Shugang EL34S biases cold?

[gadget73]

Just wondering if anyone has experience with a Shugang EL34S and wanting to run at lower than typical current? I just stuck a set in my Pilot SA-260 and the bias controls are set to max in order to get the idle current high enough. The EH 6CA7's I just pulled out were near the 1/2 point on the controls.

Just curious if thats how these tubes operate or if maybe the bias circuit is a little over-enthusiastic in this amp. They seem to sound fine, so no worries there.

 

[gadget73]

Seems to be those tubes. Stuck in the JJ EL34 set and they adjust like I'd expect.

 

[Lavane]

I had a KT-77 out of a quad of them that biased like that. The trim pot for that tube almost topped out. That tube failed along with one half of a driver tube. Not sure which tubes shorted first though.

 

[gadget73]

hm, hope that doesn't mean these are close to death. I frankly do not remember when or where I even got them. I popped the box open to pull out the JJ set, and these Shugangs were in there as well. I ran them a couple hours and nothing awful happened.

 

[Lavane]

That KT77 I have tests good. But at any given time it will short. Something is wrong with the internal structure I'm guessing. Once it gets good and hot something gets all bendy. At first I thought the voltage gain tube shorted first
But now I'm not so sure after remembering how the 77 biased up.

 

[gadget73]

Had them running at Blue_Shadow's place today, with the controls set wide open I get .45v where it should be at .5v. They sound OK and all. I might have a poke in there to see what the grid voltage adjustment range actually is. It would be easy enough to extend the adjustment range.

 

[knockbill]

Too bad original audio tubes aren't in the buck boxes at Kutztown!!!!

 

[gadget73]

Love for that to be so, but cheap EL34 old stock just doesn't happen. I have some old ones, the four mismatched tired ones that came with the amp. They work, but they're pretty whipped. I think the only way to get cheap NOS power tubes is to build an amp around some "useless" ones. Shame the sockets are so difficult to come by, some TV tubes should be very capable of good performance.

 

[knockbill]

Yep,, like the 811s,,, 6BG6s,,, 6AS7s,,, 829Bs,,, now to find some cheap OPTs that will work with them!!!!
I never had an EL34,,,

 

[gadget73]

6CA7 is the US equivalent, they're more like a 6L6GC with higher ratings, same beam pentode design. An actual EL34 is an honest to goodness pentode tube with 3 sets of grids instead of 2 plus a pair of plates. Rated for a bunch of voltage, and in certain configurations, rated for a bunch of output power too. One set of datasheet conditions is 100 watts from a pair with 800v on the plates.

 

[knockbill]

I passed on a couple of PA amps there without tubes(EL34)for very short money,,, figured the tubes were too rich for my blood,,, If I ever happen on a pair I'll let you know,,, some guitar amps use them also, but I don't have one...

 

[gadget73]

I bought the quad of JJ tubes lightly used on here for 40 bucks. 10 bucks per power tube is pretty cheap. The EH tubes new go for 190 for four, but I bought some "visual defect" tubes for a fair discount. The bottles are slightly crooked but its not obvious unless you look for it, and if I put the cage on the amp you can't see it at all. I frankly can't remember what the Shugangs cost, I don't even remember buying them. They were probably cheap though, I likely wouldn't have bought them otherwise.

 

[Phototone]

Yep,, like the 811s,,, 6BG6s,,, 6AS7s,,, 829Bs,,, now to find some cheap OPTs that will work with them!!!!
I never had an EL34,,,

6BG6 is just a 6L6 with a plate cap.