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150 µm

78 RPM

Goove depth and radii

33 1/3 RPM microgroove LP

130 µm

13 µm

Minimum depth

1 mil = 25 µm

Typical depth 

~

38 µm

Maximum  depth

5 mil = 127 µm

~

70 µm

~

250 µm

~

50 µm

0.036 mm

0.7 mil

0.5 mil

Conical

(Spherical)

Elliptical

0.2 x 0.7 mil

0.026 mm

0.036 mm

78 RPM

75 µm radius

0.15 mm

Line Contact

Figure 3.15: Dimensions of example styli, drawn to scale. The figure on the left is typical for a 78 RPM steel needle. The four examples

on the right show di

erent examples of tip shapes. These are explained in more details in the text. (For comparison, a typical diameter

of a human hair is about 0.06 mm.)

There have been a number of di

erent

designs following Shibata’s general
concept, with names such as
MicroRidge (which has an interesting,
almost blade-like shape “across” the
groove), Fritz-Geiger, Van-den-Hul, and
Optimized Contour Contact Line.
Generally, these designs have come to
be known as

line contact

(or

contact

line

) styli, because the area of contact

between the stylus and the groove wall
is a vertical line rather than a single
point.

Originally, the Beogram 4002 was
supplied with an MMC 6000 cartridge,
which featured a stylus tip designed by
Subir K. Pramanik, an engineer at Bang
& Olufsen. This became known as the
Pramanik diamond, and was designed
to ensure maximum surface area with
the groove wall on its vertical axis
while maintaining a minimum contact
along the horizontal axis.

Figure 3.16: An example of an elliptical

stylus on the left vs. a line contact Pra-

manik grind on the right. Notice the dif-

ference in the area of contact between

the styli and the groove walls.

3.4 Bonded vs. Nude

There is one small, but important point
regarding a stylus’s construction.
Although the tip of the stylus is almost

always made of diamond today, in
lower-cost units, that diamond tip is
mounted or

bonded

to a steel pin which

is, in turn, connected to the cantilever
(the long “arm” that connects back to
the cartridge housing). This bonded
design is cheaper to manufacture, but
it results in a high mass at the stylus
tip, which means that it will not move
easily at high frequencies.

Figure 3.17: Scale models (on two dif-

ferent scales) of di

erent styli. The ex-

ample on the left is bonded, the other

four are nude.

In order to reduce mass, the steel pin
is eliminated, and the entire stylus is
made of diamond instead. This makes
things more costly, but reduces the
mass dramatically, so it is preferred if
the goal is higher sound performance.
This design is known as a

nude

stylus.

3.5 Tracking force

In order to keep the stylus tip in the
groove of the record, it must have
some force pushing down on it. This
force must be enough to keep the

stylus in the groove. However, if it is
too large, then both the vinyl and the
stylus will wear more quickly. Thus a
balance must be found between “too
much” and “not enough”.

1920

1930

1940

1950

1960

1970

1980

1990

2000

2010

2020

Year

0.1

1  

10 

100

Typical tracking force (g)

Figure 3.18: Typical tracking force over

time. The red portion of the curve shows

the recommendation for Beogram 4002

and Beogram 4000c.

As can be seen in Figure

3.18

the

typical tracking force of phonograph
players has changed considerably
since the days of gramophones playing
shellac discs, with values under 10 g
being standard since the introduction
of vinyl microgroove records in 1948.
The original recommended tracking
force of the Beogram 4002 was 1 g,
however, this has been increased to
1.3 g for the Beogram 4000c in order
to help track more recent recordings
with higher modulation velocities and
displacements.

3.6 E

ective Tip Mass

The stylus’s job is to track all of the
vibrations encoded in the groove. It
stays in that groove as a result of the

12

Содержание Beogram 4000c

Страница 1: ...Beogram 4000c Technical Sound Guide Bang Olufsen A S This manual is for information purposes only and is not legally binding November 27 2020...

Страница 2: ...ross 7 3 2 Signal Levels 8 3 3 Tip shape 10 3 4 Bonded vs Nude 12 3 5 Tracking force 12 3 6 E ective Tip Mass 12 3 7 Compliance 13 3 8 Soundsmith SMMC20CL 13 4 Audio Specifications 14 4 0 1 Magnitude...

Страница 3: ...Emil Berliner was awarded a patent for a sound recording and reproducing system that was based on a groove in a rotating disc rather than Edison s cylinder the original version of the system that we k...

Страница 4: ...are the same at Time 0 ms However it is also evident that when this is true they have very di erent amplitudes in fact the amplitude would have to double for every halving of frequency a drop of 1 oc...

Страница 5: ...ns of the RIAA equalisation filter define the transition points as time constants instead of frequencies So instead of 50 Hz 500 Hz and 2122 Hz as shown in the response plots the points are listed as...

Страница 6: ...down left up right for example This means that signals that are identical in both channels move the stylus laterally exactly as in earlier monophonic discs 4 Figure 2 10 An over simplified depic tion...

Страница 7: ...eophonic Transducer Cartridge In 1963 Erik R rbaek Madsen of Bang Olufsen filed a patent for a cartridge based on the Moving Iron principle In it a cross made of Mu metal is mounted on the stylus Each...

Страница 8: ...be encoded without incurring additional distortion that is inherent in the encoding system itself is when the maximum or minimum value in the audio signal reaches the highest possible signal value of...

Страница 9: ...here is a relationship between the total playing time of a vinyl disc and the modulation velocity In order to have 20 minutes of music on a 12 LP spinning at 33 1 3 RPM then it the standard method was...

Страница 10: ...here are a number of options when choosing the shape of the playback stylus 3 3 Tip shape The earliest styli were the needles that were used on 78 RPM gramophone players These were typically made from...

Страница 11: ...k deeper into the groove making it more di cult for it to move independently on the two audio channels The second is that the point of contact between the stylus and the vinyl becomes smaller which ca...

Страница 12: ...pin which is in turn connected to the cantilever the long arm that connects back to the cartridge housing This bonded design is cheaper to manufacture but it results in a high mass at the stylus tip...

Страница 13: ...the compliance of the stylus suspension Compliance is the opposite of spring sti ness the more compliant a spring is the easier it is to compress and the less it pushes back Like many other stylus pa...

Страница 14: ...of 70 7 mm sec 4 0 3 Rotational speed Every recording playback system whether for audio or for video signals is based on the fundamental principle that the recording and the playback happen at the sam...

Страница 15: ...changes in the speed that are higher than 100 Hz This is typically only a problem with analogue tape decks caused by the magnetic tape sticking and slipping on components in its path and is not often...

Страница 16: ...nal relative to the average frequency however the e ect of very slow and very fast changes have been reduced by the filter Finally the standard deviation of the variation from the average is calculate...

Страница 17: ...mith SMMC20CL Stylus Nude 0 12 mm square Radius of curvature Contact Line Recommended tracking force 1 3 g Compliance 28 m mN E ective tip mass 0 32 mg General information Automatic speed selection Ye...

Страница 18: ...nditions in the Cutting and Playing of Stereo Disk C R Bastiaans Vol 11 Issue 1 Jan 1963 Factors A ecting the Stylus Groove Relationship in Phonograph Playback Systems C R Bastiaans Vol 15 Issue 4 Oct...

Страница 19: ...commendations for Lateral Cut Commercial and Transcription Disk Recordings 98 Processed Disk Records and Reproducing Equipment 386 Method of Measurement of Speed Fluctuations in Sound Recording and Re...

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