Accuphase DP-70
¥ 430,000 (released in June 1987)
Commentary
A CD player with a discrete D/A converter.
The D/A converter uses the world's first discrete converter developed with a separate type CD player.
This converter operates in a current addition type and consists of a current switch element and a special ultra-precision resistor connected to each bit switch. Linearity is especially excellent.
For the DP-70, current switching elements with matching temperature characteristics are carefully selected so that it can operate completely even if the temperature of the operating environment changes drastically. The resistor has an accuracy of 0.0015% or less and uses a specially developed ultra-precision metal foil resistor that does not change resistance value even if there is a large temperature change. In addition, each unit is strictly adjusted and shipped in a complete operating condition.
Since the output of the discrete converter is taken out as a current signal, an I/V conversion circuit is required. The DP-70 uses a high-performance amplifier for the I/V conversion circuit, and at the same time, a deglitch circuit using a C-MOS analog switch that eliminates pulsed glitch waves is built in.
High-speed C-MOS has small charge injection, minimizes switching noise, and has almost no effect on audio circuits.
The digital data, shift clock signal, latch clock signal, and converted deglitch signal for waveform shaping are electrically separated through four optocouplers per channel, and then fed to the D/A converter, which provides complete electrical isolation between the front and back of the converter and eliminates high-frequency noise interference caused by the ground line.
In addition, the digital and analog circuits are shielded with metal, and the power supply is completely separated by a dedicated transformer to prevent mutual interference. In addition, the audio circuit is equipped with a two winding transformer and a dedicated left and right rectifying circuit to prevent interference between channels. Unwanted radiation through the power supply is handled by a line filter.
The low-pass filter uses a 5th order GIC type Butterworth filter.
In the DP-70, the output current of the converter is set so that there is no need for amplification at the output stage. The amplifier has a simple configuration with only a buffer. In addition, the circuit uses the push-pull DC servo direct connection method which is an original of Accu-Phase.
The digital filter uses a 4 x oversampling type. The DP-70 filter has a ripple of ± 0.00005 dB or less and an attenuation of -100dB or more.
The DP-70 uses a passive filter and buffer amplifier for an emphasis circuit that can be used on CDs with emphasis.
In addition to fixed and variable RCA phono jacks, an XLR-type balanced output is also provided.
Two types of digital output are mounted : coaxial and optical.
The rotary system is controlled by a single master clock to prevent the beat that occurs when two types of clocks are used, one for digital signal processing and the other for microprocessors.
A linear motor mechanism is used to track the laser pickup.
This allows for smooth operation and, together with a specially developed 8-bit microprocessor, allows for sub-second selection.
The mechanism body is mounted on a high-rigidity ceramic special resin base to prevent resonance. In addition, the mechanism body is floated from the chassis to cut off the transmission of vibration. Thus, the mechanism body is also floated from the disk table to minimize vibration from the outside.
In addition, vibration is prevented by supporting the rotating part with a thick metal frame, and external vibration is also prevented by using the legs shaved out of pure brass.
The front panel is gold-style scratch hairline finish, and the side is equipped with natural Persimmon sideboard.
Wireless remote control is included.
.JPG)
.JPG)
Model Rating
| Type | CD-dedicated digital signal reproducer |
| Formatting | CD standard format Quantization : 16 bits Sampling frequency : 44.1 kHz Error correction method : CIRC Number of channels : 2 channels Rotation speed : 500 ~ 200 rpm (CLV) Performance speed : constant 1.2 ~ 1.4m/s |
| Reading system | Non-contact optical reading (using semiconductor laser) |
| Laser | GaAlAs (double hetero diode) |
| Frequency characteristic | 4.0 Hz to 20 kHz ± 0.3 dB |
| Total harmonic distortion factor + noise | 0.002% (between 20 Hz and 20 kHz) |
| S/N | 115dB |
| Dynamic range | 98dB |
| Channel separation | 110dB |
| Rated output / output impedance | Fixed Balanced : 2.5V/50 Ω (25 Ω / 25 Ω), balanced XLR type Unbalanced : 2.5V/50 ohm, RCA phono jack Variable Unbalanced : 0 to 2.5V/1.25k Ω max, RCA phono jack |
| Digital Output Format / Level | Formatting : Digital Audio Interface Optical Output : -20dBm Emission wavelength : 660 nm Coaxial : 0.5Vp-p/75 Ω |
| Semiconductor used | Transistor : 51 IC : 77 Diode : 94 units |
| Pwer | 100V/117V/220V/240V, 50Hz/60Hz |
| Power consumption | 25W |
| External dimensions | Width 475x Height 135 (Including Legs) x Depth 373 mm |
| Weight | 21.0kg |
| Attachment : Remote Commander RC-1 | |
| Remote control system | Infrared pulse system |
| Pwer | DC 3V |
| Dry battery | SUM-3 (IEC Designation, R6), 2 units |
| Maximum external dimensions | 64 mm wide x 149 mm high x 18 mm deep |
| Weight | 115g (including dry batteries) |