There is nothing analog about a Rack Extension, so why pretend. The Digital Filter takes full advantage of modern signal processing techniques and for the first time provides Continuously Variable Slope. You can now morph between the classic response of a 4-pole filter (Moog), to the subtle sounds of a 2-pole filter (Oberheim), and for an extremely steep cutoff all the way up to a 12-pole filter. And everything in between, you can even play with odd order filters if you like. It's shaping up to be the only filter you'll need in your toolbox, though you might want more than one instance.