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Recently on the road with an Audio Engineer, I've heared that (Coaxial) S/PDIF and AES/EBU are quite similar and could be passively adapted, and said that these two signals are the same on the logic level and just the electrical specifications are different. There are cables (e.g. http://www.funk-tonstudiotechnik.de/CASA-T-Adapterkabel.pdf, https://www.thomann.de/de/pro_snake_aes_ebu_spdif_cable_3.htm or ) that adapt RCA S/PDIF to XLR for AES/EBU however that manual states, that the receiving device needs to support S/PDIF.

Can someone give me a hint towards if this would actually work?

My Setup is:

  • Audio Interface with S/PDIF or ADAT Out (Motu 828es)
  • HDMI + AES/EBU to SDI with AES in (Blackmagic)
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  • \$\begingroup\$ Fine details in the auxiliary data (VUC bits) will differ but that shouldn't disturb normal operation. Just drive RS422 drivers from the SPDIF signal and add the recommended coupling transformers (which can be home wound on appropriate ferrites) You don't need the receive equalisation circuit unless you're trying to run signals over hundreds of metres... The original AES doc with these details should be online somewhere. \$\endgroup\$
    – user16324
    Jan 1, 2022 at 22:17
  • \$\begingroup\$ full document paywalled at aes.org/tmpFiles/aessc/20220101/aes03-set-2009-r2019-i.pdf but useful info here : ranecommercial.com/legacy/note149.html Apparenstly the EBU doesn't paywall theirs ... tech.ebu.ch/docs/tech/tech3250.pdf \$\endgroup\$
    – user16324
    Jan 1, 2022 at 22:58
  • \$\begingroup\$ 8 channels of audio with SDI, 4 with AES/EBU. What do you need? \$\endgroup\$ Jan 1, 2022 at 23:34
  • \$\begingroup\$ I need to get SDI Audio Channel 1-2 (From a playback source) deembedded into my Motu 828es (ideally digital) which is Mixed (with other signals) and Monitored and then get it back in the SDI Mixer. As I haven't found equipment that can do this on S/PDIF and the analog ones are either expensive or have noise DACs/ADCs, the best way would probably be AES. And I didn't know that AES had 4 channels, thought it would be just a Stereo Signal (And SDI has 16 according to my video mixer) \$\endgroup\$
    – Tobi
    Jan 2, 2022 at 12:30
  • \$\begingroup\$ Just found out that while the 828es has Coaxial SPDIF, the 8Pre es has not and as it should work with both, I went with a bidirectional converter Optical SPDIF to AES for round about 40 pounds \$\endgroup\$
    – Tobi
    Jan 5, 2022 at 23:28

1 Answer 1

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It might work, but the first problem may be that in reality S/PDIF and AES/EBU are not the same protocol sent over different physical interface, they really are different protocols at the metadata level too.

They are extremely similar at the data level, but the first bit in the Channel Status information defines whether the Channel Status information should be interpreted in "Consumer Mode" (S/PDIF) or "Professional Mode" (AES/EBU).

Sure, there is no problem using such a cable to adapt the Coaxial S/PDIF output to balanced XLR AES/EBU input, but it won't convert the protocol, so the AES input device must work with S/PDIF protocol. It may, or it may not, depending on the SDI transmitter.

Generally, SDI embedded audio is directly compatible with AES so it is possible that the SDI transmitter does not take in S/PDIF protocol, or if it does and embeds it to SDI stream, the SDI receiver may not be able to process it since it is not AES.

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