TX-103 break in.

Charliee, In one of your responses, you mentioned hooking the CDP to the INPUT of the SUT.  I am guessing that was a momentary lapse; Loesch and all the others are talking about hooking the signal to the OUTPUTs of the SUT.  Just to be certain.

While I do not necessarily share Robjerman's skepticism about the value of break-in, I do wonder at Loesch's comment suggesting that it is desirable to "magnetize" the core of the transformer in order to achieve proper break-in.  I would have thought that magnetization is undesirable; you'd want to break in the wire coils without magnetizing the core. But I have never played with a SUT in my own system, so I don't have a validated opinion.  And Loesch is no dummy.

Also, contrary to what Rob said in one post, a SUT has no "resistance" of its own.  There is indeed resistance presented by the wire coil on the primary side, between hot and ground, and a second analogous resistance presented by the wire on the secondary side, but these have trivial effects.  Transformers merely reflect the output and input impedances of the devices to which they are connected.  So, if you have a SUT with a 1:10 voltage gain, that means the turns ratio of the SUT is also 1:10.  (That's 20db, a little more gain than that of the SUT you own.) The impedance seen by the device on the primary side will be related to that on the secondary side (or vice-versa) by the square of the turns ratio, or in this case, 1:100.  If you drive the secondaries of such a SUT, the device connected to the primary side will "see" an impedance equal to 100X the input impedance of the driven device.  So, if it's just a 27 ohm resistor or whatever, the resistance/impedance seen by the CDP connected to the secondaries would be 2700 ohms.  Most CDPs can drive that impedance, but I did wonder why he stipulated such relatively low values of R.  Maybe so as to assure that everything heats up.

         When I bought My Bent audio mu's directly from John at Bent Audio, He asked if I wanted to have them broken in before he shipped. Of course I said yes as there was no charge just a longer wait. Your mu's just might  be broken in from the factory. I'm sure most people who bought one would have said yes to his offer.       I don't use mine anymore because I bought a phono pre that has all the gain I need. (Wright Sound Silver Top with 60db of gain).

I also have ZYX CPP-1 headamp and it's a nice device. Have you seen it inside ? Last year i opened it up to replace the batteries. It was a first time when i saw input resistors like that! Those resistors looks like an MC cartridge coil and made by winding the wire to a coil that has no inductance in a special process. Those resistors made by ZYX to transfer the output signals with no noise and no inductance at all. They are made of pure coil wire of MC cartridges, cryogenically purified. Signal from LOMC cartridge should go into ZYX CPP-1 Headamp’s resistor wihtout any influences from resistor noise and inductance. Nakatsuka-San decided to use his own resistors made of pure copper wire, same material as a copper wire of MC carts. In order to playback the sound info of LOMC carts in 100% fidelity, CPP-1 headamp has special circuit in the simplest amplification circuit. Great device to avoid Step-Up Transformers for LOMC

As for the SUT's burn-in the best option, in this case, is to buy a classic SUTs (used) made 40 years ago. There are some killer SUTs. My personal favorite is Luxman toroidal silver sut. With the set like on those pics any MC cartridge can be used with it.  

I don't believe in burn-in process of the SUT, people overestimated the importance of it, you'd better just connect it to play music from your vinyl.