Digital coaxial cables

Both carry the same SPDIF digital audio protocol with the same audio formats (PCM stereo, Dolby Digital, DTS) and the same audio quality. The difference is the physical medium. Coaxial uses a 75-ohm RCA cable carrying an electrical signal on copper; TOSLINK uses plastic optical fiber carrying light. Coaxial is more tolerant of cable length (10 to 15 meters typically, vs. 5 to 10 for TOSLINK) and reuses the same RCA connectors as analog audio, which makes it more universal. TOSLINK is immune to electrical interference and ground loops, which makes it the better choice when isolating equipment grounds or eliminating noise.

Yes, for compressed surround formats. SPDIF (the protocol that digital coaxial carries) supports Dolby Digital 5.1 and DTS 5.1, both of which are compressed multi-channel surround formats used on Blu-ray, DVD, and many streaming services. SPDIF does not have the bandwidth for uncompressed multi-channel audio like Dolby TrueHD or DTS-HD Master Audio: for those formats, you need HDMI between the source and AV receiver. So digital coaxial is fine for everyday surround sound but limits you to compressed formats.

In short runs, often it works; in long runs or where quality matters, no. A true digital coaxial cable is rated for 75-ohm impedance throughout, with proper shielding for the higher frequencies SPDIF carries. A standard analog RCA cable may or may not meet these specifications, depending on its construction. For short runs (a meter or two), an analog RCA cable usually works fine. For longer runs or higher sample rates, mismatched impedance can cause dropouts or no signal. The safest practice is to use cable rated for digital coaxial when carrying SPDIF.

SPDIF supports stereo PCM at 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, and 192 kHz; and compressed multi-channel formats including Dolby Digital 5.1 and DTS 5.1. It does not support uncompressed multi-channel formats (Dolby TrueHD, DTS-HD Master Audio, Atmos), which require HDMI. Some devices may have practical limits below the theoretical SPDIF maximum: for example, some AV receivers accept 192 kHz on optical but only 96 kHz on coaxial, or vice versa. Always check the manufacturer's specifications.

About 10 to 15 meters on quality 75-ohm cable, longer on premium cable with proper shielding. Beyond that distance, the signal may start to drop out, click, or fail entirely. For longer runs, options include digital coaxial extenders that regenerate the signal at the destination, AES/EBU on balanced XLR (which is a similar digital format but on balanced cable, going much further), or a networked audio system (Dante, AES67) if many channels are involved. In most home theater and commercial AV installs, the run is short (source to receiver in the same equipment rack) and length is not an issue.

Home theater (Blu-ray, gaming console, cable box, and streaming device to AV receiver), AV receivers (the central audio hub in most home and many commercial systems), soundbars, CD players, satellite and cable boxes, and commercial AV installations where digital audio needs to travel from a source to a downstream processor. A common pro AV use is bringing HDMI audio into an audio mixer or amplifier chain: an HDMI audio extractor outputs SPDIF coaxial, which then feeds the audio system without needing analog conversion.