From: MrT@home   
      
   "Ian Bell"  wrote in message   
   news:hnrl37$qq4$1@localhost.localdomain...   
   > No, 0dBFS refers to full scale signal in a digital system. It is common,   
   > especially in live recording to set '0dB' to -15dBFS so as to ensure   
   > sufficient headroom. In  other words, 0dB can be anything you like and   
   > therefore on  its own without context is meaningless.   
      
   You are welcome to state your context that would make a 24bit "live   
   recording" on a 110-120dB souncard at -15dBFS peak level have more noise   
   than the ambient noise? :-)   
      
   And you know what I do in the studio, (and even live if I have a spare   
   channel) simply record two channels at different peak levels and select from   
   the one that gives me the highest level with no clipping, for each song!!   
   It's easy to make sure you do NOT waste that 15dB headroom with minimal   
   effort, by simply inserting a 20dB pad in one channel and running the other   
   "hot". In any case if I ever attain a *true* 100dB DNR recording I consider   
   myself very happy. (assuming no other problems of course :-)   
      
   But then we get people like Neil Young who considers a 16-44 CD as not good   
   enough for the release of an old 2 track 1/2" live analog reording that is   
   so far below ultimate CD quality as to make him a complete wanker! I bet he   
   is the only one who considers 24-192 actually necessary in this case. I'd   
   really love to see a recent hearing test of his! :-)   
   (still love his old music though)   
      
      
   > No, but as I keep saying, manufacturers will show their product in the   
   > best light and judicious use of weighting and bandwidths will alter the   
   > 'measured' value considerably. 'A' weighting, which is pretty commonly   
   > used by manufacturers will often improve and amplifiers noise spec. by   
   10dB.   
      
   Sure, and a manufacturer who doesn't specify it as dBA, should be scorned   
   and avoided. Reputable manufacturers however provide both weighted and   
   unweighted figures.   
      
      
   > As I have said before DR and SNR are not the same and they have little   
   > relation to the actual level of noise heard in the speaker. The OP's amp   
   > for instance has an output power of 800W. Suppose this is into a load of   
   > 4 ohms then this requires over 56V rms output signal. The DR is 100dB so   
   > the noise at the output is 100dB below 56V rms which which works out at   
   > a mere -65dBu.   
   >   
   > The original all tube Leak Point One in 1949 had a measured output noise   
   > and hum of -80dB below 10W into 15 ohms which works out at just over 12V   
   > rms. So its output noise is 80dB below 12V rms which works out to be a   
   > mere -58dBu.   
   >   
   > So in 60 years of development there's been only 7dB (oh sorry I should   
   > have said 'just a few dB') of improvement due to the digital revolution.   
      
   Ah, but IF you turn down the gain on the 800W power amp so that it's output   
   power matches the Leak for the same input voltage, you may find it's DNR now   
   exceeds the Leak by a MUCH bigger margin! The choice is often in the hands   
   of the user, higher power, lower noise, or somewhere in between. Some are   
   too dumb to comprehend that higher power outputs require more gain of   
   course.   
      
      
   > Excellent, so then you must agree that SNR is always less than DR.   
      
   Nope, you must specify all your test conditions. Obviously there will be at   
   least one set of conditions where they *must* be equal for a start.   
   And if you measure DNR with an applied signal (as is usually the case for   
   soundcards) SNR may be *greater* than DNR, given any distortion products.   
   (and no headroom above 0dBFS like there was in the days of analog recorders,   
   that will actually add to the DNR)   
      
      
   > So to get back to the OP's original problem, having a DR of 100dB is   
   > irrelevant. What matters is what his SNR is. The fact he can hear hiss   
   > from an 800W amp with his ear right next to it further demonstrates this   
   > because that is not where listeners will be when the spekaer pumps outn   
   > 800W.   
      
   Exactly.   
      
   > In reality, marketing departments will aim to make crappy equipment   
   > appear much better than it is using specmanship which is what they have   
   > always done.   
      
   So true, but then the use of the term "Audiophile grade" was used frequently   
   in this thread. Your definition of "audiophile grade" may differ from mine   
   if it includes crappy equipment from disreputable manufacturers! :-)   
      
   MrT.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)