Topic: Adi-2 Pro FS: minor processing issue (1LSB asymmetric offset error)
Hi, 1st post here.
I'm the lucky owner of a Pro FS and it surely is the most versatile unit around, both for music playback and measurement tasks, with outstanding features and specs.
I'm currently doing some specialist low-level high-resolution measurements with heavy time-domain averaging of sample-synchronous periodic data blocks to dig deep into the analog noise floor down to the LSB of 24bit data. Checking signal intergrity for a basic loopback cable arrangement, it seems I have found a minor DAC data processing glitch somewhere in the device firmware or the DAC-chip itself.
The error shows up as positive (>=1) sample values of a 24-bit input data stream all being lowered by one (when measured with the ADC, running with an analog gain of 10 to reduce its error contribution). That means, for example a sample sequence of -1,0,1,2,3 is output as -1,0,0,1,2.
Of course, the error produced is way below analog noise floor and thus quite probably irrelevant, nonetheless I find this worth of further investigation. Also, this could all still be "user error" although I tried to take care as much as possible.
Please read the full story over at AudioScienceReview: https://www.audiosciencereview.com/foru … by-1.6865/
There, I present the effect of the error both on a low-level bit by bit staircase as well as a sine signal, and was able to model (and later correct for) the error in an emulator which predicted the outcome to great precision.
If these observations are real and could even be backed up by other independant measurements it is easy to fix this (very) minor issue. I'll be glad to provide further information as needed.