LINE LEVEL SOURCES

Many line level source devices available. Output is at line level.

ANALOG AND DIGITAL

Analog: continuous signals.
Digital: signal converted to string of binary numbers.

Phonographs:  the original analog recording and reproduction device.
Sound stored as wavy spiral lines on a disk.
	* Vibration of sound literally recorded in the groove.
	* Two kinds of pickups:
		+ Ceramic- high impedance, similar to crystal mics
Output about like standard line level, but at high impedance.
		+ Magnetic- similar to dynamic mics
The phono level of a mixer is lower than line level and higher than mic level.  
Separate due to imedance matching. Still one of the highest fidelity formats 
available, still popular with audiophiles. 
Media is easily damaged and wears out easily.

Tape devices
Use plastic film- acetate or polyester- with coating of magnetic film.
   Ferric oxide, Chromium Oxide
   Erase head: randomizes magnetic pattern.
   Record head: lays down magnetic pattern.
   Playback head: reads magnetic pattern.

Cheap machines use one or two heads, an erase head and a record head.
Better machines use three heads, erase, play and record.

Formats
Reel to Reel: Standard home and theatre machines based on 1/4" wide tape.
Reels typically 3 in., 5 in., 7 in., and 10 inch, dependant on speed.
Reel to reel gave good quality, and easy manual editing and cuing.
Good S-N ratio.

Machines were large, expensive, required a lot of handling. 
Was still easier than other options for creating and assembling sound.

Other tape formats
Cassette: Consumer form uses 1/8" tape, usually stereo
Tape speed is slow, 1 7/8 ips and tracks are narrow.
   Inherantly poor S-N ratio.
   Quality of equipment has done a lot to help this problem.
Media is cheap and pretty available
Rather difficult to edit and cue.

Work around: use one tape per effect, rather like a cart machine
All sounds cued up prior to use.
Risk of mixing up tapes in the dark.
Using headsets for pre-setting:  risky if you forget to pot down or cues 
are close together.
Tape machine counters, not real accurate.

DIGITAL MEDIA
Sound stored as numbers:
Translated by an algorithm into numbers at certain intervals, Sampling rate.
Translated back by another algorithm.
All digital sound is an approximation.
Faster sample, better sound.
Digital sound stored as a computer file.
Some type of processor must perform translation.
When discussing digital sound, refer to media format and file format.
Digital media breaks down to:
	* Tape:  reel to reel and DAT
	* Magnetic disk:  Hard drives, floppies, and Minidisk
	* Optical disk:  CD-ROM, CD-R, etc.
Digital Tape: one of the original magnetic storage medias.
Older mainframes used reel to reel tape
Early PCs used casettes.
Digital Audio Tape. or DAT refers: special adaptation of cassette.
Slightly different size than analog cassettes.
	* Compact, dependable, very clean and robust.
	* Very popular for field recording.
Drawback: If the tape breaks it can't be repaired, and contents are lost. 
If Table of Contents is off, even a little, nothing on tape can be located.

MAGNETIC DISKS:
Magnetic tape media placed on a platter.

Hard disks:  original disk media: like an aluminum record platter coated 
in ferric oxide.
   Relatively high storage density, but were quite expensive.

Hard Drives:  hard disks built permanently into reader casing.
   Can be built to very tight tolerances, so storage density is high.
   PC Hard drives, but used in other machines as well.
   Very dependable but mostly built into machine;
      not swappable.
Floppy disks: same thing on flexible plastic.
   Too small for most sound files.

Zip drives larger form of floppy, large enough for sound, but:
   Access rate too slow to keep up w/ sampling rate.

Minidisks: sort of a small hard disk in a floppy disk case.
	* Sony development, uses proprietary format.
	* Holds about 74 minutes of sound.
	* Like other magnetic media, can be erased and reused.
Are some issues with sound files becoming fragmented with repeated editing. 
Can cause dropout or failure of a given cut.

OPTICAL DISKS:
CD-ROM: optical interference pattern burned or pressed into reflective 
surface of disk.
Reader bounces light from laser diode off surface; reflection is scanned. 
Pits in surface recreate pattern.
Somewhat slow seek time.
CD-R: Pattern charred into subsurface to simulate ROM pattern.
Readable by most CD players.
CD-RW: similar to CD-R, but CD-ROMS players cannot always read them well or at all.

HARD DISK MACHINES
Fastest refresh rate, highest storage density.
PCs: not really a sound machine, but can be used for record
   and playback with special programs and sound cards.
Use on a "clean" machine for greatest dependability.
Hard disk machines: one of newest most dependable options available.
A dedicated computer specialized for sound.
Fast, clean, dependable, expensive.

SAMPLER: Borrowed from musicians.
Short sounds can be recorded into sampler and played back by pressing proper key.
Good for frequently repeated or random accessed sounds.

FILE FORMATS:
Dependant on device and often unique to device.
PC's the exception: can recognize many formats with
   right hardware, software.
   Not as dependable.
AU:  audio file, originally a Sun format for Unix?
AIFF:  Audio Infomation File Format: Apple format, 
   used as a cross-platform file format.
WAV:  DOS/Windows file for rendering analog sounds.
MIDI:  Musical Instrument Digital Interface.
Records keystrokes rather than sounds, like a piano roll rather than a 
recording of the piano.
Quicktime: Mac based file format, available for Windows as well.
MP3: Compressed file format for sound, uses compression algorithm to reduce 
file size. Usually involves some compromising of sound description, 
and so some loss of quality.
WMA: Windows Media Audio file, Windows answer to MP3. Proprietary. 
Similar limitations, and less supported by non-windows programs.

DISK FORMAT STANDARDS:
Redbook Audio (CD-DA):  Audio CD format.
ISO 9660:  DOS and Unix CDs and drives.
HFS (hierarchical File System):  Mac based disks.
NTFS (New Technology File System): Windows NT and XP systems.