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New to the Dynaco ST70 Community

gadget73 said:
really sort of amazed that after all these years JJ hasn't re-designed their 5AR4. Surely someone there has heard feedback about them.

Their other tubes generally seem OK, so its not like they can't figure things out.
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Right? You would think JJ would take the hint.
 
Blackdog61 said:
I’ve been using the Sovtek rectifier with no problems. Back around 1990 I bought a Mesa Boogie ‘5ar4’ which was actually a 5Y3. Hope they aren’t still doing that because a 5Y3 won’t last.
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I read good things about the Sovtek's holding up well in these amps.
 
I sell and use 5AR4 and the do work provided :
- used with in spec
- no hotswitching. The yellow sheet does protect somewhat.
 
Joth said:
I have some brand new TAD 5ar4s here, I don't think any played a single note of music before sparking out.
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The new red base TAD's flamed out? I had bought a brown base TAD 5AR4 before the fire that took out the Chinese tube factory that TAD was getting there tubes from. No issues with it. I'm using it in my 300B SET amp now.
 
The single 5AR4 failure I've had was one just marked "China". They were so proud of it the factory wouldn't even put a brand name on it. I got it in a low mileage tube set out of an ST70. I vaguely recall testing it and it was OK, tried it in a Heath W4 clone and it immediately popped a fuse. Replaced the fuse and got a lightning show. In the trash with it.

I have Sovteks in something with no issue, but they arent being abused either.
 
gadget73 said:
The single 5AR4 failure I've had was one just marked "China". They were so proud of it the factory wouldn't even put a brand name on it. I got it in a low mileage tube set out of an ST70. I vaguely recall testing it and it was OK, tried it in a Heath W4 clone and it immediately popped a fuse. Replaced the fuse and got a lightning show. In the trash with it.

I have Sovteks in something with no issue, but they arent being abused either.
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I have a quad of Chinese power tubes just marked 6L6GC and Made In China underneath that. The bottles are even crooked in the bases. I've just been using them to test in new amp builds. They've sounded bad in every amp I've tried them in. I even tried them in a couple guitar amps I built. My son spent less than 5 minutes playing through both amps before giving up on those tubes.
I picked all four up for under $10.
 
Only Chinese output tube experience I have is Shugang EL34 tubes. got them cheap, and they died from vacuum leaks for some reason but sounded OK when working. Rolled off on the top, but I ran them in amps that are on the bright side so that wasn't a problem. I found a set of Shugang 6CA7 that I forgot about, haven't really listened to them or used them so I can't comment there.


actually thinking about it, those EL34 may have come with the China 5AR4.
 
The chinese tube quality tube specs are as wide as a barn door. A real roll of the dice when you plug them in. Have bought quite a few quads of chinese power tubes. Some go super nova on first power up, some will last a few months before cashing out, and some will last several years. And if you are running them in an amp that runs B+ way above 400 to 440VDC, take a pass on them. They do not hold up well to near spec limit B+ voltages.
 
Two of my China EL34 went to air sitting on the bench, not even plugged in to an amp. Pretty sure two more are still in the tube box but maybe they went to air too. I'd actually forgive them for an in-use failure in those amps, the plate voltage runs near 700v so its not the easiest life.
 
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