McIntosh tube upgrade - worthwhile?


I'm wondering if anyone has ever experienced Sonic improvement when switching from the mediocre JJ stock tubes used by McIntosh?

They tell owners that their tube amps are designed to perform equally well regardless of tubes used.  On the surface this seems incredibly unbelievable.

Anyone notice any changes when they upgrade the tubes? And which tubes do you like to upgrade with. Mostly focused on smaller tubes versus the power tubes which I hear overall don't make much of a difference anyway. But could be wrong.

emergingsoul

Well, thanks to all-ya-all it did turn out to be an opportunity to sell tubes. I called Brent and have 4 new tubes on the way! Thanks guys!

@emergingsoul 

Posters were giving you additional advice on where the buy quality tubes. That was an opportunity to show gratitude. In that spirit, Brent is very good, but I think Vintage Tube Services with Andy Bowman is superior. Andy knows more about tubes than any of the sellers and is more thorough testing. Andy or Brent is a win. 

Pat Hickman, Oregon, knows more about Mac amps than anyone I've ever met. He would be able to answer your question. What amp are you using? What improvement are you wanting to hear? 

The Mac I own sound great with the tube that it came with.With the prices of tunes now, no thanks....I'm on a fixed income now at 72.And need new a new heating and cooling system NOW. ..

Tubes from different manufacturers each have a unique sound but the differences can be subtle and will be obvious to a careful listener when the audio equipment is high-end  

Tube swapping is very noticeable on high end equipment to a careful listener.