PARK AUDIO DF1408 MkII User manual

OWNER'S MANUAL
FOUR-CHANNEL
PROFESSIONAL POWER AMPLIFIER
DF - series
DF1408 MkII

ACCESSORIES:
1. Power cord
2. Owner’s Manual
3. Warranty

1
AVIS
RISQUE DE CHOC ELECTRIQUE
NE PAS OUVRIR
CAUTION! The amplifier runs on 230V AC voltage. Removing the cover will expose you
to a potentially dangerous voltage! Do not use the unit if the electrical power cord is frayed
or broken.
Power is supplied from 230 V AC single-phase grounded 50/60 Hz source!
CAUTION! The amplifier can yield dangerous output voltage! Do not touch the non-
insulated cable parts connected to the unit in operation!
CAUTION! The high sound pressure level of speaker systems generated by high output
power delivered by the amplifier may be hazardous to your hearing. Please, take adequate
safety precautions.
WARNING! The amplifier yields high output power. The manufacturer shall not be held
responsible for any damage to the speakers caused by excessive power from the unit.
WARNING SIGNS:
Important information! Intended to warn the user about any important
applicable information contained in this Owner’s Manual.
Hazardous voltage inside! Intended to warn the user about electric shock
hazard due to high voltage inside the product.

2
GENERAL
The DF1408MkII professional digital four-channel amplifier is designed for high
fidelity amplification of sound signals within a professional sound reproduction system.
The amplifier can be operated in a four-channel mode, three-channel mode (one pair of
channels bridged) or two-channel mode (both pairs of channels bridged).
To ensure the most advantageous and faultless operation of the amplifier, please,
read this Manual before use.
UNPACKING
The manufacturer’s quality control system provides for careful examination of each
product before it leaves the factory to ensure its flawless appearance. After unpacking,
please, check the unit for any physical damage. In case of damage, please, contact your
local dealer. Keep the shipping carton and all packing material as you may need them for
re-shipment of the unit.

3
DESIGN FEATURES
Physical Design
The amplifier is enclosed in a metal (steel) case of 88 mm (2U) height. The amplifier
is designed to be standard rack-mounted (RACK 19"). Physically, the amplifier
consists of:
• power supply unit;
• four digital amplifying units installed on a common heat sink;
• input unit;
• indication and input level control unit.
Power Supply Unit
All four channel of the amplifier share the same pulse power supply unit.
Cooling System
The amplifier features a forced cooling system which is common for all four
channels. The amplifier and the power supply unit are cooled with a single fan blowing
backwards. The cooling system provides for a double-step intensity-cooling rate switching.
At a normal temperature, the fan runs at a low speed, thus generating the least noise
possible. When the amplifier is set to deliver a high output power or when the ambient
temperature is higher than normal, the cooling system may switch the fan to the other
(higher) cooling rate.
Output Stage
The output stage of this digital power amplifier is designed according to Class D
technology to deliver high efficiency and least heat. The high switching rate ensures the
high sound quality comparable with the best analogue amplifiers.
Balanced Inputs
The use of balanced inputs provides for an essential reduction of the environment-
induced hum and noise interference with long input connecting cables.
Line Outputs(only for standart input modules or input modules with a sensitivity
The amplifier line outputs are parallel to the inputs (each along the respective
channel) and provide for parallel connection of several amplifiers with standard signal
cables using XLR connectors.
Input Filter
To improve the performance of loudspeakers, the amplifier incorporates a switch-
selectable high-pass 4-th order filter with 24dB per octave slope rate. This is the filter
recommended by all major loudspeakers manufacturers. This filter cuts off any signals
below 45Hz, which generally cannot be reproduced by most of the professional
loudspeakers.
The filter significantly reduces the travel of the LF speaker cone below the loudspeaker
frequency cut-off point (which is especially good for bass reflex loudspeakers) thus

4
making it possible to increase the power applied to the LF speaker without any danger of
its overheating. The power of the amplifier is not wasted for cone flapping and allows the
loudspeaker to achieve higher sound pressure.
When it is necessary to achieve a linear frequency response to drive full-range
loudspeakers generally used in studios or in cinema theatres, the input filter can be
disabled (bypassed for each channel individually) with the slide switches located on the
amplifier rear panel.
Below see the enabled and disabled filter low frequency response diagrams.
Built-in Two-Way Crossover
This feature is to save your money and effort when driving two-way loudspeakers.
The bandwidth (high, low, full range signal) is selected individually for each channel with
a slide switch. The crossover frequency point is factory preset (generally to 150Hz).
However, it can be changed by replacing the crossover PCB. If you need to change the
setting, please, consult our local dealer or the manufacturer’s support service by e-mail:
[e-mail]
Input Level Attenuators
These allow setting the amplifier to the required sensitivity (each channel individually)
which is very helpful when several amplifiers are used to drive different types of
loudspeakers or are used within multi-speaker sound reinforcement systems. The
attenuators are located on the front panel.
Optoelectronic Clip-Limiter
The clip-limiter is to reduce the input signal level as soon as any emergency or
overload occurs to prevent any sound distortion.
Removable Power Cord
This feature is provided for convenience of transportation and rack mounting.
Low Frequency Response for Enabled and Disabled Input Filter
20Hz 50Hz 100Hz 200Hz 900Hz
-10 dB
-5 dB
0 dB
5dB
10 dB
«ON (45Hz )»
20Hz 50Hz 100Hz 200Hz 900Hz
«OFF»
-10 dB
-5 dB
0 dB
5dB
10 dB

5
FUNCTIONAL FEATURES
Overload and Short-Circuit Protection
Individual per each channel. This protective system becomes active in case of short-
circuited output or overload caused by reduced load impedance. It disables the output
signal of the respective channel for 0.5 second and then the amplifier gradually resumes
its delivery.
DC Output Protection
The amplifier’s schematics precludes transit of any clicks or noise during the power-
on/off transition process. The power source unit is responsible for preventing any DC
damage to loudspeakers. In the event of output DC voltage or any powerful LF fluctuations,
the power source unit goes off and all indicators, including the POWER LED, go off too.
The amplifier can be restarted in 2 or 3 minutes by de-energizing and re-energizing
the amplifier with the POWER switch. If the DC is an occasional problem (which is
unlikely) the amplifier goes on and resumes its normal functioning. If, otherwise, the DC
output problem persists through the fault of the amplifier, then upon switching, the amplifier
goes on, the POWER amplifier goes on but in a short while the DC output protection
system disables the power supply source.
High Frequency Protection
Should any powerful high frequency fluctuations occur on the output either as a result
of poor contact in the input cable connectors, or being transmitted to the amplifier’s input
by any other device (such as a crossover or mixing console), the protection system
activates the built-in optoelectronic Clip-limiter to reduce the input signal level. Thus the
protection system effectively prevents any damage to tweeters as might be caused by
non-musical signals of powerful high frequency spectrum.
Thermal Protection
The continuous-operation-support protection system is common for four channels.
When the heat sink becomes heated over 50°С, the fan goes into its maximum speed
mode (normally, the fan runs at its minimum at a low speed). If the temperature of the heat
sink rises further to 65°С, the next stage of the thermal protection system goes active. It
is a built-in Clip limiter which reduces the input signal level (for all channels at a time)
without distorting the amplified signal. In this case the thermal protection LED becomes
slightly lit (dim). The higher the temperature, the lower signal level, the brighter is the LED.
Such an algorithm ensures faultless and continuous functioning of the amplifier even in
case of overheating.
The amplifier may stop functioning only in case of the fan breakdown or blocked air
flow. In this case upon reaching 85°С, the independent protection system disables the
respective channel of the amplifier. The CLIP LED goes on and the SIGNAL LED of the
affected channel goes off. The amplifier resumes its operation in the reverse order.

6
As soon as the amplifier cools down, the affected channels gradually regain their
amplification level up to the set value.
Soft Signal Start
During the power-on process, this feature ensures smooth gain from zero to the
maximum level to provide for a smooth rise of the sound level emitted from the
loudspeakers.

7
BLOCK DIAGRAM
1
+
HF
LF
TOP
THRU
SUB
CROSSOVER
C
H
1
INPUT
ON
OFF
HI PASS FILTER
(45 Hz)
45Hz
125Hz 125Hz
HF
LF
TOP
THRU
SUB
CROSSOVER
CH 2
ON
OFF
HI PASS FILTER
(45 Hz)
125Hz 125Hz
MONO
STEREO
BRIDGE
MODE
P
o
w
e
r
a
m
p
l
i
f
i
e
r
L
i
m
i
t
e
r
Powe
r
amplifi
e
r
Limiter
45Hz
1
+
2
+
2
+
O
U
T
P
U
T
O
U
T
P
U
T
1
+
HF
LF
T
O
P
TH
R
U
S
U
B
CROS
S
O
V
E
R
CH 3
INPUT
ON
OFF
HI PASS FILTER
(45 Hz)
45Hz
125Hz 125Hz
H
F
L
F
T
O
P
T
H
R
U
S
U
B
C
R
O
S
S
O
V
E
R
CH 4
INPUT
ON
O
F
F
HI PAS
S
F
I
L
T
E
R
(4
5
H
z
)
1
2
5
H
z
1
2
5
H
z
MONO
STEREO
BRIDGE
MODE
P
o
w
e
r
a
m
p
l
i
f
i
e
r
L
i
m
i
t
e
r
P
o
w
e
r
a
m
p
l
i
f
i
e
r
L
i
m
i
t
e
r
45Hz
1
+
2
+
2
+
O
U
T
P
U
T
O
U
T
P
U
T
THROUGH
INPUT
THROUGH THROUGH
INPUT
THROUGH

8
FRONT PANEL
THERMAL – overheating alarm LED.
Brightness depends on the temperature of the heat sink
(See: Thermal Protection).
POWER LED.
When the DC output protection system becomes active it goes off irrespective of
electric power applied to the amplifier.
CLIP - overload alarm LEDs for Channels 1, 2, 3 and 4, respectively.
They indicate
– overload condition causing distortion and activation of the optoelectronic Clip-
limiter of the respective channel;
– activation of thermal protection system which disables the respective channel
(the SIGNAL LED goes off). (See: Thermal Protection).
SIGNAL LEDs indicating output signal on Channels 1, 2, 3 and 4, respectively.
LEVEL - input (sensitivity) level attenuators for Channels 4, 3, 2 and 1,
respectively.
POWER switch.

9
REAR PANEL
THROUGH – line outputs for Channels 4, 3, 2 & 1, respectively (XLR male).
Are used to deliver input signal along the respective channel to the input of
another amplifier.
THROUGH connectors are parallel to INPUT connectors of respective channels.
NPUT – balanced inputs (XLR female) Channels 4, 3, 2 and 1, respectively.
Inputs for Channels 1 and 3 are also used to supply the input signal for channels
1 & 2 and Channels 3 & 4 functioning in the MONO and BRIDGE mode.
MODE switch for channel 3 and 4:
– MONO – Channels 3 and 4 drive two loads from a single input signal source;
– STEREO – Channels 3 and 4 drive two loads from two separate input signal
sources;
– BRIDGE – Channels 3 and 4 drive a common load from a single input signal
source.
MODE switch for Channels 1 and 2:
– MONO – Channels 1 and 2 drive two loads from a single input signal source;
– STEREO – Channels 1 and 2 drive two loads from two separate input signal
sources;
– BRIDGE – Channels 1 and 2 drive a common load from a single input signal
source.
MAINS IN – power cord socket for 230 V AC 50/60 Hz grounded mains.
CROSSOVER switches for Channels 4, 3, 2 and 1, respectively, to select the
required frequency band:
– TOP – higher frequency signal component;
– SUB – lower frequency signal component;
– THRU (Full Range).
Switches for Channels 1 and 3 are also used to select the required frequency
band for Channels 1 & 2 and Channels 3 & 4 functioning in the BRIDGE mode.
PROFESSIONAL POWER AMPLIFIER
230V 50/60Hz 1600VA max
Serial No D8141010A000

10
OUTPUT – output SPEAKONs for Channels 1, 2, 3 and 4, respectively, used to
connect to loudspeakes.
To connect loudspeakers to Channels 1 & 2 and 3 & 4 functioning in the BRIDGE
mode, use outputs for Channels 1 and 3, respectively.
In addition, Channel 1 output connector is interlinked with Channel 2 output, while
Channel 3 output connector with Channel 4 output, thus making it possible to use
a single NL4FC connector (wired accordingly) to connect Channel 1 and 2
loudspeakers to channel 1 output connector and Channel 3 and 4 loudspeakers
to Channel 3 output connector.
HI PASS FILTER switches for Channels 1, 2, 3 and 4, respectively, used to
enable/disable (bypass) the input filter for each channel individually.

11
CABLE REQUIREMENTS
Input Cables
Make sure to use only shielded cables whether balanced or unbalanced. Shielding
when properly grounded protects a signal against external electrical interference.
As a rule, unbalanced lines over 3 meters long are not acceptable. Greater distances
require a balanced cable. Avoid placing input cables close to power cords or power
transformers.
Output Cables
The amplifier is capable of delivering high level output current; therefore, the wire
gauge used for speaker cables is particularly important. Inadequate wire gauge adds
significant resistance to the speaker’s own impedance, reducing the power which is
actually delivered to the speaker. It will also result in a decreased damping factor and
possible fire hazard.
Since the power applied to the loudspeaker is of primary concern in system design,
we have included the table below to allow you determine the appropriate wire gauge for
your application.
Power Loss in a 10-meter Cable
Wire Gauge Cable
Resistance
Cable Power Loss
4 Ohm Load 8 Ohm Load
0.50 mm2
0.75 mm2
1.00 mm2
1.50 mm2
2.00 mm2
2.50 mm2
4.00 mm2
0.72Ohm
0.49Ohm
0.36Ohm
0.24Ohm
0.18Ohm
0.15Ohm
0.09Ohm
15.4 %
10.9 %
8.3 %
5.7 %
4.3 %
3.6 %
2.3 %
8.3 %
5.8 %
4.3 %
2.9 %
2,2 %
1.8 %
1.1 %
The table shows the percentage of the power loss in a 10-meter copper multiple-core
cable. This table reflects the power loss as a percentage of the output power of the
amplifier applied to the load. Use this table to determine the power loss to the load at other
cable lengths. For example, if you plan to deliver 100 Watts to 8-Ohms load through 20-
m cable of 0.75-mm2 gauge, the power loss in the cable would be 5.8 % x 2=11.6 % of
100W or 11.6W lost in the cable.

12
RACK-MOUNTING REQUIREMENTS
The amplifier is designed to fit a standard 19” rack. While mounting, make sure to
provide unhindered air access to the front and rear sides of the rack. Fan direction is from
front to back. It is not necessary to leave empty space above or below the amplifier.
For stationary use, it will be enough to fix securely only the front panel of the amplifier
to the rack. However, never attempt to transport the unit unless its rear end is properly
supported and/or securely fixed, as it may be fraught with danger of damage.
AC POWER REQUIREMENTS
The amplifier is supplied with a three-conductor grounded AC power cord, and
should be plugged into a standard 3-wire grounded electrical outlet which supplies
230V AC 50/60 Hz. In the event of line voltage sag, the unit will continue to operate
normally, albeit with less power. The mains lower voltage limit for the amplifier to retain its
operability is 160V.
The actual AC current consumption depends on the audio signal level and the load
impedance. While installing a sound reinforcement system, it should be taken into account
that the average rate of current consumption by the amplifier when reproducing standard
musical material at the maximum level is as follows:
– 1,.5 A into 16 Ohms (for all channels);
– 3 A into 8 Ohms (for all channels).
In order to reduce the AC hum, please, plug all sound equipment interconnected with
signal cables into the same power network outlet.

13
INPUT AND OUTPUT CONNECTORS
Input Connectors
Use XLR (male) connectors to connect to the amplifier inputs and XLR (female)
connectors to line outputs.
See the wiring on the figures below.
Output Connectors
Use SPEAKON NL2FC or NL4FC connectors to connect loudspeakers to the
amplifier individual channel outputs. For bridged connection or connection of two channels
via a single cable, use SPEAKON NL4FC.
See the wiring on the figures below.
2
1
3
XLR male
Shield (Ground)
Cold (–)
Hot (+)
XLR female
2
1
3
Shield (Ground)
Cold (–)
Hot (+)
CAUTION! Never attempt to jumper or otherwise link up any pins of output
connectors.
NL2FC for individual channel mode
Output (+)
Output (–)
NL4FC for bridge mode
(only for Channels 1 & 3 connectors)
Output (+)
Output (–)
NL4FC for individual channel mode
Output (+)
Output (–)
NL4FC for linking up two channels with a
single connector
(only for Channels 1 & 3 connectors)
Channel 1or 3
Output (–)
Channel 1or 3
Output (+)
Channel 2 or 4
Output (+)
Channel 2 or 4
Output (–)

14
OPERATING MODES
Four-Channel Mode for Four Individual Signal Sources
STEREO mode is used for both pairs of the channels.
Link up an input signal to each individual channel.
Connect a loudspeaker to each channel output with a SPEAKON NL2FC or NL4FC
connector.*
Set the MODE switches for Channels 1 & 2 and Channels 3 & 4 to STEREO.
Adjust the input signal level for each channel individually with the LEVEL attenuators
on the front panel.
Set the CROSSOVER switch of each individual channel to the required position.
Generally, it is recommended to set the input HI PASS FILTER switches to 45Hz.
However, when it is necessary to obtain a linear frequency response to drive full-range
systems used in studios or cinema theatres, set them to OFF. See: Input Filter.
Note.
* The loudspeaker rated impedance should be at least 8Ohms.
Never attempt to jumper or otherwise link up any pins of SPEAKON output connectors.
PROFESSIONAL POWER AMPLIFIER
230V 50/60Hz 1600VA max
Serial No D8141010A00 0
To Speaker Systems
MODE CH 1-2
switch is set to
STEREO
To Input Signal Sources
MODE CH 3-4
switch is set to
STEREO

15
Four-Channel Mode for Two Signal Sources
MONO mode is used for both pairs of the channels.
Apply an input signal to the inputs of Channels 1 and 3.
Connect a loudspeaker to each channel output with a SPEAKON NL2FC or NL4FC
connector.*
Set the MODE switches for Channels 1 & 2 and Channels 3 & 4 to MONO.
Adjust the input signal level for each channel individually with the LEVEL attenuators
on the front panel.
Set the CROSSOVER switch of each individual channel to the required position.
Generally, it is recommended to set the input HI PASS FILTER switches to 45Hz.
However, when it is necessary to obtain a linear frequency response to drive full-range
systems used in studios or cinema theatres, set them to OFF. See: Input Filter.
Note.
* The loudspeaker rated impedance should be at least 8Ohms.
Never attempt to jumper or otherwise link up any pins of SPEAKON output connectors.
PROFESSIONAL POWER AMPLIFIER
230V 50/60Hz 1600VA max
Serial No D8141010A0 00
To Speaker Systems
MODE CH 1-2
switch is set to
MONO
To Input Signal Sources
MODE CH 3-4
switch is set to
MONO

16
Two-Channel Mode
Both pairs of channels are bridged.
Apply an input signal to the inputs of Channels 1and 3.
Connect a loudspeaker to the output of Channels 1 and 3 with a SPEAKON NL4FC
connector wired for bridge connection.*
Set the MODE switches for Channels 1 & 2 and Channels 3 & 4 to BRIDGE.
Adjust the input signal level with the LEVEL attenuators for Channels 1 and 3.
Set the CROSSOVER switches of Channels 1 and 3 to the position required for each
pair of channels (the crossover switches of Channels 2 and 4 may be in any position).
Generally, it is recommended to set the input HI PASS FILTER switches to 45Hz (in
this case only switches for Channels 1 and 3 are involved). However, when it is necessary
to obtain a linear frequency response to drive full-range systems used in studios or cinema
theatres, set them to OFF. See: Input Filter.
Note.
* The loudspeaker rated impedance should be at least 16Ohms.
Never attempt to jumper or otherwise link up any pins of SPEAKON output connectors.
PROFESSIONAL POWER AMPLIFIER
230V 50/60Hz 1600VA max
Serial No D8141010A00 0
To Speaker Systems
MODE CH 1-2
switch is set to
BRIDGE
To Input Signal Sources
MODE CH 3-4
switch is set to
BRIDGE

17
Three-Channel Mode (Option 1)
Using the bridge mode for one pair of channels and the individual mode for the other.*
Apply an input signal to the inputs of Channels 1, 3 and 4.
Connect loudspeakers to the output of Channel 1 with a SPEAKON NL4FC
connector wired for bridge connection and to the outputs of Channel 3 and 4 with
SPEAKON NL2FC or NL4FC connectors wired individual-channel mode. **
Set the MODE switches for Channels 1 & 2 to BRIDGE and for Channels 3 & 4 to
STEREO.
Adjust the input signal level with the LEVEL attenuators for Channels 1, 3 and 4.
Set the CROSSOVER switches of Channel 1, 3 and 4 to the required position (the
crossover switch of Channel 2 may be in any position).
Generally, it is recommended to set the input HI PASS FILTER switches to 45Hz (in
this case only switches for Channel 1, 3 and 4 are involved). However, when it is necessary
to obtain a linear frequency response to drive full-range systems used in studios or cinema
theatres, set them to OFF. See: Input Filter.
Note.
* Any pair of channels (1 & 2 or 3 & 4) can be operated in the bridge mode or individual mode
if properly connected and set up.
** The loudspeaker rated impedance should be at least 8Ohms for individual connection and
16Ohms for bridge connection.
PROFESSIONAL POWER AMPLIFIER
230V 50/60Hz 1600VA max
Serial No D8141010A00 0
To Speaker Systems
MODE CH 1-2
switch is set to
BRIDGE
To Input Signal Sources
MODE CH 3-4
switch is set to
STEREO

18
Three-Channel Mode (Option 2)
Using the bridge mode for one pair of channels and the individual mode for the other.*
Apply an input signal to the inputs of Channel 1 and 3.
Connect loudspeakers to the output of Channel 1 with a SPEAKON NL4FC
connector wired for bridge connection and to the outputs of Channel 3 and 4 with
SPEAKON NL2FC or NL4FC connectors wired individual-channel mode. **
Set the MODE switches for Channels 1 & 2 to BRIDGE while for Channels 3 & 4 to
MONO.
Adjust the input signal level with the LEVEL attenuators for Channels 1, 3 and 4.
Set the CROSSOVER switches of Channel 1, 3 and 4 to the required position (the
crossover switch of Channel 2 may be in any position).
Generally, it is recommended to set the input HI PASS FILTER switches to 45Hz (in
this case only switches for Channel 1, 3 and 4 are involved). However, when it is necessary
to obtain a linear frequency response to drive full-range systems used in studios or cinema
theatres, set them to OFF. See: Input Filter.
Note.
* Any pair of channels (1 & 2 or 3 & 4) can be operated in the bridge mode or individual mode
if properly connected and set up.
** The loudspeaker rated impedance should be at least 8Ohms for individual connection and
16Ohms for bridge connection.
PROFESSIONAL POWER AMPLIFIER
230V 50/60Hz 1600VA max
Serial No D8141010A0 00
To Speaker Systems
MODE CH 1-2
switch is set to
BRIDGE
To Input Signal Sources
MODE CH 3-4
switch is set to
MONO