On a laptop, network streamer or audiophile music player, the digital output is often hidden in a 3.5 mm jack that looks deceptively like a headphone output. Connecting it to the Toslink input of a converter requires a cable with two different ends. Audioquest offers a refined version here, where the single plastic fibre used in standard cables is replaced by a bundle of fine strands.
An ordinary optical cable carries the signal through a single large-diameter plastic fibre. The light emitted by the diode enters it at a multitude of angles, reflects off the walls, and the most oblique rays travel a longer distance than those going straight through. The result: the edges of the pulse spread out over time. This is modal dispersion, and the receiving circuit, tasked with determining the precise moment when the signal switches, inherits less sharply defined transitions, resulting in timing errors: jitter.
The Carbon combines nineteen high-purity synthetic fibres with a narrow aperture. Each accepts only a tighter cone of light, reducing the difference between the shortest and longest paths. There is a trade-off: round strands placed side by side leave empty gaps, so the effective capture area is smaller and attenuation per metre is higher than with a large fibre. Over domestic distances and with standard data streams, this loss has no consequence. It does, however, explain why very long optical links become challenging at high sampling rates.
In Audioquest’s optical range, this model sits between the Cinnamon and the Vodka. The black and grey braided jacket makes the cable somewhat stiffer than PVC-jacketed cords, which is noticeable when routing it behind furniture.
The fibre faces are precision-polished. The benefit is mechanical before it is poetic: a rough face diffuses some of the light instead of properly injecting it into the photoreceiver opposite, and what is lost during coupling cannot be recovered.
The other advantage is that the connection carries no current. No metal links the two devices, so no common ground flows between them. A television connected to a communal antenna or set-top box, a converter plugged into another wall outlet: the classic ground-loop hum configuration disappears on its own, and radio-frequency interference from switch-mode power supplies finds no conductive path to the amplifier. This benefit belongs to the optical principle itself, regardless of the cable; Audioquest preserves it by avoiding any metal parts in the connection.
The optical link defines a ceiling that cable quality cannot raise. In stereo, PCM commonly passes up to 24-bit/96 kHz; 24/192 depends on the source and remains inconsistent, with many optical outputs on televisions or game consoles even limited to 48 kHz. In multichannel use, the format carries compressed Dolby Digital and DTS up to 5.1.
By contrast, neither Dolby TrueHD, DTS-HD Master Audio nor Dolby Atmos can pass through an optical link: these streams require HDMI, and HDMI eARC for return audio from the television. A good optical cable cleanly carries what the format allows; it does not extend its limits.
The mini optical connector is found on laptops equipped with a combined headphone and digital output jack, on certain network streamers, on high-end digital music players, and on some converters and network players that save the space required by a full-size Toslink connector.
Before ordering, a check is essential: not all 3.5 mm jacks are optical. On a compatible device, a red glow is visible at the bottom of the connector when the digital output is active; on a strictly analogue headphone jack, there is nothing to see and nothing to hope for. A second point to check, this time in the menus: some sources require the output to be switched to PCM or digital mode, and a few disable the optical output as soon as headphones are detected.
Synthetic fibre does not tolerate sharp bends. A cable bent at 90 degrees against a rear panel can crack without anything being visible from the outside, causing dropouts or a complete absence of signal. It is better to allow a wide loop behind the furniture than force the cable through.
The original caps are worth keeping: dust deposited on the polished face diffuses light precisely where the care taken in manufacturing was intended to prevent it. Finally, the mini plug must be inserted fully, which requires a little firmness with combined jacks fitted with a shutter.
It is possible; Audioquest sells one separately, and this solution is useful when you already own a good Toslink-to-Toslink cable. However, it adds an extra interface to the optical path: two additional surfaces and mechanical play between the adapter and the connector, with a risk of misalignment. A factory-fitted termination avoids this break.
Coaxial handles high bitrates more easily, especially 24/192, and suffers from no light dispersion. Optical provides galvanic isolation, which becomes crucial as soon as a mains-powered TV, set-top box or computer enters the chain. When faced with persistent hum, optical solves the problem; when dealing with a demanding high-resolution stream, coaxial offers greater reassurance.
No, apart from the connector shapes, which dictate the placement themselves: the mini plug goes into the device with the 3.5 mm jack, and the Toslink into the other one. No shielding or ground conductor is involved, so there is no orientation to follow.
It carries the stream exactly as the TV outputs it, without altering it. The benefit lies in cleaner transitions read by the receiver and the absence of conducted interference, not in the content. If the soundbar is connected via HDMI eARC, the optical connection is in any case a fallback, with the format limitations mentioned above.
Freddy
See the reviews already given on similar AUDIOQUEST products, a great product.
Comment from 15 February 2024 — Experience from 3 February 2024
