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AUDIO FORUMS >> General Discussion and Support >> What's the 274B life expectancy?
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Message started by yoshi carroll on 01/02/23 at 18:50:27

Title: What's the 274B life expectancy?
Post by yoshi carroll on 01/02/23 at 18:50:27

Happy New Year all!

I've had two 274B rectifiers in my SE84C and neither tube has lasted more than three months. I bought both tubes from Decware, one earlier this year and the other some time last year. I don't remember for sure, but I think they were manufactured by different companies.

It seems like particularly bad luck to have two of the same kind of tube fail early given that I've had no issues with any other tube in this amp. Could something else be going on that's making these tubes fail?

The amp averages about four hours of play per day, and I leave it powered on constantly because that seemed to be the folk wisdom for maximizing tube life.

Title: Re: What's the 274B life expectancy?
Post by lobo on 01/02/23 at 19:15:52

Get a NOS 5U4 type ,you will be fine. Might have to replace a fuse, if the other tube blew.

Title: Re: What's the 274B life expectancy?
Post by CAJames on 01/02/23 at 19:26:23

Yeah, I have very little faith is current production rectifiers. FWIW below is a post from Steve a couple years ago regarding current production vs NOS (emphasis added by me).

Quote:

...New Old Stock is the real deal. Those who like to push the envelope of what is possible with their amplifier will often go down this path with no regrets. For one thing, the tubes not only sound better, but often last longer, in some cases like with rectifier tubes up to 10 times longer.

Rectifiers are a subject all in their own. Russian rectifiers are acceptable, everything else is a no-go from a reliability standpoint with some rare exceptions that are very pricey. My advise to all Decware amplifier owners is to find yourself a New Old Stock 5U4 or a 5R4 that has never been used and comes in it's original un-molested box. Consider the current production rectifier tube we ship with the amp the best sounding and most attractive option that will last long enough for you to find a real N.O.S. replacement.

Finding N.O.S. tubes is easy, even on eBay there are millions. Since you only need one or two you will have more to choose from than you know what to do with. Finding quantity of these tubes is another story. If Decware could secure reliable inventory of 1000's of N.O.S. rectifiers, it is an investment we would gladly make but in 25 years is has yet to happen. Because we can't find N.O.S. tubes in large quantities, even batches of 100 would be gone in less than 30 days, we feel there is no point in even trying.

For the customer it is easy, just find a N.O.S. 5U4 tube on eBay that is unused, and in it's original box for $40 and it could easily last for 10 years or more and sound better the entire time.

As an amplifier designer, it is possible to create circuits that baby the rectifier tube by limiting inrush current, using smaller capacitors, running higher voltages with a choke and so on. Correctly done, this can make a Chinese rectifier tube last the full rated 500 hours or more. The problem with this is that it changes the sound quality of the amplifier well outside what we find acceptable. So, we have to make a choice, do we design tube amplifiers to baby the crappie rectifier tubes being made today, or do we design amplifiers to use REAL tubes. Of course the answer has to be REAL tubes, because we make real amps.

FWIW I would not leave the amp on 24/7. I would at least turn it off over night. I usually turn mine off if I'm not going to listen for an hour or so.

Title: Re: What's the 274B life expectancy?
Post by yoshi carroll on 01/04/23 at 01:44:13

Thanks for that context. I had expected that since Steve sells the tubes himself the vageries of modern production quality wouldn't apply. There is a warranty period, so maybe that's the best we can get.

The NOS Mazda 5Y3GB has been my go-to for a long time, and I still have a few around, but they've gotten harder to find and a lot more expensive. The 274B did sound better.

I ordered one of the new Decware branded 5U4G rectifiers and it just arrived this morning. We'll see if the Decware logo imparts it extra longevity. :)

I'll power it down overnight as well.

Title: Re: What's the 274B life expectancy?
Post by alper_yilmaz on 01/04/23 at 08:30:30

Since I have been into tube amps (that is, since 2003, I guess), two rectifier tubes went dead on me, both of which were NOS. One was a GZ32 by Mullard (with a date stamp of March 1967) on my Torii mkII and recently an RCA 5Y3GT on my SE34i.2+. In neither case, there was anything unusual happening; simply turned on the amps and no sound from one of the channels.

Of course, this is not enough statistical evidence, but in my case, the failure of the tubes were more like random and I could not pin-point the cause. The reason I use NOS is not because they are more reliable, but rather they have more signature sounds. But if you go for 274B or 5U4G from Sophia ( I have one from each), I believe they are both reliable and have great sound...

I would not leave the amp on forever either for a multitude of reasons some of which are more for environmental concerns...

Best,

Alper

Title: Re: What's the 274B life expectancy?
Post by yoshi carroll on 01/04/23 at 18:56:55

Over the last 20 years I've had many NOS Mazda rectifiers die on me, some quicker than others. Sometimes they start creating static sounds before they go, which is convenient because I can replace them while they're still working. When they die they always blow out the fuze which requires some disassembly to replace. (Interestingly when the 274B died it didn't blow the fuze.)

Since the Mazdas were cheap ($20) and easy to find I didn't mind too much if they would only last a year.

Thanks for the note about the Sophias. At $130 for the 5U4G and $250 for 274B, I would mind a lot more if I didn't get several years out of them.

Title: Re: What's the 274B life expectancy?
Post by Lon on 01/04/23 at 19:00:01

I'm on my fifth year of the Sophia Electric 274B that I have been using. I love these rectifiers.

Title: Re: What's the 274B life expectancy?
Post by duaneh on 01/05/23 at 21:33:31

I took the Sophia Electric Aqua 274B special deal—loose glass inside. About $50 off. Still a bit expensive, but it’s run wonderfully for a year and a half. I hope I haven’t jinxed it.

Title: Re: What's the 274B life expectancy?
Post by Waxspinner on 01/11/23 at 01:01:28

I have had terrible experience with the 274b. One blew and the other had a loose base. I have had great luck with nos rectifiers. Call Andy Bouwman at Vintage Tube Services, (616) 454-3467. He will guarantee your tubes, I forget how long, and he tests them better than anyone....even Decware.

Besides that, I have also had great luck with the nos Russian 5u4g equivalent. They're cheap and last at least a couple years, $15.

Goodluck