Dual CS 721 turntable

 The Dual CS721, 

single-play direct-drive turntable with fully automatic start and stop, plus continuous repeat.

 

The new Dual CS721 is the ultimate expression of the principles that determine the performance of tonearms and drive systems. Its stright line tubular tonearm pivots horizontally and vertically within a true, four-point gimbal, thus maintaining dynamic balance in all planes.

Another Dual innovation - Vertical Tonearm Control - contributes in yet another way to fine tracking performance. A vernier height adjustment over an 8 mm range paralleles the tonearm to the record with any cartridge. This eliminates the added mass of cartridge spacers, otherwise needed to achieve precise vertical tracking angle. In all, there are seven tonearm settings and adjustments - from stylus overhang to cueing height and descent speed - all serving to optimize tracking performance with any cartridge.

The direct-drive system of the CS721 is of comparable precision. The the electronically controlled DC , brushless motor is the smoothest and quietest ever made. A major contribution to this end result is an exclusive Dual feature: two stacked coil layers, each consisting of eight coreless bifilar wound coils, that overlap to achieve a gapless rotating magnetic field. This eliminates the successive magnetic pulses typical of all other motor designs.

Although the CS721 is Dual's most expensive model, it is hardly the most expensive turntable available today.

 

The direct drive Dual EDS 1000-2 motor, which was developed especially for the hi-fi record player, is a slow-running, brushless, DC supply electronic motor which gets its energy from a regulated power supply DC motors typically employ a mechanical switching commuter, but the Dual EDS 1000-2 utilizes two Hall Generators for electronic switching Hall Generators regulate four switching transistors successively to control the four windings of the motor. This cyclic switching of the field coils produces a rotational field which then causes rotary motion of the motor. The rotary field coils produce a voltage which is measured and compared to a voltage standard. Any resultant voltage differential is fed back and regulated the flow of current in the four switching transistors to regulate speed. This system of control prevents speed errors freater than 0,025%. The Dual EDS 1000-2 motor rotor is grooveless and has a magnetic interference (short circuit terminal), which runs with the rotor.the motor field coils are non-ferrous and mounted in the air gaps among the eight pole ring magnet of the rotor and the magnetic short-circuit terminal.

The unique design described above results in distinct advantages for the Dual EDS-1000-2 Without pole sensitivity, hysteresis or turbulance current loss and without disturbing groove frequencies, the Dual EDS 1000-2 guarantees you a completely vibration-free and unusually steady drive source for your hi-fi recordplayer.

 

The tonearm of Dual CS721 meets all the requirements for today's record players; maximum rigidity with lowest effective mass, and practically negligible bearing friction in the vertical and horizontal planes.

Studies of vibrations resulting from tonearm mass, weight, and compliance of the cartridge have shown that a special design of the tonearm counterbalance can increase tracking ability considerably, namely when the tonearm counterbalance is designed to absorb vibration energies within the resonant ranges of tonearm and chassis.

For this reason, the inner section of the counterbalance is tuned to the tonearm resonance and has, due to in phase-opposed vibrations, an anti-resonance effect. By excitation of the tonearm within the resonance area - energy vibrations between tonearm and anti-resonator are eliminated. The outer part of the counterbalance, designed as a higher tuned anti-resonator, prevents the transmission of chassis resonances to the tonearm.

The design of the tonearm counterbalance with twp antiresonance filters also improves the signal-to-noise ratio.

 

Specifications

Tonearm

Torsionally rigid tubular aluminum tonearm in low friction four point gimbal suspension, tonearm counterbalance with two mechanical anti-resonance filters

Effective length of Tonearm:  222 mm

Offset Angle:  25°20'

Tangential Tracking Error:  0,16°/cm

Tonearm Bearing Friction (related to stylus tip)

Vertical :  <0,07 mN (0,007 gram)

Horizontal :  <0,15 mN (0,015 gram)

Stylus Pressure:  from "0" to 30 mN (0 -3 gram) infinitely variable with 1 mN (0,1 gram) calibrations from "0" to 15 mN (0 - 1,5 grams) operable from 2,5 mN (0,25 gram) stylus pressure up

Cartridge Holder:  removable, accepting any cartridges with 1/2" mounting and a weight from 4,5 to 10 grams (including mounting hardware)

Adjustable Overhang:  5 mm

Turntable

Drive: Electronically-regulated direct-drive system, EDS 1000-2

Power Input:  approx. 2,5 watts

Motor at Playing operation: < 50mW

Power Consumption (at Start):  60 mA (220 V 50 Hz); 110 mA (110 V 60 Hz)

Time From Start to Rated Speed:  2 - 2,5 s at 33-⅓ rpm

Platter:  non-magnetic, dynamically balanced,

Mass :  1,5 kg

Diameter : 305 mm

Total Speed Load of Drive System (rotor with platter) :  3,0 kg

Moment of Inertia:  250 kp/cm²

Platter Speed:  33-⅓ and 45 rpm. Electronically adjustable. Automatic tonearm set-down coupled with speed adjustment.

Pitch Control: for both speeds, adjustable by means of variable resitor, range of regulation: 10%

Speed Contro (Monitoring)

With illuminated stroboscope for platter speed 33-⅓

Sensitvity (of the illuminated strobe for 0,1% speed deviation

3,0 division markings per minute at 50 Hz

3,6 division markings per minute at 60 Hz

Total Wow and Flutter (DIN 45 507) : < ±0,03%

Rumble (DIN 45 500)

Unweighted :  >50 dB

Weighted :  >70 dB

Line Voltage:  110  to 125 V, 220 to 240 V

Current:  AC 50 or 60 Hz

Dimensions (W x H x D):  424 x 150 x 368 mm

Weight:  8,7 kg