"Bruce J. Richman" wrote

Could be. I've used mainly Svetlanas and Ei output
tubes, and for small preamplifier tubes and those
needed for my DAC (12AX7's), matched NOS Mullards
(which are a little expensive but last a long time) and
military grade JAN's.

Richardson Electronics. Try the largest source
of guaranteed tubes (NOS & new) in the world.
http://catalog.rell.com

After reading Vacuum Tube Valley magazine’s
6DJ8 / 6922 shootout I purchased a few JAN
Philips 6922 tubes (best buy) for my pre-amp
and DAC. Up to that point I had been using
Mullard 6922. In total I've run these sets of
brands: (1) GE, (2) Dragon, (1) Yugoslavian,
(3) Sovtek, and (1) Mullard. I’ve not found any
*best* tube yet... but the Sovtek's are very good.

I'm not saying NOS is bad just much more iffy.
I've done comparisons of mail order tubes vs
best Gold Aero & RAM (sorted 3%) of 6DJ8 &
6922. The difference in noise and tonal signature
was audible. In the back of my mind I wonder if
the sonic signature of the JAN Philips (NOS) at
3% of all sorted would sound like the one I have...
but lacking the will to purchase a 3% JAN Philips
I guess I'll never know .