SUT - electrical theory and practical experience

@pindac 

You do realise that everything can be demagnetised , including the phono, preamp stages and power amps - all with subtle gains.

If you are going down that road, to the nth degree, - have you checked all your electronics for polarity ( relative to the incoming mains ) in order to minimise DC leakage. Just to make it really interesting, here in New Zealand each alternate power pole has reversed polarity - but the problem is that if there is a power outage or adverse event, the polarity can reverse. So the tests must be done after each power outage or indeed if you move house.

I don't have any detailed knowledge on the current sensing unit. I cant tell you anything about the circuit.

I would assume that many things can be demagnetised, the reasoning for demagnetising would be the more difficult reason to comprehend.

I am happy to leave the Math to those that fully understand it through creating the equations and not just merely quoting it.

The Clever Types can produce devices that cut to the quick and do what they say on the Tin.

A Degauss Device is quite affordable in some cases cheaper than a Device to control Anti-Static on a Vinyl Album and is especially cheaper than some of the SUT's and Head Amp's that can be purchased.

I have heard the positive outcome of a Degauss being administered and as stated in some cases the improvement heard has been quite notable and definitely worthwhile.

It really does not make sense to have multiple Thousands of £'s invested and not give the full electronic support to the critical devices used in the Phono Signal Path. It is not uncommon to see a Phon' Pre- Amp' set up costing close to £/$ 5K, to be used with Cart's costing upward of £/$ 2.5K.

A mechanical device to support the Cart' and serve as a conduit for a Signal Path can quite easily be seen as a cheap option at £/$ 4K.

Spending £/$ 200ish on a Degauss Device does not seem to be the purchase that is a ninth-degree approach.    

What Dover posted above about proper gain structure being the main objective is shared by quite a few experts.  A good long explanation of why loading, of either the primary side or secondary side is not very important, but, preventing overloading of the phonostage by selecting the proper gain IS important is described in a "white paper" posted on the Rothwell site:

http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html

I believe others, like Jonathan Carr of Lyra, believe in utilizing very little loading (i.e., HIGH value loading resistor or no added resistor) unless the phonostage is prone to overloading from the ultrasonic peak of the cartridge or RFI breaks through.

I utilize a tube phono stage that is not prone to ultrasonic overloading, and I agree that very little loading usually works the best.  My phono stage has a built in SUT, so I cannot fool around with gain, but, I do know that gain is a bit low for my particular cartridge (Transfiguration Orpheus L), but, given that I have zero noise breakthrough, I don't worry about cranking the volume up a little bit to compensate.

Dear @o_holter  : The best SUT is no SUT at all. If you want another all tube unit where maybe you can use that Lyra SL cartridge you like then exist the Wavesteram Kinetics  designed by Scott Farkland:

Wavestream Kinetics Archival Phono Stage (theaudioarchive.com)

R.

@rauliruegas 

You say that "the best SUT is no SUT at all."   What structure(s) in your ideal phono stage replaces the gain that the SUT provides, and how is that necessarily better than an SUT?