Audio playback once seemed as
simple as placing a record on a turntable and engaging the
play button. But 20th century memories can be
It wasn't always that simple. For example, the playback
of a vinyl record could include several sizes in one of four
speeds. And prior to 1954 vinyl enthusiast confronted
several playback equalization choices. In addition,
audio tape formats such as the open reel or cassette included
options such as tape size, speed, noise reduction, playback
equalization, and recording bias.
Given this history, it shouldn't
be surprising that the 21st digital century has also generated
yet another collection of audio options wrapped in terms such
as file and format, compressed or uncompressed, lossless or
lossy, WMA, ACC, MQA.
Files & Formats
Digital audio organizes data into
files and formats. The file is the container. The
format is the storing method.
For example, the compact disc
files audio to an optical discs and uses the Sony/Phillips
16-bit 44.1KHz sampling rate format. Digital audio can also be
filed to a music server hard drive, solid state drive, or
streamed from an Internet cloud server. This type of
audio file management must choose between a compressed or
An uncompressed format records
the entire audio waveform.
But this format also devours computer storage and Internet
Uncompressed formats include FLAC, WAV, AIFF, and DSD formats.
Note: Codec is shorthand for encode/decode
A compressed format saves
computer storage and bandwidth. It shrinks data files by
removing "unneeded" data with masking codec software.
Masking records louder audio while removing less loud audio
data. The missing audio data is said to go unnoticed because
its loss is hidden or masked by the louder audio. There
are two versions of compressed formats, lossless and lossy.
Lossless compression reduces
data and data storage by 50%. Lossless can compete with
or improve CD quality audio. Lossless lost redundant
data can be less damaging than CD optical-laser jitter-phase
distortion. Popular lossless formats include ALAC and
Lossy compression reduces data and data storage by 90%.
But lossy does not approach CD audio fidelity. Lossy
audio quality ranges from a cell phone to good FM radio.
MP3, ACC, WAV, OGG are popular lossy formats.
Masking implies that the lost redundant audio data is
insignificant. However, that data includes essential
HiFi phase information. Sound engineers have proven that the
human ear is more sensitive to phase than frequency. A
friend once explained it was more important for early caveman
to determine which direction (phase) a tiger was coming from
than which tiger (frequency). We are descendants of the
Phase distortion is a well know issue in high fidelity
circles. Phase distortion has long been identified as a
key-hindrance to compact disc fidelity. Masking can also
create audible phase distortion. Check out The Absolute
Sound MQA story "Musical Origami
Stuart of Meridian introduced a digital audio format that
purports to eliminate phase distortion.
The 20th Analog Century
LP Record / Magnetic Tape
The following is from the original 2007 Ed's AV Handbook;
deleted due to perceived lack of interest. I have
reintroduced analog reproduction due to the renaissance of
vinyl LPs, and to some degree, analog tape sources.
Reinforcing the understanding of audio reproduction alone
justifies a revisit to analog audio sources.
Vinyl LP Record
The successful archival of sound
began with the Edison phonograph and continued through the
20th Century with its ultimate successor, the LP record.
The following illustrates how the
stereo LP works.
The voltage form a microphone, or
studio master tape, fed to an assembled coil & magnet,
somewhat similar to a speaker, is attached to a cutting stylus
rather than a speaker cone. The stylus etches a spiral
groove of its movement onto a rotating flat circular master
engraving. The groove begins at the outer edge and
terminates near the center. The engraved master is used
to create vinyl LP records.
During playback, another stylus
riding in the groove of the rotating LP record traces the
mechanical movement. The stylus modulates a
small-magnet/coil assembly, which generates a small
voltage. The voltage of the groove recreates an
equivalence of the original microphone voltage. The
voltage is routed to an amplifier and delivered to a speaker
that reproduces the original recorded sound waves.
Select this link Vinyl
Recorder.com or the image below.
Then scroll down the link page to view a series of images.
The analog magnetic tape recorder
is the principal record medium of the last half of the 20th
Century. The most popular formats included
open-reel-to-reel and the compact cassette. The tape
recorder magnetically imprints a microphone's modulating
voltage onto a coating of metal oxide glued to the surface of
a strip of Mylar tape. The process begins as the
microphone's voltage is applied to a coiled wire within the
recording head of the tape recorder. The electrified
coil generates a modulating magnetic field.
Select this link
or the image below to MagLab.com.
Then scroll down the linked
page to the recording animation --- it's takes a moment to
The record head produces a
modulating field that leave a magnetic imprint on a Mylar tape
drawn/pulled across the recording head. Playback
reverses the process. The magnetically imprinted Mylar
tape, drawn/pulled across a coiled wire in a playback head,
generates a small voltage. This voltage is an analog of
the microphone's voltage. The voltage is amplified and
then routed to a speaker.
Select this Link
for a more comprehensive 'the absolute sound' explanation of
the open-reel tape primer.
Select this Link to EMI Archive Trust for a
history of recording timeline.