Are JJ E34L's 25 watt or 30 watt?

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Vrad

Vrad

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I'm confuzzled.. some folks say it's 25 watts, some say it's 30 watts.
 
I had a set of Tesla EL34's a long time ago. Dark blue glass. Those were really good tubes.
 
Guess it can't hurt to bias them to 25 watts just to be safe...
 
baron55":2fydobiq said:
Yea to be safe would be a good idea, especially since JJ's quality has been spotty as of late.
Yeah tell me about it... I got EL34's that were all wooshy... and 2 dead 12AX7's!
 
neither ......

max is about 17 watts .. there are other factors that make up an amps total output in wattage.
 
jerrydyer":653uz1es said:
neither ......

max is about 17 watts .. there are other factors that make up an amps total output in wattage.

Now I'm even more confused... LOL! :D
I should bias it like it's a 17 watt tube?
 
Jerry has it right. It's not the tube itself that determines power output. It's a combination of the tubes, OT, speakers, voltage, bias.... The only way to really see what we are talking about is to draw out some proper load lines using all the variables, which not even a lot of amp builders and techs can do properly.

I have a feeling you are getting the whole 'plate dissipation' confused with output wattage.
 
I would have sworn that they were rated at 27 watts, but I just check their spec sheet and they're 25.
 
Vrad":2l7yj388 said:
Looks I be biasing them to 33-35 mA?

Depends on the plate voltage. Without knowing what that is you are biasing in the dark.
 
Meh... fuck it...
I'll just bias them like regular EL34's.
my plate voltage is ~499. So 34mA or so should be fine. I was just wondering if I had them biased too cold.
 
Jerry,
i have never heard this before. so everyone is biasing the JJ incorrectly? .70x25w/ B+ ... which should be .70x17/B+? you're kidding me!
seems to me you are thinking that when biased using the 70 percent method they now put out 17 watts. no?
Mark
 
el34 12 to 19 watts 21 pushing it
70% of 19 to 21 is apprx 17
doing the formula based on 17 would be more accurate than 25. but when it all comes back down to MA and MV's its not too much of a jump.

I use the formula and a compubias then average the two. my Hybrid has a voltage switch on it to vary 499 apprx to 520 apprx I think Im somewhere around 32 34 MA .. Im at work now i can double check all my stuff tonight and get back. but just saying a jj els4 is 25 watts would be incorrect math. there all a little diff. thats why we have dudes check em and match first.

I love the compibias though it shows plate voltage. exact wattage and MA's... very cool device.
 
so then you are saying someone biasing using .70x25(for el34's) = 17.5 / B+ = mA's is incorrect in that they are biasing tubes to draw too much current?

Mark
 
no this formula looks dead on. :thumbsup: simply adjusting your MA based on 25 watts would be incorrect. thats what some do mistakenly.
 
%70 of max plate dis.
the other guys are looking for a shortcut really. they dont realize there is no one MA setting that suits all el34. You have to do the math. OR get a COMPUBIAS
 
okay so then you were saying its a 17watt tube when bias correctly? it confused me when you said its a 17watt tube.

el34's are 25watt tubes - biased at 70 percent MPD they put out around 17.5 watts.
Mark
 
exactly. its a 25 watt tube but if you run it a 25 watts it wont be one for long.
 
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