Kazuma
Apart from yet unknown reasons (that will be discovered in the future) of why it influences the resulting sound, i think the main culprits are: 1) RF poisoning 2) noise coupling 3) square bus signals ringning.
Those are what we are want to mitigate and clean, basically.
For example, lets see how Berkeley solved those in one of its product:
– (RF poisoning) The “dirty” and ” clean” parts of board are separated by isolated chip. The inscription on the chip has been erased, but I am absolutely sure that it is an AD ADuM chip, isolating the I2S interface channels between the XMOS chip and the SPDIF output.
– (square bus signals ringning) The chip is protected by an unusual ferrite flap. The flap forms a kind of a ring that encloses the chip 360 degrees (above and below the circuit board).
– (RF poisoning) The metal shield further improves the isolation by dividing the internal space into two compartments.
– (noise coupling) One of the coolest design elements of the Alpha USB is the design of the USB input connector. MOST manufacturers make a matching hole in the metal housing and
and put the USB connector in there. But not Berkeley. They made an inch-by-inch slot in the case and inserted the USB connector into a plastic plate to reduce the possible
capacitive coupling between the two elements. Clever move.
Also there is a picture of lossless tech explaining what they have invented as a filter