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Old 13th Dec 2018, 8:49 am   #42
tri-comp
Heptode
 
Join Date: Oct 2008
Location: Aalborg, Denmark
Posts: 903
Default Re: 120W PP EL34 amplifier re-born.

Hi Andy,

Good to see you made it home
There a blunder in you schematic for the output-stage.
Take a look at where you feed the signal from the Cathode-Follower stage.
It isn't Grid-1 but that of course has to be a schematic error and not the actual wiring.
Then I'm confused about why to use the CF-stage at all ?
Usually you put an amplifying stage between the Phase-splitter and the output-stage to have enough voltage swing for the grids.
Thankfully EL34 doesn't need that much and in you circuit they don't get any more than is leaving the Phase-splitter anyway.
I can understand using the CF when DC-driving the EL34 grids but you have coupling cap's to the grids.
Low driving impedance source is good but is it needed when you are not driving the output valves into Grid-1 current as in Class AB2 ?

/Torben
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