Wow, and she's a Chicago girl that says she's a Particle Accelerator technician (probably at Fermi Lab if it's true!).

I think I might be smitten!  

I noticed how highly she rated the RCA 5U4G.  The one she reviewed is a civilian production 1940's smooth plate bottom getter.  I do like that tube in Torii amps.

Mike in Seattle area

thanks for running this.  i ordered 3 of the RCA's.  i gave some thought to the GECs, but just can't pony up that money. the rca's were about $150 for one pair and a singleton (needed for phono pre).

got the rca's for the amp.  i must say that the improvement was immediate.  already clear went to clearer and layers went to more layering.  they sounded like the el34s were back in, but with the power of the kt66.  can't wait to hear what one does for the phonopre, probably tomorrow.  when i look at these tubes to compare, my theory as to why the old ones beat the chinese tubes is the construction.  the glass is thicker, but there is a glass support from the base of the tube that supports the wires that lead to the plates that is absent on the chinese tubes.  so, my theory is that the rigidity of the construction of the old tubes quells the microdynamic vibration thus allowing greater clarity.  highly recommended for less than $50 per tube.

got the phono pre tube yesterday.  as my listening friend Ed suggested, a larger change came from that one.  what i get now is a top to bottom balance that i did not have before where no range of the sound spectrum sticks out or is missing.  wanting to try the el34's i put them back in and noticed a greater midrange prominence than even before, think of the sound spectrum as a frown.  this would be the preferred setup for any kind of voices.  the ladies are just heavenly with this arrangement, but on balance, not as realistic.  a girl with a guitar would be the ultimate or solo voice.  what these rectifiers seemed to do was accentuate the traits that were already there, must be the clarity allowing this to come through.
now, maybe with all that clarity, i need another benz cartridge (just kidding) for use with the kt66s to have the sweetness and the clarity all in one.  my lyra does not sound lean in this setup, but it sounded sweeter before, i would say neutral now.  does it ever end?

for the money ($150), i would be hard pressed to think of another upgrade that made such a positive change.