Connections & formats
Coaxial (S/PDIF)
Also called coax, S/PDIF, coaxial digital, digital coax
Coaxial S/PDIF carries a digital audio signal on a single electrical cable with an RCA or BNC plug. It is the wired twin of the optical TOSLINK connection, with the same data format, slightly higher bandwidth and no immunity to ground hum.
S/PDIF, the Sony/Philips Digital Interface, dates from the CD era and carries two channels of PCM up to 24-bit/192 kHz, or compressed Dolby Digital and DTS surround. On a coaxial link the signal is an electrical pulse train on a 75 Ω cable, so any RCA cable will work over a short distance but a proper 75 Ω cable avoids reflections on longer runs.
Compared with optical, coaxial supports higher rates, and some listeners report a cleaner result, though a well-designed receiver makes either a non-issue; compared with USB, it is limited in rate and cannot carry DSD without a workaround. CD transports and many streamers offer it as their main digital output. I2S is the unpackaged signal this format wraps up.
Where you’ll see this on tonistry.
- Coaxial is one of the connection types members pick when they draw a signal chain.