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August 18, 2019, 06:16:46 AM

Author Topic: Output tube plate resistance and OT Impedance matching  (Read 154 times)

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Offline Deke609

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Output tube plate resistance and OT Impedance matching
« on: June 30, 2019, 05:43:51 AM »
In Doc B's Blues Master article in Valve Vol. 1 1998 at p. 9, Doc notes that "the rule thumb for SE amps is that the impedance of the output transformer primary should be a minimum of 3 times the output tube’s plate resistance."

What is the reason for this? Not just the approx. target ratio (3+:1), but the need for a ratio at all? 

Many thanks in advance,

Derek
Derek
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Online Paul Birkeland

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Re: Output tube plate resistance and OT Impedance matching
« Reply #1 on: June 30, 2019, 06:31:38 AM »
Valve 1998 volumes 3 and 4 cover this pretty well.  You can also look at the giant table of operating points from Western Electric for the 300B.
Paul "PB" Birkeland

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Offline Deke609

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Re: Output tube plate resistance and OT Impedance matching
« Reply #2 on: June 30, 2019, 08:12:31 AM »
Thanks PB. I see that PJ's 3-part article deals with my question in great detail. This is gonna take me some serious time to make sense of. 
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Stereomour IIs (2A3 [EML 2A3 Mesh] and 45 Conversion [EML 45B] - both fully upgraded)  -> Audeze LCD4