Digital
Digital connection choice
USB, coax, optical or AES — ranked by clocking architecture and isolation, not sound.
Simple
When both devices share several digital inputs, any of them will deliver the identical bits — so the engine ranks them by engineering margin instead: asynchronous USB is immune to source timing, coax and AES depend on the receiver's clock handling, and optical is immune to hum loops but limited in bandwidth. Pick the top one, use the matching cable, and stop thinking about it.
The theory
The ranking starts from each interface's clocking architecture (async USB removes source jitter by construction; embedded-clock links inherit whatever the receiver's PLL or reclocking buffer achieves), adds galvanic isolation where present (optical inherently; some USB and coax inputs add it), and subtracts a penalty when the connector's practical bandwidth caps the source — TOSLINK's ~96 kHz limit against a 384 kHz source, or DSD beyond DSD64 over DoP.
For experts
Base ordering (AES > coax > I2S > USB > optical) reflects transport robustness: AES3's 110 Ω balanced spec drives 100 m runs, coax S/PDIF is solid to ~10 m, TOSLINK's LED rise time limits both length and rate. The async-USB bonus (+25) then usually promotes USB to the top when the input declares its mode, because clock immunity outweighs transport pedigree at domestic cable lengths. Receiver-side jitter rejection earns +10 (reclocking) or +5 (PLL) on embedded-clock links; isolation +5; a bandwidth cap costs −20. Confidence is "spec-based" only when at least one declared interface spec informed the ranking — a table of defaults is honest as a rule of thumb, not as a measurement.