SUT - electrical theory and practical experience

antinn,

A friend has the Tron and it is indeed a good pono stage.  You can tailor the sound to your specific system and taste by trying different tubes.  This is a component worth going that extra mile to optimize.

As to the issue of built in or separate SUT, I have mixed feelings.  A built in SUT of good quality will save one the expense and trouble with finding the right interconnect.  Also, outboard SUT tend to be more prone to picking up noise and hum from external electrical fields.  On the other hand, one can, with separate SUTs, one can find the best match for your choice of cartridge and one can move the SUT around to minimize hum and other noise issues, whereas, if the built in SUT is the source of such noise, one cannot change its location and orientation.  As to the optimizing of the choice of SUT.  I agree with what Art Dudley said many years ago.  He noted that even when a particular SUT supposedly has non-optimal gain or other characteristics for a particular cartridge, he noted that they usually still sound very good.  He said that he never found a SUT that he didn't like.

SUTs are all about the quality of the transformers. I run a Bob‘s Devices Altec Lansing TBB103 and can confirm that using the gain stage of my Zyx Artisan instead leads to a major deterioration from my Zyx Universe. 

I ask this question strictly for my own education and interest in this thread from a science point of view.  I have no opinion.  Having taken college level physics I understand the principal, windings,  etc.  As far as audio SQ  though, would it be safe to say that it should be a perfect conversion as long as they dont have frequency/phase dependent properties?  Is there a physics reason to think they are dispersive?  If they can be, then the materials, construction, etc matter.  Then we run down that rabbit hole and in this case yes, they affect SQ unless built in the best possible manner.  In any case it would need to be shielded from EM as that induces a stray current ie noise (actually how they work really).  

not sure you clearly understand the need to use a SUT.

Moving Coil cartridges are different technology than Moving Magnet. MC, the small lightweight coil moves (rather than the heavy magnet moving). Allowing a refined and more accurate signal fidelity (or so most believe to be true).

Lightweight moving coil makes a weaker signal strength. That low signal needs to be MAGNIFIED (not enhanced), just boosted in strength enough to be essentially as strong as a MM cartridge’s strength.

At MM strength, the/any phono signal needs to be ’equalized’ by the industry standard RIAA curve. That is what a ’PHONO STAGE’ does. Phono stage can be a dedicated phono input in a preamp or built into a separate Phono Stage.

Once ’equalized’, it is equal to any LINE level input, i.e. AUX, line 1,2,3 ...

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SUTs, MC cartridge (step up transformers), need no power, their internal transformers have alternate windings that modify/boost (but not enhance) the signal strength simply by the specific design of the transformer.

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Voltage Transformers are very different. i.e. My Japanese Turntable is designed to run on Japanese standard voltage of 100 volts. I need a STEP DOWN transformer, that converts my USA 110/120 volt down to 100 volts, and I plug my 100 volt TT into it. Those are powered devices.

Step Down transformers exist also. They alter Voltage.

To answer the OP's question re: what does the SUT do to the sound quality...

For what it's worth,I have several phono stages and several active step up devices/ SUTs and generally, the SUTs are quieter and more open (when properly matched etc...)

I currently run a Sunvalley Audio SV-EQ1616D phono stage and ZYX cartridge. The Sunvalley has a built in " FET head amplifier that adds another 25–32dB gain with fixed 50 ohm loading for use with low-output moving-coil cartridges". The MM stage is good, the FET is NO Match for a good SUT. (n.b. the proper load for the cart is +100 ohm). I am using a copper wound SUT in custom housing and sheilding. Best combo I've had since the 70's.