Table of Contents
Advertisement
The Groove:
Nature and Problems
The musical information on a record is contained in the w i g g l e s of the groove as
it spirals in across the disc. T h e s e w i g g l e s are a mechanical analog of the
w a v e f o r m s originally generated by the musicians at the recording s e s s i o n , and
subsequently p i c k e d up by the microphones w i t h the ultimate goal of being f e d
from the disc into your audio s y s t e m without any modification whatsoever. For
this to h a p p e n , the stylus must vibrate mechanically in exact a c c o r d a n c e w i t h
the undulations in the groove. S i n c e it is the m o v e m e n t of the stylus relative to
the cartridge b o d y that enables an electrical signal to be generated, it f o l l o w s
that the cartridge b o d y itself must not vibrate, otherwise unwanted electrical
signals w o u l d be generated and s o m e of the desired groove information w o u l d
be cancelled out. For the s a m e reason, the record's grooves t h e m s e l v e s must
not vibrate.
Unfortunately, this delicate interrelationship is threatened through the very act of
playing a record. Airborne and structure-borne vibrations are c o n d u c t e d to the
turntable as a direct result of the acoustical energy produced by your
loudspeakers.
The vinyl disc is excited by the very action of the stylus upon it. T h e cartridge
b o d y is also excited into resonance by the motion of the stylus, and this energy
is c o n d u c t e d into the tonearm, causing it to vibrate.
Other sources of u n w a n t e d vibrations include the turntable motor, bearings — in
fact, all of its m o v i n g parts.
T h e measure of excellence of any turntable / arm c o m b i n a t i o n lies in its ability to
protect the cartridge / groove relationship from extraneous vibrations.
Every element of the P R E M I E R E turntable has been d e s i g n e d to preserve the
integrity of this relationship.
The PREMIERE Turntable
Record Coupling System™ ^ - ^ ^ 1
This s y s t e m , w h i c h has been successfully e m p l o y e d in other O R A C L E turntables
is c o m p r i s e d of a special turntable mat, a screw-on record c l a m p , and a tapered
spacer w h i c h is inserted through the threaded platter spindle.
The s y s t e m uses the elasticity of the vinyl itself to force the grooved surface of
the disc into close contact with the turntable mat. This results in virtually perfect
d a m p i n g of vinyl resonances w h i c h are absorbed by the mat and not reflected
back to the stylus.
This treatment also flattens all but the most severe of w a r p s .
The Mat
It can be seen that the properties of the mat are very important. It must be flat
(and have no sculpted ridges) to ensure that no air pockets are trapped under
the disc; these air pockets w o u l d resonate and excite the vinyl above t h e m . It
must also be slightly smaller in diameter thant the disc in order to avoid the
formation of an air cavity caused by the raised lip at the lead-in groove. For
similar reasons, a recess should be provided to a c c o m m o d a t e the raised area at
the label.
The c o m p o s i t i o n of the mat must be carefully determined to optimize its
absorbtive capabilities.
A l l of these features have been incorporated into the Groove Isolator M a t
included with the P R E M I E R E turntable.
3
Advertisement
Table of Contents
