So potentially, we have the onstage actual guitar amp path, we have possibly another monitoring path and then the front of house path. A show could vary, with an amp filling all three roles, but for a bigger show, these may be separate things.
And here’s where things get sticky. The monitors and FOH DEFINITELY need the sound of the speaker cabinet, which of course is why the guitar amp is often mic’d. On the other hand, if you have your head or combo or 4×12 or what have you, you don’t want that speaker cabinet emulation. It’ll sound like sticking a bandpass filter in your FX loop.
In general, the devices and software I’ve seen for iOS seem philosophically aimed at the home user and this is one area where it hits you like a Mac truck. I guess one easy solution is to play thru a full range speaker. One of those self powered PA speakers would fit the bill nicely. That way you could just leave the cabinet emulation on, and all three paths get the same signal, thru some splitting or separate outputs (and yet another infuriating disconnect, and hopefully, you guessed it, more on this later).
Your other choice could be going thru the actual guitar input of a normal guitar amp. In this case, software side, you’d want the cabinet off, probably any possible power amp simulation/transformer type stuff off as well, and depending on your desired outcome, whatever FX you were planning on using the amp for as well (distortion, compression, reverb, you name it), but I figure this probably defeats the purpose of the iThing. I would think you’d set the amp pretty flat, bypass most of its stuff (though the amp’s EQ could be used pretty handily in a live situation and again, and ENRAGING more on this later), and use the iBox to handle the FX. Interface levels, noise, design, and *watch out!* stereo vs mono and potentially painful summing (sorry, yet again, more on this later!) are issues you need to watch out for here.
Another choice could be to use the power amp in or FX loop return of many decent guitar amps. In this case, you’d wan’t the cabinet emulator off and again, levels and summing need to be looked at. Knowing the topology of your amp is pretty critical here. You may or may not have EQ and pretty importantly, master volume after this insert point, which could be ideal. Depending on the particular amp, you *may* have a “recording” or “emulated” output which sources after the FX loop return and gives you, tada (!) a speaker emulated output to hand to the soundguy! Really convenient! These aren’t always the bestest Rosen Digital impulse sounding emultors, but whatever, its a hugely far cry from some knucklehead micing the floor of the stage while pretending to mic your amp.
For many amps you are still looking at the problem of providing the soundguy with a speaker simulator output. [rant mode on again]…Target market guys! If you’re developing for the home guitar player, aimed at playing thru headphones and recording to Garage Band or whatever, no problem, this works out pretty well. For a guitarist hitting the stage at a venue where the guitar signal will have to go to Front of House, these apps fall short, though there are some workarounds. This isn’t just the app developers’ fault, some serious blame needs to go to the interface makers as well…sorry, you guessed it, more on this later.