That’s a bummer! My Sophia is still going strong 11 months in. Did you speak with Sue?

Yes the mesh plate still appears to be designed for lower value caps, like 10 uF I think?

I agree, the last version of the Aqua solid plate is theoretically compatible with our higher value rectifier caps used in a lot of Decware...supposed to tolerate 47uF and be a direct 5U4G replacement. And some folks have had really good luck with it, but I wonder if that is extra-ordinary. Don't I recall others who had failures on the forum using the same more tolerant solid plate Aqua version? Maybe Joman was one, but I think others???

Recently I was using them in my new/used 300B, and saw one of the 274B Aquas flash on a couple of startup occasions... I think this amp has a 50uF cap with the rectifier, so a few microfarads higher than 47, and 47 being used in a lot of Decware as I recall??? They are still working, but worrisome how these tubes appear to be a little touch and go for these larger caps.

It sounded fantastic; that I have to say.  it was replacing a 5Y3GT.  However, I checked with Dennis Had before purchasing it to use in his LP-2 preamp, and it said it was a perfect fit and others had used it there with success, so it seems I just bought a dud tube.
Oh well. Just my bad luck, I guess.

I’ve had nothing but fantastic experiences with Sophia Electric tubes, including multiple 274B Aquas, a pair of 2.5 volt 300B’s, and a current pair of 300B Classics. In addition, I have been given great tube advice by both Sue and Richard.  

For me, an important aspect of buying tubes is having a substantial warranty in place at purchase.  Though I’ve not seen any Sophia tube fail in the first year, I will continue to buy Sophia tubes only with their one year warranty.

As Kamran suggested, it might be worth your time to chat with Sue.  If they won’t replace the tube for free, and I doubt they will, they very well may give you a nice discount on another one.  

So…….sorry to hear about the premature failure of your Sophia 274B.  This is the very reason many have a love-hate relationship with tubes and tube equipment.  We love the sound quality, but pretty much hate everything else about tubes and tube gear. Maybe that’s being a bit harsh, but I have spent at least $10,000 on tubes during the past thirty plus years and it has driven me nearly to the point of insanity.  

To Doug’s point, I also opted for their highest (longest?) warranty available for my Aqua 274B.  Can’t recall now, whether that was 1 yr or longer at this point. Not saying that guarantees longevity, but it definitely decreases the probability of a premature failure and recourse if it does.

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A bottom line is all the UFO amps have a 47 uF input capacitor.

That part is unambiguous, what you do about it gets more fuzzy. If you want to play by the "rules" the two common rectifiers that are spec'd for a 47 uF input capacitor are the 5U4G and 5AR4 aka GZ34. If you buy those (assuming they meet the spec for a new tube) you are playing by the rules and done all you can. Maybe...

But, at least IMO, the real situation is more complicated. The rectifier can't know and doesn't care specifically what the the value of the input capacitor is. What it cares about is the so called "inrush current" that it sees as the input cap gets  charged up when you turn on your amp. The bigger the input cap the bigger the inrush current. And while it is possible to calculate the current based on some assumptions I think it is fair to say the capacitor value is more of a guideline than a rule. And hence the complication/ambiguity/confusion.

I just checked the datasheet for one of the few current production tubes I own, the Genalex Gold Lion GZ34 and it doesn't specify the input cap, it specifies the "current surge at turn on" which is 3.7 amps which is a really big number. Many NOS rectifiers (from back when more people cared about datasheets and read them carefully) specify both a max input cap and a max current value and in many cases they are wildly inconsistent. The example I point to is what many consider the ultimate 5U4 type rectifier, the Western Electric 422A. The datasheet specs are a max input cap of 8 uF and a max input current of 4 amps (!!!!). So if you have a UFO amp and are considering a 422A rectifier (which would cost as much as your amp) you have to decide if the 8 uF first cap spec would scare you away or the 4 amp current spec would give you confidence that the rectifier is more than up to the task. I would go by the latter.

My bottom line is many (most) common NOS rectifiers are spec'd for relatively small input caps, typically much smaller than 47 uF, but for big inrush currents, typically at least 1 amp. Likely much bigger than the UFO amp will ever see (for higher powered amps I suspect the situation is similar, but I can't say for sure). Also, tubes made during the "golden age of tube tech" often greatly exceed their datasheet requirements, which are a minimum requirements tube must meet to be considered "good". Current production is much more of a question, again JMO YMMV.

So, lots of people use lots of different rectifiers in their UFO amps a usually they last a long time. But there are no guarantees (well some tubes are sold with guarantees, but what I'm talking about is their actual service life), for good or bad. Any tube, and esp. any rectifier is subject to failure at any time. And any tube, even the cheapest current production Chinese, can give you years of trouble free service. That's what you sign up for when you buy a tube amp.

Thanks, CAJames.

From one with little technical knowledge, and endless curiosity, I found your "unpacking" very helpful, and it also points me in some other directions to explore.

I wish I had come across this thread before I purchased my Sophia Electric 274B mesh plate. I have it in my Inspire by Dennis Had Fire-Bottle Kleen-Sweep amp. So far, it's working great and I haven't had any issues - so I'll keep my fingers crossed I am in the camp with good luck.

It does sound great, and as the OP said, Dennis very much endorses the tube and says it works great with his amps.

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Yes that is correct CA.  

We're in the process of a move and I thought that I should see what's happening on the Forum and came across this thread.  I'll digress a little first... I concur in what CA stated about the first cap value and the risks associated with tubes.

As far as Sophia tubes...

Yes, good sounding tubes.  I purchased 2 274B at the same time, one was a back up.  One failed at the end of the first year.  The second, a back up that I bought, didn't use, failed on start up.  When I called Sophia Electric, the second tube, the back up, was also out of warrantee and didn't qualify for consideration.  I was offered a discount on a replacement.

My issue with Sophia Electric wasn't the fact that the tubes failed.  My issue was that I felt that under these circumstances the second tube should have been replaced N/C, I was more than willing to pay for the cost of shipping.  That is known as a "good will warrantee" and that type of warrantee is more important to me than what is written on a document because documents often contain "fine print".

To be clear, I take the same approach on anything that I buy.  It isn't limited to Sophia Electric.  It's about the company policy regardless of what the item is.  A rigid application of a warrantee under any circumstances is not the type of policy that is a good fit for me and so I avoid purchases of anything that falls in that context.

If that second tube would have been replaced N/C, not including the cost of shipping, I still might be buying Sophia Electric tubes, at least until Cryotone, it was a good sounding tube.

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Sure, using a Variac would absolutely make life easier on the rectifier. But everything has a price and I would be afraid that it would slow down the transient response, at least, by limiting the current into the amp. That is based on theory, not actual experience.