I have never used the capture feature on my Quad Cortex until the other day. If you are not familiar with this feature, in a nutshell, you plug the QC (Or Fractal, Kemper, etc) into your amp and it digitally captures the amp and stores it for you. You can then call it up and voila, you can use that amp sound anywhere, anytime. My friend has a Brown Super and a Tweed Deluxe. HIs assistant captured both amps for me and sent it to the QC Cloud and then I was able to download it. It was mind blowing. Matt took several captures for me and I finally get what this is about. Modeling digitally models an amp.....all controls, eq, bright switch volume, gain, etc. Captures capture only one moment. So I have a capture of the Tweed Deluxe at volume 5 and the tone control on 5. Or another capture of the amp with everything dimed. When I call it up, that is what I get. I can turn the volume up and down, but I cannot change the eq, even though the screen has some eq controls. They work like a studio where you record a guitar through an amp and then you can add treble, bass, etc in the mix but you are not changing the eq of the actual amp.
So if I want a nicely overdriven Super sound for a rhythym part, I call that up. If I want a nasty distorted tweed deluxe sound for the solo, I call that up. This thing can also captrueOD/Distortion pedals, mic preamps and a host of other cool things. Again, I am a tube guy, but damn! This thing is pretty amazing.
Here is the Anderton boys doing the A/B thing with the QC capture feature. They also demo how to do the captures, which takes only a couple of minutes.