Which SUT? .... for .3mv/10 ohms MC cartridge into 3mv MM input sensitivity

What a complex exchange for a relatively straight forward issue.  Look up the Black Swan, fully front panel continuously adjustable loading and gain, tweak it by what I call earball, set all the variables while listening to it.

barry

thanks, I'll check it out. I get the earball thing, now that I realize what it's all about.

I've resisted even mouthing the words Moving Coil since they needed humming boosters when I was young, it is all new to me. I enjoy learning, and sharing my finds with 'imagined' others.

I'm a retired Interior Designer, specialized in Corporate Headquarters: New, Relocations, Renovations. Interior Architect  actually, as practiced in NYC, PA, Wash DC, traveled hither and thither. I became more informed bit by bit progressively for 50  years. I researched everything, designed much custom work, selecting, presenting options to my clients, ordering a gazillion things. Select and present a full line of chairs, mail room to President's office, for a new 250,000 sq ft headquarters project, it's exhausting. I was not going to tell a client 'this is the best choice', and find something 'better' that I didn't know about a week later.

Now, for myself, i.e. that Fidelity Research FR-4. It truly appeals to me, and it did not pop up in my search until after a lot of searching. No one mentioned it. New, it's features and quality, would cost ___? It's hard for me not to 'add to cart' and put this search to bed.

Demagnetizer, who loses sleep over this?

Miyajima Labs sometimes include demagnitizing built in

"When several months pass, a stepup transformer and the cartridge are magnetized.
The demagnetizer short-circuits ... "

If true, couldn’t I use my demagnetizing wand for my reel to reel decks for this?

You may want to do some reading here. I think it will help answer many of your questions, and answers to your questions, about cartridges and SUT. Lots of great info on all things hi fi.

https://www.audioasylum.com/cgi/d.mpl?audio/faq.html

Air Tight SUTs have bypass for MM.