XPost: rec.audio.pro, comp.dsp   
   From: mrivers@d-and-d.com   
      
   On 11/22/2010 7:41 AM, Adrian Tuddenham wrote:   
      
   > The convenient shortcut dB formula relating voltages is often taught   
   > with insufficient emphasis being placed on the conditions for which it   
   > is valid.   
      
   This is why it's only been used over the last 30 or maybe 40   
   years, while the "power dB" goes back 80 years or so. It's   
   only been since the adoption of the nearly universal   
   voltage-not-power scheme of interfacing. This is primarily a   
   result of the use of solid state electronics which   
   characteristically have nearly zero output (source)   
   impedance but without the ability to supply any significant   
   amount of current. It's just how things work now.   
      
   > After a while, people begin to believe that the voltage   
   > formula is the true representation of dB until a situation arises where   
   > it generates nonsense results   
      
   Not a lot of confusion, because, in general, audio people   
   TODAY work with dB of gain or voltage levels, and absolute   
   (not relative) watts when dealing with power levels. Someone   
   will understand a 100W or 200W amplifier, but won't think of   
   one having 3 dB more (power) gain than the other.   
      
   --   
   "Today's production equipment is IT based and cannot be   
   operated without a passing knowledge of computing, although   
   it seems that it can be operated without a passing knowledge   
   of audio." - John Watkinson   
      
   http://mikeriversaudio.wordpress.com - useful and   
   interesting audio stuff   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)