Dual AES is a digital audio interface invented by dCS in 1995 to allow high sample rate data to be split between two base-rate data streams for easy storage on the digital recorders of the time. For example, a stereo pair of 96kHz data could be split into two 48kHz streams and recorded as 4 tracks on a 48kS/s recorder. To replay, the 4 tracks are transmitted over two AES3 cables to the DAC, which reconstructs the original 96kS/s data.
Dual AES was offered as an open standard and it was added to the AES3 specification. Almost 20 years later, we use Dual AES at sample rates as high as 384kS/s. Dual AES features lower jitter than Single AES or S/PDIF, so there is a sonic benefit.
The raw data must be specially formatted as a Dual AES pair at the transmitter and then decoded at the receiver. Two identical Single AES streams used together will be decoded by the DAC as a strange ‘phasey’ mono – this is not the same as Dual AES at twice the sample rate.