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Audio and Video Talk
Valves / Vacuum Tubes
Radford STA 15 Technical Discussion
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<blockquote data-quote="handsome" data-source="post: 1043130" data-attributes="member: 772"><p>I stand corrected: Radford never used the ?traditional? pentode configuration in any of their designs they always connected screen bypass to 0V.</p><p></p><p>The advantage of the ?buffered Schmitt? and ?pentode-triode Schmitt? was simply wider bandwidth which I presume allowed those designers to use more feedback. But as [member=144]Ampdog[/member] notes it wasn?t really a problem that anyone else found. Interestingly the Radford design still utilised a step network on the input pentode despite its bandwidth enhancing splitter. </p><p></p><p>In those days of course LOTS of feedback was normal as was ridiculously high sensitivity, making for rather noisy amplifiers from Leak, Mullard et al (unlike the Quad II which refreshingly, was designed far more appropriately ~1.4V sensitivity) All of these amplifiers were power amplifiers after all and had matching preamps, so didnt need all that sensitivity . substituting the 12AX7 in the splitter with a 12AU7 would have mitigated the bandwidth issue and lowered the gain assisting with both the noise issue and providing a far more useful input sensitivity.</p></blockquote><p></p>
[QUOTE="handsome, post: 1043130, member: 772"] I stand corrected: Radford never used the ?traditional? pentode configuration in any of their designs they always connected screen bypass to 0V. The advantage of the ?buffered Schmitt? and ?pentode-triode Schmitt? was simply wider bandwidth which I presume allowed those designers to use more feedback. But as [member=144]Ampdog[/member] notes it wasn?t really a problem that anyone else found. Interestingly the Radford design still utilised a step network on the input pentode despite its bandwidth enhancing splitter. In those days of course LOTS of feedback was normal as was ridiculously high sensitivity, making for rather noisy amplifiers from Leak, Mullard et al (unlike the Quad II which refreshingly, was designed far more appropriately ~1.4V sensitivity) All of these amplifiers were power amplifiers after all and had matching preamps, so didnt need all that sensitivity . substituting the 12AX7 in the splitter with a 12AU7 would have mitigated the bandwidth issue and lowered the gain assisting with both the noise issue and providing a far more useful input sensitivity. [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
Radford STA 15 Technical Discussion
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