I used fake or modeled software versions of amps. I did this with a hardware/software combo called the POD Studio GX, by Line 6. It’s a small interface box that hooks up to your computer via USB. The interface has an input (standard quarter-inch plug) for a guitar or bass. POD Studio also comes with POD Farm, which is huge collection of guitar and bass amplfier models. The Line 6 site describes the collection as an arsenal of vintage and modern amps, cabs, studio-standard effects, classic stompboxes and preamps.
Read the full article here: http://www.homebrewaudio.com/guitar-recordings-for-that-thing-you-do-cover-line-6-pod-farm