From: spam@spam.com   
      
   On Wed, 29 Dec 2010 12:05:12 -0500, Randy Yates    
   wrote:   
      
   >An open-circuit, class D amplifier output has extremely sharp   
   >edges due to the switching of the bridge. The expectation is that,   
   >somehow, the output is averaged over at least one cycle of the switching   
   >period to form a continuous, analog voltage.   
   >   
   >If this output is connected to a speaker with a mechanical lowpass   
   >characteristic, then the speaker's mass will effectively average   
   >the "digital" output into a continous position.   
   >   
   >Thus my question is, when connecting a class D output to a speaker,   
   >why do we need filtering at all? That is, why wouldn't the mechanical   
   >lowpass filtering of the speaker be sufficient?   
      
   Because there are EMI regulations that seriously frown upon high power   
   transmitters that broadcast a signal every 40kHz from DC to light.   
      
   d   
      
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