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Push-pull EL802 spud amplifier

i've been playing with a push-pull "spud" amp using el802 tubes.  el802's are high gm pentodes.  for this experiment i have them connected as triodes.

here's a schematic (click for full size):

i used some output transformers pulled from an old console, which i think are 8k:4.  the input transformers are a pair of sescom mi-19's a found cheap on e-bay.  the breadboard looks like this...

it actually sounds very good, and measures well also.

here are some numbers:

b+ = 300v

vplate-cathode = 287v

600彩好的vcathode = 3.27v

rcathode = 72 ohms

600彩好的icathode = 45ma

ptube = 7w

ig2 = 4.2ma

pg2 = 1.2w

600彩好的pplate = 5.8w


1w thd < 0.18%, as low as 0.05%

6.78w @ 5% thd


the downside is that the el802 has quite high input miller capacitance.  driven with a 600 ohms source it's -3db at 20khz.  driven with a 50 ohm source it goes out past 50khz.


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