Seems like the best "upgrade" for tube amps....

Grannyring, that's why I sais I WAS dubious.
My ears know 10 minutes is all it takes on my AVA 450 .
FWIW, I never met anyone I agreed with on everything.

QuickSilver, VTL or Manley poweramps operate in 5...10min according to the measurements I've done in the past with analysing bias and transient responses via oscilloscope.
If I play same record first in 10m and then play it again in half-our, it might seem to sound different and so is CD. If I turn off the poweramp no matter tube or SS and turn back-on and after the settle time play the same, it will sound different again(actually that's the case of the most of improvement I've experienced).

Frank is a wonderful designer and like many skilled designers they simply don't have the desire or curiosity to try and experiment with "boutique" parts assuming they are a rip off sold to unsuspecting novices like me:)

I have owned one of his amps and heard his latest top model. Very good sounding for sure. He knows his stuff and I just wish he was more open minded to learn and give due diligence to "boutique" parts.

I have heard the same distain for upgraded parts, wire, tweaks etc.. from other very gifted designers. I suppose it is hard for them to find the time or passion to fully dive Into this world. I understand. So much to learn and experiment with and it is so hard to be expert in all things.

Schubert, yes your comment was understood and my comments are not all all intended to poke at you. I would also be dubious of that statement and may still be :)

The human brains goal is to provide a stasis, both psychical and mental.
If you make a design at first to keep costs at a minimum, you will not only believe that is the correct course, but if you are highly invested in that belief the brain will not let you hear any difference. Not saying Frank or anyone did this.

The main reason not to lie is soon you will believe you own lies.

Interesting thought and one that causes me to reflect on my own beliefs and biases on all things audio. Thanks much.