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Audio and Video Talk
Valves / Vacuum Tubes
Mars 5-10 stereo - update
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<blockquote data-quote="Qualityten" data-source="post: 1076305" data-attributes="member: 17776"><p>I have been thinking about optimal NFB in my build of Karel's earlier 5-10 design, using ECF82s combining first stage amplification and phase splitting duties. There his schematic calls for a 100K NFB resistor, with no capacitor bypass. As 100K is much more than I am used to seeing in this place, I wonder whether this means that there is little NFB being applied?</p><p></p><p>In my particular build I am using 8K Vortexion output transformers intended for an EL84 valve amplifier and I can see oscillation or ringing when viewed on a scope with a 10KHz square wave. As shown in Figure 5 example (d) in: https://www.rfcafe.com/references/radio-news/practical-techniques-square-wave-testing-july-1957-radio-tv-news.htm. Should I add a capacitor in parallel with the 100K to control this?</p><p></p><p>Thanks for this interesting thread.</p></blockquote><p></p>
[QUOTE="Qualityten, post: 1076305, member: 17776"] I have been thinking about optimal NFB in my build of Karel's earlier 5-10 design, using ECF82s combining first stage amplification and phase splitting duties. There his schematic calls for a 100K NFB resistor, with no capacitor bypass. As 100K is much more than I am used to seeing in this place, I wonder whether this means that there is little NFB being applied? In my particular build I am using 8K Vortexion output transformers intended for an EL84 valve amplifier and I can see oscillation or ringing when viewed on a scope with a 10KHz square wave. As shown in Figure 5 example (d) in: https://www.rfcafe.com/references/radio-news/practical-techniques-square-wave-testing-july-1957-radio-tv-news.htm. Should I add a capacitor in parallel with the 100K to control this? Thanks for this interesting thread. [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
Mars 5-10 stereo - update
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