From: a@b.com   
      
   flipper  wrote in   
   news:47d2r5l49vosnek0jhla7vu3b48jduj8lg@4ax.com:   
      
   >   
   > Interesting but, unless I'm missing something, that's a different   
   > 'surge' issue and, as you mentioned, doesn't address the supposed   
   > 'cathode stripping', which is the argued reason for a delayed B+.   
   >   
   >   
   >>Cathode followers driving the output tubes can also act as a slow   
   >>start up circuit. For example, the Acrosound 209 uses cathode   
   >>followers driving the 6146s directly. The cathode resistors are   
   >>connected to the bias supply, so at startup, the output tube grids see   
   >>full negative bias voltage until the 6SN7s warm up. The Allen Type 75,   
   >>which has a solid state rectifiers, also has this design.   
   >   
   > Yes, but don't all the tubes, whether there's cathode follower drive   
   > or not, 'slow start' anyway?   
   >   
      
   I think the full negative bias voltage on the grid might prevent cathode   
   stripping since the cathode is shielded from the plate B+ by the high   
   negative grid voltage. There is no or little current even when the cathode   
   is fully warmed up and boiling off electrons.   
      
   If this method does work to prevent cathode stripping, the cathode follower   
   would help to prevent cathode stripping in the solid state B+ Allen 75. The   
   output tube grids would have full negative bias voltage through the cathode   
   follower cathode resistors shortly after the amp is powered up. As the 6SN7   
   warms up, the output tube grid voltage slowly increases to the idle bias   
   voltage. A 6CG7 would have slower startup and work even better.   
      
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