HDfury Diva

Audio

S/PDIF

Optical and coaxial digital audio

In short

A two channel digital audio interface, on optical or coaxial cable, which can also carry a compressed multichannel bitstream.

S/PDIF predates HDMI and its bandwidth has not grown since. On the Diva it shares one 3.5mm jack with the analogue stereo output, and the two are alternatives.

S/PDIF is the consumer form of the AES3 digital audio interface, carried either on optical fibre with TOSLINK connectors or on a 75 ohm coaxial cable. It was designed in the 1980s for two channels of LPCM, and its bandwidth has not grown since. That single figure is the root of every limitation people meet with it.

Multichannel sound gets through only by being compressed first. Dolby Digital and DTS fit inside roughly the same bit rate as two channels of LPCM because they are coded, so a 5.1 soundtrack arrives as a bitstream that the receiver decodes. Lossless formats such as TrueHD and DTS-HD Master Audio do not fit at all, and neither does uncompressed multichannel LPCM.

The S/PDIF output on the HDfury Diva

One 3.5mm combo jack, labelled SPDIF + L/R, carries either analogue left and right stereo or optical S/PDIF up to 5.1. The supplied 4.5ft jack optical cable breaks it out to a standard TOSLINK input, and a 3.5mm mini-TOSLINK to TOSLINK adapter does the same job if you already own a full size optical lead. A plain 3.5mm stereo cable takes the analogue side instead.

The jack extracts the HDMI sound from any source at the Diva inputs, and it can also output ARC audio taken from TX0, which is how a television app's soundtrack reaches an AVR that has nothing but an optical input. The analogue side has its own controls: set analogvolume runs from -30 to +10 dB, and set analogbass and set analogtreble from -10 to +10.

What will and will not come out of it

  • Only stereo and 5.1 sound can leave by the optical output, and the analogue side is stereo only.
  • Nothing is downconverted. The Diva does not strip DTS-HD Master Audio to its DTS core or TrueHD to Dolby Digital, so a lossless soundtrack leaves by HDMI or not at all.
  • If you want stereo from the jack, the signal arriving at the input has to be stereo already, which is what the EDID you present controls.
  • DD+ and Atmos pulled back from a television over ARC can be sent here, but that needs an AVR able to accept 192kHz on its optical input, and very few can.

Related terms

LPCMUncompressed digital audio sent as raw samples, rather than as a coded bitstream the receiving device has to decode first.Audio extractionTaking the audio out of an HDMI stream and delivering it on a separate output, so a receiver can hear it without having to handle the video.Dolby Digital PlusThe lossy Dolby codec used by streaming services and by ARC, capable of 7.1 channels and of carrying Atmos as an extra layer.ARCThe HDMI feature that sends sound backwards along the cable, from a television to an amplifier or a soundbar.

In the manual

The pages of the HDfury Diva manual where this comes up.

All glossary terms