From: pfjw@aol.com   
      
   On Monday, October 3, 2016 at 1:28:20 PM UTC-4, Big Bad Bob wrote:   
      
   > I would only guess as to how that should be done.  I would expect equal   
   > cutoff voltages for G-K and similar mu/voltage/current curves, but   
   > someplace there's probably a spec.  and being tubes, they won't stay   
   > "matched" forever.   
   >   
      
   There is that, but I betcha that this guy matches by lot number, if even that.   
   And as tubes are about as similar as potatoes, electrically, that 'matching'   
   will make them no better than third-cousins-by-marriage.   
      
   Peter Wieck   
   Melrose Park, PA   
      
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