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. 

drbond

Perhaps they do, I don't care about religious arguments over purity or neutrality, etc. because I like many tube phono stages that employ a SUT.  My own, a Viva Fono has a built in SUT.  The Audio Note phonostages are all MM stages with the expectation that an SUT will be used ahead of he stage (they sell some very pricey SUT for that purpose).  Zanden's phono stages employ Jensen SUT.  

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.  

 

SUTs are about gain. You can increase gain via a transformer or a circuit. As with most things audio some methods sound better and have other advantages than others 

All these things can be covered by a good phono pre-amp with adjustments for such things.

 

I can only talk a little to the practice. An excellent SUT represents a real improvement over most transformers present in phono stages.