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as title.I've seen the mullard datasheet and it list 70mA. I've also looked at the Philips datasheet and all I can see is 70 to 100mA and no reference to pentode or triode mode.
which is true?
Follow Ups:
The max rating is for wattage. It is speced at 25 for the anode and 8 for the grid.So how many milliamps depends on plate voltage.
RussNot quite true.
The max current is 150mA according to the spec sheet.
I doubt in REAL use anybody approaches that though.
Russ is right; there is no rating for plate current. The plate is primarily damaged by heat which is the product of voltage and current. There is a rating for plate dissipation, 25 watts for the EL34.The screen grid also has a dissipation rating of 8 watts. In triode mode the two can be combined for a total dissipation of 33 watts.The current limit is at the cathode. The EL34 is rated for 150 mA of cathode current. This is average current, not peak current. Class A amps will sometimes be bias at or near this current but the plate voltage must be low enough to prevent over dissipating the plate. In class AB amps the idle current is generally much less than this limit and the plate voltage is higher than the class A amp so the plate dissipation still limits the idle current. In class AB amps the cathode current rises as the output power rises and at full power it can easily approach the rating limits.
Keep in mind that the cathode current is the sum of plate current, screen grid current and control grid current. Since most audio amps do not drive the control grids positive there is no grid current (class AB2 amps are an exception). When designing an amp all these parameters need to be included in the design process so as not to risk exceeding the tubes ratings.
Jarthel
In the days that data was written,tubes were plentiful and cheap and mullard and genelex used to publish exhorbatant numbers like that but you would be running the tube as a true pentode meaning the screen grid should be about half of what the plate voltage is and should be regulated.Typically an el34 should be biased at 50ma or 60ma tops and some say much less.
I have seen the genelex kt88 sheet saying run them at 700 or 800v I forget and with half the voltage on the screen regulated and they were claiming 125 or 150 watts.It was really something I wouldnt do.
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