Discussion related to the QA402 and QA403 Audio Analyzer
Hi Matt,
my name is Alfred, I am new to this blog.
I worked 36 years as a HW design engineer before I retired 2 years ago.
In the company I had access to Audio Precision instruments like 2722 and APx555.
At home I am using a RME Babyface Pro USB interface and the AudioTester V3.0 SW.
Now I am trying a QA403.
I have some comments and questions. (Sorry, I did not search the complete blog)
Power Supply:
I have seen values above 1 A, so far the QA403 works fine at a USB 3.0 connector of my desktop PC. The reported Voltage is 4.75 V. But to be honest, I do not have a good feeling. I tried my laptop too. The QA403 works fine at the USB 3 and even better at the USB C, Voltage about 4.8 and 4.85 V. I tried 7 cables I found in my cable box and only 3 worked. One is marked with AWG 24 for power, this was the best.
I think most users would appreciate if you would offer a good cable for USB 3 or USB C or with 2 USB A and one USB B connector. Even for 10$ or so. It is hard to find a good one beneath all this junk.
My RME interface can work from the USB, but it has also an additional power input for a 12V external power supply. The USB current then drops to almost zero.
Would be a good idea for the next generation. Including offering a good tested power supply.
Appending Traces:
Both the AP and Audiotester SW allow to freeze a trace in the display and append a new one after a change at the DUT. Would be nice to have this feature too including selecting colors and trace thickness. (for better readable documentation)
Expo Chirp:
Allows quick frequency responses, much faster than Audiotester SW. Good!!
Start and Stop frequencies are fixed (Stop depending on Sample rate) even so there are fields to enter them in the sub menu. But they are “greyed” out, so not usable.
Only log sweep, no linear sweep. At Audiotester you can choose.
Generator Signals:
Multitones: Very good to have this!
No rectangular, no triangle, no pink noise, no pulses with time window(frequency response of speakers)
Signal Quality:
I was able to get access to the APx555 over the weekend.
Quality of the QA403 is very good for the price.
The analog generator of the APx555 is very good, but its digital one is worse than the QA403.
I know you offer the QA480, I will try to get one over time.
Generated Signal:
Seems to be present at both outputs all the time.
AudioTester can output two different sines left and right.
Is there only one DAC?
Level
I would like to see not only dBV, but also Vrms and Vpp. Of course I know the relation, but since I often measure with the scope I am used to Vpp.
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