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Audio and Video Talk
Valves / Vacuum Tubes
100 watt push-pull fixed bias amplifier
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<blockquote data-quote="Mars" data-source="post: 859038" data-attributes="member: 817"><p>Update: the amp has been playing for a week now. The high frequency response was extreme and I had to listen to music at whisper levels to not get a head ache. This is an amp that needs taming. And the bass response is lacking.</p><p></p><p>I tackled the bass response first. I tried more capacitance at each PSU node; no improvement. Enlarging the coupling caps to from 0.22 to 0.47uF did give me the bass I needed.</p><p></p><p>I did the aikido trick and coupled the PSU rail to the phase inverter grid via a 0.22uF cap. I also bypassed the all the PSU electrolytics with polypropylene caps. Lastly I enlarged the 220pF NFB cap to 1000pF.</p><p></p><p><img src="https://www.tubecad.com/2007/10/28/long-tail%20phase%20splitter%202.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Listening to music is much more fun now. I might remove the 1000pF NFB bypass cap next.</p><p></p><p>The sound is very clear and powerful.</p></blockquote><p></p>
[QUOTE="Mars, post: 859038, member: 817"] Update: the amp has been playing for a week now. The high frequency response was extreme and I had to listen to music at whisper levels to not get a head ache. This is an amp that needs taming. And the bass response is lacking. I tackled the bass response first. I tried more capacitance at each PSU node; no improvement. Enlarging the coupling caps to from 0.22 to 0.47uF did give me the bass I needed. I did the aikido trick and coupled the PSU rail to the phase inverter grid via a 0.22uF cap. I also bypassed the all the PSU electrolytics with polypropylene caps. Lastly I enlarged the 220pF NFB cap to 1000pF. [IMG]https://www.tubecad.com/2007/10/28/long-tail%20phase%20splitter%202.png[/IMG] Listening to music is much more fun now. I might remove the 1000pF NFB bypass cap next. The sound is very clear and powerful. [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
100 watt push-pull fixed bias amplifier
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