six year old 6sn7's, pushing my luck?

Hi Rich

You may not THINK there is a degradation of sound but are you sure you are not maybe acclimating? it can be a subtle process and 45K hours is a LOT of hours, depending of course on the circuit and the quality of the tube itself. The only way to know for sure is to test the tubes if you can. Aside from testing trying a good set of new tubes will tell you what you need to know. I agree with Brownsfan, the Sophias are really excellent sounding tubes and worth having around if you can swing the 600.00 it will cost you. They stack up well sonically with ANY 6SN7 type I've heard.

Rodman99999 while I would certainly LOVE an alternative to purchasing anything from China and always make a concerted effort to do my part in that manner the real problem is that good NOS tubes are getting harder to find. Many of the 6SN7s are used, not always a bad thing if they have been tested and you know what you are getting. One area I suspect the NOS tubes may be better overall is longevity over the tubes currently being manufactured. The metals, coatings and quality control were almost certainly better than anything we get today because they were made to military standards that were critical. Your Tung Sols, lucky you, are probably among the best along with several of the Sylvanias which I keep as back-up, the Ken-Rads well, to each his own. Have you actually listened to them?

As the NOS tubes become more scarce the price is going to continue escalating. 15-20 years ago you could purchase these tubes for a song, not today. I purchased a pair of the Sophias to try as an alternative 9 months ago and was quite taken back by their performance after reading good things about them. They really are that good. The one thing that remains to be seen is how long they will last along with the Pavanne and Black Treasures. They haven't been around long enough to determine. I generally agree with you concerning Chinese tubes, at least in my experience.