If you use lots of Microphones on sources, such as Drums. If you use two or more mics on a gtr cab. you record DI and a mic aon the cab for bass. If you Record Agtr & Vocal at the sme time with two mics. If you do all of the above and you want maximum Bottem end and phase....here's a great way to get it: http://www.littlelabs.com/ibp.html $550 http://www.littlelabs.com/ibpjr.html $375 These boxes will let you adjust phase in the analog domain between 0 through/to 360 degrees. Example: Bass DI (being only an electronic only path) is 'faster' than the mic'd amp path...therefore there is always a little phase issue betweem the Di & the Mic. You can move the mic relative to the DI, Flip the phase (only in or out), but essentially a comprimise. The IBP lets you dial in the phase diff. exactly! Maximum bottom! I own two and wish I had more...better than EQ in alot of situations. Check 'em out.