So when is a SUT really needed?

OP: "So when is a SUT really needed?" Ignoring Esoteric Designs:

When, in the natural progression of things, 5 below, you finally try a LOMC Cartridge (Low Output Moving Coil).

MC theory: precisely controlling the movement of a smaller/lighter mass, the coil, can be better than controlling the movement of a larger/heavier mass, the magnet). The smaller/lighter the coil, the lower the output signal strength.

Makes Undeniable Sense, thus Eventually you must hear LOMC for yourself. 

1st you get a TT with a Moving Magnet Cartridge, probably elliptical stylus shape, more than likely aluminum cantilever.

2. You need a MM Phono Stage to both boost the signal and perform reverse RIAA Equalization that occurred during recording, which boosts the highs to minimize noise and cuts the lows to reduce the bass wave lengths to reduce the wide bass groove widths, to get more music on the 12" disc, which, because of the benefits of this scheme was designated ’Long Play’.

3. you learn about advanced stylus shapes, and stiffer/lighter cantilever materials, move up the chain of MM cartridges, perhaps buy used, perhaps get involved in re-tip/re-build/upgrade worn or broken cartridges.

4. you ’improve’ your MM Phono stage. All my preferred choices have been Tube MM Phono Inputs, either in a vintage receiver; preamp; integrated; or separate MM phono stage.

5, Finally Try a LOMC Cartridge. They have ____? signal strength; and their coils have _____? Impedance

6. Learn about Step-Up Transformers, because MM Phono EQ Gain is not enough for LOMC weaker output signal strength.

7. Learn about Impedance (Ohms), because while SUTs are Passive, and might include optional windings to produce optional voltage gains, they also passively/resultantly effect the impedance that the cartridge’s coil will be loaded by. Each gain option effects the Impedance Load differently. 

8. Impedance Guidance Formula: Coil Impedance ____ Ohms x 10.

A LOMC cartridge with a coil impedance of 10 Ohms would have a recommendation for Impedance Load of 100.

Many (I’m tempted to say most) simple/basic MM/MC Phono stages, the MC impedance load is 100 ohms. Specs, often found in the device's manual, should give the Gain and Impedance answer(s), as well as minimum signal sensitivity and overload.

Coil of 12 Ohms ....

My chosen SUT and some info I gathered

https://www.audiogon.com/systems/11318

Elliott, that is all quite true and correct and pretty accurately reflects the path that probably most of us followed.  The realization dawned on me, though, that following this path is not necessary.  The truth of the matter is that a good MM is good enough for all practical purposes.  Or a HOMI.  

Bill,

After a few years with two great sounding LOMC cartridges (you need to hear them for yourself), I also went back to MM, they sound terrific, excellent imaging resulting from both wide channel separation and especially tight channel balance of 0.5db.

Also a primary consideration is to get back to lighter tracking weights of 1.25 gm and I just acquired an OEM VN5xMR stylus to track my V15VxMR MM at 1.0 gm. Both my LOMC track at 2.0gm, not high, but our friend Mies taught us that 'less is more'.

Elliott,

You are right.  I agree with you.  I have to not to try to be another catcher in the rye.

@lewm 

What’s a “SUP”?

Longer explanation of SUT to follow when I get out of bed

It is a form of typo caused by insufficient sleep.  I meant SUT.  Get some more sleep - SUP is entirely my fault