Denon DP-2500 turntable

Direct Drive Quartz Control Turntable

Denon knows what recording and reproducing system are. The fact that Japanese radio, TV and recording studios are using Denon audio equipments and system proves it.

Model DP-2500 was developed with this technology, i.e. experience and innovation; Servo system is phase-locked to a quartz crystal oscillation ; materials and parts subject to vibration were analized with the aid of laser optics. Model DP-2500 direct-drive record player consists of this Model DP-2000 mounted on a vinyl veneered playwood cabinet; feddback insulator legs; a dynamically damped tonearm with convenient facilities.

 

Direct drive turntable assisted by quartz-lock

Quartz crystal oscillation is so stable that it is applied in a system where a very high stability and accuracy are essential against temperature change or in a long period of time. In a quartz-lock record player, rotation accuracy is brought up very high (99,998% for the DP-2000/DP-2500). Stylus pressure of cartridges or ordinary fluctuation of supply voltage or frequency can hardly disturb the speed.

The function of servo circuit forces the phase of speed data pulses to synchronize to that of quartz controlled oscillator pulses. Accordingly, speed variation in the range of low frequency (Wow) down to DC can be kept much smaller than that of conventional servo system. However, the Wow could increase if the speed detecter alignment were inaccurate (a wow per rotation could arise) or if the speed data pulse generator were poor. That is, a higher accuracy of speed data pulses is also inevitable.

Denon has established a unique method to keep the accuracy of speed data pulse generator at a professional atandard. 1000 pulses with the accuracy of 99,99% are magnetically recorded on the inside circumference of the turntable platter by a Denon exclusive method. This allows a quick response and a high gain of servomechanism and, assisted by the quartz-lock system, has driven away the wow and flutter into less than 0,015% WRMS.

 

AC motor gives quiet and smooth rotation

Signal-to-Noise Ratio or mechanical vibration (rumble) are unfortunately not under control of quartz-lock system. Instead, motor and its driving method are the keystone. The AC motor on Model DP-2000 is driven by a smooth rotation of magnetic field with an optimum condition. The result is the signal to noise ratio of 75 dB (DIN-B)

 

A unique DC brake controlls deceleration

The stop time and duration after speed change over from 45 rpm to 33-⅓ rpm are short and smooth. This has been achieved by an excellent servo system free from overshoot and by a special DC brake (Pated pending). This new type brake neither produces mechanical friction noise not causes reverse movement of platter as is the case of stopping a DC motor. So, the cartridge stylus will not be affected by an irregular motion of the turntable platter.

The electrical brake is applied at stop (or decelation) mode only and disengaged automatically after the platter is completely motionless. The turntable will be set free for easier cueing or selection of bands on the record.

 

Stroboscope lighted synchronously to the quartz oscillation

The neonlamp for speed monitoring is lighted by pulse voltage whose frequency is divided down suitable for each speed from the quartz oscillation time base. Only one strobo pattern is needed and it is completely immune to the supply source frequency which commolny lights the neon lamp in a record player without quartz-lock. Accordingly, the strobo pattern is clear and stable.

 

Turntable mat developed through vibration analysis.

New material of turntable mat for Model DP-2500 has been developed through a vibration analysis with laser beams. The new turntable mat effectively damps the vibration of record disk. The sound quality a step higher has been realized here also.

 

Dynamically damped tonearm for DP-2500

Denon has developed a dynamic damping system to effectively damp the partial resonance of tonearm pipe (patent pending). This damping system also prevents acoustic feedback to the cartridge. Through the careful study and craftsmanship, the tonearm of Model DP-2500 draws the performance of your cartridge in every detail without any modification or colouring. Anti-skating device and cueing device provide stable and convenient operation.

 

Acoustic feedback prevention

Feedback insulator legs shut off external vibrations while supporting the cabinet. Paying good attention even to small parts or components, Denon has made this cabinet most suited for deriving every benefit of combination of Model DP-2000 and the tonearm

 

Specifications

Drive System:  Direct drive by AC Servo motor

Speed Control:  frequency detection dervo system phase-locked to a quartz crystal oscillation

Speed:  33-⅓ and 45 rpm

Speed Selection:  Slide switched

Wow and Flutter:  less Than 0,015% WRMS

Signal-to-Noise Ratio:  over 75 dB (DIN-B)

Starting Time:  less than 1,5 sec (33-⅓ rpm)

Absolute Speed Accuracy:  over 99,998%

Turntable Platter:  Aluminium alloy diecast

Diameter Platter:  300 mm

Moment of Inertia of 200 kg / cm² (including turntable mat)

Tonearm

Type :  Dynamically damped, static balance type

Effective Length:  244 mm overhang:  14 mm

Tracking Error:  less than 2,5°

Cartridge Weight:  5 - 11 grams

Head Shell:  Aluminium alloy (PLC-3)

Other Facilities:  Oil damped cueing; Anti-skating

General

Cabinet:  Vinyl veneered plywood

Power Requirements:  AC 120/200/220/240 V; 50/60 Hz

Power Consumption:  15 W

Dimensions (W x H x D):  485 x 175 x 405

Weight:  12 kg