Please note that this is an unofficial L-07D website.

The following text is taken from the L-07D owner's manual, and is reproduced here by kind permission of Kenwood Electronics.

x
INTRODUCTION

Your choice of this product indicates that you are a devotee of excellence in sound reproduction. We appreciate your patronage and take pride in the long tradition of quality components that the name Kenwood represents.

So that you can get the most out of your L-07D, we suggest that you take the time to read through this manual before you hook up and operate your system. This will acquaint you with operating features, and system-connection considerations, so that your listening pleasure will be enhanced right from the start. You will notice that in all aspects of planning, engineering, styling, operating convenience and adaptability, we have sought to anticipate your needs and desires.

In the more than 100 years since Edison invented the phonograph, a lot of progress has been made. The L-07D was designed and developed with a view to making an ultimate record playing system, which converts the music information cut in the record with 100% accuracy into an electrical signal; in other words, it achieves "perfect conversion" from the engraved groove into the reproduced signal.

Various new techniques have been developed and applied in the L-07D to achieve this "perfect conversion". However, any one of these techniques cannot exhibit its full effect on its own: they work together to make a total system effective. Kenwood's engineers are proud of the L-07D; it is a high precision turntable which will give a new appreciation of the capabilities of records.

The L-07D was designed giving priority to the following:

1. High rigidity and good anti-vibration properties.
2. The three supporting points in the pickup loop are extremely accurate.
3. High transient load characteristics.
4. High fidelity electrical signal transmission.

Super-heavy, metal-inserted cabinet with complex structure providing high rigidity and good anti-vibration properties

The cabinet has a complex structure which is basically a double-layer structure and metal is inserted into important parts, so that the center of gravity is lowered, the tonearm and the phono-motor are completely supported and anti-vibration properties are greatly improved.

The upper layer of the cabinet is made of the new ARCB material which can be precisely molded and has outstanding rigidity. Further, diecast aluminum is inserted into important parts of the upper layer. The lower layer of the cabinet is made from mahogany complite which has superior rigidity and anti-vibration properties. Thus, the cabinet has very high rigidity and is almost perfectly vibration-free.
x

The most important point in improving the phono-motor is to remove cogging and torque ripple. Theoretically, it is possible to build a motor without torque ripple, but in practice such a motor is impossible because of machining accuracy and viscous resistance. The motor coil was formerly driven at constant voltage. In the L-07D, however, the motor coil is driven at constant current. Therefore, counter-electromotive force in the coil can be ignored and control can be more precise.

The L-07D uses double servo coupling, which automatically switches the control method when the speed differs by +/-3% from the rated speed. When the speed difference is beyond +/-3%, the speed is controlled to obtain a large torque and, when it is less than +/-3%, the phase is controlled to obtain a wide lock range and large phase gain. Further, at a speed of +/-3%, the circuit coupling is changed from DC to AC to reduce influences from the motor drive circuit and the motor offset.

If the moment of inertia varies to a great extent (e.g. if KENWOOD's disc stabilizer DS-20/DS-21 are used), the dynamic parameter (time constant) can be changed.
x

A moment of inertia of 1,025kg/cm2 is obtained (when the turntable sheet is attached), resulting in high kinetic energy of rotation. Therefore, the platter rotates stably even if the transient load from the stylus varies. The mechanical impedance supporting the record is kept high, so that signals cut in the record can be traced exactly by the stylus.

The turntable platter is made of diecast aluminum inside of which there is Duralumin 4mm thick. The top surface of the platter is finished accurately. Further, a non-magnetic stainless steel turntable sheet is mounted on the platter so that good anti-vibration properties are obtained.
x

Light and rigid materials must be used for the tonearm to raise the resonant frequency of the tonearm. In the L-07D, super-hard aluminum as used in air frames together with carbon and boron fibers are used for the tonearm. This 3-layer structured tonearm has high stiffness and, because of the combination of different materials, resonance is suppressed and influences degrading stylus performance are eliminated.

The head shell attached is a 7-layer carbon-boron laminated structure, therefore it is light as well as extremely stiff.
x

The pickup loop, which is the signal conversion system of the turntable and picks up the signal cut in the record, includes "3 fulcra" - the platter support point (center shaft), the tonearm support point (pivot) and the cantilever supporting point. These are most important in any turntable system. The accuracy of the positions of these "3 fulcra" is generally accepted as determining the performance of the turntable. The most important requirement of "ideal conversion" is that the locations of these "3 fulcura" relative to the groove of the record do not change.

In the L-07D, 12mm (15/32in.) diameter hard stainless steel is used for the precision finished center shaft so that performance is improved. To support the heavy turntable platter, a floating magnet is used, so that viscous resistance of the thrust pad, etc. is reduced and the cutoff frequency of the motor is lowered.

Carbon tool steel is used for the tonearm pivot and stainless steel is used for the rotating shaft together with over-sized bearings. Therefore, the tonearm turns smoothly around the supporting point and all other motions are eliminated. The cantilever supporting point must be 100% stationary. If not, unnecessary signals wil be picked up or the music signal will be modulated, resulting in degraded sound.
x

The tonearm shaft is fixed by means of a collet chuck to the tonearm base which is made of brass and stainless steel. The tonearm base is equipped with the helicoid height adjustment mechanism which enables highly accurate height adjustment at a rate of 0.1mm per turn for a total height of 7mm. The tonearm shaft is also made of BSBM material and has a diameter of 27.6mm (1-3/32in.)

Whatever the force from the collet chuck the tonearm shaft is never deformed. The tonearm base and tonearm shaft weigh a total of 3kg. This mass-concentration design improves strength and resistance to external mechanical interference.
x

Pure copper litz wire is used throughout the electrical transmission system. Our unique penta-structure and two-core shielded cable gives optimum performance.

In the output cord, + and - signal lines are arranged symmetrically and they are completely shielded. Each conductor is a litz wire consisting of 168 wires of 80um dia., thus DC resistance is reduced to the limit. For the inner cord in the tonearm, a penta-litz wire, each conductor of which consists of 56 wires of 50um dia., is used. For the head-shell wires, silk-covered litz wires of 12mOhms are used.

New type connector of the output cord can be locked, giving a contact area several times as great as that formerly used in KENWOOD turntables. All terminals are gold plated to assure low contact resistance for years of operation.
x