Digital Theory

The Digital Sound-path

Sound Wave (Acoustic Energy) > Microphone Transducer (Electrical Energy) > A/D Converter (Digital Bits, numbers representing voltages) > CPU (Stored as bits of data) > D/A Converter (Converts digital bits into voltages) > Smoothing Filter in D/A converter (white noise is applied) > Speaker Transducer (Electrical energy is converted back into acoustic energy)

White Noise - All frequencies at equal levels.

Pink Noise - All frequencies adjusted to sound equal to the human ear.

Breakdown of Binary. Analog = Continuous Data
 * A single digit is a bit
 * Four Bits is a nibble
 * Eight bits is a byte

Digital = Enough information to seem continuous

Quantization - The act of converting voltage level and expressing it into Binary code.

Sample - Digital representation of an analog signal (Voltage). The digital recorder takes a sample of an analog signal and goes through the process of quantization to create a sample.
 * CD sample rate - 44.1k [Red Book Audio Standard] This sample rate is used because of the Nyquist Theorum - The maximum frequency a digital system can represent is equal to 1/2 the sample rate. This allows for a maximum frequency of 22k.

The downside of the Nyquist Theorum was that if you tried to record a tone that was above your maximum frequency you run into alising, and transfers any frequencies above your maximum get transferred downward. To combat that all A to D converters have Anti-Aliasing filters (low pass/highcut filter)

Resolution - The number of bits used express a sample.Represented (a 0 or 1). You always have at least 8-bit which is a Byte. In an 8-bit sample we have a maximum of 256 values possible.
 * CD Resolution - 16-bit (1 Word) In this resolution you have 65k.
 * Many audio interfaces are capable of recording in 24-bit resolution.

Memory Formula

44.1k/16-bit = 5mb/minute/track

The path to the M.D.M. - Early M.T.R. (Multi-Track Recorder)

 * The D.A.S.H. Recorder (Digital Audio Stationary Head) - This is a reel-to-reel digital recorder used in early digital recording. The DASH format became the standard.

D.A.T. (Digital Audio Tape) - Digital Audio Recorder that recorded in Stereo.
 * V.H.S. - Closed Reel Video format
 * Betamax - Closed reel video format that competed with VHS and lost.
 * Alesis ADAT (Alesis Digital Audio Tape) - Multi-track format that used the V.H.S. format and recorded with a rotating head with a helical scanpath. Each could record 8 Tracks for 41 minutes of recording time on a Super-VHS.
 * Tascam DTRS (Digital Tape Recording System) - Multi-track format that used the Hi-8mm format. Competetor to ADAT.
 * Alesis HD-24 (Hard Disk - 24bit)

C.D. (Compact Disk) - Optical digital system.