this assertion correct ??
With arta set to -100 dBFS, windows volume set to 12%, amp volume set to 0dB can I conclude my headset will see a signal about -118 dBFS and the the 102 dB/mW looks correct ?
It looks wrong because Arta print a value of 7.08ĀµV for -100dBFS, with a windows volume set to 12% this lead to a value of 0.85ĀµV RMS; 1.22ĀµV pk-pk I doubt my design achieve such low noise performance ?
Of course my old scope is totally of range with such low signal and I donāt own a proper loboratory DVM.
Start to be impatient to receive a QA403!!
Hi @Briks, I think your approach can definitely get you close. If, for example, you had a 20W power amp, then 20W into 4 ohms that would be 9Vrms = 19 dBV. A very good analog amp might have 80-90 dB SNR, so your noise might be -71 dBV = 300 uVrms or so (20 kHz BW).
Some very good class D amps are approaching 80uVrms or so.
When you get your QA403, it should be easy to measure. I think the orders outside of the US will start to go out early next week.
Hi @matt !
So very curious to do a noise measure with QA403; The DUT is an analog amp from my design, a 30W/8R, 60W/4R with analog triks to keep work area of transistor in class A whatever the load. The analog parts should be good performance as I use a differential topology but the digital/low signal part use classic topology with TI/BB chips inside (pcm1792, pga4311, opa1612, opa1632 and a very low cost/simple analog psu a LM27762). Also main PSU is a Meanwell switcher, prupose is to make a good sounding amps at reasonnable cost.
Anyway Iām newbi in audio field and I donāt really understand the extremely low noise of an audio amp, who can heard something with a 10mV rms noise and even speaker rated at 100dB/W ? In other field from I had experience like long range ultrasonic radar where noise is directly linked to performance I understand. Anyway maybe the answer is that audio designer are geek who loves make ultra high performer device (and this is what I love in this field).
Thanks for your answer!
Hey Matt,
I see that you suspended sales of the 403. I was possibly one of the very first purchasers, and wanted to know when shipping is scheduled for mine - I am located in Italy.
All my best,
Franco
Hi @pizzigri, we generally start shipping to the US first, and once confidence is gained in the update process, we ship more broadly. I think orders outside the US will start later this week.
If the software update process doesnāt work for some reason, the logistics + customs associated with moving bricked devices back and forth is really messy. Sorry if this wasnāt clear. Thanks, Matt
I presently own a model QA401 and use it with an ASIO driver (on github) that allows me to use SpectraPlus SC software.
SpectraPlus works very well with the QA401. Any knowledge if the same ASIO driver will be compatible with the QA403?
-Paul
Hi @Matt. Any news on shipping orders outside the US? Iām especially interested in my order since Iām in Italy. Thanks for any information on this
Hi @Claudio, they will begin shipping this week outside of the US and will resume shipping inside the US this week.
Just received a QA403!
What a wonderfull device!
First measures soud good for my hifi amp project!!
THD behaviour just as expected, off course a little bit high especially from right chan but the concept of my amp works.
Here the first measure run, amp attached to 4R resistive load, both chan:
Noise look good:
Expected with the tests I did with headset. The config for noise measure is to leave QA403 generator ON and lower the volume from my digital volume inside the amp (a PGA4311).
Now can go to fine analog work yes!! Thanks QuantAsylum for your wonderfull device!
Nice set up- thanks for sharing!
Very nice. My QA403 will be delivered tomorrow by DHL. Iām getting the setup ready to get familiar with the QA403.