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.

Channel dividers based on fully digital signal
processing

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 freeselection of the lower and upper cutoff frequency,
for configuration as a low-pass, bandpass, orhigh-pass filter.

The central task of a multi-amp system is ofcourse the division of the frequency spectrum into
multiple bands or channels. The channel dividers
in the DF-45 feature an impressive array ofsophisticated 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 infully digital form. With minimal temperature driftand excellent long-term stability, this ensuresfiltering performance of the highest order.

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, 24dB/octave, 48 dB/octave, or 96 dB/octave. Withineach unit, separate settings for lower and upper
slope are possible, resulting in a wide variety ofcombinations.

[dBr]
PASS

dBt/o

12ct

18ct

Left
AnalogOutputs

AnalogAttenuator
ON/OFFDSP
Microcomputer

Optical
OpticalReceiver
DAI
DecoderBuffer

Frequency

Level

Phase

Slope

Delay

Delay Comp

OutputSubwoofer

Clock
Distributor

A/D
Converter

BalancedMDS++
D/A Conversion System X4
Unbalanced

Digital Filter
Master Level

Right
AnalogOutputs

AnalogAttenuator
ON/OFFBalanced
Coefficient
MemoryBufferBalanced

AnalogInputsA/D
Converter

Sampling
Rate
Converter

Unbalanced

Channel B

Same as Channel A (no Subwoofer in DSP )Channel C

Same as Channel A (no Subwoofer in DSP )Channel D

Same as Channel A (no Subwoofer in DSP )Coaxial
CoaxialTransceiverFig. 1 DF-45 Block Diagram

96dB/oct

B/o48dDigital Filter

CoaxialEncoderct

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 soundat the listener's ears. Time alignment is afunction designed to compensate for such

Unbalanced

CoaxialReceiver[Hz]

Time alignment function allows adjustment in1-cm steps

MDS++
D/A Conversion System X4

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

Filter frequency points can be set over the range
from 31.5 Hz to 22.4 kHz in 1/6-octave intervals.

DSP : Digital Signal Processor/oc

ct

Fig. 2 Divider unit slope characteristics (bandpass filter)

59 selectable cutoff frequency points

Display/o/oFrequency

As a crucial circuit element, the digital filter isconfigured 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 implementationof extremely steep filter slopes of up to 96 dB/octave.

Master LevelDigitalInputs

ct
96dB/oHigh-speed 40-bit floating point DSP assures
precision digital filtering

dBt
B/oc
48d

Circuit assemblywith high-speed DSP

dBdB18Channel ADigital
Output6dB/octoc

B/24dB/oct

d12

HS-Link
HS-Link
Receiver

PASS

ct

/o6dB

24

Multi-amplification is regarded as the pinnacle of theaudio world. The term refers to dividing the musicalspectrum into several distinct bands and handling eachof these using a dedicated power amplifier and directly
connected speaker unit. When configured and adjusted
properly, such a system can achieve soundreproduction on a scale that is not possible by anyother means. Sonic definition and spatial imaging canbe 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 evolutionof the model DF-35.
Only the latest digitaltechnology is employedthroughout, and all internal signal processing
occurs fully in the digitaldomain. High-speed 40High-speed 40-bit floating point
Digital Signal Processor (DSP)
bit floating point DSP
chips allow super-precise high-order filtering with aslope 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 dedicatedunit. A full array of functions including frequency dividing
filters (low-pass, band-pass, high-pass), attenuation
slope characteristics, delay and delay compensatorfunction, level control, and phase switching are
implemented in the digital domain. To store parametersettings 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 andensuring exactly the desired overall energy balance. A
high-quality multi-amp system built with the DF-45 willsound its very best.

differences. The DF-45
incorporates this in the form ofa DELAY function thatelectrically adjusts the time
when the sound from eachdriver reaches the listener.
In Figure 3, the sound from thetwo speaker units [L and H]
at the star t exhibits a timedifference of t seconds due tothe front/back distance d (cm)of their respective diaphragms.
In order to eliminate thisdifference, the delay function
delays the sound of the (H) unit
by t seconds. Normally, a delay
would be expressed as a timevalue, but since the delay hereis caused by a spatial distance(of the two diaphragms), theDF-45 converts the delay intoa distance value (cm) andshows this value on the display
for easier understanding.

Further Improved MDS++ D/A Converter<Time alignment using delay>t seconds

d cm

t seconds
Delay function
delays H waveformby t seconds

DelayHH

Delay

B TimeMDS (Multiple Delta Sigma) is a revolutionary design

summing and voltage summing is used.

which employs several delta sigma type converters in

The overall result is further improved stability and top-a parallel configuration. In the combined output ofnotch performance. The music emerges from a totallythese multiple converters, conversion errors cancel

silent background, with breathtaking detail resolution

each other out, resulting in a drastic improvement inand accurate spatial information.

all relevant aspects of converter performance, such
Input

as accuracy, S/N ratio, dynamic range, linearity, andLL

THD. In the DF-45, four delta sigma type D/A convert-

Delay ensures that Land H signals
arrive at the ear at the same timeallel. Compared to a single

In the example above, when DELAY function for H is set to d cm, thesignal start for H will be delayed by t seconds (✽), causing the soundfrom L and H to reach the listener at the same time.

d34,000

improvement by a factor ofDAC 2

As shown in the diagram, the MDS++ features ann Individual output ON/OFF control for each channel.
n Individual 4-position phase control for each channel.
n Digital attenuator with setting range from -40.0 dB to+12.0 dB (in 0.1-dB steps) allows precise leveladjustments for left and right channel.
n Memory for five sets of parameter and function settingsin each channel.
n Unused channels can be set to OFF (all display
elements and LED indicators are out).
n Safety Lock prevents inadvertently changing anysettings.
n “Full Level Output Protection” function safeguards thespeakers if a digital signal without volume control data
is input (output level is reduced by 40.0 dB).
n Versatile input connector array comprises coaxial,
optical and HS-Link inputs for digital signals andbalanced and unbalanced inputs for analog
signals.

Subtraction

DAC output

DAC 4

enhanced current-to-voltage (I/V) conver ter forprocessing the D/A converter output current. To reduce(seconds)

DAC 3

2 (= √4 ).

the load on the current adder, a combination of current

Other Functions and Featuresn 5-way and higher configurations canbe realized by using more than
one DF-45 unit.

DAC 1(Reverse phase output)

an overall perfor mance

Speed of sound = 331.5 + 0.607 T [ms]T: temperature (°C)
Consequently, at 14°C, sound travels at about 340 m/s.

t=Devices) are driven in parconverter, this results inFig. 3 Principle of time alignment(✽)

I (current) /V (voltage)
converterers (AD1955 from Analog

Start time
Speaker units L and H (diaphragm)
are d centimeters apart(Normal phase output)

n “Analog ATT” function (–10 dB) can be activated forspecific channels to reduce residual noise when using
high-efficiency midrange or high range speaker units.
n Display indication can show predefined strings orcustom strings entered by the user (max. 8 characters,
character set with 97 characters).
n Easy selection of Subwoofer (3D) mode using
dedicated switch in channel A.
n Analog output for each channel supports
balanced connection.

Current summing

Voltage summing

Block diagram of MDS++ convertern The DF-45 incorporates four units named CHANNELA - D (4-way configuration). The assembly shown here
carries the coaxial digital input and output connectors,
unbalanced analog input connectors, MDS++ D/A
converter modules for 4 channels, and unbalanced
analog output connectors.

Delay Compensator Function of DF-45 (providing automatic compensation for signal delays)
When a signal passes through a filter circuit, a certaindelay will necessarily occur. The DF-45 incorporates
a function called “DELAY COMP” that compensates
for such delays. As an example, the illustration atright shows how the delay compensator function
works in a 3-way system. This is not a representationof the actual circuit, but rather a simplified
representation of the operating principle.

<Operation principle of delay ompensator in DF-45>[Channel A]

ON/OFFb and c are delayed, using
slowest a as reference

When OFF:a is slowest, delayed by
t3 seconds versus c[Channel A]

OFF[Channel B]

b is delayed
ON/OFFInput

Output b(Bandpass filter)

ONby t2 seconds
versus c

Delayed by
t3 - t2
secondst2

t3 - t2

Delay: t2 sn The lower the filter frequency and the steeper thefilter slope, the longer the delay.

OFFb is delayed by [t3 - t2]
seconds(b compensation time)

t3 - t2[Channel B]

ONc is delayed by t3 seconds[Channel C]

The DF-45 calculates and displays thetheoretical delay time, and automaticallyprovides compensation. (Default setting)(a compensation time)

0Output a(Low-pass filter)n Generally, a low-pass filter will have more delay.
The DF-45 therefore only provides compensation
when low-pass filtering is used.

OFF:

When DELAY COMP is ON

ON or OFF

Delay: t3 s

n Regardless of whether a circuit is analog or digital,
when the signal has to pass through a filter, theoutput will be delayed by a certain amount, causing
a delay in step response and impulse response.

ON:

Time lag (delay) of output
signal with regard to input
in each channel[DELAY COMP]
function

ON/OFFt3

Delay: 0 s(c compensation time)t3

Delayed by t3 seconds

Output c[Channel C](High-pass filter)

The DF-45 calculates and displays thetheoretical delay time for reference, andthe user can manually set any desiredvalue.

As shown above, the signal will
be delayed by a different duration when passing through different filter circuits.

When DELAY COMP isOFF, the output signals ineach channel will be shifted,
causing time misalignment.

n DF-45 default settings and display indication

Actual delay compensator indication is in cm, converted fromthe above compensation timevalue.

When DELAY COMP is ON,
the time difference between
output signals a, b, andc is eliminated.

Cutoff frequency settings (Hz)Display indication

Function

Guaranteed Specifications[Guaranteed characteristics measured in compliance with JEITA standard method CP-2402]
m ()symbol at top right of level indication is shown when “Full Level Output Protection” function is set to ON.

n Front panel

Divider units

Channel A

Channel B

Channel C

Channel D

m Digital inputs
COAXIAL format:
JEITA CP-1201/AES3 compliant
OPTICAL format:
JEITA CP-1201 compliant
Sampling frequencies:
32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz,96 kHz (16 - 24-bit 2-channel PCM)
HS-Link
RJ-45 type connector (dedicated cable)
Sampling frequencies:
176.4 kHz, 192 kHz (24-bit 2-channel PCM)
m Digital output
COAXIALn Rear panel

Analog outputs
UNBALANCED/BALANCED
Channel Channel Channel Channel
DC
B
A

Format: JEITA CP-1201 compliant
Level:
0.5 Vp-p, 75 ohms

m Frequency response

2.0 - 44,000 Hz +0 –3 dB

m D/A converter

24-bit MDS++ typem THD

0.001% (20 - 20,000 Hz)

m S/N ratio

COAXIAL/OPTICAL
HS-Link
Analog input114 dB
116 dB112 dBm Dynamic range“Analog ATT” OFF:
“Analog ATT” ON:

112 dB
109 dBm Channel separation

108 dB (20 - 20,000 Hz)

m Cutoff frequencies

59 pointsm Slope characteristics

6 dB/octave,
24 dB/octave,

12 dB/octave,
48 dB/octave,

18 dB/octave
96 dB/octave* When cutoff frequency is 10 Hz or 20 Hz, only 6 dB/octave, 12 dB/octave, 18 dB/octave are available.

★
A POWER switch
B FUNCTION knob
C ENCODER knob
D Input selector
E Memory selector
F Display
INPUT: BAL, UNBAL, COAX, HS-LINK, OPTOMEMORY: 1, 2, 3, 4, 5

G Digital inputs
COAXIAL OPTICAL
HS-LINK
H Digital output COAXIAL
I Analog inputs
UNBALANCED BALANCED
J Subwoofer output selector
K AC power connector(for supplied power cord)★

m Delay setting range (converted into distance)

0 to 3000 cm (1-cm steps)

m Level adjustment range–40 to +12.0 dB (0.1-dB steps)–50 to +2.0 dB (0.1-dB steps)“Analog ATT” OFF:
“Analog ATT” ON:

m Output voltage/impedance BALANCED:
2.5 V, 50 ohms, balanced XLR connector
UNBALANCED: 2.5 V, 50 ohms, RCA-type phono connectorm Minimum load impedance BALANCED:UNBALANCED:

600 ohms
600 ohms

m Power requirements

AC 120 V/230 V, 50/60 Hz (Voltage as indicated on rear panel)m Power consumption

36 watts

m Maximun Dimensions

Width 465 mm (18-5/16”)
Height 150.6 mm (5-15/16”)
Depth 395.8 mm (15-9/16”)

m Mass

14.1 kg (31.1 lbs) net
20.0 kg (44.1 lbs) in shipping carton

Remarks★ This product is available in versions for 120/230 V AC. Make sure that the voltage shown on the rear panel matches the AC line voltage in your area.
★ The shape of the AC inlet and plug of the supplied power cord depends on the voltage rating and destination country.

n Supplied accessories:• AC power cord

• Specifications and design subject to change without notice for improvements.

http://www.accuphase.com/H0505Y

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