Genalex GL GZ-34 Rectifier...Did I just get a bad one? Five months seems

It's more difficult to quantify old tubes than most people think.  Simply paying more for supposedly higher quality is often a roll of the dice.

Personally, going against the opinion of most here, I prefer lower cost older tubes on ebay, and skip the price premium.  My experience is that I can usually get at least 2, and often a lot more, very good older tubes for the price of one tube that others fight over.

As far as new 5AR4 tubes go, Sovtek and Shuguang show very good reliability.  Sovteks typically sound worse than any other tubes, and that hold true in this case.  Shuguangs sound a lot better, but still not good enough, in my opinion.  JJ sound best today, unfortunately, they're as brittle as fine porcelain.  That means, Shuguangs offer the best compromise today, even if it's not very good

@artemus_5, thank you for clarifying.

That's certainly disappointing news.  Given Genalex is the premium Russian tube, even more so.  Over time, I've gravitated away from the majority of new production European tubes, both for sonic and reliability reasons.  There certainly are Euro tubes I still prefer, but all things being equal, Chinese tubes tend to sound better, last longer, and cost less

@artemus_5 consider folks who never previously built anything assembled all but a few of the 300,000 ST70s, the fact that most of them that came up on the used market sported their original (5AR4 and all) tubes, and the majority of that number still worked mostly fine even after all those many, many years.

Unless Bob's using too big a capacitor in the first position of the power supply, which WILL blow rectifier tubes with regularity, there's no need to sweat it.  Just get another 5AR4. I recommend spending for a vintage tube for best sonics and reliability. After that, sit back, and enjoy.

Thank you, Ralph.

I’ve seen excellent reliability out of current production Shuguang 5AR4. I think the one I use logged 7 years of steady rotation. My issue with them is that they barely reach a sonic level of adequacy. No idea on how my Sovtek holds up, as I find it unlistenable, and it has little more than break-in hours on it. JJ definitely sound the best of today's tubes that I've tried, though still not as good as vintage Mullard.  But after blowing a half dozen between my various amplifiers inside a year, I’ve grown tired of buying more.

You’re right about the ST70. I consider it a fantastic amplifier, and my Jadis (one of their best) Orchestra Reference and Quicksilver (considered their finest) 8417 both employ the same design even if Leo Fender implemented it prior to Dynaco. I’ve run the gamut on Dynaco "improvements", most of which swap the circuit for a Mullard long-tail pair. None of which improve upon the original. In my experience, presuming a person doesn’t demand more power, there’s just one sonic flaw, which takes less than $20 to address

@artemus_5, yes, the Quicksilver 8417 monoblocks each have dual 5AR4 rectifiers, and use the same circuit as the Dyanco.  Most have converted to EL34 or KT88 operation, as the 8417 became difficult and expensive to source.  This amplifier was the first Quicksilver, and considered by most their best sounding.

However, we need to look at things in totality.  I've actually blown more rectifiers in the Quicksilvers than the Dynaco ST70, as the amps use an initial power supply capacitor too large by a factor of about 4.

The Jadis Orchestra / Orchestra Reference integrateds also use this circuit, though with solid state rectification.  And in this application, with the right tubes, the results sound exceptional.  Still, I'm a fan of tube rectification, and the sonic beauty it lends