Using a totally different set up while recording?

I record with different gear than I play out with most of the time. For one thing, I store them in different places.
For another, just because you have an amp or guitar that works well live doesn't mean it does well in the studio.
For one thing, some amps are a hassle to use in the studio because they are noisy. I would rather just use a different amp if the cab in one has a rattle that you cannot hear but that a microphone can. Chasing cab noises down is too much trouble.
Volume is another, sometimes it is easier to bet a bigger sound with a small amp than a large one. Dropping a mic in front of a 5 watt tube amp can sound HUGE.
Think about it, if you want that nice fat sustaining high gain sound from a 100 watt amp, you gotta be pushing ear splitting DBs to get that sound. You can get it by pushing 5 watts that hard and have the amp in the same room with you, and get the edge of feedback sound. You need to be in the room with the amp to get that kind of sustain and reaction.
Seems I read somewhere years ago that it wasn't unusual for jimmy Page to record Zep stuff through a little Supro amp.

 

Exactly. Small amps cranked for studio use is an age-old technique that's actually migrating a bit to the stage nowadays since sound reinforcement gear has become pretty good and you can mic a little amp, and get good sound to the monitors and the FOH.

In the old days you needed hundreds of watts and huge cabs to play big spaces and anyone who lived through the early 1960s and 1970s and even into the 1980s playing live or seeing live rock and roll knows how freaking bad and inadequate FOH sound systems were, especially in big rooms. But when you got into the studio you couldn't always play your daisy chained 100 watt amps dimmed into two 4X12s without pinning desks, or blowing out your ears or living with all kinds of room rattle, etc.

These day you still often see guys using big amps and cabs live of course, but switching to 5, 10, 15 watters for recording very often.