I have been pretty happy with my setup. The BeePre (with BeeQuiet and output cap mod) sounds fantastic. But as usual, I can't leave well enough alone. I bought another pair of Nordost Heimdall rcas, and while the imaging and detail are outstanding, they added a bit of brightness that put my system over the top (the Maggie 1.7s are already pretty lively).
I researched and bought a pair of Sophia Electric Princess carbon plate 300Bs. I thought their slightly darker sound would be a good match for my system. The results? WOW! The stock EH 300B are quite good, but these tubes got my toes tapping. They are a bit darker, but with a midrange woodiness that works great. They have a timing, punch, and something that makes you want to dance. I can't really put it into words. The best review I saw to hit it right said that these tubes put you in the 20th row (vs some that put you in the 2nd row).
When warming up, there is lots of chiming and kliiiinggg... kllllooooonnng. But after a few minutes they are quiet and are slightly less microphonic than the stock EH 300Bs. At about 10 hours they sounded fantastic, with a great woodiness, but still clarity all the way up to the high end. They don't show high end details like the EH 300Bs.... yet. At about 30 hours, they have bit of midrange resonance that is annoying. I'm hoping they settle in by around 100 hours. I had heard that power cycling causes more change than actual hours of playing with these tubes.
Someday I'd love to hear the Royal Princess tubes in the BeePre, but these will do just fine
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Mac mini running Roon->
Mytek Brooklyn DAC+->
Darwin Truth RCA IC->
BeePre (BeeQuiet, Mundorf Ag/Au/Oil, Sophia Royal Princess 300B)->
Audioquest Colorado->
Rogue Audio Atlas Magnum amp (Psvane small signal tubes, KT150s)->
Audioquest Gibraltar-speaker cables>
Magnepan 1.7 & REL T-5