Accuphase DF-55 User Manual

●Channel divider units with high-speed DSP for fully digital signal processing

●Standard configuration allows 4 -channel (4-way) system setup ● 59 selectable cutoff frequency points ●Highly accurate 96 dB/oct attenuation slope

●Time alignment function allows delay time setting in 0.5-cm steps ● Delay

compensator offsets signal delays in filter circuitry ● Further refined MDS++ D/A converter ● Output mode can be set to monophonic specifications

Multi-channel divider with fully digital signal processing – High-speed 40-bit floating point DSP provides the processing power for four channel units supplied in standard configuration. Highly accurate digital filters offer a choice of 59 cutoff frequency points and up to 96 dB/octave attenuation. Integrated time alignment function adjustable in 0.5-cm steps, and delay compensator for automatically offsetting any filter circuit delays. Output mode can be changed to monophonic specifications.

Multi-amplification is regarded as the pinnacle of the audio world. The term refers to dividing the musical spectrum into several distinct bands and handling each of these using a dedicated power amplifier and directly connected speaker unit. Such a system is necessarily more complex, but when configured and adjusted properly, it can achieve sound reproduction on a scale that is not possible by any other means. Sonic definition and sound quality can be optimized by the user to obtain exactly the desired result. Configuring a multi-amplified system affords truly one of the greatest pleasures of audio. The Digital Frequency Dividing Network DF-55 represents a full model change of the model DF-45. A high-speed, high-precision DSP further minimizes any calculation errors, implementing accurate filtering of the highest order. Each bandwidth is handled by a dedicated divider unit, and a full array of functions including

High-speed 40-bit floating point

Digital Signal Processor (DSP)

frequency dividing filters (low-pass, band-pass, high-pass) with 96 dB/octave attenuation, delay and delay compensation, level control, and phase switching are implemented in the digital domain. Digital as well as analog line and balanced inputs are provided, and the unit comes as a 4-channel device (for 4-way amplification) in its standard configuration.

High-speed, high-precision DSP

implements fully digital signal processing

The DF-55 features high-speed digital signal processing with amazing power. Latest digital circuit topology and advanced technology come together in a filtering DSP that has a 32-bit mantissa and 8-bit exponent section. The floating point principle enhances calculation accuracy by dividing numeric values into mantissa and exponent, thereby preventing errors even when handling very small values. This results in dramatically improved dynamic range and superior precision, allowing very steep cutoff slope settings of 48 dB or 96 dB per octave.

Assembly with

high-speed DSP chip

59 selectable cutoff frequency points

Filter frequency points can be set over the range from 31.5 Hz to 22.4 kHz in 1/6-octave intervals. In addition, 10, 20, and 290 Hz points are also provided, resulting in a total of 59 points. Each divider unit is fully flexible and allows free selection of the lower and upper cutoff frequency.

Six filter slope characteristics up to 96 dB

per octave

The filter attenuation characteristics can be set to 6 dB, 12 dB, 18 dB, 24 dB, 48 dB, or 96 dB per octave. The 96 dB/octave setting in particular allows the driver unit to reproduce only its intended frequency without being affected by adjacent frequency bands. This makes it possible to create a multi-amped system that takes musical accuracy to an unprecedented level.

〔dBr〕

PASS

−

6dB/oct

−

12dB/oct

−

18dB/oct

−

24dB/oct

−

100

[Cutoff frequency setting 100 Hz for lower and 1 kHz for upper range]

48dB/oct

10 20 30 50 70 100 200 500 1k 2k 3k 5k 7k 10k

96dB/oct

Frequency

Fig. 1 Divider Unit Slope Characteristics (Bandpass Filter)

96dB/oct

48dB/oct

PASS

12dB/oct

18dB/oct

24dB/oct

6dB/oct

(Hz)

Output mode of each divider unit can be set to

STEREO, MONO L+R

, MONO L ,

MONO R

or

In normal use, the divider units will be set to the STEREO position, but by changing the setting to monophonic (MONO) operation, the left-channel and right-channel DAC outputs within the unit are added up, resulting in a parallel drive configuration that further reduces residual noise.

❶Use for a subwoofer (3D) system

In 3-way system, channel D is set to OFF

Display

Micro-

Computer

Date/Clock Distributor

DF-55

Ultra-low range (monophonic)

Preamplifier

HS-Link

Receiver

Coaxial

Digital Inputs

Analog Inputs

Digital Output

Optical

Balanced

Line

Hs-Link

Coaxial

Receiver

Optical

Receiver

A/D

Converter

A/D

Converter

Hs-Link

Transceiver

Fig. 2 DF-55 Block Diagram

Cutoff frequency

Low range High range

Channel A Channel B Channel C

MONO L＋R

Encoder

DAI

Decoder

STEREO

In this example, the left and right signals in the ultra-low frequency range are mixed (channel A output mode is set to "MONO L+R" position), for configuring a three-way system with a subwoofer.

❷

2-way system for left and right 2-way monophonic setup

Preampliﬁer

Two of the four divider units in the DF-55 are set to the "MONO L" position and the other two units to the "MONO R" position. This allows setting up a 2-way monophonic spec system.

❸

2-way to 4-way system, using two DF-55 units

The divider units of one DF-55 are set to the "MONO L" position, and the units of the other DF-55 to the "MONO R" position. This allows setting up a 2-way to 4-way monophonic spec multi-amped system.

Time alignment function allows delay

adjustment in 0.5-cm steps

The sound emanating from a speaker travels through the air at a speed of about 343.5 meters per second (when the ambient temperature is 20 degrees centigrade). Compared to the propagation speed of light or of electrical signals, this is extremely slow. When multiple speaker units are used, necessarily located at different positions, there will be differences in the time required for the sound to reach the ear of the listener. In a multi-speaker system, each sound source position, namely the position of the diaphragm in the respective driver unit, is not aligned on the front/back plane, also leading to different arrival times of the sound. Compensating for such differences is called time alignment (see Figure 3).The DF-55 incorporates a DELAY function that uses digital signal processing to electrically adjust the time when the sound from each driver reaches the listener. Normally, a delay would be expressed as a time value, but since the delay here is caused by spatial distance, the DF-55 converts the delay into a distance value (cm) for easier understanding.

Channel A

DSP：Digital Signal Processor

Floating Point

DSP

Master Level

Frequency

Channel B

Channel C

Channel D

Level

Phase Slope

Delay Delay Comp

Output

Coefficient

Memory

Cutoff frequency

Forleftchannel

Low range Low range

Channel A

MONO L

D/A Conversion System×4

Cutoff frequency

High range High range

Channel B Channel D

Channel C

MONO R

＋＋

MDS

Digital Filter

DAC

＋＋

MDS

Digital Filter

DAC

Same as Channel A

Analog

Attenuator

ON/OFF

Analog

Attenuator

ON/OFF

Forrightchannel

DF-55

Mono

ON/OFF

Buffer

Line

Balanced

Line

Balanced

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