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Seems like the discussion has died down a bit.
I'd like to contribute as well in measuring DAC's or headphone amps, however I do agree we need to standardize our results.
As I understand from the recent discussion, allow me to summarize and correct me if i'm wrong.
Testing items is listed below:
Could we standardize all tests to either 16bit 44.1kHz or 24bit 96kHz?
- Frequency response - 44, 48, 88 & 96 kHz replay bandwidth. Extend acquisition bandwidth beyond replay to show filter roll off and out of band noise (is 15Hz -> 24kHz enough?, is 88.1 really necessary? is 61 points slow sweep enough?)
- No signal noise floor (FFT's at 32K, low average,)
- 1kHz tone @ 0dB, -1dB, -60dB FS. THD + Noise (1 graph with overlapped results?)
- 48kHz J test. USB and spdif input (if available) (FFT's at 32K, low average)
- Small signal time waveform 16 bit and 24 bit @ -90 something dB (is 24 bit necessary?)
Based on Amir's test , can we also standardize the graphs to dBv vs freq? however we would need a reference voltage @ 0dB
Amir wants to keep the test threads streamlined so they will be attractive to more people. Probably a good idea. So I would suggest we do fairly comprehensive testing. Yet much of the results we need only check and actually show in detail if something is unexpected. Like frequency response. Pretty unusual for that not to be very good. So sure check it, but unless something odd shows up, just say it was fine. Then move on.
About your #3 above, yes, but I don't think that will work for one graph. All the results would be right on top of each other. Even with color coding it will get hard to read.
I also think lots of this testing will be to show exemplary performance need not involve megabuck gear. So what does lower priced gear skimp on and sometimes fall short? Power supplies, and low noise seem the two most common areas they fall short. And output signal level too. So maybe you show a couple areas a given bit of gear over-achieves and a couple areas it is less than stellar. You still have to do comprehensive testing to find those places.
It need not be that hard. Myself, I made up a short file with all the various test signals in it. Few seconds of silence in between. Made the tests at different sample rates. So I set up the file, run it to set levels on the DAC and ADC. Then run it again. Record the result and analyse it after the fact. Not terribly burdensome or time consuming that way.