DIY Audio Home

EL34 active-load (SRPP) parallel-feed amplifier

600彩好的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.

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)

2?????????? 2?????????? 2?????1??????? 2????????? 2????????? 2???????? 2????? 2????10????? 2?????1??????? 2???????????