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EL34 active-load (SRPP) parallel-feed amplifier

this is a little experiment i've been playing with.  it uses el34's in srpp, or active-loaded, with a parallel feed (no dc) output transformer.  running on a b+ of 600-650v, it puts out around 8 watts.

i connected the lower el34 as a triode, and the upper as a pentode.  this arrangement provided low distortion and really good psrr.  details forthcoming...

i tried both a radio shack 70v line transformer and a hammond 125j as the opt.  the rs worked pretty well for a really cheap tx, but distorted pretty badly below 100hz.  the hammond 125j did better, fairly decent at 20hz up to a couple of watts.

双色球模拟选号器i used a hybrid tube/ss rectifier to get ~650vdc from a 270-0-270 vac transformer.  this worked really well.

Schematic (PDF file, 31k)

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