I am missing a cross measurement to evaluate the performance of ADC and DAC path separately. ...
I had to send the 516 back already as it was on a short fuse. I thought about using APx555 as a source for the 516 but then thought no one would be in a situation to have both and use them that way. So instead, I ran the DAC test which only used the ADC.
I have received feedback on this review from students (first year electrical engineering students): 'They would have worked through the night to fully test the APx516B with the (calibrated?) APx555!
This is your forum, you determine the quantity and quality of your measurements. This review also shows us your progress in testing devices. Here is just one example of how you manage measurement errors:
Output impedance was excellent at just 1.1 ohm:
I'm puzzled by the 1.1 Ω output impedance measured here. That's way higher than the 35 mΩ I measured. Is part of the wiring harness used for testing included in that 1.1 Ω by any chance?
Yes, the best case scenario on my setup is around 0.9 ohm so 1.1 ohm is almost as good as it gets. I have not tried to optimize this for consistency and the fact that it shows what a typical headphone would see.
If you are happy that many people today seem to buy Audio-components according to the "SINAD" table and no longer, for example, according to the output power "watts" as in the past, then that is fine with you. But, as you have already read here several times, there are people in this forum with very specialised knowledge: People who could help you take your measurements to a higher level and, above all, develop new, additional (!) measurement methods. Only then would a presentation at an AES (Audio Engineering Society) conference be logical and useful.
I would be very happy if I could read it one day:
... developed the new measurement methods with members of the ASR Forum ...
BTW:
Elsewhere here, you started a discussion about the planned measurement of MIC preamps. I have the feeling that you are (again) driven by the marketing aspect, i.e. that there will be an "EIN" table *) that is not based on the standard dBu but on dBV - simply because the dBV figures have higher values.
*)
Equivalent Input Noise table:
The input is shorted to 150 ohms, for example, to simulate the typical source resistance of a microphone. If a preamplifier does not add any noise, only the noise of the resistor (here 150 ohms) is measured:
150 ohms, 23 °C, 20 - 20,000 Hz results in -130.87 dBu or -133.09 dBV