Coaxial vs Optical Audio: Which Digital Cable Should You Choose?

4/17/2026 · Audio · 8 min read

TL;DR

• Both coaxial and optical carry the same digital audio signal — PCM stereo or compressed 5.1 surround — so raw sound quality is identical in most setups.
• Coaxial uses a copper RCA cable and is more resistant to physical damage, making it the better pick for permanent installations.
• Optical (TOSLINK) uses a fiber-optic cable and is immune to electrical interference, which matters when your gear sits near power supplies or other noisy electronics.
• Neither cable supports uncompressed 7.1 or Dolby Atmos — you need HDMI eARC or a direct HDMI connection for those formats.
• Coaxial supports slightly longer reliable runs (about 10 m vs 5 m for optical without signal loss).
• If your devices have both ports, coaxial is generally the safer default; optical is the smarter choice when ground-loop hum is a problem.

What are these cables, exactly?

Coaxial digital audio — technically called S/PDIF over coaxial — sends a digital bitstream through a 75-ohm copper cable terminated with standard RCA connectors (the orange or black jack often labelled "Digital Out" on receivers and soundbars). It looks identical to an analog RCA cable, but the internal shielding and impedance are tuned for digital signals.

Optical audio — also known as TOSLINK or S/PDIF over optical — sends that same digital bitstream as pulses of light through a thin fiber-optic cable. The connector is a distinctive square plug with a small red LED glow when the port is active.

Both carry the same S/PDIF protocol, so the data riding the wire is identical. The difference is in how that data gets from A to B.

Sound quality: is there really a difference?

In a word, no — at least not from the cable itself. Both coaxial and optical are carrying a digital signal, so as long as the signal arrives intact, the bits your DAC receives are the same bits your source sent. There is no "warmer" or "brighter" tone from one cable type over the other.

Where things can diverge is at the endpoints. Coaxial relies on the electrical characteristics of both devices sharing a ground, which occasionally introduces jitter (tiny timing errors in the clock signal). Optical decouples the two devices electrically, so jitter from the source's power supply cannot leak through the cable. In practice, the jitter difference on modern equipment is vanishingly small and inaudible to most listeners.

If you are chasing the absolute lowest jitter numbers — say, for a high-end two-channel stereo system with a standalone DAC — some audiophiles prefer coaxial because good coaxial receivers re-clock the signal more accurately than many optical receivers. But for a TV-to-soundbar connection or a game console to an AV receiver, the difference is academic.

Supported audio formats

This is the area where both cables share a limitation. The S/PDIF standard maxes out at roughly 1.5 Mbit/s of bandwidth. That is enough for:

• Uncompressed 2-channel PCM up to 24-bit / 192 kHz (stereo hi-res audio).
• Compressed multi-channel formats: Dolby Digital 5.1 (AC-3) and DTS 5.1.

It is not enough for:

• Uncompressed 5.1 or 7.1 PCM.
• Dolby TrueHD or DTS-HD Master Audio (lossless surround).
• Dolby Atmos or DTS:X object-based audio.

If you need any of the above, you must use HDMI (ideally eARC) instead. This limitation applies equally to coaxial and optical, so it should not influence your choice between the two.

Comparison table

Cable length and signal reliability

Coaxial wins on distance. A decent 75-ohm coaxial cable can reliably carry a digital signal 10 metres or more without dropouts. Optical cables start to lose light intensity beyond about 5 metres, and cheap plastic-fiber TOSLINK cables can struggle even at 3 metres if they have tight bends.

Premium glass-core optical cables push the useful range closer to 10–15 metres, but they cost significantly more and are far more fragile. If your equipment is in different rooms or on opposite sides of a large media cabinet, coaxial is the pragmatic choice.

Interference and ground loops

This is optical's party trick. Because the signal is carried by light, there is zero possibility of electrical noise coupling into the cable. If you are running cables near power transformers, fluorescent lights, or other noisy electronics, optical is inherently immune.

More importantly, optical eliminates ground-loop hum. Ground loops happen when two devices plugged into different power outlets create a small voltage difference on their shared ground wire, producing an audible 50/60 Hz buzz. Since optical has no electrical connection between devices, the loop is physically broken. If you have ever heard a persistent low hum through your speakers and traced it back to your cable box or game console, switching to optical is often the cheapest fix.

Durability and practicality

Coaxial cables are essentially the same build as standard RCA interconnects: copper core, braided shield, rubber jacket. They bend, coil, and survive being stepped on without complaint. The RCA connectors lock on with a firm push and rarely wiggle loose.

Optical cables are more delicate. The fiber — whether plastic or glass — can crack or lose transparency if bent too sharply, and the TOSLINK connector is a friction fit with no locking mechanism. It is easy to accidentally knock a TOSLINK cable out of its socket. Dust caps are recommended for unused optical ports because even a small speck on the lens can degrade the signal.

For a set-it-and-forget-it installation behind a media console, either cable is fine. For a portable setup or anywhere cables might get tugged, coaxial is more forgiving.

Common use cases

TV to soundbar: Most modern TVs include an optical output and many budget soundbars only offer optical input. In this scenario, optical is the natural choice — it works, it eliminates ground-loop risk, and the short cable run (usually under 2 m) is well within TOSLINK's comfort zone.

Game console to AV receiver: If you are already passing video through HDMI but want a separate audio path (perhaps to bypass ARC quirks), either cable works. Coaxial is slightly more reliable for quick connect/disconnect since the RCA plug stays seated better.

CD transport to standalone DAC: Audiophile setups often prefer coaxial because the DAC can re-clock the signal from the electrical domain more precisely than from an optical-to-electrical conversion. The difference is subtle, but in a system where every component is optimized, coaxial is the traditional choice.

PC to external DAC: Desktop PCs with a coaxial S/PDIF output (usually via a 3.5 mm combo jack or a dedicated RCA) paired with a good external DAC can deliver clean, jitter-free audio. If your PC does not have a coaxial output, a USB connection to the DAC is almost always a better option than adding an optical card.

When to pick coaxial

• Your cable run is longer than 3 metres.
• You want a physically robust connection that will not work itself loose.
• You are connecting a CD transport or dedicated music streamer to a standalone DAC.
• Both devices already have coaxial ports and you do not have ground-loop issues.

When to pick optical

• You hear a ground-loop hum through your speakers.
• Your cable runs near power supplies, dimmers, or other sources of electrical noise.
• Your TV or soundbar only offers an optical port (very common on budget models).
• You want complete electrical isolation between two components.

Do expensive cables matter?

For digital audio, the cable either works or it does not — there is no analog-style degradation that a "better" cable can reduce. A $7 Amazon Basics coaxial or optical cable performs identically to a $50 boutique cable as long as the signal arrives intact.

The one area where spending a bit more helps is build quality: thicker jackets, gold-plated RCA connectors (for corrosion resistance, not sound quality), and glass-core optical fibers (for longer runs). But you do not need to spend more than $10–$20 for a cable that will last years in a typical home setup.

What about HDMI ARC and eARC?

If your TV and receiver both support HDMI eARC, that connection supersedes both coaxial and optical. eARC handles uncompressed 7.1 PCM, Dolby Atmos, and DTS:X — formats that S/PDIF simply cannot carry. For a modern home-theater setup, HDMI eARC should be your primary audio link, with coaxial or optical as a fallback for older devices or secondary zones.

Standard HDMI ARC (without the "e") has roughly the same bandwidth as S/PDIF, so it offers no format advantage over coaxial or optical. If your TV only supports ARC (not eARC), using optical instead is a perfectly valid choice and avoids the HDMI-CEC handshake issues that sometimes plague ARC connections.

Bottom line

Coaxial and optical are two flavors of the same digital audio standard. Pick coaxial for longer runs, sturdier connections, and audiophile DAC setups. Pick optical when ground-loop hum or electrical interference is the enemy, or when your gear simply only has a TOSLINK port. Either way, the sound quality you hear depends far more on your speakers, room acoustics, and source material than on which of these two cables carries the signal. Spend your budget on better speakers, not fancier cables.

Found this helpful? Check our curated picks on the home page.