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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: 574243" data-attributes="member: 144"><p>Gentlemen,</p><p></p><p>I said there was the 'possibility of', under certain conditions. Not every model would have exhibited this. Showed up at tests as a very mild signal, some 10 mV on output in the present model, but could be excited by a certain rythm, particularly with a high loudspeaker impedance at l.f.. I do not think HJ would have released it if it occurred with any regularity. Nyquist stability analysis reveals the possibility of, but cumbersome to calculate for worst-case scenarios. E.g. high-gain ECC83s would have exacerbated this; most however test lower than published (see Charles's previous post on this). See other Leak designs of similar topology, where the relevant cap was often 250NF. But no quibble; those were my findings for unconditional stability. Enough maths for now. </p><p> </p><p>Charles, Skollie, others: What value for C5 does your amplifiers have? My schematic shows 20 NF, amplifiers that came my way had 100 NFs. Can anybody point me to a schematic specifically stating the use of the 3125 OPT? (Why oh why do designers often have so many different designs for the same thing?)</p><p></p><p>Skollie,</p><p></p><p>Put away your protection gear, or rather have it more ready for the weather you are having these days!</p></blockquote><p></p>
[QUOTE="Ampdog, post: 574243, member: 144"] Gentlemen, I said there was the 'possibility of', under certain conditions. Not every model would have exhibited this. Showed up at tests as a very mild signal, some 10 mV on output in the present model, but could be excited by a certain rythm, particularly with a high loudspeaker impedance at l.f.. I do not think HJ would have released it if it occurred with any regularity. Nyquist stability analysis reveals the possibility of, but cumbersome to calculate for worst-case scenarios. E.g. high-gain ECC83s would have exacerbated this; most however test lower than published (see Charles's previous post on this). See other Leak designs of similar topology, where the relevant cap was often 250NF. But no quibble; those were my findings for unconditional stability. Enough maths for now. Charles, Skollie, others: What value for C5 does your amplifiers have? My schematic shows 20 NF, amplifiers that came my way had 100 NFs. Can anybody point me to a schematic specifically stating the use of the 3125 OPT? (Why oh why do designers often have so many different designs for the same thing?) Skollie, Put away your protection gear, or rather have it more ready for the weather you are having these days! [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
Leak Stereo 20 restoration/mods
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