Digital Audio Out Coaxial: How to Connect a Coaxial Digital Output

A ‘digital audio out coaxial’ port is the orange, RCA-shaped socket on TVs, set-top boxes, soundbars and receivers. It sends a one-way S/PDIF digital audio stream over a 75 ohm coaxial cable to a receiver, DAC or soundbar. This guide covers what the port actually outputs, how to wire it step by step, which menu settings matter on both devices, and the four failure modes that cause most ‘no sound’ problems with this connection.

Quick Answer

To connect a coaxial digital audio out, use a 75 ohm S/PDIF coax cable with RCA plugs (usually orange) and plug one end into the port labeled ‘Digital Out Coaxial’, ‘Coax Out’ or ‘S/PDIF Out’ on the source, and the other into ‘Digital In Coaxial’ on the receiver. Then select that input on the receiver and set the source’s audio output to PCM or bitstream: bitstream lets the receiver decode Dolby Digital/DTS 5.1, PCM sends already-decoded stereo. The signal is one-way – a coaxial cable cannot send audio back toward the source.

What the Coaxial Digital Output Actually Sends

The port transmits S/PDIF: bit-level JDS-encoded audio at 0.5 Vpp over 75 ohm. Two modes matter. In PCM mode the source decodes everything and sends a raw stereo stream – the receiver just amplifies it. In bitstream mode the source forwards the original compressed 5.1 stream (Dolby Digital or DTS) and the receiver’s decoder reconstructs surround. The ceiling is fixed by the standard: uncompressed PCM up to 24-bit/192 kHz, but compressed surround only at 48 kHz, and nothing above 5.1 – Dolby Digital Plus and DTS-HD require HDMI.

PCM vs bitstream from a digital out

Choose bitstream when the receiving device has a decoder and you want the source’s original surround encoding. Choose PCM when the receiver is a simple amp or DAC, or when the source supports a higher PCM rate than 48 kHz (for example 96 kHz stereo from a music app). Some TVs let you lock the output rate; match it to what the receiver accepts.

Wiring a Coaxial Digital Out: Step by Step

First, identify the port: it is almost always orange and labeled ‘Digital Out Coaxial’ next to a matching optical port. Second, pick the cable: a 75 ohm S/PDIF coaxial cable with RCA plugs, long enough to drape without tension – for what the cable must be, see our coaxial RCA guide. Third, plug in, power on both devices, and select the coaxial digital input on the receiver. Fourth, open the source’s audio menu and set the digital output to bitstream or PCM as your chain requires. Finally, play a known 5.1 test track to confirm the receiver shows the correct format.

Cable choice: 75 ohm S/PDIF coax, not cable-TV coax

A 75 ohm RF cable from an antenna install may carry S/PDIF over a short run, but it is not specified for baseband digital audio: shield coverage and termination tolerance differ. For a permanent connection, buy cable marketed as digital coax / S/PDIF with RCA plugs.

Common Problems and Fixes

No sound at all: check the receiver input selection (coaxial, not optical), check that the source output is enabled, and try the other digital port to isolate the fault. Crackle or dropouts mid-playback: usually a marginal cable or loose RCA – reseat both ends or swap in a known-good 75 ohm cable. Stereo instead of 5.1: the source is set to PCM, or the content is not encoded 5.1. No signal at 96/192 kHz: the receiver may only accept up to 48 kHz for compressed formats; lock the source rate lower. If the coax path keeps failing but optical works, the problem is the cable or termination, not the standard.

Settings Checklist for Both Devices

Source side: digital audio output on, format set to bitstream (or PCM for stereo-only chains), sample rate matched to the receiver’s support, and any ‘speaker setup’ not overriding the digital out. Receiver side: input set to coaxial digital, decoder enabled, and zone routing correct if the receiver drives multiple rooms. After any menu change, power-cycle the receiver – some units re-detect formats only on boot.

Digital Out Coaxial: Typical Settings by Scenario

Real-World Applications

A coaxial digital out is the fallback input in most real home theaters: a TV with only coax out feeding an older AV receiver; a soundbar with a coax in receiving the living-room TV; a set-top box feeding a zone-2 amplifier in the kitchen; a PC or streaming box feeding a standalone DAC and bookshelf pair; a home server pushing background audio to a bedroom amp; and commercial installs where a rack receiver aggregates several digital sources. It is also the standard for test benches, because a coax out gives a clean, ground-isolated signal to measure. Wherever HDMI is unavailable or the receiver predates HDMI audio, the coaxial digital out is the highest-quality path left on the box.

Related Guides

• CoaxialOutput
• DigitalCoaxialCableForTv
• Cable selection FAQ

Frequently Asked Questions

Is digital audio out coaxial the same as RCA audio out?

No. ‘RCA audio out’ (white/red) carries analog line-level stereo. ‘Digital out coaxial’ carries the S/PDIF bit stream on a 75 ohm coaxial cable. They can share the same plug shape, but the signals and required cables are different.

Can I extend a coaxial digital out beyond 5 meters?

Yes, up to roughly 15 meters with a properly built 75 ohm cable and clean terminations. Beyond that, bit errors become likely; reroute the cable or add a short digital pass-through device.

Why is there no sound after connecting the coaxial digital out?

Work the list: receiver input not set to coaxial, source output disabled or set to a rate the receiver rejects, or a cable that is not 75 ohm S/PDIF grade. Swap in a known-good digital coax cable first – it fixes the majority of cases.

Can a coaxial digital out carry 7.1 surround?

Only compressed 5.1 at 48 kHz. True 7.1 and the HD codecs (Dolby Digital Plus, TrueHD, DTS-HD) do not fit on S/PDIF and require HDMI.