ARC Ref 3: Tung-Sol 6550 in power supply?

You are probably right Oneobgyn. Probably however we are talking about a different philosophy of "the zen of listening to music". From my experience infact, everytime I change something in my system (BTW Soon I will pubblish it to give more clarity about my listening experience), I'm prepared to maximize the benefit (If I sense there is a potential for improvement) by tweaking here and there. Sometimes even changing the Cartridge weight of 0,1 Gram forces me to change something in the system. So for me it is not strange that changing tubes I have to change something to get a new set-up. In this case I'm not saying I obtained miracles; I'm just sharing my experience and adding to the thread (And this is in accordance to Guido conclusions) that the 2 solutions give a different Sound...and that I like what I have with the new set-up because I can hear for many hours without feeling tired. On the other side I understand also that the better definition of Original 6550C is beneficial for easier interpretation of words of singers and or to catch the notes while listening to instruments. This is probably why Guido being a professional musician (I'm jealous!) is looking for the max detail and myself as a concert listener I'm looking for the closest "Concert like" experience....And I believe the current set-up is closer to the timbre I hear in Jazz concerts for a piano or classical orchestra being in the 15th row. Just to correct one sentence in your post, The bass with TS is more in quantity and extension. It is the tightness that I was mentioning as not as good as before. I look forward to getting more on the subject

Being involved in this hobby for well over 35 years has always shown me that when something is changed I always ask "did I hear something different or did I hear something better"

Perhaps the chaanges in your system is what minimized fatigue as you were hearing something different, not neecessarily better. Nonetheless hearing from you about your conclusions will be informative

Marco_esposito - your findings seem to confirm what Guido has written before - the current production TungSol 6550 (so called "reissue") does not bring a net benefit compared to SED 6550C.

When I was talking about the improvment I got by inserting a TungSol 6550, I meant the NOS (New Old Stock) TungSol 6550 Black Plate from the early 50s - which is a totally different tube to the one you have tried.

I cannot recomment it (NOS TungSol Black Plate) highly enough.

Thank you Marco, please keep us posted on Black Sable. . . I wish there were a 6550 variant that would outdo the SED 6550C with greater top to bottom extension, tighter bass control, and greater harmonic development. . . . as you may notice, I am not necessarily seeking 'warmth'.

As anticipated here you can find my system to better understand my findings:
http://forum.audiogon.com/cgi-bin/fr.pl?vopin&1220291925&view