Digitech RPs have a button on the back panel labeled “Amp/Mixer.” We get a lot of questions about that button, all of which boil down to “which way should I set that button?” To answer that question we need to start with “what exactly does that button do?”
The short answer is that the amp/mixer button enables and disables cabinet modeling. You know, when you set up a patch, after you choose the amp model, you choose a cabinet to go with it? When you set the amp/mixer button to AMP, the cabinet model is bypassed, i.e. the signal goes to the outputs without a cabinet model in the path.
At least two important things happen when you pull the cabinet from the signal path. First, as anyone who’s experimented with the cabinet models knows, the specific cabinet configuration has a powerful effect on the tone. So when you pull the cabinet from the path, the sound of the patch changes. (If you’ve never experimented with different cabinet models, take a few minutes soon to bring up one of your favorite patches and run through every cabinet model in your RP. You’ll certainly hear the differences, and you may discover a new favorite or two.)
Second, and just as importantly, when you take the cabinet out of the path the sound gets a lot more raw. If you’ve ever tried running a simple tube preamp like the ART Tube MP directly into a PA, you’ve probably noticed that it sounds pretty rough and tough, and not necessarily in a good way. Putting a cabinet after an amplifier, whether it’s a “real” amp and cab or modeled versions, smooths out the sound and makes it a lot easier to listen to. When you set the amp/mixer button to MIXER, the cabinet model is in the signal path, and the sound is less harsh, with more individual character (assuming you change up your cabinet models from patch to patch, or at least when you change amp models).
So that’s what the button does. How should I set it?
If you’re running your RP directly to a mixer, to an input on a recording console or audio interface, a PA or keyboard amp, or any other amp, like a Fishman Loudbox, designed to reproduce sounds as clearly and cleanly as possible, you DEFINITELY want that button set to MIXER. I find that the RPs put out a very edgy, sharp tone when the cabinet model is defeated via the amp/mixer button, and it becomes tiring to the ear before long. Granted that there are occasions on which that kind of sound is useful; for the most part, it’s excessively grating. It’s also not as good for looping, because when none of the amp models are coming through a cabinet, they sound more alike, which is not what you want for the layers in a loop.
As it happens, a couple of days ago I suddenly found that my RP500 had taken on a very sharp tonal character. I wondered whether I’d had some kind of failure in the device that pushed up all the treble frequencies. But when I looked more closely, I realized that I’d somehow set the amp/mixer button to AMP. I reset it to MIXER, and all was as it should be, with every sound exhibiting its own (cabinet) character.
If you’re running the RP to a guitar amp—which of course I DO NOT RECOMMEND, but still—you definitely want that button set to AMP. A guitar amp has its own cabinet, and that cabinet will take the edge off the RP’s sound and impart its own character to your tone. Of course you lose something when you go this route, which is the particular characters that different modeled cabinets bring to the sound, but that’s the price you pay for using a guitar amp with your RP. Did I mention that I DO NOT RECOMMEND using a guitar amp with the RP? Stick with the keyboard and PA amps if you want to get the most from the RP. If that’s not possible, set the amp/mixer button to AMP and get on with it.
That’s how to set the amp/mixer button. Now go forth and make some great sounds.