The Lexicon Pro MX400XL Dual Stereo/Surround Reverb Processor is a single rackspace, four-channel unit with an intuitive front-panel interface. It uses Lexicon's unique hardware plug-in technology through USB connection and a VST/AU interface to operate as a plug-in with software recording applications. The MX400XL features four separate effects processors to deliver 17 legendary reverbs alongside a powerful array of delays, effects, and dbx® dynamics. Four-in, four-out design uses XLR I/O, offering four-channel surround processing and seven effect routing options. You can switch effect routings via front panel controls, so you don't have to spend time changing cables. You also get 99 factory/99 user programs for both stereo and dual-stereo mode, as well as 25 factory/25 user surround programs.