Sony PS-6750 - Product Features; Servo-Controlled System Principle; Technical Specifications

FEATURES
Your PS-6750 assures excellent signal-to-noise ratio and excep-
tionally tow-degree of wow-and-flutter due to:
eServo-controlled direct drive de motor
@innovative frequency generator for servo-controlled system
e@Non-resonant material SBMC (Sony Bulk Mould Compound)
used for case
Other featuring characteristics are:
@ Sensitive carbon fiber tonearm reducing resonance interference
@ Precisely manufactured rubber insulation mat isolating mechani-
cal vibrations
@ Height-adjustable resilient feet absorbing external vibration
SERVO-CONTROLLED SYSTEM PRINCIPLE
A servo-controlled system is one in which a driven device, in
this case the turntable platter, maintains the motor speed con-
stant at any predetermined value by furnishing the output signal
proportional to its speed, then feeding back this signal into a
control mechanism that regulates the input power to the driven
device.
The servo-controlled system used in the PS-6750 consists of a
dc motor (platter drive), a frequency generator (hereafter called
F.G.) and an IC servo amplifier as a regulating device, as shown.
The F.G. takes, in the PS-6750, the form of a magnetic coating
around the turntable and a sensing head inside the platter.
Drive motor
When the power is turned on, the de servo motor begins its
operation. A frequency proportional to motor speed is produced
by the F.G., then passed through the IC processing circuit where
it is converted to a dc output proportional to the frequency.
The dc output in turn controls the output of the dc servo ampli-
fier that powers the dc motor. Thus variations in the drive
motor speed are automatically perceived.
If the motor speeds up due to an external cause, the output
of the F.G. increases in frequency by +4f. This decreases motor
voltage: to reduce the motor speed until the F.G. frequency
returns tofo. On the other hand, if the motor slows down, the
output of the F.G. decreases by —4f. This increases motor
voltage to augment the motor speed until the F.G. frequency
returns to fo.
+Av
Operating point at the predetermined
Wo speed
—Av
SAS fo +f
Frequency produced by F.G.
Output voltage of the motor
10
Thus the servo-controlled system maintains an equilibrium condi-
tion at fo and the motor maintains its selected speed under vary-
ing operating conditions.
Pitch controls are provided for vernier adjustments that permit
varying the rotational speed by +4% of the nominal values of
33 1/3 and 45 rpm.
SPECIFICATIONS
Turntable
Platter 32cm (12 5/g”), diecast aluminum
alloy
Drive system Dc sevo-controlled motor, direct drive
Speeds 33 1/3 and 45 rpm
Speed control range +4%
Starting time Within 1/2 turn (33 1/3 rpm)
Wow and flutter Less than +0.045% (DIN 45 507
weighted)
S/N ratio Better than 70 dB (DIN 45 539,
B-curve weighted)
Tonearm
Type Statically balanced
237 mm (9 3/3”)
320 mm (12 5/8”)
Pivot to stylus length
Overall arm length
Overhang 15mm (5/g”)
Tracking error +2°30' ~—1°20'
Tracking-force adjustment range
0-3 g
Arm height adjustment range
O-7mm
Shell weight 10.5g
4-10g (without extra weight)
10-15g (with extra weight)
Cartridge weight range
General
Power requirements 110, 127, 220 or 240V ac ~
(adjustable), 50/60 Hz
—factory-set at 220V
Power consumption 6W
Dimensions Approx. 442 x 182 x 390 mm (W/H/D)
(Approx. 17 3/gx 7 3/16 x 15 3/8”)
including projecting parts and
controls
Net: approx. 10 kg (20 Ib 10 0z)
In shipping carton: approx. 13 kg
(28 lb 7 oz)
45-rpm adaptor
Alignement Protractor
Spacer for cartridge height adjustment
Cartridge mounting screws 3 pairs
Screwdriver for cueing height
adjustment
Arm height adjustment lever
Extra weight
Shell
Phono cord 1 set
Weight
Supplied accessories
While the information given is true at the time of printing, small
production changes in the course of our company’s polcy of
improvement through research and design might not necessarily
be indicated in the specifications. We would ask you to check
your appointed Sony dealer if clarification on any point is re-
quired.