Discussion in 'General Electronics Chat' started by n9xv, Apr 6, 2005.

  1. n9xv

    Thread Starter Senior Member

    Jan 18, 2005
    Here's a question for all you audio files out there. One of my bigger (more expensive) hobbies is sound reproduction. I like "BIG" audio. I like to feel as if I'am actually in concert when I listen to a sound system etc. I also do alot of track ripping for MP3/portabl players etc. I am up to speed as far as the basic understanding of how recording/playing a CD works. The CD is composed of pits and lands that a laser reflects on/off from to produce the digital output which is then converted to analogue etc.

    What I dont quite understand is this:

    If a CD is digital (on/off), why do some CDs have lower output than others for the same volume level on the amplifier?

    I know that many CD track ripping utilities have an option for adjusting volume level to account for this phenomena.

    But, on any CD the pits & lands are all the same (same depth, width etc) so what causes different volume levels from one CD to another?
  2. hgmjr

    Retired Moderator

    Jan 28, 2005
    Take a look at the How Stuff Works Website. There is a lot of information and some neat animation on encoding CD's.
  3. mozikluv

    AAC Fanatic!

    Jan 22, 2004

    i believe not all recording companies use the same volume level and equipments. likewise there are pirated cds which has poor sound reproduction. :rolleyes:
  4. Brandon

    Senior Member

    Dec 14, 2004
    Same way that a computer can run a program even tho its just 1s and 0s. A collection of 1s and 0s (its 16 bit, so every 16 digits) corresponds to a voltage level stored as a 16 bit number. This number basically gets converted (D to A) into a voltage level which is driven by a power amp and you have sound. Also, the CD is sampled normally at 44.1 Khz so 44100 of those 16bit words get read per second.

    Additionally, all recording media has a voltage head room which corresponds to the effective range that a stored media has to play with in term of volumes of sounds which can be heard on that media. CDs typically have 120-130 dB of head room. Tapes in the 80-90 range, records in the 60-80 range. Maximum headroom is about 150 dB, but its not possible to get it right now since the act of A to D conversion adds noise into all digital recordings.
  5. n9xv

    Thread Starter Senior Member

    Jan 18, 2005
    I've never encountered that asspect before - From the recording end of the equation. Can you tell me where I might find more research/info on that concept?

    Thanks and I'll keep checking.