DENON DP-100M

Commentary

A record player equipped with a dynamic servo tracer as a tone arm in the mechanism of the DP-100.

The DP-100M has a dynamic servo tracer in its tone arm.
The low resonance frequency (fo) set by the cartridge compliance and the effective mass of the tone arm should ideally be around 10 Hz in order to avoid the effects of record warping and eccentricity. In DENON, the negative effects such as modulation distortion were reduced by making the single tone arm and the tone arm of the player system lighter. However, if the fo peak (Q) remains high, the cantilever of the arm and cartridge vibrates more than expected in records with warpage, etc., and the needle pressure changes occur and the tracing capability deteriorates, causing intermodulation distortion.
In the dynamic servo tracer, the Q of fo is electronically damped to prevent deterioration of sound quality due to increase of intermodulation distortion caused by low-frequency resonance and deterioration of crosstalk.
First, the vibration of the tone arm is detected as an electric signal by two detection coils (vertical and horizontal). This signal is passed through a high-pass filter with a variable cut-off frequency volume. After passing through a gain volume, the signal is applied to a power amplification drive coil to provide a signal opposite to the vibration of the tone arm, and the vibration of the arm is controlled.
This effectively dampens the low-frequency resonance compared to the non-damped fo characteristic, approaching the ideal low-frequency reproduction with no peaks.

Since the low resonance frequency and peak vary depending on the type of cartridge, it is equipped with a variable filter and can be used with various cartridges by adjusting the gain volume.

The tone arm is equipped with a long type light weight, high rigidity straight arm.
The straight pipe part is heat-cured with a special light alloy similar to the cantilever of the cartridge to achieve weight reduction and sufficient strength.

The head shell adopts a three layer laminate structure, and the division vibration of the head shell part is damped by combining a viscoelastic material with moderate viscous and large internal loss between two layers of hard light alloy.

The arm pipe is replaceable, and by replacing it with a universal S-shaped arm pipe, it is possible to replace cartridges attached to general head shells.

Equipped with an anti-skating mechanism.
The DP-100M uses the fo damping mechanism to control the current flowing in the horizontal damping control coil to obtain a canceling effect corresponding to the needle pressure without contact in order to optimally cancel the inside force which changes from the outer circumference to the inner circumference of the record every moment.

The arm lifter of the tone arm is driven by a special angular control motor. The speed at the time of descent is variable type, and the signal detected by the speed detection coil for the lifter is amplified and compared with the reference voltage proportional to the set speed to servo the effective speed. In addition, the width of the needle pressure up to approximately 20g is covered for the same set speed.
The lifter can be operated with the lifter Up/Dow switch. It is also linked with the phono motor Start/Stop switch so that the motor starts to lift down and stops to lift up.

The height adjustment mechanism of the tone arm adopts a precision helicoid type arm elevation mechanism similar to the rotation mechanism of the lens image of the camera, and it can be smoothly adjusted only by the back and forth operation of the lever.
The adjustment range is as wide as 8 mm, and most of the cartridges for purpura can be used while keeping them horizontal.

The drive motor employs a 10 kg out Rocester 3-phase AC servo motor with a torque of 10kg-cm that is used for cutting machines as well as for broadcasting station players. This powerful motor has a weight of 6.5 kg and a moment of inertia of 1,260kg-cm.²To 33 1/3 revolutions in only 0.4 seconds from the start.
A high S / N ratio has been achieved by the adoption of an AC3-phase drive system that eliminates the third harmonic of the rotating magnetic field, which causes vibration and reversing torque, and by the adoption of a winding system that ensures uniform magnetic flux between the rotor and stator, even if there is a gap between the rotor and stator, and by the consistent vibration resistant structure including the frame.
The shaft is made of special stainless steel with a diameter of 14 mm. After heat treatment and high-precision polishing, it is wrapped.
A special alloy is used for the radial bearing, and smooth rotation is obtained by lapping, and high durability is obtained by using a mirror-finished sapphire bearing for the thrust bearing that supports the entire rotating system.
It is equipped with a safety mechanism to prevent troubles caused by unexpected external forces. It operates when a load of approximately 50 kg or more is applied to the turntable to prevent damage to sapphire bearings, etc.

For the turntable, we have further developed the double-structured turntable used in the DP-80 and so on.
Structurally, the upper and lower turntables are connected by a spring and a fluid damper, and the lower part is fixed to the motor rotor, so that the upper part where records are placed is vibrationally isolated from the motor and frame, and a high-cut filter is formed by the mass of the upper turntables and the compliance of the spring.
In addition, the adverse effect of acoustic feedback caused by sound pressure transmitted directly from the speaker to the record and upper turntable is solved by the difference in vibration mode due to the difference in mass between the two turntables, the fluid damper between the two turntables, and the turntable seat with high vibration absorption effect.
These measures eliminate harmful vibrations and eliminate sound coloring, as well as problems such as poor crosstalk caused by affecting the opposite channel in the heavy low-frequency portion of a record, resulting in an unclear sound image.
The upper and lower turntables are integrated in the direction of rotation.

The servo mechanism uses a double PLL servo system combining DENON quartz and PLL synthesizer IC.
DENON quartz has developed and adopted DENON's original magnetic recording detection method that applies 1000 pulse signals. Two pulse detection heads are attached at two opposing positions. This has the effect of mutually canceling the very slight eccentricity of the magnetic pulse recording surface, making it possible to pick up a highly accurate detection signal. By comparing the phases of the obtained signal with the phases of the signal generated by the reference oscillator (crystal), a powerful two way servomechanism that can control the rotational speed more severely is realized. In addition, it is an advanced method that detects the speed at the periphery of the turntable where the wow flutter phenomenon can be detected most prominently.
In the double PLL servo system, the oscillation frequency is accurately changed while maintaining the accuracy of the quartz oscillator. This frequency is used as the reference frequency for the phase comparator circuit of the motor servo system, and the pitch can be controlled in a quartz-locked state.
The pitch control circuit can be combined with a digital display to set an accurate pitch from high9.9% to low9.9% with an accuracy of 0.1% pitch (half tone = 5.9%) at each specified rotation speed.
This powerful servomechanism has achieved load resistance of 1.5 kg in terms of needle pressure.

The frame is made of thick cast aluminum with a total weight of 13 kg and is less susceptible to the effects of floors and sound pressure.
In addition, a servo circuit, various control circuits, transformers, etc. are mounted floating, and at the same time, vibration and noise are taken into consideration.

A solid insulator composed of a spring and a fluid damper is used for the insulator.
The low-frequency cutoff frequency is set to 3.5 kg, and vibration transmitted from the floor to the frame body is prevented. Natural vibration caused by the insulator and frame noise are also prevented by the fluid damper.

The arm board adopts an arm board exchange system that enables the mounting of internal and external long type tone arms. The arm board is made of aluminum casting, and by floating the board itself, a strong anti-vibration structure is realized.
The floating arm board is structurally similar to a turntable. Vibration from the frame is eliminated by a spring and a fluid damper, and disturbance energy due to acoustic feedback and vibration of the arm board are absorbed and attenuated.
The replacement armboard was sold separately and made to order.

Model Rating

Type	Double PLL servo turntable
<Phono motor>
Drive system	Bidirectional servo direct drive
Motor	Out Rocester 3-phase AC servo motor
Speed control system	Speed servo and phase servo by frequency detection
Number of revolutions	33 1/3, 45, 78 rpm
Rotational speed deviation	Not more than 0.002%
Rotational speed variable range	± 9.9% (0.1% pitch) of the specified speed Speed servo and phase servo for fine adjustment of rotational speed
Speed change	Electronic
Wow and flutter	0.003% w. rms or less (rotating system) 0.02% w. rms or Less (JIS)
Signal-to-noise ratio	90 dB or more (DIN-B)
Starting torque	10kg-cm
Startup time	Within 0.4 Seconds (33 1/3)
Load characteristic	0% (for the load of 1.5 kg of the outermost peripheral needle pressure)
Power supply voltage characteristics	0% for 90 ~ 110 V
Brake	Electronic brake
Turntable	33 cm, Both upper and lower parts made of aluminum die-cast, 6.5 kg Dual structure of the fluid dump system
Moment of inertia	1,260kg-cm2(including rotors, etc.)
<General>
Frame	Aluminum casting
Insulator	Coil spring and fluid damping
Armboard	Replacement system, aluminum casting Fluid dump system floating Tone arm with effective length of 282 mm ~ 292 mm can be attached
Pwer	100 VAC, 50Hz/60Hz
Power consumption	25W
External dimensions	Width 570x Height 285x Depth 465 mm
Weight	Approx. 46 kg
Sold Separately	Replacement Pipe Arm PCL-100 Replacement Pipe Arm PCL-75