From: ruffrecords@yahoo.com   
      
   Arny Krueger wrote:   
   > "Ian Bell"  wrote in message   
   > news:hnp867$4i2$1@localhost.localdomain   
   >   
   >> Indeed, and most professional equipment operates at +4dBu   
   >> and some at +8dBu and then again a lot of commercial   
   >> power amps have an input sensitivity of 2V for full   
   >> output.   
   >   
   > What you've missed is that there is only a few dB between all of these   
   > numbers. The difference between an objectionally noisy system and an   
   > aceeptable system is generally far more than just a few dB, no matter how   
   > you measure things.   
   >   
   >> Any of these would do, the point is we are not told which.   
   >   
   > It's a hair-splitting, misleading point.   
   >   
   >> I very much doubt the manufacturer says how the input is   
   >> terminated when he measures the amp output noise but I   
   >> very strongly suspect he short circuits it to give him   
   >> the lowest noise figure. Of course you will not achieve   
   >> this figure when connected to a real source.   
   >   
   > Again, there are only a few dB difference in the noise floor of line-level   
   > products with reasonable variations in source impedance or load.   
   >   
   >>>> Output termination is unspecified.   
   >>> As per manufacturers guidelines   
   >>>   
   >> Which are what?   
   >>   
   >>>> No bandwidth is specified.   
   >>> We are talking "audio" so perhaps we can suggest it just   
   >>> might be somewhere between 20Hz and 20,000Hz?   
   >   
   >> Yes, but when measuring noise it is very important. Often   
   >> a 15KHz bandwidth with well defined slopes is used   
   >> because it gives a total equivalent noise bandwidth of   
   >> 20KHz which is not the same as a flat response from 20Hz   
   >> to 20KHz but is does give a better figure.   
   >   
   > Again, there are only a few dB difference in the noise floor of line-level   
   > products with reasonable variations in measurement bandwidth.   
   >   
   > Many of these issues are bigger issues for legacy vacuum tube equipment,   
   > where the noise levels were generally closer to the edge of perception.   
   >   
   >   
      
   And you add up these several instances of 'a few dBs' as the marketing   
   guys will certainly do, plus the judicious choice of weighting for the   
   noise and your 100dB DR spec suddenly becomes in reality in the 80 to   
   90dB region.   
      
   The point is, using several unqualified specs of differing pieces of   
   connected equipment made by differing manufacturers is not going to tell   
   the whole story by a long way.   
      
   Cheers   
      
   ian   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)