Manufacturers of expensive microphone preamps usually write a lot about transformers and how good they are. I know transformers have been used often in the past, but with modern electronics, this is somewhat unusual and typical budget preamps do not use them.
If I buy a microphone preamp with a transformer in the circuitry, under what circumstances would I expect it to sound better than a cheaper, transformer less design? Would a high quality microphone be required to notice the difference?