I have my AU-X11 back from the dealers last week after they fixed the problems concerning the external pre-am in connection and no sound out from HP out . My original non-vinatge SS amplifier also came back from repairs for direct comparison. After listening for a week it's time for me to report to you guys . SCD-777ES →AU-XII →Fischer & Fischer Floorstander: AU-X11 added warmth and smoothness to the mid and high , while rounding off the highs and adding bump to the low end ,compared with my modern SS . Male voices benefit all along the spectrum. The same happens to female voices , except that the Suprano sometimes happens to be round off too much, adding warmth at the expense of timbre and detail. Adding a tube pre-am Melody 1688 between SCD777Es and AU-X11 further enhanced smoothness and sweetness to the female voice. This is the combination which my wife prefers most. However, my speakers is not full range , and start to decay below 60hz. The bump in the low tends to exaggerate the mid-low and create an unneceassary mid-low boom for some of the recordings . This is especially so now that the gears are placed in a small bedroom ( the sitting room is occupied by the AV rack) . Turning back to my modern SS amplifier, the sound become clearer , much faster and more focused , revealing more details and tonally more balanced . Overall I prefer the modern sound more, although there is a special open and warm sound associated with this Sansui AU-X11. An audiophie friend auditioned the system . He commented that the good thing about this Sansui can also be achieved by a modern high end high powered tube amplifer , with better extended high frequencies. He believed that my accurate and fast speakers does not have good synegy with the Sansui. A better synergy would be with those old school vintage speakers with horn or ribbon mid and high and 15 inch woofer . I tend to agree with him, these vinatge amplifers are designed to sound best with the speakers of their time. Now let's turn to computer tempotec digital only sound card → Audio GD NFB 10SE DAC/pre → AU-X11 ( pre in ) HP out →HE-6 At first I listened to male and female voices . This is where it shined . The HP out of AU-X11 is more than enough to drive the HE-6. The Audio GD 10SE is already powerful enough to drive HE-6 , pumping 7ws into 50ohm. Using the pre-out of 10SE to AU-X11 , the difference is obvious: a richer and more open sound , added warmed and authority , added sweetness of the female voices and presence of the male voice . It was audio nirvana ! As for comparison with tube amplifer for driving the HE-6, I have only tried Audio Note P-2 before. Audio Note P-2 obviously does not have the juice to drive HE-6 properly . P-2 sounds very rich and smooth ,but for some music will appear dull and lacking in dynamics , the highs are not so extended and the bass is not so plenty and bumpy compared with AU-X11. However, as in the case of speakers, I believe the modern high end and high powered tube headphone amplifers ( Leben , or Hifiman EF6 , or maybe even darkvoice or LD Mk.VIII ) might match AU-XII in it's strengths and have better clarity, higher extension , better layering and detail . This is only what I deduce from my above experience and may not necessarily be true. When it comes to human voice backed up by layers of electronic instruments, or large scale violin concertos , it's another story . AU-X11 gives a rich and authoritative sound . But since there are so many voices and instruments involved, the scene become more congested or chaotic ( only comparatively). The violin and the orchestra obviously suffer from the loss of clarity , micro-detail and speed. This is only when compared with the high powered , accurate and fast modern SS gear . BY itself the AU-X11 is already producing a very convincing and engaging sound . AU-X11 is the first vintage amplifer I tried, and I deliberately chose the TOTL of the TOTL , in order not to be preduiced against the vinatge . The Sansui engineers took the AU919 circuit to the extreme and produced the AU-X1 with the up till then unknown speed and ability to capture the transience , while maintaning the traditional Sansui bass and warmth and round off high . They further refined the AU-X1 by removing the fault in the circuit which leads to the propensity of oscillation . There came AU-X11 . I believe at 1983 AU-X11 might represent the pinnacle of vinatge SS gear . However, I believe also that modern high end SS gear on a whole is of a different league and surpass the level of AU-X11 . But the warm and rich mid , and bumpy bass and round off smooth high of Sansui still works magic for a lot of music , especially the male and female voices ( may be except soprano in my opinion, unless you are using horn or ribbon tweeter). My conclusions is , the more a piece of music require resolution and speed , the less AU-X11 will excel. For example , the Hi-Rez Leonard Cohen album sound so hynoptic and warm on AU-X11 , but the Hi-Rez Aaron Neville album of "Summertime "sounds much better on Audio GD NFB 10-SE alone, which captured the transience, minute details and nuances much better than AU-X11. Although I have not had the chance to compare with Leben , or EF-6, I believe these modern high end high powered tube HP will also on a whole surpass AU-X11 in terms of clarity, layering , tibre, etc. I do hope that some other guys can provide a comparison for Leben a or EF-6 , if not against AU-X11 , then at least against an AU919 to prove or disprove the point.
Right now there are a couple dings and a missing mic level knob, but other than that it's in fantastic shape 
