Optical, Coaxial, and HDMI Cables: What is Preferable for Your Audio Connection?

Choosing the right cable for an audio or audiovisual system can affect compatibility, installation complexity, and the features available to your equipment. Optical, digital coaxial, and HDMI connections are commonly used with televisions, soundbars, home theater receivers, gaming consoles, DVD and Blu-ray players, and other audiovisual devices.

Although all three connection types can carry digital audio in supported configurations, they differ in how they transmit signals and which audio formats they support. Optical and digital coaxial connections are primarily used for audio, while HDMI can carry both digital audio and video through a single cable.

Understanding these differences makes it easier to select a connection that meets your equipment's requirements without paying for features you do not need.

Understanding HDMI, Optical, and Digital Coaxial Cables

Before comparing their performance, it is important to understand how each cable type works and where it is commonly used.

Digital Coaxial Cables

Digital coaxial audio cables carry electrical digital signals through a shielded copper conductor. They commonly use RCA-style connectors and are designed to connect compatible audio sources, televisions, receivers, and other equipment.

Their coaxial construction helps protect the signal from external interference, although performance depends on the cable design, shielding, connectors, and installation. Digital coaxial audio connections can support stereo PCM and certain multichannel compressed audio formats when the connected equipment supports them.

Digital coaxial audio should not be confused with the coaxial cables used for cable television, broadband, or other radio-frequency applications. Although the cable construction may be similar, the connectors, specifications, and intended uses can differ.

Optical Audio Cables

Optical audio cables, commonly known as TOSLINK cables, transmit digital audio using light rather than electrical signals. The transmitter converts the audio data into optical signals, and the receiving device converts those signals back into an electrical format for processing.

Depending on the cable design, the optical fiber may be made from plastic or glass. Because the signal travels as light, optical audio connections are not susceptible to electromagnetic interference in the same way as copper-based connections.

Optical audio is commonly used to connect televisions, soundbars, receivers, and other compatible equipment. However, supported audio formats depend on the source device, receiving equipment, and connection specifications.

HDMI Cables

High-Definition Multimedia Interface (HDMI) cables carry digital video and audio through a single connection. HDMI is widely used with televisions, gaming consoles, streaming devices, Blu-ray players, home theater receivers, and soundbars.

Unlike optical and digital coaxial audio connections, HDMI supports video transmission as well as audio. It can also support advanced audio formats and features when the connected devices and HDMI versions are compatible.

HDMI capabilities vary by specification. For example, HDMI 2.1 supports a maximum data rate of up to 48 Gbps, while actual supported features depend on the cable certification, device hardware, and configuration.

Optical vs. Digital Coaxial vs. HDMI: Key Differences

The best connection depends on your equipment, required audio formats, video requirements, cable routing, and installation environment.

1. Cable Construction

Digital coaxial cables use copper conductors and shielding to carry electrical signals. HDMI cables also use copper conductors, arranged in a more complex assembly designed to carry high-speed digital video and audio data.

Optical audio cables transmit signals using light through optical fiber. This provides electrical isolation between connected devices and makes the connection resistant to electromagnetic interference.

For installations near electrical equipment or sources of interference, optical audio may offer an advantage. For typical home entertainment setups, however, all three connection types can provide reliable performance when used within their specifications.

2. Audio Quality and Supported Formats

The audio formats supported by a connection depend on its technical capabilities and the devices at both ends.

Optical audio commonly supports stereo PCM and compressed multichannel formats such as Dolby Digital and DTS, subject to equipment compatibility. It generally does not support the full range of high-bandwidth, lossless multichannel audio formats available through modern HDMI connections.

Digital coaxial audio can support stereo PCM and certain compressed multichannel formats, depending on the source and receiver. Its capabilities are broadly similar to those of optical audio for many everyday applications.

HDMI audio supports a wider range of audio formats, including multichannel PCM, Dolby TrueHD, DTS-HD Master Audio, and, in compatible configurations, Dolby Atmos and DTS. Some of these formats require particular HDMI capabilities, and Atmos or DTS support also depends on how the audio is encoded and delivered.

For standard stereo playback, the audible difference between correctly functioning digital connections is often negligible. The most important considerations are format compatibility, the quality of the source material, and the capabilities of the connected equipment.

3. Video Transmission

Optical and digital coaxial audio connections are primarily designed for audio and do not carry HDMI video signals.

HDMI carries both audio and video, allowing a single cable to connect compatible source devices to televisions, displays, receivers, or soundbars. This can reduce cable clutter and simplify installations.

If your setup requires both high-resolution video and advanced audio features, HDMI is generally the most practical option.

4. Bandwidth and Technical Limitations

Audio bandwidth should not be confused with an audio sampling rate. Values such as 96 kHz and 192 kHz describe sampling rates commonly associated with digital audio, not the maximum bandwidth of the cable itself.

Optical and digital coaxial connections have format and interface limitations that vary by implementation. They may support stereo high-resolution PCM or certain compressed multichannel formats, but their capabilities should be verified against the equipment specifications.

HDMI supports substantially higher overall data rates. HDMI 2.1 specifies a maximum data rate of 48 Gbps, enabling support for compatible high-resolution video modes and advanced audio capabilities.

The cable alone does not guarantee support for every format. The source, receiver, display, and cable must all support the required features.

5. Cost and Installation

Optical and digital coaxial audio cables are often economical choices when only audio needs to be transmitted. They can be suitable for connecting a television to a soundbar or receiver when HDMI audio features are unnecessary or unavailable.

HDMI cables may cost more depending on their length, certification, and supported data rate. However, because one cable can carry both audio and video, HDMI may simplify the overall installation and reduce the need for separate connections.

When selecting a cable, consider the equipment's available ports, the required cable length, supported formats, and any special installation conditions.

Benefits and Limitations of Each Connection Type

Digital Coaxial Audio

Benefits

• Provides a digital audio connection using a conventional copper cable.
• Supports stereo PCM and certain compatible compressed multichannel formats.
• Offers a practical option for devices equipped with digital coaxial audio ports.
• Uses a sturdy cable construction suitable for many standard installations.

Limitations

• Does not carry HDMI video.
• Uses electrical signals and can be affected by electromagnetic interference under some conditions.
• Does not support every advanced multichannel audio format.
• Requires compatible digital coaxial inputs and outputs.

Digital coaxial audio is a useful choice when both devices support the connection and the required audio formats do not call for HDMI.

Optical Audio

Benefits

• Transmits audio using light and provides electrical isolation.
• Is resistant to electromagnetic interference.
• Works well for many television, soundbar, and receiver connections.
• Can simplify connections where compatible optical audio ports are available.

Limitations

• Does not carry video.
• Has format and bandwidth limitations compared with modern HDMI connections.
• Requires careful handling because some optical cables can be damaged by excessive bending.
• Cannot provide advanced audio formats that exceed the capabilities of the interface or connected devices.

Optical audio is particularly useful when you need a simple digital audio connection and electrical isolation is desirable.

HDMI Audio

Benefits

• Carries digital audio and video through one cable.
• Supports a broad range of audio formats with compatible equipment.
• Can support high-resolution video, HDR, and high refresh rates when the connected devices and cable meet the required specifications.
• Supports features such as Audio Return Channel (ARC) and Enhanced Audio Return Channel (eARC) on compatible devices.
• Reduces the need for separate audio and video cables.

Limitations

• Requires compatible HDMI ports and supported features at both ends.
• Cable capability depends on its specification, certification, and length.
• Longer or more demanding installations may require an appropriate active cable, extender, or fiber-based solution.
• Advanced audio and video features may require compatible source devices, displays, and receivers.

HDMI is generally the most versatile option for modern home theater and audiovisual systems that require both audio and video or advanced multichannel sound.

Which Audio Connection Should You Choose?

The right connection depends on what your equipment supports and which features you want to use.

• Choose optical audio when you need a straightforward digital audio connection, particularly between compatible televisions and soundbars or receivers, and do not require advanced HDMI-only audio formats.
• Choose digital coaxial audio when your equipment has compatible coaxial audio ports and the connection meets your audio requirements.
• Choose HDMI when you need to transmit both audio and video, use advanced multichannel audio formats, or support modern audiovisual features.

Before purchasing a cable, check the input and output ports on each device, the supported audio formats, and the requirements of your installation. A more expensive cable will not automatically improve sound quality when a suitable cable already supports the connection correctly.

Extending Audio and Video Connections Over Longer Distances

Standard cable connections may not be sufficient for every installation. Conference rooms, commercial displays, control rooms, industrial facilities, and other specialized environments can require audio or video signals to travel farther than a conventional cable connection supports.

The appropriate extension method depends on the signal being transmitted. HDMI extension systems may carry compatible audiovisual signals over copper, fiber optic cable, or other supported transmission media. Ethernet media converters, meanwhile, are designed to convert compatible Ethernet interfaces between copper and fiber; they do not automatically convert HDMI or digital audio signals into Ethernet.

Fiber optic transmission can be useful for supported audiovisual applications that require longer distances or electrical isolation. However, the transmitter, receiver, cable, and signal format must be designed to work together.

Conclusion

Optical, digital coaxial, and HDMI cables each serve useful roles in audio and audiovisual installations. Optical and coaxial connections can provide dependable digital audio for compatible devices, while HDMI offers greater versatility by combining audio and video transmission and supporting a wider range of modern audiovisual features.

For a simple audio connection, optical or digital coaxial may be all you need. For modern home theater systems, gaming setups, and installations requiring high-resolution video alongside advanced audio, HDMI is generally the more flexible choice.

Always confirm the capabilities of your equipment and the cable specification before selecting a connection. For longer-distance installations, use extension equipment designed for the specific audio, video, or network signal being transported.