SUT's clearly can work. And an argument can be made against them.
For those designing 'minimalist' vacuum tube stages they are 'free gain'
For others they are a bandwidth limiter. But this could be a good thing depending on your school of thought.
SUT - electrical theory and practical experience
Some vinyl users use a SUT to enhance the signal of the MC cartridge so that it can be used in the MM input of a phono stage. Although I don't understand the theory behind it, I realize that a SUT should be matched individually to a particular cartridge, depending on the internal impedance of the MC, among other things.
Assuming an appropriately / ideally matched SUT and MC, What are the inherent advantages or disadvantages of inserting a SUT after the MC in the audio chain? Does the SUT theoretically enhance or degrade the sound quality? What does the SUT actually do to the sound quality?
Thanks.