(compMus1) Analog and Digital

The terms analog and digital only have meaning for audio when it is recorded or reproduced using electronic means (including computers).

Fundamental Stuff

  • Analog is continuous; Digital is discrete
  • Analog refers to analogous (one thing is similar to another thing); Digital refers to numbers.

Analog Recording/Reproduction

  • Fundamental principle: transduction (the changing of energy from one form to another).
  • Whenever transduction takes place, the resulting energy is analogous to the input energy.
  • Recording Chain: Sound (air pressure) -> microphone (air pressure to electrical fluctuation) -> record head of tape deck (electrical fluctuation to magnetic fluctuation) -> Magnetic fluctuation stored on tape.
  • Reproduction Chain: storage (magnetic) -> playback head of tape deck (magnetic to electrical) -> amplifier (increase in electrical energy) -> loudspeaker (electrical to magnetic to drive speaker cone, to air pressure resulting from speaker cone movement)

Digital Recording/Reproduction

  • Fundamental principle: sampling (measuring a property and storing the measurement as a number)
  • The conversion from energy to numbers is not analogous.
  • Recording chain: sound (air pressure) -> microphone (air to electrical) -> analog-to-digital converter (ADC) (electrical to numbers) -> storage (usually in magnetic form, but fluctuation only represents a 1 or 0).
  • Reproduction Chain: storage -> digital-to-analog converter (DAC) (numbers to electrical) -> amplifier (bigger electrical) -> loudspeaker (electrical to magnetic to air pressure).

Recording Quality

  • Analog quality depends on quality at every point of transduction in the chain.
  • Analog copies involve transduction – hence, some energy loss.
  • Digital quality depends on quality and resolution of ADC and DAC.
  • Digital copies do not have generational loss.


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