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Is this too much plate voltage for EL34's???


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4/5/2000 8:33 PM
kevin Hamilton
Is this too much plate voltage for EL34's???
Hi all,  
 
I have a Seymour Duncan KTG2100 power amp that I use in my rack setup. It's awesome using 4 KT88 tubes in stereo for 100 watts per side.  
 
I never use it as a stereo setup and as a result I have one side running on KT88's and the other running on EL34's.  
 
Each side has it's own bias trimmer with a large range, so biasing is no problem.  
 
Here's my only concern. The plate voltage is 660 DC volts. I've got the EL34's biased at 26ma, but is the 660 DCV too much for the tubes? So far I've only ran it for a limited amount of time. Usually no more than 30 minutes at a time.  
 
BTW, switching between the EL34's and KT88's really reveals the tonal differences between the 2 types of power tubes. I like the KT88's for clean stuff and being a Marshal fan, I really like the EL34's for everything else.  
 
Thanks,  
 
Kevin
 
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4/5/2000 8:36 PM
Rebel420

quote:
"Here's my only concern. The plate voltage is 660 DC volts. I've got the EL34's biased at 26ma, but is the 660 DCV too much for the tubes? So far I've only ran it for a limited amount of time. Usually no more than 30 minutes at a time."
The Mullard spec states that 800V is the max plate voltage on an EL34. SO if you have mullards of Svets I'm sure you will be ok, I woudnt try this with some of hte cheaper chinese el34s etc. Music Man amps ran at 725v on the plates give or take a few, and mullards, and the Ruby STR-el34b's are fine with this (about the only Chnese tube I like!)
 
4/5/2000 8:39 PM
kevin Hamilton
Thanks Rebel......
I'm using Svet's. I just had never seen plate voltage that high and didn't want to waste a good set of tubes.  
 
Kevin
 
4/5/2000 10:15 PM
Aaron V.

You might want to check the screens. KT88's can take more than the 500V the EL34's are good for. If the screens aren't turning red, I wouldn't worry about it.  
If your over 500V on the screens of the EL34's and that makes you nervous, you can jack up the screen resistor - maybe on the order of 2K or more. I'd be more worried about the screen current than the absolute level of voltage.  
 
 
Aaron
 
4/5/2000 10:30 PM
anonymous Re: Is this too much plate voltage for EL34's???
 
In addition to the other responses:  
 
If your tubes can handle the high plate voltages, you're probably okay. You're dissipating less than the tubes' rating.
 
4/6/2000 4:46 PM
Bare
Try a set of 6CA7's instead, they are designed for substantially higher plate currents than the EL34s, and their sound is a bit brighter and tighter as well. Well worth trying a set of good ones, my faves are the Edicron 6CA7s
 
4/6/2000 8:59 PM
kevin Hamilton
Edicron 6CA7's.....Are they cheap?
I would love to find some 6CA7's. Where should I look and how much should I expect to pay?  
 
Kevin
 

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