Coaxial to Optical Converter: Two S/PDIF Transports
Quick answer / TL;DR: Short answer: a coaxial to optical converter takes an RCA coaxial S/PDIF signal and outputs TOSLINK. Both carry identical data, so conversion adds no quality. It needs power, supports stereo PCM reliably and passes Dolby or DTS bitstreams only if the unit states it. Optical gives galvanic isolation, which can remove hum.
Three coaxial families: BNC for CCTV, F-type for TV, N for RF – each with its impedance.Coaxial and optical S/PDIF carry the same digital audio data over different physical layers. A converter changes the transport without changing the content.
The usual reason to convert is ground isolation or the ports available at each end.
Transport Comparison
| Property | Coaxial S/PDIF | Optical TOSLINK |
|---|
| Cable | 75 ohm coax | Plastic or glass fibre |
| Isolation | Electrical connection | Galvanic isolation |
| Length | Tens of metres | About 10 m typical |
| Formats | PCM and bitstream | PCM and bitstream |
Because the data is identical, any audible difference comes from grounding or from a faulty cable, not from the format itself.
Selection Points
- Bitstream support, not just PCM
- Sample rate ceiling
- Power source
- Jacket and connector quality
- Whether both directions are supported
Direction matters: many units are one-way, so check whether you need coax-to-optical or the reverse.
Real-World Applications
A television with optical output feeding an older amplifier with coaxial input needs one converter, and the optical side also breaks a hum loop caused by the aerial ground. A streamer with coaxial output feeding a soundbar with optical input is the same job in reverse.
Standards and Verification
| Reference | Relevance |
|---|
| IEC 60958 | S/PDIF interface |
| EIAJ CP-340 | Optical interface |
| HDCP not applicable | Audio only |
Format support for a specific converter is not provided in the knowledge base. Check the datasheet for Dolby and DTS support.
Practical Notes
Set the source to PCM output first when testing. A bitstream that the converter does not pass sounds like a broken unit.
Related reading: audio cable — blogs/news/audio-cable
Related reading: optical to rca converter — blogs/news/optical-to-rca-converter
Related reading: optical to analog converter — blogs/news/optical-to-analog-converter
Frequently Asked Questions
Does conversion affect quality?
No. The data is identical.
Will it pass Dolby Digital?
Only if the unit states bitstream support.
Why use optical?
It breaks ground loops between devices.
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