When is it time to consider adding a SUT?

So we now have many posts quoting the science and others quoting user experience indicating that a quality SUT and cables may in fact improve the end to end performance of a high quality and capable PS even if they have sufficient gain required for LOMCs.
I am still waiting for my cartridge to come in and I will listen carefully for any anomalies even though one might not know what is missing until you try a SUT in the chain.  

Dear @billstevenson : Well, that kind of designs exist in the market. I'm using one for some years now and outperforms not mid-level tube designs but any one .

@gtaphile :   "" not know what is missing until you try a SUT in the chain.  "

for " thousands " of years I used SUTs with either: tube and SS designs. I owned almost every SUT in the market. In those time I really did not know nothing of what " today " I learned/experienced on the SUT subject.
As a fact I still own Denon, Entré and Audiocraft SUTs. I still use it time to time, so I have past and today first hand experiences.

I can tell you that you can't miss anything through the SUT experiences against a today good active design using today bipolar devices. A SUT can't compete in anyway against today bipolar transistor. The audio signal is degraded at higher levels through a SUT than a transistor. Problem is that the audio signal in your system pass through tubes in the AR item.

Audiophiles have different kind of experiences and learn different " things " and sometimes exist misunderstood in what we learned.

Regards and enjoy the MUSIC not DISTORTIONS,
R.
  

rauliruegas,

Please provide facts to back up your claims.  What phono stage are you referring to?  What tube phono stages have you compared it with?  What is your criteria for deciding what phono stage "outperforms" others?  Try and stick to facts.  Making a statement that you have used something for "thousands" of years, does not help your credibility. 

I will state for the record that I have personally listened to high end phono stages from Conrad Johnson, Audio Research and Manley that sound better to me, in my system, than a solid state phono stage that I have compared them with.  My solid state reference has been a Lehmann Silver Cube.

Dear @billstevenson : No problem because exist several facts about but before that is important that you and me talk in the same " audio language ".

All the audio items are designed to accomplish specific targets and I would like that you share from your point of view which of those item targets are the main ones in a phono stage .?

Could you, please?

Thank's in advance.

Regards and enjoy the MUSIC not DISTORTIONS,
R.

Raul and I are more often than not on opposite sides of controversies like this one.  However, in this case, we are on the same page. On the other hand, I could well imagine that a tube phono stage with marginal gain when matched to a particular LOMC cartridge would sound better if a SUT is interposed between the two. That's no surprise to me, either.  So, this could also be a case where both sides are "right", because no one has defined the terms of the argument. How low does the output of the cartridge have to be in relation to the gain of the phono stage before noise and reduced dynamics become obtrusive, whereupon things get better if you add a SUT?  To some degree, that is a subjective judgement, unless we are talking about ridiculous mismatches.  However, in my opinion, the particular example posed by the OP should not benefit much from adding a SUT.

I use a bipolar transistor input stage at the front end of an otherwise all-tube phono stage. Raul doesn't like this, because it uses mostly tubes, but the tremendous gain afforded by the transistor does result in an easy, dynamic, unstrained, and very low noise (not to say "no noise" that I can perceive) presentation that was not obtainable prior to introduction of the solid state input device.  In fact, there is no LOMC that my preamp cannot handle with ease, up to and including an Ortofon MC2000 with an output of 0.05 mV.  But again, this is my subjective opinion.