Mixing AES3 and S/PDIF Digital Audio Signals in the Same System
January 23, 2006
When designing a digital audio system with both pro AES3 and consumer S/PDIF digital audio signals, here are some things to consider.
Is the system primarily AES3-based with a few S/PDIF devices that will have to interconnect with the AES3 devices? In that case the most reliable way of interfacing S/PDIF devices to AES3 devices is through a format converter.
A format converter will, at a minimum, change appropriate sub-code bits in the S/PDIF signal to convert it to the AES3 format. Conversely, this type of device can also change the AES3 format into S/PDIF.
In addition, look for a format converter that will produce the correct voltages that is nominal for each format, namely 4 volts for AES3, 1 volt for AES3id, and 0.5 volts for S/PDIF.
One disadvantage of format converters is the additional expense, plus the extra rack space and power strip outlets (if the converters use external power supplies) needed to accommodate them. If there are many S/PDIF devices, with one format converter for each input or output, the dollars add up pretty quickly.
Another way of handling this situation is to wire all the S/PDIF devices to patchbays dedicated just to S/PDIF, and AES3 devices on their own set of patchbays. Label each clearly as to signal type. Install a few utility format converters with their inputs and outputs on the appropriate patchbays. That way you will be able to patch S/PDIF and AES3 devices together through a format converter as needed.
Often modern AES3 devices can accept S/PDIF signals as inputs. So check the specs on the AES3 equipment you are using, and if you're able, test with actual equipment. If all of the AES3 equipment (inputs) in your system works well with all of your S/PDIF equipment (outputs), you may not need converters for the outputs of the S/PDIF devices.
But it is a lot less certain that a S/PDIF device will accept an AES3 signal because of the sub-code incompatibility. A format converter is the only way to go here.