Accuphase DC-300 (1996)
The world’s first digital stereo preamplifier, released by Accuphase in November 1996.
Overview
The Accuphase DC-300 is the first digital stereo preamplifier ever made, introduced in November 1996 by Accuphase Laboratory, Inc., originally known as Kensonic Laboratory, Inc. It processes all audio signals digitally, with volume, balance, tone control, and compensation handled entirely in the digital domain using DSP. The unit was designed in Japan and features a fully balanced analog output stage isolated from the ground line.
Specifications
| Production Year | November 1996 |
| Product Type | Digital stereo preamplifier |
| D/A Converter | MMB (Multiple Multi-Bit) principle, 20-bit linearity |
| Digital Signal Path | 48-bit |
| Input Sampling Frequency | 32 kHz, 44.1 kHz, 48 kHz (automatic detection) |
| Input Format Quantization | 16-bit to 24-bit line |
| Digital Input Format | Level (EIAJ CP-1201) |
| Digital Input Optical Level | -27dBm to -15dBm |
| Digital Input Coaxial Level | 0.5Vp-p/75 Ω |
| Digital Output Optical Level | -21dBm to -15dBm, 660 nm wavelength |
| Digital Output Coaxial Level | 0.5Vp-p/75 Ω |
| Frequency Response | 4.0 Hz to 20 kHz ± 0.3 dB |
| Total Harmonic Distortion | 0.002% (20 Hz–20 kHz) |
| S/N Ratio | 122 dB |
| Dynamic Range | 112 dB (24-bit input, LPF off) |
| Channel Separation | 112 dB (20 Hz–20 kHz) |
| Output Voltage / Impedance (Balanced) | 5V / 50 Ω, XLR |
| Output Voltage / Impedance (Unbalanced) | 5V / 50 Ω, RCA |
| Volume Control | DSP, speed sensing rotation, 0 to -95dB in 0.1–5 dB steps, ∞ |
| Balance Control | DSP, speed sensing rotation, 0 to -95dB difference, ∞ |
| Tone Control (Low 200 Hz) | ±6 dB at 40 Hz, 0.5 dB steps |
| Tone Control (Low 500 Hz) | ±6 dB at 100 Hz, 0.5 dB steps |
| Tone Control (High 2 kHz) | ±6 dB at 10 kHz, 0.5 dB steps |
| Tone Control (High 7 kHz) | ±6 dB at 20 kHz, 0.5 dB steps |
| Compensator | +6 dB at 100 Hz |
| Attenuator | -20 dB |
| Digital Inputs (Standard) | 2 optical, 2 coaxial |
| Digital Inputs (Optional) | BNC, HPC optical, HPC balanced |
| Analog Inputs (Standard) | Analog Line Input Board |
| Analog Inputs (Optional) | Analog Disc Input Board for MM/MC cartridges, with switchable subsonic filter |
| Internal Option Slots | Up to six optional boards |
| Power Supply | 100 VAC, 50/60 Hz |
| Power Consumption | 25W |
| Dimensions | 475 mm W × 150 mm H × 406 mm D |
| Weight | 21.5 kg |
| Country of Manufacture | Japan |
| Original Price | ¥980,000 (1996) |
Design
The DC-300 uses eight hand-selected 20-bit D/A converters per channel in parallel, applying Accuphase’s MMB (Multiple Multi-Bit) method. A high-speed 40 MBPS optocoupler isolates the digital and analog sections. The analog filter is a 4-pole Butterworth design with precisely selected components. All signal adjustments—volume, balance, tone, and compensation—are processed digitally using DSP, including a patented "noise shaping principle for digital level control." The unit features an Ultra Jitter-Free PLL circuit with a quartz-based VCO and a high-precision sampling frequency converter.
Context
Accuphase was founded by former Kenwood engineer Jiro Kasuga in late 1972 under the name Kensonic Laboratory, Inc., with Kenwood as a part owner. Kenwood retained partial ownership until the mid-1990s. Kensonic’s first products were the P-300 amplifier, C-200 preamp, and T-100 tuner. The DC-300 marked a milestone as the world’s first digital preamplifier.
Market
The DC-300 had an original retail price of ¥980,000 in 1996, equivalent to about $9,500 in today’s US dollars. Vintage Accuphase equipment is sought after for its construction quality, Japanese engineering, and consistent appreciation in value.
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