6922's Replaced......It was time.

cjlover,
It was mostly an improvement in the midrange and highs.  More detailed and unveiled.  Not a huge improvement, but noticeable.  

They (signal tubes) seem to slowly lose their ability to accurately replicate the full frequency spectrum of human hearing.  In my opinion loss occurs from the high end down.  

BTW...I treated myself to a matched, burned in, quad of 6550's for Xmas....Installed and biased them.  No real improvement was noticed after several days listening.  Not a bad thing.  It tells me the older power tubes are still in good condition and can be used as backup as necessary.  

If you have ~2-3 thousand hours on your 6922's it may be time for some fresh ones. 

Thanks for your input on the Gold Lions
it is always good to know which current production tubes  sound good

I know too many Audio Research owners that feel reluctant to use anything but the stock tubes. Although do so with caution

I paid handsomely (reasonably handsomely)for a stock of Amerex Bugle Boy nos 6922s and only from a reliable source. There is a lot of stuff sold as NOS that are used or would be rejected from those who sell tubes for a living.  Having a sorce of good modern tubes is great

My local electronics wizard found me two quad sets of early 70s Genelec 6550 gold lions in his private stash.  They took my amp to fabulous new levels, worth every pretty penny.

You can get a lot more hours out of nos tubes from Telefunken, Mullard, Amperex