Audio Systems: Volume mesurement, macintosh cpus, signal to noise ratio

Question
Hi Cleggsan,

When turning volume up in a normal home theatre why does it go up frm -80db to 0 or +10..?

Shirantha

Answer
Can you give me the make and model number of the unit?  That way I can give you a specific reply based on the design philosophy of that company and that product.

The markings are for reference and can be referenced in any way.  Decibels (in db) are linear so you can merely add or subtract accordingly.  The difference in level going from 30db to 40db is 10db and is the same as if going from 60db to 70db and so on.  Therefore, you can consider the dynamic range of your unit at 90b.  If you look at the technical specifications of your unit you will probably note the signal to noise ratio near the 80 to 90 db  figure.

However, probably the reason for this marking is to relate to digital reference standards of the compact disc and other digital audio devices.  They set the audio output level when audio level reaches its maximum (based on the highest digital number) at some voltage and call it "0db".  Then in your case another 10db is added for extra range in case some incoming voltage hits a little over the standard mark.

Hope this is helpful for you.

Cleggsan

PS: There is a nice discussion about voltage levels and the AES standards on an Apple site where they are talking about this very idea of making sure the reference standards are accommodated.  Please refer to it.

http://developer.apple.com/documentation/Hardware/Developer_Notes/Macintosh_CPUs...