Cutting a Record
To manufacture a vinyl record you start with a master
tape, these days usually recorded to DAT (Digital Audio Tape) or CD. The master should be compiled in order and preferably have gaps between tracks, the running times should also be included. Further processing such as
EQ and compression should not be necessary but can be done if kept to a minimum. The music is then transferred to an aluminium disc covered with lacquer, This is done using a 'Cutting Lathe', hence the term 'Cutting a record'.
The lathe works with a slightly heated sapphire or
diamond tipped stylus that etches the groove into the soft oil-based lacquer.
The stylus has two coils (one for each the left & right amp channels) that
are positioned between magnets. The programme material is fed into the magnets,
varying the magnetism, which in turn causes the stylus to vibrate left and
right. The stylus can oscillate at up to 16,000 times per second. The greater
the volume of the programme material, the wider the spiral groove. This process
is almost the exact reverse of playing a record in the usual manner using a
turntable, normal stylus and cartridge. Each lacquer disc is single sided so two
must be produced for a regular two sided record, one-sided records are possible
and are one of many manufacturing "gimmicks" that are gaining
popularity. Cutting is the last stage at which the sound can be altered (and
only to a limited extent). To ensure a consistent, distortion-free transfer of
the signal to the blank disc great care must be taken not to cut too deep,
shallow, loud or quiet. If the cut is too deep the playback needle may not sit
snugly in the groove or reach the bottom, if it is too shallow the
needle may skip tracks.
If the volume is too loud at the cut, one groove may encroach upon the next causing skips, and if the volume is too soft the intended sound may fall below the noise threshold and become swamped with hiss and crackles.
There is a trade off between recording level and duration per side. Whilst operating the cutting lathe the cutting engineer may need to alter the master recording in terms of dynamics, frequency, and phase response to ensure that none of the previously mentioned problems occur. This will usually at least mean
limiting the signal to prevent any loud passages or pops making the groove too wide or making a kink that would kick the needle out of the groove.
As each side is 'cut' in one continuous process it is important to ensure that
there are no errors which would result in expensively wasted Lacquers.
Also at this time an essential component of record pressing, the catalogue number, is added in the lead-out groove and on the spare space at the edge of the disc. The number should be unique to the particular record and is best suffixed with an 'A' for side A and a 'B' for side B. Lacquers have a fragile and short life span and should be processed as quickly as possible before they deteriorate.
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