If the SPDIF interface is really bad, with severe impedance mismatches, then a huge amount of signal reflections are generated, which means that during the 'decision point' of a timing signal can be corrupted by a reflection. It is RF engineering, not audio engineering! The problem is that is is physically impossible to get true 75 Ohm impedance with RCAs no matter what the marketing blurbs tell you. BNC is the way, to make cables and RCAs a non-issue.

My DAC has a true 75 Ohm connection, and with the Halide Bridge BNC connected there are no reflections, low jitter and low clock drift. Longer cables will help if reflections are an issue. I have a 5m one. Read about A-RT's UBYTE SPDIF cable for good insights into cables.

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