The Well Audio
They are high speed optical isolators.
They don’t affect the audio signals since they carry the dirty parts of the audio digital signals (BCK and DATA).
The only crucial signal for PCM DACs like AD1862, TDA1541A and our DAC Lite is the LRCK, which comes directly from the clean section of the FIFO Lite (Master clock and dividers), and this clock comes via copper.
You cannot bypass them, and moreover it would be wrong because the optical isolators are just used to isolate the dirty and the clean part of the digital audio signal, so that the signals coming from the FPGA of the FIFO Lite cannot affect the DAC.
You could use the AD1862 DAC board without the FIFO Lite but since the DAC has sign magnitude notation you have to drive it with such architecture (LRCK, BCK, DRP, DRN, DLP, DLN).
When ad1862 take 24bit audio input you can select one of the 8 dithering options, which include truncate.
If you download the Windows application you can see by yourself the available options and setting parameters in unplugged mode.