I've had issues with my Aqua II rectifiers, but not that one. If it is indeed a normal thing. . . that shouldn't last long. But as I have had several and have not had that issue. . . it makes me think that it is not a normal thing if it persists. I'd ask Sue if she would allow you to return it for assessment and replacement.

The issues I had were of my own making I believe. I've come to realize that they may not be an ideal tube for the SEWE300B, though they work great in the CSP3 and the Zen-clone amp I have. I blew one of them by turning my amp on and off too often when testing fuses and the direction of the fuses. And then I blew a second when I was installing a Swiss Digital Fuse Box. . . I am not sure exactly why that happened, whether the initial turn on of the Fuse Box caused it to blow, or if it was a defective one (only had it going a few hours at that time). I got a third and it seemed to work okay with the SEWE300B but I just was anxious and untrusting and put it into the CSP3 and then the Zen-clone amp. It was hard to find a rectifier to replace it with. I have three of the original Aquas which are great tubes but not quite like the II. And then I had a hunch that a Psvane Treasure 274B-Z might be a good one, as it resembles so much the Shuguang Black Treasure 300B-Z tubes I adore in the SEWE300B and it has proven to be a fantastic rectifier for that amp. And I bought another that is fantastic in the CSP3 and I put the Aqua II in the Zen Clone amp (the CSP3 and the Zen-clone amp are the heartbeat of my living-room audio/visual system).

So. . . that's my history. I don't think the failures were the Aqua II's fault though I do think the demand that the SEWE300B seems to put on it may mean it's best for me not to use it there.

The original Aqua amazed me at first listening and I used them for years. . . . The II is an improvement, a bit better bass, a bit sweeter treble, a bit blacker background--they are both excellent rectifiers.

I had a Sophia Aqua II Rectifier that was dead on arrival.  No sound at all.  Seems failures are the risk you take buying these rectifiers.  Not for me. Lon recommended the Psvane 274B-Z Treasure series and they are a really nice sounding tube.  Checks all the boxes and can be bought for $60 on Aliexpress.  2 weeks delivery.  I am shocked how good they sound on my set up after 100 hrs.

Thanks Lon, Tony, and Hearafter. I appreciate your input. I'm keeping my fingers crossed that the new Aqua II heading my way isn't another dud.

Those of you who've heard both the Aqua II and the Psvane 274B-Z, how would you compare them? I am considering picking up a Psvane 274B-Z because the price is right, and I might as well have a safety net to keep rocking should the new tube fail too.

Did a little digging to get info on the PSvane 274B-Z to give it a try. The concern I have is that the tube looks to be spec’ed for max filter capacitor rating of 4uf, which is fine for the Sarah, but the UFO25 uses a 47uf cap. Don’t know if the tube would have risk of failure much sooner, as such. The Sophia AquaII is rated to 47uf. It’s a shame people have had such reliability issues. It’s a great sounding tube. I’ve had one in for 9 months and knock on wood it’s worked fine so far.

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Here's my thing, which is totally JMO/FWIW/YMMV and all that. The rectifier can't know and can't tell the size of the first power supply cap. What it sees and actually cares about is the "inrush current" when you turn on the amp and charge the power supply filter capacitors. In theory you can derive the inrush current from the cap size and some assumptions, but at best that is a very rough approximation of real life. Most rectifiers have two different but (IMO) related specs: the max capacitor and the max current. According to the data sheet I found the PSVane 274B-Z says the filter capacitor should be 4 uF, which is really small. But the peak anode current is 750 mA (i.e. 3/4 of an amp) which is a lot of current in the context of a Decware amp, esp. a preamp or a UFO amp.

So if it were me, I would focus on the 750 mA spec and be confident the rectifier is safe in my low power amp or pre. But, if it were really me, I'm pretty allergic to current production tubes because in my experience the quality control seems to be lacking. At least compared to the tubes made during the "golden age of tube tech" which was generally the 40s into the 60s. So I stick with NOS. Again, JMO and all that.

Actually, there's far more to what's going on than the inrush current. There's a reason rectifier tubes have max ratings for the first filter cap.

this is a little long, but explains it far better than I could.

https://www.youtube.com/watch?v=Iizt5cnq2oY

Cheers,            Crazy Bill

PS. For some reason when you click on the link the video does not start at the beginning. Couldn't fix it.