From: ruffrecords@yahoo.com   
      
   Arny Krueger wrote:   
   > "Ian Bell"  wrote in message   
   > news:hnmbmi$p5e$1@localhost.localdomain   
   >   
   >> 0dB has no meaning.   
   >   
   > Actually, it does. In the digital domain 0 dB is commonly equated with FS.   
      
   No, that is 0dBFS.   
      
   > While the units are arbitrary and may be confusing to people who still think   
   > 100% analog, it is both meaningful and commonly used.   
   >   
      
   No it is not.   
      
   >> Input termination in both cases is unspecified.   
   >   
   > If the input is a mic input, then the usual standard of 300 ohms applies.   
   >   
      
   It is a power amp, it does not have a mic input. 300 ohms is NOT the   
   'usual standard for a mic input'   
      
   > If the input is a line level input, then the source impedance is usually   
   > such that system performance is not affected that much by probable   
   > variations.   
   >   
      
   You miss the point. How is the input terminated when noise is measured -   
   obviously it is not left open circuit is it?   
      
      
   >> Output termination is unspecified.   
   >   
   > The noise performance of line level outputs is minimally affected by   
   > probable  and reasonable variations in load impedance.   
   >   
   >> No bandwidth is specified.   
   >   
   > Relevant and already mentioned   
   >   
   >> No weighting or not is specified.   
   >   
   > Relevant and already mentioned   
   >   
   >> No mention of whether the measurements are rms, peak, quasi-peak   
   >   
   > Both SNR and DR are ratios of two measurements. It is most important that   
   > both measurements be done under the same circumstances.   
   >   
      
   In fact they generally are not since a signal and noise have quite   
   different characteristics. The signal will be measured rms. The noise   
   can be measured in several ways each giving a different figure.   
      
     >> Variations in the way the above are specified can make a   
   >> large difference to the 'measured' value   
   >   
   > Some yes, some no.   
   >   
   >>  and I bet you   
   >> can guess which set the marketing department will want to choose.   
   >   
   > One other benefit of the solid state/digital revolution is that SNR and DR   
   > performance is often so good (> 100 dB) that most variations in how they are   
   > mentioned don't matter that much.   
   >   
   Rubbish. Once again, SNR and DR are different animals. Achieving a 100dB   
   DR is not hard but unless you run your amp close to clipping all the   
   time you will not achieve that as a SNR.   
      
      
   The marketing guys are as active as ever in trying to make their product   
   appear superior to its competitors and will choose the measurement   
   methods that best do that.   
      
   Cheers   
      
   ian   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)