The Retro Doublewide is a true variable-mu tube compressor module designed from the ground up for the 500 series. It's authentic Retro compression for the masses. The Doublewide delivers the tube compression sound you expect because it is exactly that.
Single channel Variable-Mu Tube Compression in a two-slot 500 series module
Continuously variable input and output levels with fixed threshold
Continuously variable attack and recovery time