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Q. Can I connect an AES output to an S/PDIF input?

Liquid Channel offers AES digital in/out on XLRs.Liquid Channel offers AES digital in/out on XLRs.

I own a Focusrite Liquid Channel (which is great!) and would like to connect it to my MOTU 828's digital input. However, on the digital side of things the Liquid Channel only has an AES-EBU input and output, and the MOTU 828 only has S/PDIF and ADAT digital connections. How can I connect them together?

Bernhard Wagner

Technical Editor Hugh Robjohns replies: The proper way to connect AES to S/PDIF is to use a dedicated digital format converter, of which there are plenty around (although some older designs only pass 16 bits rather than the full 24, so check before buying). The M Audio CO3 and the Behringer Ultramatch and Ultramatch Pro probably represent the most affordable options.

However, although it is a rather makeshift solution (a 'bodge', to use the technical term), if you only need the signal to travel a fairly short distance — say, no more than two metres — you can get an AES output to feed an S/PDIF input with just a simple XLR-to-phono cable. Wire pin 2 of the XLR to the tip of the RCA phono jack, and pin 3 of the XLR to the sleeve of the phono. Pin 1 of the XLR should remain wired to the cable screen at the XLR end, but leave it disconnected and insulated at the phono end.

Strictly speaking, the Channel Status and other subcode data is formatted differently between AES and S/PDIF, but very little equipment bothers to send or read the full subcode data set anyway, so it is rarely a problem.

Published November 2005