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Audio and Video Talk
Valves / Vacuum Tubes
Leak Stereo 20 restoration/mods
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<blockquote data-quote="Ampdog" data-source="post: 580357" data-attributes="member: 144"><p>I promised an alternative for those who find the 70 mV input sensitivity to much.</p><p></p><p>By removing C2 the loop gain is lowered (current degeneration in the first stage) and NFB restored by lowering R18 to 5,6K and increasing C5 to 270pF to maintain stability. The input then becomes 200 mV.rms for full output, perhaps more managable with high intput signals. This could be further increased by replacing V1 with an ECC81, but one then has to also slightly change R2 etc. This is going away from the original and I did not investigate this, though I personally would rather have used an ECC81 (12AT7) to begin with.</p><p></p><p>There is a further option to make the output 'stiffer', but let us not deviate too far from the original. </p></blockquote><p></p>
[QUOTE="Ampdog, post: 580357, member: 144"] I promised an alternative for those who find the 70 mV input sensitivity to much. By removing C2 the loop gain is lowered (current degeneration in the first stage) and NFB restored by lowering R18 to 5,6K and increasing C5 to 270pF to maintain stability. The input then becomes 200 mV.rms for full output, perhaps more managable with high intput signals. This could be further increased by replacing V1 with an ECC81, but one then has to also slightly change R2 etc. This is going away from the original and I did not investigate this, though I personally would rather have used an ECC81 (12AT7) to begin with. There is a further option to make the output 'stiffer', but let us not deviate too far from the original. [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
Leak Stereo 20 restoration/mods
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