Soundcraft Si Series 4x4 XLR AES/EBU Expansion CardAn XLR based card for the Si Series with 2 pairs of AES EBU inputs and outputs (4 in 4 out). By adding option cards to the Soundcraft Si range of digital consoles, you can interface your desk with a multitude of digital systems. The Si range of consoles features a versatile 128 channel expansion bus offering 64 discrete additional input sources and 64 additional output patches that may be used in parallel to fan out to multiple destinations. Routing