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Audio and Video Talk
Valves / Vacuum Tubes
How big should an EL84 push-pull amplifier transformer be?
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<blockquote data-quote="Mars" data-source="post: 805079" data-attributes="member: 817"><p>Hi El Sid</p><p></p><p>The screen taps can be anywhere from 20% to 43%</p><p></p><p><img src="http://www.r-type.org/articles/art003k.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>The screen taps are out of phase to the anode, thus if the same signal that appears on the anodes are sent to the screen grids, you have max negative feedback. That would be 100% of windings. So called triode mode. Lots of local negative feedback=low distortion and high linearity. Half the power of the pentode configuration.</p><p></p><p>If the taps are at 0% of windings, you have a pentode output stage: max power/high distortion. </p><p></p><p>I use 33%, since I'm rolling a 3 section transformer to accommodate a 4 and 8 ohm tap. It is just convenient. Slightly less distortion/power than 20% taps.</p></blockquote><p></p>
[QUOTE="Mars, post: 805079, member: 817"] Hi El Sid The screen taps can be anywhere from 20% to 43% [IMG]http://www.r-type.org/articles/art003k.jpg[/IMG] The screen taps are out of phase to the anode, thus if the same signal that appears on the anodes are sent to the screen grids, you have max negative feedback. That would be 100% of windings. So called triode mode. Lots of local negative feedback=low distortion and high linearity. Half the power of the pentode configuration. If the taps are at 0% of windings, you have a pentode output stage: max power/high distortion. I use 33%, since I'm rolling a 3 section transformer to accommodate a 4 and 8 ohm tap. It is just convenient. Slightly less distortion/power than 20% taps. [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
How big should an EL84 push-pull amplifier transformer be?
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