[Laser] discrete vs op amp sensitivity

[F1AVYopto at aol.com]

Hello  all 
To stay about  the sound cards and the dynamic range it is possible to do the 
small experiment  describe after. 
The goal is  to extract a very small audio signal in a nearly white  noise. 
Use the  SPECTROGRAM program V6.6. (If you have not sent me a direct  mail) 
In this  program we can set the dynamic range of the FFTDSP  operations. 
Use  "function", "signal scan and range", "range dB" 
So you can  choose 30 60 or 90 dB. 
Of  course the input gain must be adjusted by the "function", "volume  
control" or/and the "function", "signal scan and range", "gain  cursor".  
Connect in  dark night your optical front end to the PC audio input, run the 
program  and adjust the input noise to get a deep blue waterfall display at 90 
dB  range. 
Use a small  optical beacon to get a very small signal line in the  
waterfall. 
You will  notice if you restart the operation with the 60 and 30 dB range the 
 sensitivity goes up strongly. 
This seems  very normal because the display ratio between the useful signal 
and the global  noise increase in the waterfall with the chosen range... 
It seems to  me the dynamic range is not a fundamental improvement when the 
goal is to  extract a small signal in noise? 
What do you  think about this effect with the very wide dynamic range of the  
new sound cards for this application? 
73 Yves  F1AVY.