Byron wrote:
But then howcome we spend oodles of cash on big fancy tube amp stacks instead of just one of these thingies?
The digital circuits merely emulate the sound of the analog circuits. A digital piano like a clavinova can only come so close to sounding like a steinway for obvious reasons. The small nuances in the sounds that arise as a result of the intricacies of the original circuits are lost when you use emulated sounds. However, a steinway grand that is recorded and played back through a PA system will sound very similar to a digital piano played through the same PA as the sound is altered in the PA anyway. The same applies to guitars. A great guitar amp will lose tone if it is sent through lots of cables and mic's and speakers and amps and mixing decks and whatever else.
Then these digital effects make sense - lots of sounds from a compact box that sound similar to the real deal.
But if you listen carefully to the actual guitar amp, there is quite a difference between the digital amp model and the real thing, especially when you listen to harmonics and overdrive and resonant frequencies. Of course things like the amp cabinet also add or take away tone depending on the design.
Things that make an amp famous might actually be it's shortcomings - a steinway will actually show flaws when compared to a yamaha if the sound is analyzed. So why get the steinway? Because it has character, something that will make the yamaha sound more like a synthesizer than a living breathing piano. (generalizing of course, I don't even play piano)