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

like a terribly short lifespan. I bought it in May and spent the extra money to get a "good" tube. It sounded good while it lived. But it went in a fiery inferno last weekend.  Fortunately it only took out a fuse.

It was running in a Bob Latino VTA ST-70 Dynaco amp. It's a great amp but runs the rectifier a bit hard from my understanding. However the original tube lasted at least 3-4 yrs IIRC. I tried a SS rectifier. YUK!! I put the tube (a spare Sovtek) back in place I've had good luck with the KT-66 Genalex GL's and they have a good reputation (I think). Is this just the luck of the draw. IOW, even a new tube can have a short life span? Or is this odd? Is there any way to avoid it? I'd buy another Gennalex GL if it will last. But I can buy 2 Sovteks for the price of one GL. Sovtek sounds good too.

FWIW, The tube that failed was cryo treated. Could that make a difference in a rectifier tube? As always, Thanks for your help.
128x128artemus_5
teo_audio
2,197 posts
 
It may have been a gassy tube or a bit close to it’s limits, or both.

NOS tubes are a bit of a dice roll.

OK, just looked, this is likely a new issue copy you are speaking of.

Sounds like it is more likely you hit it’s current limits in repeated ’turn on surge’ spiking and it finally took the tube out.

Sometimes (more likely, actually) it is a VOLTAGE over peak, due to how a power supply is built. Ie, cascading draw that has one tube come on after another and the voltages can spike until all tubes are on line and the current draw increases, which brings the voltage down to manageable levels. Always a problem that one has to plan for when designing or building new power supplies in tube gear. The genalex may have been hit with one over voltage too many. And possibly been a weak example, in the first place.

Check voltage limits in the spec sheets of the given rectifier tube before you try again.
trelja
3,224 posts
 
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
hifiman5's avatar
hifiman5
1,832 posts
 
@artemus_5 You didn’t mention where you sourced your Gold Lion from. I have had great success with Gold Lions sourced from Cryoset. I have been using their 12AU7’s for many years with great results and long life. I just recently replaced the 5AR4 rectifier tube in my SACD player power supply with a Gold Lion GZ34 from Cryoset. I also added a Herbie’s Audio Lab HAL-O III-30 Stabilizer to the GL. The sound is a bit warmer than what I was getting with the Sovtek and the soundstage has opened up a bit. All is good. If you haven’t tried Cryoset, you may at least want to give Ron Sheldon a call and discuss your situation with him.

Good luck!
jond's avatar
jond
5,919 posts
 
I believe the OP is talking about a current production Genalex since he mentions the tube being cryoed. As others have stated sometimes a tube is just bad old or new.  A rectifier generally should last a fairly long time. I had a NOS Philco 5ar4 go out with a flash and a bang a few years ago and at the suggestion of my dealer got a variac. For around $100 off eBay it has a 2k transformer and ramps the voltage up slowly. I’ve used it ever since haven’t lost a rectifier.Look for good deals on rectifier tubes on here, I picked up some NOS RCA 5ar4 60s era tubes from member aztubes. They sound fantastic and have been perfectly reliable.
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