Dear
@thuchan : Over the years I made it and still do several tests with vintage and today SUTs and with different phono stages and cartridges in my audio system and other well know friend's systems.
I'm not an expert on SUTs I'm still learning about and what I find out is that the most important subject is to match the SUT , NO that's not the whole word but I have no other, to the phono stage and not mainly to the cartridge as almost all we can think.What we are looking here is for enough additional gain to play LOMC cartridges with no " noise " levels.
LOMC cartridges are non-sensible to impedance and capacitance and its has very low inductance. We use a SUT because we need gain that our phono stage can't do it by it self.
Changes in impedance affects that gain/SPL and when we make changes on impedance and we hear changes in the frequency response range those changes comes not from the cartridge directly but comes from the interaction between the phono stage/SUT impedance/inductance.
Sometimes those changes in what we listen comes too because we are not even the SPL before and after any change we do and our ears are extremly sensitive to minute SPL changes, this issue is critic on any evaluation/comparation we do on audio.
Look here what Ortofon recomend to his customers about impedance subject where you can read is almost totally OPEN the impedance range because they know what I said above. Here too can you read the Lyra recomendation with his SL models :
http://www.ortofon.com/hifi/products/hifi-cartridges/mc-anna/technical-dataLyra: """
Recommended load directly into MC phono input: Determine by listening . """
Sometimes those changes in what we listen comes too because we are not even the SPL before and after any change we do and our ears are extremly sensitive to minute SPL changes, this issue is critic on any evaluation we do on audio.
The real problem on those changes on tonality or balance in the quality level performance comes mainly because the phono stage design is not really a good design that can't handle the complex impedances/inductances generated when we make changes about.
It's not a fault from the SUT or that the cartridge likes or does not likes the changes. As I said is a trade-off coming from the phono stage it self.
Is it the SUT a perfect device?, no it's not: it generate its own distotions, it has limtations at both frequency ranges, it's suceptible to takes electro magnetic pollution, generates its own noise levels and some other trade-offs.
Then why exist the SUTs as a gain external or internal to phono stages?
externally because could be that our PS can't handle LOMC cartridges, we need additional gain that comes with additional distortions including the ones generated by the IC cables and input/output connectors.
internal SUT comes because for almost all tube designers is the easiest design way to achieve the cartridge needs gain and in SS designs because that PS was designed thinking on MM cartridges and not LOMC ones or just was what the designer likes it.
Now, if we want the best " perfect " quality performance level on any LOMC cartridge then the best SUT is NO SUT.
Here we need a good designed active high gain Phonolinepreamp that has not or at least are at really minimum all the SUT limitations that per se goes against that sensitive and critical very low signal that comes from the cartridges.
Yes, everything belongs to the quality level design, selected design ( active and passive ) parts and quality level on the design excecution. Btw, the right active device for LOMC cartridges is bipolar one that we don't see it often because bipolars are a " pain in the ass " for this kind of unit designs. Designers on SS and tube designs that don't use bipolars they choose for JFET or the like because is more easy the whole Phonolinepreamp but exist a detriment in the quality levels against the use of bipolars. No, this is not an additional window to " discuss " in this thread.
In the past Lyra designers had a Phonolinepreamp with no internal SUT but was an active high gain Phono Stage. JC had very good reasons for that.
So, SUTs exist and will exist because something of what I'm posting here.
Btw, your sentence:
"""
. The windings are manually done with enough space """
IMHO this kind of work with a transformer must be achieved by a machine noit manually because manually there is no human been that can stay always not only with the required distance but tension too and other subjects.
Anyway, here is my " take " about and of course that I can be wrong but till I learn something " new " from the real experts that's my point of view.
Regards and enjoy the music,
R.
So, if your quality sound level change when using a SUT don't change the SUT but your Phono Stage!.