• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

El509 Plate current question

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fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
MINDBOGGLING...

Hi,

Wow...Are you reading my mind or what?:cannotbe:

As it happens I was busy reading your replies to arthur on the Transcendent forum:

However, in AB mode, where the operating point is very low(~40mA idle current per tube in the T8), during each power cycle, one set of tubes is completely cut off because their grids are going very negative driving the current to zero quickly and providing no current sinking for the load. Therefore, the only current into load comes from the conducting tubes and so the maximum load current is whatever the conducting tubes can provide (assuming they can also make the voltage necessary). In this case, a little over 4A for 4 real EL509s in parallel.
Click to expand...

Talk about coincidence...

Cheers,;)
 
A

audio_siuming

Member
Joined 2003
My friend have a El509 tester (same config as Bruce amp).

I tested 40 tubes, most of them showing 80mA - 130mA at -40V bias, around 7 tubes showing 40mA - 79mA, few tubes showing >130mA.

Is it my El509 not real El509?

I selected the tubes showing 80mA - 130mA in my T8 amp.

Comment, please.

Thank you!
 
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