I did lots of measurements today.
I first check the consistency and accuracy of my UCA202 single channel measurements.
With E30 volume set at -8.5db, using filter 1, I measured 2Khz and 10Khz tone 3 times each. I confirmed I got matching db numbers for all 3 captures per freq.
E30 (-8.5db, filter 1, 2Khz tone generated at 0.8 out of 1 in Audacity): 0.9db
E30 (-8.5db, filter 1, 10Khz tone generated at 0.8 out of 1 in Audacity):0.8db
There is a drop of 0.1db between 2Khz and 10Khz.
I then checked E30 measurements by Johnyoung89 from Topping. Indeed there is a slight drop in dB for filter 1 in 10Khz. Not exactly 0.1 db, but Audacity can only show 0.1db increment.
View attachment 112768
Now that I established my UCA202 can accurately and consistently do single tone measurements, I checked Gustard x16 measurements next.
I have previously established that E30 has higher output than X16, thus I measured x16 at -8db, using same test files.
Gustard X16, -8db, filter 1:
2KHz: 0.7db, 10Khz 0.4db
Gustard X16, -8db, filter 2:
2KHz: 0.6db, 10Khz 0.4db
Gustard X16, -8db, filter 3:
2KHz: 0.7db, 10Khz 0.4db
So, it looks like X16 drop from 2Khz to 10Khz is either 0.2 or 0.3db.
E30 has a drop of 0.1db with filter 1 at around 10Khz.
Gustard X16 (I was using filter 3) has a drop of 0.3 db at around 10Khz.
The question is: Can one sense such small difference of 0.2db between DAC at 10Khz? How about more and more db differences at freq higher than 10Khz?