SUT - electrical theory and practical experience

@rauliruegas,

For the record and no pun intended, TI did not exclude wide bandwidth MM.  Their written statement was "This is generally not a problem with moving magnet cartridges, since they are usually severely band-limited above 20 kHz...".

Otherwise, your preamp spec with slew-rate 350 V/us and 1.5MHz bandwidth mathematically (using the equation to determine slew rate at frequency) is capable of a peak voltage (at 1.5MHz) of about 3.7V.  Any more than this and at 1.5MHz, the amp becomes unstable.

What does this mean in real-life?  Well, that's a good question.  There are obvious 'designers" such as Goldmund and Spectral WELCOME to Spectral Audio'sHome Page who adhere to very high 'speed' high slew-rate (Spectral is >1000 V/us with bandwidth 1.5 MHz) designs as the optimum.  While others do not.  

The 'bandwidth' (no pun intended) of audio design and followers of each is equally wide (no pun intended).  For one to stipulate that one is better than the other, IMHO is an exercise in futility given the wide variation in just individual sensitivity to sound which academia has indicated can be a factor of 10:1:  

Consider what is written page 16 – of Microsoft Word - P406POM_Lect5.doc (illinois.edu) UIUC Physics 406 Acoustical Physics of Music ©Professor Steven Errede, Department of Physics, University of Illinois at Urbana-Champaign, Illinois 2002 - 2017. The Human Ear ⎯ Hearing, Sound Intensity and Loudness Levels (78) "The time-averaged, or RMS sound intensity threshold of hearing (@ f = 1 KHz) is: ~ 2.5x10-12 RMS Watts/m2 = 2.5 RMS pico-Watts/m2. Individual people may hear better/worse than the average person, and so threshold of hearing from one person to another can vary as much as 1/10 or 10X this!!!".

Take care and best wishes for the holidays,

antinn, In your quoted paragraph, I think they are using "Watts" as an expression of acoustic power or energy.  On that assumption, and wanting to know how acoustic watts is defined, I found this on Wiki: "Sound power or acoustic power is the rate at which sound energy is emitted, reflected, transmitted or received, per unit time.^[1] It is defined^[2] as "through a surface, the product of the sound pressure, and the component of the particle velocity, at a point on the surface in the direction normal to the surface, integrated over that surface." The SI unit of sound power is the watt (W).^[1] It relates to the power of the sound force on a surface enclosing a sound source, in air. For a sound source, unlike sound pressure, sound power is neither room-dependent nor distance-dependent. Sound pressure is a property of the field at a point in space, while sound power is a property of a sound source, equal to the total power emitted by that source in all directions."  It's not an easy concept to grasp.

It is now within this thread, having evolved from a useful supply of information, that most visitors would like to take something from, to a very unusual concern, where a minuscule quantity of individuals concern themselves.

The presenting of a Math as the reasoning to impose the notion that another method is lesser and not the optimised circuit is really starting to taint a well presented thread, as result of its former contributions.

The thread now is grounded with ones intention to attempt to impress their Mathematical Preference as being the better over another.

This attempt to hold centre stage, is being met by others, with a countering of this  very obvious intention at large, especially where the Math has been used as the support for the notion being proposed.

The Mass of Users of Devices as a Listener, do not care for such a Topic of Discussion.

As said many times, the Judgement made on a device is commonly born from there being an attraction toward it, either through Clever Marketing, Word of Mouth, Aesthetic appeal, Cost, Discounted Cost, Gifted, Impact Made During a Demonstration, Stimulus Created, Attractive Experience Worthwhile to Maintain.

Somewhere behind all the above that coming together in one permutation or another is Math. It is quite difficult to see where the individual place much care on the Math that is not the commonly used criteria for matching a Device to another Device.

The Topic of Math most recently under discussion and now dominating as a Spoiler, is as far to the extremities and circumscribed in content, as can be imagined, when comparing the content to the OP's original request for information. 

…
 

Somewhere behind all the above that coming together in one permutation or another is Math. It is quite difficult to see where the individual place much care on the Math that is not the commonly used criteria for matching a Device to another Device.

The Topic of Math most recently under discussion and now dominating as a Spoiler, is as far to the extremities and circumscribed in content, as can be imagined, when comparing the content to the OP's original request for information.

Respectfully I’ll offer an alternative…

The section with the URL link on “the gain of SUTs” had some compelling maths that to help to show how some SUTs may be a better match for some carts.

I would say that that “linked info” falls squarely within the second paragraph of the OP’s ( @drbond  ) question.

Para2:

…
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? 

Even the OP’s first paragraph mentioned wanting to understand the theory behind a SUT. So the beauty of Maxwell’s equations sort of is a real manifestation of scientific understanding becoming an engineered product.

While many an end user may not want to understand it, and would rather have a recommendation of one particular SUT and similarly one specific cart… it is none the less a true thing of beauty how both the cart and SUT work.
There is more science and math in it than magic .

But the OP can (and should) certainly drive the conversation in a way that helps them.

+1 @fuzztone …..it’s about gain, simple.