Modern EL34s VS NOS Winged C - and return policies?

@brighamdoc The KT120s and 150s had been in the amp for about 3 weeks listening about 3 hours a night.  Maybe not enough to really be "burnt in".  I may have to give each another month of listening.  I've heard the KT150s can take months to really shine.  They did sound good in the system so it would be interesting to see.

Yep. When I first purchased my last pairs of tube mono amps which run KT150s or KT120s, I kept going back and forth comparing the sound to my local dealer, same amps. He had 300-400 hours on his demos, I had 40,80, 100 on mine. Not the same.   Breaking in, wearing out, smoothing out, whatever you want to think about it - both quads of these sounded nicer after 200-300 hours on them fwiw.  As the time goes on and highs round off just a tad with wear, the midrange and body comes in more, also a little more euphoric now too -  from my experience with them. The difference is noticeable even with the most primitive listening to my FM tuner or CDs or high-res streaming. Not all agree but some good time on them can help change the sound. Wether you like the changes or not is up to you.   

Does anyone have an opinion on original Tesla EL34s (not JJ) and how they compare to the aforementioned SED Winged C?   I've been running these in my QS MidMonos for several years and love the sound. The original set says 'Made in Czechoslovakia' on the box while a more recent set was revised to 'Made in Slovakia'.  That country split happened in 1993 so not sure the age of these tubes.

Mike Sanders at QS sells them as an upgrade to his standard offering.  Just curious.

@pdreher 

http://www.audiotubes.com/warranty.htm

@pdreher 

new stock tubes, particularly Tung Sol KT150's take a long time to settle in... at least that has been my experience

I can't disagree with you. My only experience with Tung Sol KT150's was in an overpriced, crappy, US made integrated. It was red. Not that I'm naming names:)

The best they sounded was they day I boxed them up to trade it in.  

Conversely, the best power tubes I've owned were NOS Shuguang 6L6GC "coke bottle" (circa 1970's I believe). They did sound great as soon as they warmed up.

All fun stuff but I've simplified things with a SS amp and tube sources; DAC and phono stage that both use 12AX7's.

@whiteknee IMO original Tesla EL34s are a great sounding tube. I have two small amps that can run EL34s.  My Inspire KT-88 can also run 6L6, 6550, KT-66, 77, 88, 120, etc. I have pairs of St Pete SED S, Winged C EL34s, Tesla, RFT, GE and Sovtek 6CA7s (American EL34 equivalent).  The Teslas have that warm, rich, midrange, are balanced, with a touch of treble roll off, and good bass response. IMO, second only to the St Pete Svets.  The Svets have a little more treble extension and perhaps bigger soundstage, although in a blind A/B probably difficult to distinguish the two. 

RFTs brighter, edgier, with less warmth in the midrange. 6CA7s are more balanced than all of the above, almost clinical transparency without richness, like a studio monitor!  GL KT-77 are also super balanced but with a touch more musicality. NOS Svets and Tesla rule in my two rigs.