SUT - electrical theory and practical experience

"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"? 

It does seem from the descriptions supplied from certain individuals who have taken the time to check for an appropriately / ideally matched SUT > MC, set up as an optimised interface, that there are attractive presentations that can be discovered, and in comparisons, to other interfaces using a different SUT or Cart', that are again an appropriately / ideally matched SUT > Cart', that there are discoveries made that are not so attractive.

Being Wed to one type of Phonostage and its MC Input will not allow for the discovery to be made, that the Cart' in use is able to present in manner that has increased appeal and attraction.

Through using a method that restricts the experiences to be had with the Cart', where it is to be used with limitations to the interfaces that can be produced, is an OK method, but certainly a method not embraced by all.

To add ancillaries to work in conjunction with a Cart' and Phon', the method when chosen can prove be quite valuable as well as limiting, the experimentation required to discover the ideal interface and optimisation is a process and requires time to finalise the ideal set up. 

Again, as a method it is OK and not embraced by all. Where it has merit, is that the permutations that can be put in place are certainly expansive in the introducing of new discoveries of how the Cart' can present.     

Dear @o_holter  : I think your PS is high gain active unit then why a SUT?

R.

@lewm 

I was about to ask details about the transimpedance phono stages, such as exactly how the current is converted to voltage, and where / if a load is added, and how it automatically detects how to do the voltage conversion, but maybe that's a college course, so I decided to do a simple google search, and found this seemingly very informative video reviewing the advantages of the current mode phono stages, which apparently is getting a better signal to noise ratio, amongst other things. . . and he does recommend a cartridge with an internal impedance under 10 ohms, but maybe he doesn't know everything. . . 

yet another very dogmatic thread, this. If SUTs are evil, why do designers like Ortofon, Yamamoto, shindo et al use them rather than active circuits? Surely there are many ways to Rome and implementation matters.

@drbond 

Basically a voltage amplifier will deliver voltage gain with whatever current is required to do the job.
Hence in a power amp, sometimes there is not enough current to maintain the voltage at the speaker

If there is not much voltage, but a bit of current then a current amplifier can be a good solution.

A current amplifier can later push that current across a resistor to compare the voltage… and drive a voltage amplifier in an output stage or RIAA circuit.

I think I mentioned earlier that this is using “the natural” ohms law.

and, in fact, the cartridge itself can push try and push the current across a resistor and use compare the voltage with a voltage amplifier.