re: Sophia Aqua II 274B
I freely admit to being a newcomer to tubes. I have a Modwright KWH 225i hybrid integrated amp that came with a pair of JJ E88CC triodes (upgraded to 1960s-era Holland Amperex 6DJ8s) in the preamp section and a Modwright PH 9.0XT phono stage that employs a Russian 5AR4 rectifier in its separate power supply and a pair of 6C45s and a couple of 6DJ8s in the phono stage itself.
After the phono stage's 5AR4 died I replaced it with an identical new Russian tube. As I spent more time listening, however, I kept feeling that the tube might be holding the sound back a bit. Notably, there was a bit of upper midrange mud that I didn't hear when listening to my digital side, along with some soundstage constriction.
I decided to take a chance and replace the phono stage rectifier with a Sophia Electric Aqua II 274B. I'm an experienced and careful listener, but as a relative tube neophyte, I was uncomfortable taking my chances in the obscure world of tube vendors and the questionable provenances of many of their wares, particularly as I was only taking an educated guess that spending several hundred dollars on a phono stage power supply rectifier might make the difference I was looking for. But I decided that investing less than $300 (with tax and shipping) on a new Sophia was worth a shot.
As a brand new tube, I expected the Aqua II to take some time to get comfortable. Right out of the box, however, the upper midrange was significantly cleaner. It wasn't that the overall sound had become leaner; rather, it had eliminated the slightly muffled thickness that was there previously while leaving the overall weight and timbre intact.
I've continued to enjoy the Aqua II's performance, noting a wider and deeper soundstage as time goes on. I'm quite sure that the success of any tube is system-dependent, but the Sophia Electric Aqua II 274B rectifier works for me. Yes, I'd like to try a pinched-waist Valvo CCA, but that kind of money, that kind of wait, and that level of risk is not my personal style.