Have you ever wondered which one gives sound between digital connection standards on TV, DVD Player, HD Box, TV Box, or multi-channel soundbar speakers and receivers such as optical, coaxial, or HDMI? One gives sound quality “better” than the rest of the standards? If yes, please read the following article. Well, first of all, this is for home theater sound or popular entertainment; going into Hi-fi, it also has a lot of “black art” in these wires.
The most commonly seen connection standards for the above devices will be coaxial, optical, and a bit newer, HDMI. All three of these connection standards are digital but coaxial and optical can only transmit audio data, while HDMI supports both audio and video simultaneously.
Coaxial connection standard
Newer TVs or TV Boxes often no longer support coaxial connections; as mentioned above, they can only transmit audio signals. The coaxial plug belongs to the RCA standard and has a round shape, similar to the RCA phono jack structure. Still, there are some technical differences; for example, the normal RCA wire does not need to be shielded against interference, but the Coaxial wire will only have 1. The core conducts the digital signal. To the insulation layer and the outside is a metal mesh shielded against interference. The most noticeable point is that their impedance values are different (1 type is 50 ohm and the other is 75 ohm), so it will cause flickering when used, or can’t be used, usually nowadays. I see mostly 75 ohms. Compared to optical, coaxial gives better sound quality due to its higher bandwidth, supporting 24-bit/192kHz signal quality. Optical only stops at 96kHz.
The biggest minus point of coaxial is the possibility of electrical interference and affect sound quality; the longer the wire, the louder the noise because it is like an antenna that receives exogenous noise. The noise signal will travel through the cable and enter the decoder circuit, causing glare and loss of clarity.
Although it has a higher bandwidth than optical, coaxial can still support high-end audio standards such as Dolby TrueHD or DTS-HD Master Audio, thus limiting the necessary convenience of home cinema systems.
Optical connection standard
The optical connection uses light to transmit information through optical fibers, eliminating exogenous interference effects, if any, when transmitting signals. That is the main reason why optical connections are often used to connect directly between the player and the DAC or AV receiver. In-home cinema systems, optical connections transmit compressed audio signals according to Dolby Digital and DTS Surround standards. Optical cable with Toslink (Toshiba Link) pin can also be plugged directly between the transmitter and receiver in the same system. Although slightly inferior to HDMI, the optical standard is still equipped on game consoles, Blu-ray players, TV Boxes, or many newer TV models. The optical port is always available on soundbar speakers or AV receivers with a DAC/amplifier feature.
Optical also encounters the weakness of coaxial that is not enough bandwidth to transmit high-end audio signal standards such as Dolby TrueHD or DTS-HD Master Audio. The optical standard also only supports up to 2 PCM channels and comes with a cable structure with not high durability, easy to break if rolled up too closely.
HDMI connection standard
HDMI was introduced in 2002 to solve the problem of information transmission, possessing the ability to transmit video and audio signals simultaneously. This connection standard possesses a much larger bandwidth than optical and coaxial, allowing lossless audio signal transmission (such as Dolby TrueHD or DTS-HD Master Audio), far ahead of its two seniors.
The HDMI port is always available on TVs, Blu-ray players, AV receivers, or, most recently, soundbar speakers. The HDMI standard is also increasingly being upgraded with more advanced technologies; now, there is a huge bandwidth to support more audio channels such as Dolby Atmos or DTS: X.
It also supports new video formats, including Ultra HD 4K and some HDR formats. It promises to add new features such as HFR (High Frame Rate) or eARC (for the ability to transmit 32 audio channels simultaneously) in the future. HDMI 2.1 standard (8K image format support) is also coming soon.
So which one should you choose?
The answer will depend a lot on the system you own. If you are limited between coaxial and optical, your advice would be coaxial. This connection standard will give higher sound quality than optical and make the sound more vivid and detailed. However, if possible, choosing an HDMI connection would be the best due to the convenience it brings. HDMI also supports more advanced features and can upgrade and reduce the amount of cable needed (because it can transmit video and audio signals). Lastly, you don’t have to sacrifice system performance.