Accuphase DF-45 Brochure

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

processing m Equipped for 4-channel (4-way) system configuration m 59 selectable cutoff frequency points m Highly accurate 96 dB/oct attenuation slope m Time alignment function allows delay time setting in 1-cm steps m Delay compensator offsets signal delays in filter circuitry m Further refined MDS++ D/A converter m Digital input possible in conjunction with DC-330

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. Choice of 59 cutoff frequency points ensures total flexibility. Highly

accurate digital filters enable 96 dB/octave slope characteristics. Time alignment

function adjustable in 1-cm steps, plus delay compensator for offsetting filter circuit

delays ensure superb spatial accuracy. HS-Link capability provides SA-CD support.

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. When configured and adjusted properly, such a system can achieve sound reproduction on a scale that is not possible by any other means. Sonic definition and spatial imaging 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-45 represents a further evolution of the model DF-35. Only the latest digital technology is employed throughout, and all internal signal processing occurs fully in the digital domain. High-speed 40bit floating point DSP

High-speed 40-bit floating point

Digital Signal Processor (DSP)

chips allow super-precise high-order filtering with a slope of 96 dB/octave. This in turn enables the digital input to handle sources up to SA-CD quality. In addition, balanced and unbalanced analog inputs are also provided, and the unit comes as a 4-channel device (for 4-way amplification) in its standard configuration. Each channel in the DF-45 is handled by a dedicated unit. A full array of functions including frequency dividing filters (low-pass, band-pass, high-pass), attenuation slope characteristics, delay and delay compensator function, level control, and phase switching are implemented in the digital domain. To store parameter settings for various scenarios, five memory positions are provided. The DF-45 allows the user to select cutoff frequency settings for adjacent bands from 59 choices, plus six different attenuation slope settings (max. 96 dB/oct). This unprecedented flexibility makes it possible to elicit optimum performance from every speaker unit, achieving a smooth transition between bands and ensuring exactly the desired overall energy balance. A high-quality multi-amp system built with the DF-45 will sound its very best.

HS-Link

Digital Inputs

Analog Inputs

Digital Output

HS-Link

Receiver

Coaxial

Receiver

Optical

Receiver

Balanced

A/D

Converter

A/D

Converter

Unbalanced

Coaxial

Transceiver

Fig. 1 DF-45 Block Diagram

Encoder

DAI

Decoder

Display

Micro-

computer

Clock

Distributor

Sampling

Rate

Converter

Channel dividers based on fully digital signal processing

The central task of a multi-amp system is of course the division of the frequency spectrum into multiple bands or channels. The channel dividers in the DF-45 feature an impressive array of sophisticated digital technology based on a DSP chip with amazing power. The high-speed 40-bit floating point design of this device makes it possible to implement all filtering and delay functions as well as phase and level control in fully digital form. With minimal temperature drift and excellent long-term stability, this ensures filtering performance of the highest order.

Circuit assembly

with high-speed DSP

High-speed 40-bit floating point DSP assures precision digital filtering

As a crucial circuit element, the digital filter is configured with a high-speed 40-bit DSP that has a 32-bit mantissa and 8-bit exponent section. The floating point principle enhances calculation accuracy and results in dramatically improved dynamic range. This allows the implementation of extremely steep filter slopes of up to 96 dB/ octave.

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.

Channel A

DSP : Digital Signal Processor

Floating Point

DSP

Frequency Level

Phase

Slope

Delay Delay Comp

Subwoofer

Output

Coefficient

Memory

Channel B

Channel C

Channel D

D/A Conversion System X4

Same as Channel A (no Subwoofer in DSP )

MDS

Digital Filter

Master Level

MDS++

Digital Filter

Master Level

Analog

Attenuator

ON/OFF

Analog

Attenuator

ON/OFF

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, for configuration as a low-pass, bandpass, or high-pass filter.

Six filter slope characteristics up to 96 dB/ octave

The filter attenuation characteristics can be set to 6 dB/octave, 12 dB/octave, 18 dB/octave, 24 dB/octave, 48 dB/octave, or 96 dB/octave. Within each unit, separate settings for lower and upper slope are possible, resulting in a wide variety of combinations.

[dBr]

PASS

6dB/oct

18dB/oct

24dB/oct

48dB/oct

c o

/ B d

6 9

Fig. 2 Divider unit slope characteristics (bandpass filter)

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

Frequency

4 8

d B

/ o

d B

/ o c

Time alignment function allows adjustment in 1-cm steps

When multiple speaker units are used, differences in sound source location (diaphragm position on the front/back plane) will lead to different arrival times of the sound at the listener's ears. Time alignment is a function designed to compensate for such

differences. The DF-45 incorporates this in the form of a DELAY function that electrically adjusts the time when the sound from each driver reaches the listener. In Figure 3, the sound from the two speaker units [L and H] at the start exhibits a time difference of t seconds due to

Buffer

Unbalanced

Balanced

Unbalanced

Left Analog Outputs

the front/back distance d (cm)

Buffer

Balanced

Right Analog Outputs

of their respective diaphragms. In order to eliminate this difference, the delay function delays the sound of the (H) unit by t seconds. Normally, a delay would be expressed as a time value, but since the delay here is caused by a spatial distance (of the two diaphragms), the DF-45 converts the delay into a distance value (cm) and shows this value on the display for easier understanding.

PASS

18dB/oct

6dB

12dB/oct

/oct

[Hz]

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