p>When you do Replication of cd’s a glass master is created. This glass master has physical groves providing peaks and valleys. The glass master is used to physically stamp/mold the disc with the associated peaks and valleys. A fine reflective protective coatting is then placed over this and hardens. The peaks and valleys are read by as cd player as 1′s and 0′s. The player/computer reinterpits the 1′s and 0′s.
IF you are doing large runs of several hundred to several thousands this is the way to go. This method is to qurantee the same quality and sound for the 1st disc made to the 100,000.

CD Duplication uses CD burners found in your home computer. The laser in the player heats/burns the chemicals placed inside the disc causing a chemical reaction. The difference in burned and none burned areas causes the peaks and valleys (1′s,0′s). Everytime you burn a disc from a computer there is now garuntee that the machine, burner, will burn the cd the exact same way as it did the last time. Power fluctuations, errors in the origional music file can commenly cause the computer/burner to re-interpet the file differently and have it burn the file with slight alterations. These alteration can cause small changes in the audio. That you could burn 100,000 cd’s and produce an equal ammount of variations to tone quiality to the audio when it is then played.

One final note. If you are burning a Music CD, especially if this is to be used to be the master for creating a glass master for Replication. Make sure you burn the CD at the lowest possible burn rate. 1x speed is ideal. The slow burning process helps insure that there is no errors in burning. Error’s in burning and errors in orginal source music files(such as clipping) can cause the burn to register and error. Again computers/players use high order math/calculus/algorythms to re-convert those 1′ and 0′s into the line the creates a sound wave that our ears pick up. Through interpulation between two points( using many points to create the soundfile line). When an error occurs the computer/player makes up a number between the the path where it thinks the line should be. Everytime that disc is player the error needs to be re-interperted and this isn’t done always the same way. All depends on what the machine want to do as a guess.

Example here is what the line should be …Connect the dots to make the line. The X will be the point an error occurs. Imagine this is a instruments volume slowly getting quiet

*
  *
   *
     x
      *
        *

The above is how the original sound wave should interpertted.

But because of the error you could get.
*   x
  *
   *

      *
        *
Or
*
  *
   *
    
       *
     x   *

See how error clipping can cause havic to your music. Now imagine again pressing 100,000 copies and each copy 100,000 combinations. This does happen, especially if the mastering engineer did not pay attention when creating the premaster.

Anthony Sellitto

http://www.a3mediallc.com