XPost: alt.engineering.electrical, sci.electronics.design, sci.e   
   ectronics.repair   
   From: dachthetniet@net.invalid   
      
   On 11/12/2011 7:21 PM, John Fields wrote:   
   > On Wed, 9 Nov 2011 12:31:43 -0800, DaveC  wrote:   
   >   
      
   >   
   > .     E1                  -0.621V   
   > .     |   0.621V     R3    /   
   > .    [Ra] /       +-[10k]-+   
   > .     |  /   R2   |       |   
   > .     +-+--[10k]--+--|-\  |   
   > .     |          /   |>-+   
   > .    [Rb]       / +--|+/   
   > .     |       0V  |   
   > .    GND         GND   
   >   
   > "OK", you may say, "but what on Earth does that have to do with a 50k   
   > pot feeding a 10k load?"   
   >   
   >   
   > If we make a table of changes in output voltage as a function of   
   > successive 5kohm changes in pot resistance, we'll have:   
   >   
   > .  R       V      dV   
   > .--------------------   
   > . 50k    1.000   0.379   
   > . 45k    0.621   0.177   
   > . 40k    0.444   0.103   
   > . 35k    0.341   0.069   
   > . 30k    0.272   0.050   
   > . 25k    0.222   0.040   
   > . 20k    0.182   0.036   
   > . 15k    0.146   0.035   
   > . 10k    0.111   0.042   
   > .  5k    0.069   0.069   
   > .  0k    0.000   -----   
   >   
   > You can see from dV that the change in voltage isn't very linear.   
      
   Our hearing is more or less logarithmic, so it might be about right.   
      
   Further more most volume pots in audio are logarithmic.   
      
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