Mastering insert switcher. Great unit with 2 separate signal paths, presets, order flipping and parallel mix options, as well as one insert on the front panel. Very very handy unit. Used daily in a professional mastering studio. Works perfectly. Comes in original box

The Dangerous Music Liaison is a 100% analog, programmable outboard gear router and patchbay designed to seamlessly integrate analog hardware into modern studio workflows. Built to mastering-grade specifications, it allows engineers to manage up to six stereo (or 12 mono) hardware processors entirely in the analog domain without adding any sonic coloration. 

• Dual Stereo Buses: It features two completely independent stereo buses (Bus A and Bus B), allowing you to route tracking chains on one bus while simultaneously mixing or mastering on the other. 
• Instant Order Swapping ("Flip"): Each pair of inserts (1-2, 3-4, 5-6) features a dedicated Flip button on the front panel. This allows you to instantly swap the processing order in the signal chain (e.g., placing an EQ before a compressor, then instantly switching to compressor before EQ) to audition changes dynamically.
• Onboard Memory & Instant A/B: Includes four onboard memory slots to save entire signal path configurations. You can seamlessly toggle between a saved patch and a modified hardware combination to execute instant, gapless A/B audio comparisons without the 1.5-second lag of manual re-patching. 
• Analog Parallel Processing: It features a built-in, latency-free parallel processing loop with a variable blend pot. Senders can tap the signal from any active insert, send it to a secondary parallel path (such as a crushed drum compressor), and seamlessly blend it back with the pristine dry signal without phase issues.
• Mastering-Grade Topology: Designed by legendary equipment engineer Chris Muth, the unit utilizes audiophile-grade physical relays for true hard-wire bypass on every single loop. When a piece of gear is bypassed, it is entirely removed from the electrical circuit.