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Audio and Video Talk
General Discussion
Autoformer? isolation is a 'transformer' Why?
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<blockquote data-quote="fredeb" data-source="post: 1126883" data-attributes="member: 13623"><p>I was looking for Dick Olsher Interstage amplifier designs (which I still can't find) , where in his "tip of the month" section I started looking at his review of a modified to pentode mode version of a Leak Stereo 20 . I respect Dick's opinion , and love my recently acquired Stereo 20 , so I decided to check it out . The Stereo 20 has an extremely high input sensitivity , so much so that it requires a pre that is only a unity gain buffer or passive pre . It struck me that his volume control of choice happened to be an autoformer volume control - there must be something to it , and somehow this relates ?</p><p></p><p><a href="http://www.blackdahlia.com/tipofthemonth" target="_blank">Dick Olsher's Tip of the Month</a></p><p></p><p><a href="http://www.blackdahlia.com/html/Tip_93.htm" target="_blank">Leak Stereo 20 Tube Amplifier on Steroids</a></p><p></p><p><a href="https://jandkaudiodesign.blogspot.com/2017/09/autoformer-volume-control.html" target="_blank">Autoformer Volume Control</a></p><p></p><p>Certainly more research to be done , post your findings .</p><p></p><p>If the autoformer output was not used , there would possibly be a switch , switching resistor networks to alter speaker impedance choice , or the amplifier would be designed so-as to be able to drive a wide range of different impedance speakers . So perhaps added inductance makes a change in sound as opposed to using resistors ? Perhaps there are advantages to designing an amplifier with a smaller range of driving capability ? Another thought is changes it might bring to negative feedback .</p></blockquote><p></p>
[QUOTE="fredeb, post: 1126883, member: 13623"] I was looking for Dick Olsher Interstage amplifier designs (which I still can't find) , where in his "tip of the month" section I started looking at his review of a modified to pentode mode version of a Leak Stereo 20 . I respect Dick's opinion , and love my recently acquired Stereo 20 , so I decided to check it out . The Stereo 20 has an extremely high input sensitivity , so much so that it requires a pre that is only a unity gain buffer or passive pre . It struck me that his volume control of choice happened to be an autoformer volume control - there must be something to it , and somehow this relates ? [URL='http://www.blackdahlia.com/tipofthemonth']Dick Olsher's Tip of the Month[/URL] [URL='http://www.blackdahlia.com/html/Tip_93.htm']Leak Stereo 20 Tube Amplifier on Steroids[/URL] [URL='https://jandkaudiodesign.blogspot.com/2017/09/autoformer-volume-control.html']Autoformer Volume Control[/URL] Certainly more research to be done , post your findings . If the autoformer output was not used , there would possibly be a switch , switching resistor networks to alter speaker impedance choice , or the amplifier would be designed so-as to be able to drive a wide range of different impedance speakers . So perhaps added inductance makes a change in sound as opposed to using resistors ? Perhaps there are advantages to designing an amplifier with a smaller range of driving capability ? Another thought is changes it might bring to negative feedback . [/QUOTE]
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General Discussion
Autoformer? isolation is a 'transformer' Why?
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