SPDIF vs Coaxial

What’s the Bottom Line Regarding SPDIF vs. Coaxial?

 In today’s modern world that’s overrun with all sorts of consumer electronics and formats that come and go, it might be tough to keep up with the latest cables and ports to stick them into, from HDMI to RCA or Composite to Component or DVI to DisplayPort or Mini DisplayPort to USB-C or USB 3.0 to USB 4.0. It can be quite confusing, especially if you have to deal with old-timey AV connectors like SCART for 1980s TVs or VGA for 1980s-1990s computer monitors. It can all be quite confusing or disorientating.

In the realm of audio, you have to deal with the same kind of issues. You have to choose between the old-school RCA, the still-in-use digital coaxial and optical formats, and HDMI for your audio needs, with the last option being the best and the least format available. In this article, we will discuss spdif vs coaxial—or, in other words, “Which is better, SPDIF (or S/PDIF) or digital coaxial ports?”

What Is The Deal with SPDIF and Coaxial? 

The coaxial audio cable can be used on a coaxial port or a SPDIF port. Actually, you can use either an optical/TOSLINK fiber-optic cable or a coaxial digital cable on the SPDIF port while the coaxial port can only use the coaxial cable alone. Coaxial and SPDIF inputs are both digital connections. Coaxial cables also have an RCA connector present to allow you to interface with the RCA ports in speakers and sound-system interfaces.


  • What Is SPDIF? SPDIF or S/PDIF is the Sony/Philips Digital Interface or the Sony/Philips Digital Interconnect Format. Ostensibly developed by Sony and Philips, it’s a data link or 16-bit encoding protocol that’s designed to send signals to either optical or coaxial cables. It doesn’t have a specific SPDIF cable. It was also standardized in IEC 60958 as IEC 60958 Type II. Again, it’s a protocol instead of the cable that transmits the info it sends out.


It can also be used to connect HDTVs, set-top receiver boxes for satellite or cable TV, and DVD/Blu-Ray Disc players to surround-sound stereo receivers. In other words, it’s another connection format used to for home theaters or entertainment systems so that you can have high-fidelity sound and music using dedicated speakers instead of just the speakers on your HDTV. It uses the AES3 interconnect standard and carries compressed 5.1/7.1 surround sound (e.g., the DTS audio codec) or uncompressed PCM audio unto two channels.


  • What Is Coaxial? Digital coaxial cables connect to the coaxial RF or radio frequency connector. It was invented by English physicist, engineer, and mathematician Oliver Heaviside back in the 19th Century, with it getting a patent in 1880. This is an electrical output that works at multiple megahertz ranges of radio frequencies in order to digitally transmit information like audio through its cables. The cables it makes use of have all the necessary shielding against electromagnetic interference (EMI) and radio frequency interference (RFI). Such cables are tougher and harder wearing than your average optical or TOSLINK cables to boot.


More to the point, you won’t have to worry about kinks or bends destroying the integrity of the coaxial cable compared to the more sensitive optical cable. Unlike SPDIF, which was made to work with various cables because it doesn’t have a SPDIF-specific cable, the coaxial format only uses coaxial cables from RG6 to RG11. This cable is one of the most common ways to transfer digital audio from one device to another. In terms of audio quality, there’s little to no difference between an optical or coaxial (whether it’s the cables or the format).


  • Coaxial vs. Optical: This is a related debate to coaxial vs. SPDIF. Why? It’s because either cable can be used on SPDIF and optical can serve as a good frame of reference in regards to the coaxial format’s quality in light of how similar they are port-wise and cable-wise. The coaxial cable is characterized for having a tubular insulating layer surrounding an inner conductor that tends in turn covered by another tubular conducting shield, all for the sake of avoiding RFI and EMI. It can be as thin as RG6 cables or as thick as RG11 cables.


The thicker the cable the less attenuation or signal loss will happen over the length of the cable but at the cost of expensiveness and more inflexible cables. In contrast, you won’t have to worry about attenuation or signal loss proportional to cable thickness with fiber-optic TOSLINK cables. However, it comes at the cost of cable fragility or sensitivity to kinks and bends that aren’t as big of an issue with optical cables. You have to choose between physical toughness and attenuation problems versus fewer attenuation problems but less durability.


  • Coaxial vs. SPDIF: Instead of comparing cables, let’s compare formats or digital connection protocols. SPDIF can cater to both cable types of either coaxial or optical formats. However, SPDIF only works with 2 channels of audio (in stereo) versus both optical and coaxial formats showing the ability to carry 4 channels at 88.2 or 96 kHz or up to 8 channels at 44.1 or 48 kHz depending on the situation. The only cables and format better at carrying audio with amazing quality is the HDMI series of cables, from the most basic to ultra-high-speed cables for HDMI 2.1.


On the other hand, before you wave off SPDIF as automatically inferior to optical or coaxial input formats, bear in mind that you don’t always need all 4 or all 8 channels to listen to music or atmospheric games. What’s more, you can use monitors with digital output or external Digital Analog Converter (DAC) if you want.  It’s also easier to interface multiple units that might only use TOSLINK or digital coaxial connectors since it’s more universal.

The Bottom Line 

SPDIF adds a new dimension in multiple-unit interfacing exactly because it’s able to receive either optical or coaxial cables with RCA-style connectors as though it’s a converter in its own right. If you’re in an environment with excessive interference or have attenuation issues, you can shift from coaxial to optical. If the optical cables are in danger of getting kinks or damage from rough-handling then use coaxial cables instead. However, format to format, SPDIF has less audio and fidelity potential than the 8-channel RF coaxial format whose only rival is the TOSLINK optical format and whose only superior is the HDMI format.


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