Tube microphonics

Edit-It's a free exercise to move them, so try it.

Agree 100% in general, and while OP carried them up a flight of stairs, they do weigh 170 lbs each.  And I am pretty sure the more delicate tubes weren't in them as they are now. 

Those Ref 750s have 16 KT 88s sitting on top of the amps with only air around them, right? You did not say what speakers you have.  If you have speakers that have large woofers pointed at your tubes, I think they could affect the sound. 

I suggest you move the amps around the speakers, to the sides, behind the speakers, etc. until you find where your system sounds the best, and that may be with the amps in front of the speakers.😁  Use some furniture sliders to move the amps around.  We don't want to hear about you ending up in the hospital.☹

i haven’t bought new audio research tube amp in a few years but i have over a half dozen of them, and in every case, the company puts thick rubber tube dampers on every low level tube when the amp is shipped from the factory, and when replacement tubes are shipped there are instructions to move the old dampers over to the new tubes to be installed

this shows that as designers/makers of the gear, they are definitely concerned about unwanted microphonics affecting the sound produced, and are making an effort to damp them out

so i think it is worthwhile for the op to make an effort to move the amps, as hard as that might be, away from the speakers, to see if a positive sonic difference results

These days ARC only puts dampening rings on small tubes. Not big power tubes. 
 

This does not take away from the argument that tubes can be microphonic. I suspect the large power tubes may run so hot, that they cannot use those dampeners.

@carlsbad2   Kinda both. Because I really don’t want to move those amps with the full sets of tubes already in them. Don’t want anything happening to the tubes by a bump or so. I already had one tube arc on me the first time I tried my amps when they got delivered. And it took out a resistor and fuse also. Don’t want that to happen again.    @jetter That sounds like a good idea. I will definitely try it. And yes. I did carry them upstairs but like u said there were no tubes in them. @ghdprentice Right. They don’t have rubber dampers for the KT150s.