Audio Database
DC-300
Commentary

Based on advanced digital technology, this digital preamplifier was developed for the first time in the world by combining new circuits using high-speed DSP technology.

The coaxial and optical input terminals can receive digital signals of up to 24 bits at sampling frequencies of 32/44.1/48kHz. Audio Interface) decoder automatically locks the sampling frequency, and the high-precision 44.1/48kHz, level I input signal uses an ultra-jitter-free PLL circuit to extract the master clock without pulse transmission distortion or jitter, and serves as the system reference.
All other low precision signals are converted to 48 kHz, level I signal by SFC (Sampling Frequency Converter) before clock extraction.
The DSP (Digital Signal Processor) is used for digital processing of tone control, compensator and monophonic phase switching functions which are heavy for a preamplifier.
Then, the signal whose sampling frequency is converted to 8 times by the digital filter is used one by one for one channel and entered into the ultra-high-speed DSP. Here, the digital gain control by the special noise shaper process adjusts the volume to -95dB with little degradation of sound quality. At the same time, the DSP processes the balance adjustment and attenuator.
An ultrafast optocoupler is then used to electrically separate the digital and analog sections completely. It is converted to an analog signal by a Multi-Bit) D/A converter, cut by a fourth order analog filter and output.

The volume adjustment section is equipped with a digital volume developed using special noise shaper processing technology.
A special noise shaper processing technique using a digital signal processor (DSP) can reduce the noise level in the audible band to the theoretical limit. Therefore, the digital time-division feedback of the data which is lost bit by the noise is improved to the resolution higher than the D/A converter.

Equipped with digital volume control with analogue operation feeling.
A disk with radial slits is attached to the shaft of a large knob. When the disk passes through a phase detector, a pulse is generated, and this pulse is input to a microcomputer to adjust the volume.
This has been further developed into a high-quality volume by thoroughly pursuing matching of the sense of rotational speed and sound quality change.

With DSP tone control and compensator, only the frequency can be changed, making it possible to control the sound quality without changing.

The D/A converter uses the MMB method D/A converter.
In the MMB method, a large number of carefully selected 20bitD/A converters (8 per channel in the DC-300) are driven in parallel. The high-speed output of an 8 x oversampling digital filter is input to all converters, D/A converted and added.
This matches the phase at higher frequencies and improves performance at all frequencies and signal levels.

Ultra-jitter-free PLL (Phase Locked Loop) circuit to extract the master clock which is the system reference.
The ultra jitter-free PLL circuit includes a preamble signal (marker indicating the head of the LR signal) detection circuit and a VCO (Voltage) The master clock extracted by this circuit is not affected by jitter and pulse transmission distortion.

In order to up-convert the sampling frequency to a higher frequency once and resample at the desired frequency (48 kHz, level I), SFC (Sampling Frequency Converter).

The Oversampling Digital Filter has a 20-bit 8 x oversampling digital filter.

The analog filter is a 4th-order Butterworth filter. This filter circuit optimizes the cut-off frequencies to minimize phase rotation in the passband and is combined with carefully selected elements to improve sound quality.

Using a high-speed optocoupler with a transmission capacity of 40 MBPS, the digital and analog sections are completely separated. The high-speed transmission characteristics allow the digital signal to be transmitted to the analog section without noise.

The display of the input position can be changed. It is possible to change the name to the name stored in advance, or to create a unique name by combining 8 letters from 96 kinds of letters and symbols.

The analog output consists of a fully balanced circuit floating from ground.
The output jacks have balanced XLR and unbalanced RCA connectors.

The optional board slot allows analog inputs and outputs to be operated in the same way as a conventional preamplifier using an ADB-compliant option board.
The analog input is converted to a digital signal by an A/D converter on the board and to an analog signal by an D/A converter on the board.
In addition, a line input board is mounted as standard.

Model Rating
Type Digital Preamp
Input Format
(EIA standard format)
Quantization : 16-bit to 24-bit line
Sampling frequency : 32 kHz, 44.1 kHz, 48 kHz (automatic detection)
Digital Input Format Level
(EIAJ CP-1201)
Format : Digital Audio Interface
Optical : optical input -27dBm to -15dBm
Coaxial : 0.5Vp-p/75 Ω
Digital Output Format Level
(EIAJ CP-1201)
Format : Digital Audio Interface
Optical : Light output from -21dBm to -15dBm, emission wavelength 660 nm
Coaxial : 0.5Vp-p/75 Ω
Frequency Response 4.0 Hz to 20 kHz ± 0.3 dB
D/A converter MMB, 20-bit
Digital Filter 20-bit, 8 x oversampling
Total Harmonic Distortion Factor 0.002% (20 Hz-20 kHz)
S/N 122dB
Dynamic Range 112 dB (24-bit input, LPF : off)
Channel Separation 112 dB (20 Hz to 20 kHz)
Output Voltage / Impedance Balanced : 5V/50 Ω, balanced XLR type
Unbalanced : 5V/50 ohm, RCA phono jack
Volume Control (DSP) Speed sensing rotation method
0 ~ -95dB Step Variable (0.1 ~ 5 dB Step), ∞
balance control (DSP) Speed sensing rotation method
Difference between right and left : 0 ~ -95dB step variable (0.1 ~ 5 dB step), ∞
Tone Control (DSP)
Low 200 Hz : ± 6 dB (40 Hz), 0.5 dB step
500 Hz : ± 6 dB (100 Hz) in 0.5 dB steps
High 2 kHz : ± 6 dB (10 kHz), 0.5 dB step
7 kHz : ± 6 dB (20 kHz), 0.5 dB step
Compensator (DSP) +6dB(100Hz)
Attenuator (DSP) -20dB
Power Supply 100 VAC, 50Hz/60Hz
Power Consumption 25W
Maximum External Dimensions 475 mm wide x 150 mm high x 406 mm deep
Weight 21.5kg
Attachments Line Input Board AI-U1
Remote Commander RC-19
Sold Separately : Option Board
Digital
di-bnc1 HPC Coaxial Input Board DI-BNC1 (¥ 30,000)
Coaxial cable with 75 Ω BNC connector can be connected.
Digital Input : 0.5Vp-p/75 Ω

* 1 slot is used
dio-oc1 Digital I/O Board DIO-OC1 (¥ 40,000)
Optional board with coaxial and fiber-optic input / output terminals.

* 1 slot used
di-st1 HPC Optical Input Board DI-ST1 (¥ 40,000)
Optional board with ST-type Optical Link Input Connector.
The terminal uses a high-speed link with a transmission capacity of 150 Mbps.
Optical input : -30dBm to -10dBm

* 1 slot is used
dio-pro1 AES/EBU I/O INPUT / Output Board DIO-PRO1 (¥ 60,000)
Optional board with input / output XLR AES/EBU (professional digital standard).

* 2 slots used

Analog
The analog input is converted to a digital signal by an A/D converter on the board.
The output is converted to an analog signal by an on-board D/A converter.
ai-u1 Line Input Board AI-U1 (¥ 50,000)
Contains a high-level (analog signal) input for unbalanced connections.
Built-in 20 bit, 64 times oversampling, 5th order ⊿ Σ A/D converter.

* Standard in Option1 slot
* 1 slot is used
ai-b1 Balance Input Board AI-B1 (¥ 60,000)
Equipped with a high-level (analog signal) input terminal for balance connection.
Built-in 20 bit, 64 times oversampling, 5th order ⊿ Σ A/D converter.

* 2 slots used
ao-u1 Line Output Board AO-U1 (¥ 70,000)
Output terminal for analog recording with unbalanced connection.
D/A converter : 20-bit 4 mmb method
Digital Filter : 20-bit 8 x Oversampling

* 1 slot is used
AO-B1 Balanced Output Board AO-B1 (¥ 80,000)
Analog recording output terminal with balanced connection.
D/A converter : 20-bit 4 mmb method
Digital Filter : 20-bit 8 x Oversampling

* 2 slots used
ai-ad1 Analog Disk Input Board AI-AD1 (¥ 100,000)
Optional board with high-gain equalizer for analog record playback.
MM/MC Compatible (Gain : MM30dB, MC60dB)
Sampling frequency : 48 kHz

* 2 slots used
AIO-U1 Line I/O Board AIO-U1 (¥ 60,000)
Analog recording and playback jacks for unbalanced connections.
Sampling frequency : 48 kHz

* 1 slot is used