Audio Research CD7's 6H30 tube rolling

I had both Audio Research and Conrad-Johnson power amps with new production 6H30-EB drivers a few years ago. I replaced them with pricey NOS -DR versions and I couldn't tell much difference. Maybe it might make a difference in a CD player, but based on my experience, I doubt it would be worth the difference in price.

I went ahead and ordered 4 NOS tubes for the output stage. The seller was kind enough to confirm that I could return them in mint condition less a restocking fee should I find that there is no change in sound.

The CD7 (brand new) started by sounding extremely detailed but bright. Perhaps bright isn't the correct term - more like forward. To the extent that it was tiring to listen to for long periods. I attributed some of this sound to the tubes and thus the search of a solution.

But after burining in for 150 hours or so, it's much better. The detail remains but the sound is now rounder and sweeter. The treble performance of the standard new tubes is now outstanding and I'm wondering if the NOS can do any better. It's already pretty incredible as it is now.

You mean to say that your cd player only has 150 hours on it? That's early to tube roll. This player would need about 400 hours of playing before you can judge the sound. To try to alter the sound now seems like a bad idea to me.