Accuphase DC-81L

Commentary

A D/A converter compatible with 3 sampling frequencies released simultaneously with the DP-81L.

The D/A converter uses the world's first 20-bit discrete method for consumer use.
The operating precision is different from the usual way of adding bits above or below 16 bits, and the precision of each bit is 1/2 of the original.²⁰=9.54x10^-7As a result, an excellent performance of 0.0005% actual distortion factor (pure distortion component only, 1 kHz) has been realized. In addition, quantization noise, which interferes with high-quality sound reproduction, is greatly reduced.
The conversion method is a current addition type which is superior in linearity. It is a discrete method to realize the performance of the 20-bit theoretical limit value. Therefore, the circuit is composed of current switching elements and ultra-precision resistors. Each unit is strictly adjusted to realize the complete operation, and the strain (0 cross strain) at small output is removed.

The digital filter uses an independent 20-bit 8 x oversampling digital filter on the left and right sides.
The DC-81L filter uses digital calculation techniques to achieve an attenuation of -110dB between 24.1 and 328.7 kHz and a passband ripple within ± 0.00005%, which can degrade sound quality.

An audio low-pass filter that cuts out unwanted bands uses a highly selected discrete GIC third order Butterworth active filter.

As a measure against high-frequency noise, the digital filter and D/A converter are electrically isolated by an opto-coupler.
Each bit signal output from the digital filter is optically transmitted through an opto-coupler (transmission band 7Mbit/sec) and converted back into an electrical signal, ensuring complete electrical isolation and preventing noise interference through the conductor.
The output of the opto-coupler is fed to a magnetically and electrically isolated analog converter through a mother printed board outside the shield frame.

Three sampling frequencies of 48 kHz, 44.1 kHz and 32 kHz are available.
Switching is performed by automatically determining the frequency of the input signal. Since each of the three frequencies is equipped with a dedicated oscillator, out-of-band noise is reduced and jitter is prevented.

The input terminals are equipped with a total Route 3 of a Route 3 for optical fiber and a Route 6 for coaxial cable.

A noise shaper is installed to further reduce quantization noise.
The noise shaper reduces noise within the audible band by using a technique that reduces noise by feeding back the rounding error generated by the digital filter to the next data.

Equipped with digital de-emphasis, it is possible to play high-quality CDs with emphasis applied.
The DC-81L achieves a deviation of ± 0.001 dB and a phase difference of less than 1.5 degrees with respect to the specified characteristics.

The output of the converter is set to a level that does not require amplification, and the S/N and distortion characteristics are improved by only buffering in the audio stage.
The circuit configuration of the audio stage is a discrete configuration push-pull DC servo connection system.

Equipped with digital level control.
The Remote Commander included with the DP-80L allows volume control from a remote location and was sold separately.

Two RCA-type output terminals and one XLR-type balanced output terminal are installed.

The digital and analog circuits are shielded with metal and each power supply is provided with a dedicated transformer to eliminate mutual interference. The left and right circuits are laid out on an independent printed board to prevent interference between channels together with a two winding transformer on the left and right.

Measures against unwanted external radiation are taken, and leakage through the power supply is dealt with by a full-scale line filter.
It is also shielded inside.

The exterior is gold-style scratch hairline finish, and the side is equipped with a natural Persimmon sideboard.

Model Rating

Type	Digital processor
Formatting	EIA standard format Quantize Number : Sampling frequency : 16-bit straight line 32.0 kHz ± 0.1% 44.1 kHz ± 0.1% 48.0 kHz ± 0.1%
Frequency characteristic	4.0 Hz to 20 kHz ± 0.3 dB
D/A converter	Discrete 20-bit
Digital filter	20-bit 8 x oversampling Noise shaper function Digital de-emphasis function Deviation ± 0.001 dB
Total harmonic distortion factor + noise	0.0016%(1,000Hz) 0.002% (20 Hz to 20 kHz)
S/N	120dB
Dynamic range	98dB
Channel separation	112dB
Rated Output / Impedance	Balanced : 2.5V/50 Ω (25 Ω / 25 Ω), balanced XLR type Unbalanced : 2.5V/50 ohm, RCA phono jack
Output level control	0 ~ -40dB, 1 dB step (digital type)
Digital input format level (in accordance with EIA)	Formatting : Digital Audio Interface Optical : Received power of -15 to -27dBm Coaxial : 0.5Vp-p/75 Ω
Semiconductor used	Transistor : 89 FET : 5 pcs IC : 98 Diode : 54 pcs
Power supply voltage	AC100V/117V/220V/240V, 50Hz/60Hz
Power consumption	35W
External dimensions	Width 475x Height 135 (Including Legs) x Depth 373 mm
Weight	15.9kg
Sold Separately	Remote Commander RC-2 (¥ 8,000)