Gramophone record

A gramophone record, (also phonograph record - often simply record) is an analog sound recording medium: a flat disc rotating at a constant angular velocity, with inscribed spiral grooves in which a stylus or needle rides. Analogue audio recording onto a disc was the main technology used for the storing of recorded sound for most of the 20th century. By 1988 digital media such as the compact disc surpassed the gramophone record in popularity, but gramophone records continue to be made (although in very limited quantities) into the 21st century, particularly for DJs doing live remixes and for local acts recording on small regional labels. Used records are still sold in decent numbers and remain a common part of many music collections. Most major releases still recieve a vinyl release, sometimes with bonus tracks and artwork.

Stereo and beyond

In 1958 the first stereo two-channel records were issued – by Audio Fidelity in the USA and Pye in Britain, using the Westrex "45/45" single-groove system. On stereo records the stylus moves vertically as well as horizontally.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

One could envision a system in which the left channel was recorded laterally and the right channel was recorded with a "hill-and-dale" vertical motion, and such systems were actually proposed, but not adopted. In the Westrex system, each channel drives the stylus at a 45 degree angle to the vertical. During playback, the combined signal is sensed by a left channel coil mounted diagonally opposite the inner side of the groove, and a right channel coil mounted diagonally opposite the outer side of the groove http://www.vinylrecorder.com/stereo.html.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

It is, however, helpful to think of the motion in terms of the vector sum and difference of the two channels. Effectively, horizontal stylus motion carries an L+R sum signal, and vertical stylus motion carries an L-R difference signal.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The advantages of the 45/45 system are:

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• greater compatibility with monophonic recording and playback systems. A monophonic cartridge will reproduce an equal blend of the left and right channels instead of reproducing only one channel. Conversely, a stereo cartridge reproduces the lateral grooves of monophonic recording equally through both channels, rather than one channel.
• a more balanced sound, because the two channels have equal fidelity (rather than providing one higher-fidelity laterally recorded channel and one lower-fidelity vertically-recorded channel);
• higher fidelity in general, because the "difference" signal is usually of low power and thus less affected by the intrinsic distortion of hill-and-dale recording.

This system was invented by Alan Blumlein of EMI in 1931, and patented the same year. EMI cut the first stereo test dics using the system in 1933. However it was not exploited commercially until a quarter of a century later.

Related Topics:
Alan Blumlein - EMI

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Stereo sound provides a more natural listening experience where the spatial location of the source of a sound is, at least in part, reproduced.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The development of quadraphonic records was announced in 1971 - which recorded four separate sound signals. This was achieved on the two stereo channels by electronic matrixing, where the additional channels were combined into the main signal. When the records were played, circuits in the amplifiers were able to decode the signals into four separate channels. There were two main systems of matrixed quadrophonic records produced, confusingly named SQ (by CBS) and QS (by Sansui). They proved commercially unsuccessful, but were an important precursor to later 'surround sound' systems, as seen in SACD and home cinema today. A different format, CD-4 (by RCA), encoded rear-channel information on an ultrasonic carrier, which required a special wideband cartridge to pick it up. Typically the high-frequency information wore off after only a few playings, and CD-4 was even less successful than the two matrixed formats.

Related Topics:
Quadraphonic - CBS - Sansui - CD-4 - RCA

~ ~ ~ ~ ~ ~ ~ ~ ~ ~