OK I obviously don't know a lot about this so I'm here. I have a SABDDI and was thinking of getting the RBI. I was looking over some postings and saw that a lot of you use both of them as a preamp. What exactly is a preamp. I am playing an Ibanez SDGR 500 into my SABDDI then directly into my active input on my Hartke HA4000. I am having a real hard time getting a good tone. Is this how it should be run? So if I use either one as a preamp, does that mean I should zero out all my settings on the Hartke and strictly use the Sans amp. I guess that's where I'm confused. Is a preamp supposed to be the source for your tone? Any help is appreciated.