Modern EL34s VS NOS Winged C - and return policies?

Awise1961 I do have NOS Mullards in the preamp and RCA clear tops in the power amp. I always get a little rush when the Mullards flash at startups. 
 

pdreher I totally understand your sentiments and in general I agree.  Maybe it's more like test driving a car?  I’m guessing most of these tubes I’d consider returning would be NOS that have probably been put on a tester and maybe even listened to and checked for microphonics before they are shipped. At least I hope they are. They’re also lamped when they’re being matched.  I would only return tubes if the seller understood what I would be doing with them and knew how long I had them running in my amp.

Besides, tubes take time to burn in and sound optimal... anywhere from 50 to 250 hours depending on the tube.
 

@pdreher This has not been my experience. Not even close. Even if it was, there are 720 hours in a month. Plenty of time to determine if the tube works for you and return it in 30 days assuming that’s what the return policy is.

The only way I know how to mitigate losses over purchased tubes would be to do what everyone else does.  Try them out and if you don't like them, you just have to sell them at a loss.  Just explain in your ads that they didn't have the synergy you were looking for in your system.

Also, as was mentioned above the Electro-Harmonix 6CA7 are surprisingly good.  I had a set in my Cary integrated and they were the best of all my tubes, some of which cost considerably more than the EH's.  I'll probably get another set for my other Cary amp, as well.

@macg19 while I agree that old stock tubes need minimal burn in and often sounds great from the start, new stock tubes, particularly Tung Sol KT150's take a long time to settle in... at least that has been my experience.

@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.