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EL34 high plate voltage options?

Dave Paetow

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Jul 15, 2001
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13,524
I need some new EL34's for an amp that runs 575 volts on the plates. I heard that will nuke Seimens, what are my options? I can't afford NOS Mullards! Will the Winged C or JJ E34L hold up?
 

jcs

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Oct 31, 2001
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find some nos sylvania 6ca7....hell find a set of slightly used mullards that have the labels rubbed off or have a different label,the corksniffers havent ran the price on these thru the sky(not yet anyway)

if i had to choose new production, the older svet el34 are good,but regardless make certain whatever you get is screened and burned in well and hopefully has passed the hammer test as well.....i am hearing all kinds of quality issues with some of these brands as of late....
 

jakthekat

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Nov 11, 2003
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The reason modern EL34s will survive in Music Man amps is because the screen grid voltage is low, half the voltage than appears at the plate. Dave, you can have your amp modded by a competent tech to do just that. If your amp has a solid state rectifier, configure the first power filter section just like a twin reverb. If it has a tube rectifier reduce the values of the two filter caps to 20 to 30 microfarads.
 

jakthekat

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Nov 11, 2003
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I should have included this info in my last post but after the first power filter stage is reconfigured a la twin reverb you would take the ot center tap and connect it at the first filter stage which is also the output of the rectifier. Then you take the screen grid supply from where the two capacitors in series are connected. (Where the neg. end of cap 1 and the pos. end of cap 2 are joined.) The voltage there will be very close if not exactly half the voltage at the center tap. I've only seen a few Music Man amps on the inside but I believe that is the method used. Don't forget the 220K resistors in parallel with each series filter cap.
 

Dave Paetow

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Jul 15, 2001
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13,524
I have a set of older Tesla EL34's in the amp now, and they seem to be working OK, but I just was wondering if there was something that would work or sound better. I do have some NOS 6CA7's and some RCA rebranded Mullards, but I'm saving those for the right amp.
 

sickboy79

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Apr 2, 2002
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5,161
Just about all NOS EL34s will hang at those plate voltages. The Seimens will be a bit sketchy at those voltages though. New stuff....Svet/SED and JJs will hang just fine.
 

EdMan57

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Oct 1, 2002
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106
According to Myles at Groove Tubes,their new USA made 6CA7 can handle well over 600 volts on the plates.I just might snag a pair for my Bedrock 1600.
Ed
 

Dave Paetow

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Jul 15, 2001
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I'm trying a pair of JJ E34L's, and they are working good so far.
 

sickboy79

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Apr 2, 2002
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Dave Paetow said:
I'm trying a pair of JJ E34L's, and they are working good so far.

Those will definatly hang. No prob. Definatly my least fav EL34 as far as tone.....the JJ E34L Just my opinion though. Too much headroom, low end, and too aggressive for my ears.

.I like the regular JJ EL34 better (there a big difference between their E34L and EL34). Definatly check these out if you don't dig Svetlana or EH.
 

jcs

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Oct 31, 2001
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what amp are you speaking about with the high plate volts? i would at least try the 6ca7 and mullard el34s for a reference....i would loan you some of my strong el34 -6ca7 pulls if you want...those nos 6ca7 sylvania-ge have a 'very long life' provided the screen volts are reasonable....
 
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