Handbook for Sound Engineers

1026 Chapter 27

by Pickering and Stanton since 1971, except that the
Shure stabilizer brush had its pivots filled with damping

fluid. These devices helped to various degrees to stabi-

lize the tonearm as the brush cleaned the record groove.

The other approach was to adjust the effective mass

of the tonearm by pivoting only the front part of the

tonearm and selecting a cartridge with compliance that

would match the mass of this portion of the arm, Fig.

27-17. Dynavector tonearm is an example of such

design. Another variation is the design by Sony that

employs electronic control of the tonearm motion.

Instead of relying on weights, springs, or magnets, the

Sony tonearm uses linear dc electromotors driven, oper-

ated, and controlled by electrical signals. Unfortu-

nately, not all functions of the tonearm are controlled

automatically and are subject to misadjustment.

27.6 Phono Pickup/Transducers and Styli

In order to reproduce signals recorded on the phono-

graph record, a transducer (phonograph pickup, phono

cartridge, or needle) converts the groove modulation

into the electrical signals. Unlike microphones, loud-

speakers, and other types of devices or transducers that

convert one form of energy into another, the phonograph

pickup has to perform more than one function. The pho-

nograph pickup or cartridge, so called since the inven-

tion of the removable stylus or needle assembly, has to

convert modulation of the record groove into the electri-

cal signals, and at the same time support the tonearm at

Figure 27-15. Examples of how dynamic balance of the
tonearm can be achieved.

Figure 27-16. Schematic representation of the moving
system of a pickup, illustrating the vertical tracking angle.

Balance weight

Spiral spring Magnet

Balance weight

Spring

Balance weight

Stylus

adjustment

knob

Stylus adjustment

knob wire Spring

Balance weight

Electrical compensation

N

S

NS

B. Cartridge designed to produce lowest distortion

when playing vertical modulation.

A. Tonearm is parallel to turntable.

Tone arm is parallel to turntable

Center of rotation

Moving magnet

Stylus arm

Direction of groove travel

10 o—15o

Figure 27-17. Dynavector tonearm with pivoted front

portion for lower dynamic tonearm mass. Courtesy Onlife

Research, Inc.