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.


I swapped stock tubes to Telefunken and the sound improved significantly. Once I swapped, I didn't want to go back to stock tubes. I sold all my McIntosh preamplifier and amplifier and I still have a pretty good inventory of Telefunken over the years.

I swapped out the original mac tubes for Golden Lions and only saw a minimal improvement in sound. It was better but not by much. 

Yes, I put in vintage medical grade Amprex 12ax7s in my c2300 and it makes a great improvement in lowering the noise floor. As for my vintage mc30 s, mx 110z and MC 240 I use vintage telefunkens in the signal tubes, and some rca black plates in the phono section of the mx110.