DPR-504 User Manual version 4.0
BSS Audio
V 4.0
DPR-504 User Manual version 4.0
1 December 1997
User Manual
This equipment has been tested and found to comply with the following European and
international Standards for Electromagnetic Compatibility and Electrical Safety:
Radiated Emissions (EU):
RF Immunity (EU):
Mains Disturbance (EU):
Electrical Safety (EU):
Radiated Emissions (USA):
Electrical Safety (USA):
Electrical Safety (CAN):
FCC part 15 Class B
(1990) Associated Equipment
(1992) RF Immunity, Fast Transients
(1996) Commercial Audio Equipment
(1996) Commercial Audio Equipment
For continued compliance with international EMC legislation ensure that all input and
output cables are wired with the cable screen connected to Pin 1 of the XLR connectors.
The input XLR Pin 1 is connected to the chassis via a low value capacitor, providing high
immunity from ground loops whilst ensuring good EMC performance.
We have written this manual with the aim of helping installers and sound engineers to get
to grips with the DPR-504 and obtain its maximum capability. If you are new to BSS
products, we recommend that you begin at the start of the manual.
We welcome any comments or questions regarding the DPR-504 or other BSS products,
and you may contact us at the address or World Wide Web site given in the warranty
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BSS Audio
DPR-504 User Manual version 4.0
1 Introduction
2 Unpacking
3 Mechanical installation
4 Mains power connection
5 Audio connections
5.1 Main inputs
5.2 Main outputs
5.3 EXT Key input
6 Getting started
7 Operating instructions
7.1 Filter and width
7.2 Key listen
7.3 Threshold
7.4 Key level meter
7.5 Gate open indicator
7.6 Attack, release and hold
7.7 Range
7.8 Link
7.9 EXT
7.10 IN
8 Service section
8.1 Transient suppressor replacement
8.2 Separating signal and chassis ground
9 Warranty Information
10 Specifications
10.1 Input section
10.2 Output section
10.3 Operating controls
10.4 Metering
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1 Introduction
The BSS DPR 504 is a four channel professional noise gate which has been
designed for simple and intuitive use, and yet is capable of producing the best
results in a wide range of applications. It incorporates modern integrated circuit
technology for high packing density and long term reliability. Some of the more
advanced features within the product are not necessarily obvious from the front
panel, and to ensure the unit is used to its fullest, it is recommended that the
manual is read thoroughly.
Ingenious proprietary techniques are employed to make the engineers life easier
without compromise to performance or versatility. A summary of its features are
highlighted below, with a more in depth discussion following within the manual.
• Four independent channels that are linkable to give either one or two stereo
linked master/slave modes.
• Flexible parametric Key filter for frequency conscious gating with absolute
precision. The parametric EQ approach provides a higher degree of control for
accurately rejecting spurious unwanted gate triggers than similar shelving filters.
• Key listen provides operator with the facility to hear the effect of Key side-chain
EQ or other processing effect as an aid to setting up.
• Dual metering system which indicates both average and peak responses
simultaneously and gives the operator precise information regarding the signal
levels around the threshold point. Separate 'gate open' marker LED, linked to gate
dynamics, continually monitors interrelation between gate activity and the actual
• IN switch which allows the operator to force open the gate, in the absence of
signal, to check the integrity of the signal lines, and observe set dynamics. This also
functions as channel bypass.
• Selectable 'Fast and auto' attack modes which have been optimised for accurate
and transparent performance over the widest variety of program material. Self
adjusting Auto mode deals cleanly with varying dynamics whilst a super fast mode
is available for demanding percussion and synthesiser transients.
• Simple to operate, combined Hold and Release control which has special audio-
tapered characteristics to give subtle 'musical' envelope shaping.
• Rear mounted electronically balanced XLR input and output connectors.
• Rear mounted 1/4" jack socket allows access to external side-chain key input for
uses such as external EQ, delay or keying by and unrelated signal.
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2 Unpacking
As part of the BSS system of quality control, we check every product carefully
before packing to ensure that it reaches you in flawless condition.
Before you go any further, please check the unit for any physical damage and
retain the shipping carton and all relevant packing materials for use, should the
unit need returning.
In the event that damage has occurred, please notify your dealer immediately, so
that a written claim to cover the damages can be initiated. Check out section 9;
Warranty Information for more info on the warranty, and also to record your
dealer details.
3 Mechanical installation
A vertical rack space of 1U (1 3/4"/44.5mm high) is required, with a depth of
220mm, excluding connectors. Ventilation gaps are unnecessary.
If the unit is likely to undergo extreme vibration through extensive road trucking
and touring, the unit must be supported at the rear and/or sides to lessen the stress
on the front mounting flange. The necessary support can generally be bought
ready-built, as a rack tray, or the DPR 504 can be mounted between other units.
Damage caused by insufficient support is not covered by the warranty. To prevent
cosmetic damage to the front panel paint finish, always use protective plastic cups
under the rack mounting bolts.
As with any low-level signal processing electronics, it is best to avoid mounting the
DPR 504 next to a strong source of magnetic radiation or heat, for example, a high
power amplifier. The internal power supply regulators are mounted on the case
sides and use this as their heatsink. After a period of time in an enclosure, the
metal case will feel hot to the touch, but this is quite normal and should not be
cause for alarm.
4 Mains power connection
The DPR 504 must always be connected to a 3-wire earthed AC outlet. The rack
framework must also be connected to the same grounding circuit. The unit must
NOT be operated unless the power cables' EARTH (ground) wire is properly
terminated - this is important for personal safety as well as for proper control over
the system grounding.
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The wires in the mains lead are colour coded in accordance with the following
Green and Yellow......Earth
Those units supplied to the North American market will have an integral moulded
3 pin connector which is provided to satisfy required local standards.
IMPORTANT: The DPR 504 is designed to use 50/60Hz AC power in one of two
voltage ranges, selectable with the mains voltage selector switch on the rear of the
unit. It is vital that the position of this switch is checked BEFORE initial power up
to ensure that it matches the local mains supply. Acceptable input AC supply
voltages range from:
120V switch position
240V switch position
@@V to @@V
@@V to @@V
The application of voltages outside these ranges may cause permanent damage or
erratic operation of the unit, and will invalidate the warranty.
The mains fuse carrier on the rear of the unit must be fitted with the correct type
and rating of fuse, depending on the position of the mains voltage selector switch:
120V switch position
240V switch position
T250mA fuse
T200mA fuse
In the unlikely event of the mains fuse failing without good reason, DISCONNECT
THE UNIT FROM THE MAINS SUPPLY, and always replace with the appropriately
rated fuse (as specified above) for continued protection against damage and fire.
Note: For USA and Canadian users, the replacement fuse must be of an identical
UL rated type fuse for continued compliance with safety standards.
It is very unlikely that fuses will blow during normal use, but if replaced fuses
continue to blow, then the internal transient suppressors may have become
damaged. If this case, you should refer to section 8.1 for the replacement
5 Audio connections
The DPR 504 is designed to operate at nominal line levels and not at microphone
signal levels. The gating of microphone signals must be done after the mic-amp, or
gain increase section of a mixing console input channel, and would generally
occur at the pre-fader or pre-equaliser insert point of the particular channel.
We would recommend all wiring to be done with two-conductor shielded cable.
The shield should not carry any signal currents, and be used only for shielding. It is
ordinarily connected to a ground point at one end only.
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5.1 Main inputs
The electronically balanced input of each channel is compatible with all
professional and semi-professional sound equipment, balanced or unbalanced,
whose source impedance is 600 ohms or less. The nominal input level is between 10dBv and +10dBv, with an upper maximum or +20dBv.
There is no internal connection to the Pin 1 terminal, and therefore the cable shield
grounding must be derived from the source equipment. This arrangement provides
an automatic break in the grounding of interconnected equipment and will ensure
noiseless operation of the equipment. If European 4 conductor cable is being used
for interconnections, then special attention must be given to avoiding earth loops
through multiple chassis ground connections.
For non standard connections, such as unbalanced lines, remember:
• Always use Hot '+' and Cold '-' signal pins as the two input terminals.
• When driven from an unbalanced source, connect the '-' terminal to the source
ground connection, as well as to the shield of the cable.
• When driven from a balanced source, connect the cable shield to chassis ground
at the source end only.
5.2 Main outputs
The outputs of each channel are electronically balanced and floating, and provide
ample power to drive all professional and semi-professional audio equipment
whose input impedance is 600 ohms or greater. The nominal input impedance will
be the same as the input level when the gate is 'open', as the DPR 504 makes no
gain contribution. The maximum output level is +20dBv into a load of 600 ohms.
Should an unbalanced output be required, then the Cold '-' pin must be connected
to Pin 1 to ensure no loss of output level.
For some rack mounted systems, the chassis or safety power ground might need to
be isolated from the signal ground. Reference should be made to section 7.2; Key
listen for further information.
5.3 EXT Key input
This rear mounted 1/4" RTS jack socket provides an input to the key side chain.
Refer to section 7.9; EXT for an explanation of its use and operation. Wiring is
shown for a mono plug, as the input is unbalanced. However, an RTS stereo plug
will be automatically unbalanced when inserted.
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6 Getting started
The instructions in this section are intended to help those people unfamiliar with
noise gates and their terminology, and to provide a means of 'getting started'. The
DPR 504 has been designed to need the minimum of operator knowledge and
setup procedures, and is capable of producing excellent results with the adjustment
of only one control.
The front panel is divided equally into four identical sections, with each section, or
channel, being numbered on the IN switch. There is no difference in operation
between any of the four channels except in respect of LINK switching. This is
covered separately in section 7.8. The following discussions apply to all channels
In operation, the DPR 504 can be considered as an automatic on-off switch that is
placed into the signal line. The switching operation is controlled by the loudness
level and the frequency content of the signal. The best way to understand its basic
operation is to connect one channel to a program source and operate the controls
whilst listening to their effect.
Connect a suitable program source, such as a CD player, to one of the channel
inputs and a suitable monitoring system to the same channels output. Section 5;
Audio connections shows the correct wiring configurations.
• Set
• Set
• Set
• Set
• Set
all the switches to their 'out' positions.
the threshold control to 'out'.
the release control to 1 sec.
the key filter control to 1kHz
the width control to 10.
The gate open triangular LED will be illuminated and the program signal should be
heard at the same level as if it were not connected through the gate channel.
This condition is known as 'bypass', and the gate is being forced to remain open
and pass the program unaffected.
Now push the IN switch. The red LED underneath will illuminate to confirm that
the gate is now in control, and the program signal level will drop to very nearly
nothing. The gate has closed and is cutting off the signal.
Now slowly rotate the threshold control anticlockwise and an indication will start
to show on the key level meter. Note that this display has two parts - a single
segment ahead of a bar display (refer to section 7.4; Key level meter for more
detail). The single segment is responding to the peaks of the program material, and
the bar display is indicating the average volume level of the program. As soon as
the display exceeds the 'gate open' marker, the program signal will be passed
through to the output and the gate has 'opened'. Spend a few minutes adjusting
this control and watching the display.
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For close-mic gating, as would be used on acoustic drums, the threshold trigger
point should be set close to the signal peaks to avoid spill triggering effects from
adjacent drums. In other applications, such as to remove low level background
electronic noise, a threshold trigger point might be used that is a long way down
from the program signal peaks to avoid losing any quiet passages. Each application
will require a slightly different approach to be used, and the key level meter has
been designed to provide accurate information for a whole range of operation
methods. The threshold control is the most important control on the gate and is the
only one that will need adjusting to perform simple gating.
These controls can be separated into three classifications depending on their
function and usage on the gate.
Key functions are those that help to determine how to open the gate.
Dynamic functions are those that determine when to open and close the gate.
Mode functions are those that determine why the gate opens and by how much.
Control classification:
Key functions :
Key filter, Width, Key listen, Threshold, Key level
Dynamic functions :
Attack, Release, Auto Attack.
Mode functions :
Int/ext, Range, Link, IN.
Section 7 describes in more detail how these functions work and how best to set
them for particular tasks.
Remember that automatic channel switching, such as gating, can have many uses
other than simple cleaning up applications for noisy microphone lines etc., don't
be afraid to experiment.
7 Operating instructions
7.1 Filter and width
These two controls adjust the internal key side-chain filters. These filters are used
to control the frequency content of the signal being sent to the gate control
circuitry and allow the filtering-out of information not required to control the
gating action. They are not placed in the main signal path, and therefore have no
effect whatsoever on the program material. In use, the filters should be considered
as a pair of tracking high pass and low pass filters, with the space between them
controlled by the width control. Thus it is possible to achieve a variety of key sidechain filter responses from a very broad filter set giving a wide band response, to a
quite narrow set for a very selective response.
The frequency scaling around the key filter control knob is the approximate value
for the centre of the response, without regard to the octave value set by the width
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control. In use, the user should commence with a fairly wide width setting, and
then progressively narrow the response down whilst sweeping the frequency to
isolate the dominant frequency of the program, thus rendering the threshold
control sensitive only to the required signal.
This type of filter realisation not only allows band-pass filter configurations, but
also the conventional low pass or high pass configurations by the appropriate
setting of the key filter and width control. Experience will show that this approach
gives considerable operational advantages for the user over the more elementary
separate low/high pass filter approach.
In application, the frequency response of the filter is set to coincide with that of the
signal to be gated, or a smaller but stronger part of it that is always present. This
will ensure for example, on microphone signals, that out of band information close
in level to the required signal will not cause spurious openings of the gate. Should
this facility not be required then the controls should be set as indicated in the
section 6; Getting started.
7.2 Key listen
This momentary switch allows the operator to listen to the program material after it
has been processed by the key filters. This also applies to any external equipment
connected via the EXT key input socket.
In application it would be used during the setup of the side-chain key filter and
width controls, as it is often easier to more accurately set them whilst listening to
their effect.
The key listen signal appears at the output connector of the channel, and overrides
the normal program material. In this sense it must be used with caution, as
accidental operation will cause temporary loss of program signal at the output
7.3 Threshold
As previously mentioned in 'getting started', the threshold control is one of the
most important functions on any gate, and is used to set the level at which the gate
open sequence will commence, in relation to the input program signal level.
With the control fully clockwise, at 'out', the gate will be held closed at all times,
and as the control is rotated counter-clockwise, the threshold point is progressively
reduced until at the -50dBv scale setting, the gate would be virtually open at all
In application the control should be set to give the required degree of low level
signal block. The key level meter is used in conjunction with this control as it gives
precise information relating to this setting.
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7.4 Key level meter
The total key side-chain signal level, after any external processing, is displayed on
this meter in two modes: as a bar indicating the average signal level, and as a
single segment indicating the instantaneous peak level. The peak level always
exceeds the average level and is displayed as a moving dot above the average
column, in a simultaneous manner. The dynamics of this display are optimised for
user visibility and accuracy, with the peak dot exhibiting a damped decay response
like a PPM meter.
The meter scale is centred around a 0dB calibration point which corresponds to
the level that initiates the 'gate open' sequence. Rotation of the threshold control
moves the key side-chain signal into this meter 'window', and gives the operator a
real-time picture of the relative position of the signal in relation to the point at
which the gate will trigger.
It is important to remember that this meter is showing the side chain signal, and
not the actual opening and closing of the gate. This is indicated by the triangular
gate open marker LED underneath. The meter scale is designed to allow sufficient
usable range both below and above the gate open point.
In application when the program signal is present, the meter will show below full
scale but above the threshold gate opening point. When the program signal is not
present, the meter will show spurious background noise at a level which is below
the 0dB scale point, and therefore not opening the gate. For very 'safe' gating such
as for vocals, the signal will show nearer full scale, and for critical close-mic gating
such as for drums, the signal peaks will show only a few dBs above the 0dB
threshold point.
7.5 Gate open indicator
The triangular LED mounted underneath the 0dB scale point of the key level meter
is provided to give a visual indication of the actual activity of the gate at all times.
This does not necessarily correspond to the key signal passing the 0dB meter scale
point, as the various dynamic controls of the gate modify this correlation. The
dynamic response of this gate open indicator matches that of the gate action, and
thus is dependent on the attack and release control settings.
If for example, the release control is set at 1 sec, then this LED will be seen to
remain on, and therefore the gate to remain open, for a period of one second
following the side chain key level meter display falling below the 0dB point.
In application it is good practice to periodically monitor the operation of this LED
in conjunction with the key level meter display, to check for consistency of
operation and to anticipate potential problems more easily.
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7.6 Attack, release and hold
These two controls (attack & release) determine how the gate responds, in time,
once it has received instructions to open or close.
Attack is the time taken for the gate to fully open once threshold level has been
exceeded. This opening sequence will continue, once triggered, even if the signal
level falls below threshold during the cycle.
Release is the time taken for the gate to fully close once the signal has dropped
below threshold. Contrary to attack, this closing sequence will be overridden
should the signal level rise above threshold during the cycle.
Within gating terminology there is another timing sequence which is called hold.
Hold is a period of time for which the gate will remain fully open once the signal
has dropped below threshold level, and is necessary to avoid the gate 'chattering'
on and off during natural short pauses in program material, such as speech. It
always precedes the start of release. To minimise operator set up time, the DPR
504 incorporates the hold function by combining it with the release function.
These two functions still remain independent, however their adjustments have
been combined onto the one control. In general, at small release time settings the
hold time will be small; at longer release times the hold time will be
correspondingly longer.
The auto attack facility of the DPR 504 will cover all but the most transient of
program sources, and has been carefully optimised to produce good envelope
control. For super fast attack times, the user can select the fast position.
The release control can be set to around 1 second for many applications, but
provides control over a wide range to allow more critical tuning in sensitive
applications. The decay contour has been given a special audio taper which
ensures that even relatively fast releases can occur unobtrusively and musically. It
is also highly operator fault tolerant, and the user will soon appreciate the
improvement this makes over the more conventional linear or logarithmic decay.
The audible character of any release setting is significantly altered by changing the
range (refer to section 7.7; Range) between -70dB and -20dB. Whilst the -20dB
setting provides sufficient attenuation for effective but more gentle gating than the 70dB range, it also gives the audio tapered release envelope a subtly different
musical feel. For a given release time setting, the gate has less 'far to go' on the 20dB range setting, and this variation effectively doubles the range of decay
contour options available to the operator.
Notice, that once the attack sequence has been initiated by an event (that is the
key side-chain signal has exceeded 0dB on the key level meter) it will continue
through to the end of the timing cycle regardless as to whether the key signal has
since fallen below 0dB threshold.
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Similarly, the hold sequence continues for its set duration, and avoids the starting
of another attack sequence should the key signal momentarily fall below 0dB
Release will commence following the ending of a complete hold timing period, but
it will be overridden by another attack sequence should this be initiated by a
subsequent event.
7.7 Range
This switch sets the difference in program signal level between its value when the
gate is open to that when it is closed, and is marked in dBs.
The output program signal level when the gate is open is the same as the input
level, and is taken to be 0dB relative. When the gate is closed, the range switch
allows the program level to be set to either -20dB or -70dB of this gate open level.
In application, when the switch is set to -20dB, the gate action will be very much
like a 'dim' function. This is ideal for use when cleaning up acoustic microphone
lines and other noisy sources during live sound reinforcement shows. When the
switch is set to -70dB, the gate action will be very much 'on-off'. This is needed in
applications where signals are to be switched on and off under dynamic control,
and in studio recording environments where electronic noise from amplifiers and
keyboards need to be eliminated.
It is worth noting that the effective audible attack time will be shorter for the -20dB
range setting than for the -70dB setting, as it will take longer for the gate to rise
from a level of -70dB to 0dB, than from -20dB to 0dB for the same fixed attack
7.8 Link
Both channel 2 and channel 4 on the DPR 504 have a push switch which alters the
normal operational mode of the unit from four separate channels of gates into one
in which channel 1 plus 2 and channel 3 plus 4 work together. The first group is
operated by the controls of channel 1 only; the second group is operated by the
controls of channel 3 only. The two switches work independently of each other so
that the unit can be configured as two groups of two channels, or one group of two
channels and two independent channels. The associated LED on channel one and
three indicate that they are working as the master control for the group.
When this mode is selected, the key side-chain signals from both the group
channels are summed together to provide a common mono signal. This is then
used by the master channel of the group for processing in the normal manner. In
addition, the VCA on the other group channel (slave channel) is disabled from its
own drive circuitry and connected in parallel with that of the master channel, such
that the action of the slave channel is now totally controlled by the master.
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If it is not required for the side-chain key signal of the slave channel to be summed
with that of the master channel, or visa versa, then the respective EXT switch
should be pressed. This then disconnects that channels signal - provided nothing is
externally connected to the rear panel external key input jack socket. In
application, it might be necessary to use the master/slave linking facility when
using two channels of the unit on a stereo program source. It can also be useful
when gating two microphone lines from similar sources, such as backing vocals or
orchestral overheads, or when gating stereo effects returns or submixes from other
program sources.
7.9 EXT
This switch selects the signal source for the key side-chain.
In the normal 'out' position, the signal path is continuous, and the side-chain uses
the normal program material appearing at the input connector as its control.
If the EXT (external) position is chosen, then the key side-chain looks to the rear
mounted jack socket marked EXTernal key input for its source of signal. This allows
the gate to be triggered by an event that is not the same program event connected
to the input connector.
In application this allows the gate channel to be controlled by two other methods.
Firstly, a totally independent signal can be connected at this point, such that the
gate will be triggered open by an event which is not related to the program
appearing at the input connector. Secondly, extra equalisation, or time delay can
be added with the existing internal signal to enhance the selectiveness of the gate
7.10 IN
This switch selects whether the gating action is active or not. When the switch is
'out', the gate will be held permanently closed allowing the program signal to pass
uninterrupted. When the switch is depressed, the gate will be active and controlled
by the key level signal.
In application this switch can be used to check that signal lines are active, or to
temporarily suspend the action of the gate.
Repeated switching will also allow checking of the dynamic action of the gate, as
the set attack and release times will be operative on the opening and closing
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8 Service section
8.1 Transient suppressor replacement
The primary of the input transformer is protected against high voltage spike
interference by two voltage dependent resistors (VDR). These provide a momentary
short circuit to voltage peaks in excess of the normal power voltage rating.
Should the DPR 504 be inadvertently connected to 3-phase line/line voltages or to
240V when selected for 120V, or any other incorrect voltage, these suppressors are
likely to fail in a short circuit mode. This will be demonstrated by repeated mains
fuse failure at power up.
Even in this case of extreme over-voltage, the DPR 504 is protected against failure,
and the simple removal of the damaged suppressors will allow the unit to be used
again. It is important, however, that they are replaced immediately to ensure
continued protection.
Before attempting to remove the damaged suppressors, ensure that the unit is
unplugged and totally isolated from any power supply.
8.2 Separating signal and chassis ground
In some installations, it might be necessary to separate the electronic signal 0V
ground from the chassis ground to avoid earth loops.
Since both the inputs and outputs of the DPR 504 are balanced, correct connector
wiring should be alleviate this problem. Prior to continuing with this procedure, it
is recommended that you recheck all audio wiring for correctness.
Should it be necessary, then the simple removal of an internal wire link
accomplishes this task.
To remove the wire link, you will need to remove the top cover of the unit, and
then remove the top PCB, and 4 LED PCBs. The chassis link point will then be
accessible, located between C512 and C502 labels (white silk screen) on the main
On no occasion should the incoming safety ground wire be disconnected from
the line cord or from the internal chassis connection as an alternative to this
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9 Warranty Information
When sold to an end user by BSS Audio or a BSS Audio Authorised Reseller, this
unit is warranted by the seller to the purchaser against defects in workmanship and
the materials used in its manufacture for a period of one year from the date of sale.
Faults arising from misuse, unauthorised modifications or accidents are not
covered under this warranty. No other warranty is expressed or implied.
If the unit is faulty it should be sent to the seller of the equipment, in its original
packaging with shipping prepaid. The unit will be returned to you when the repair
has been completed. If the unit was purchased in the European Union, you may, as
an alternative, return the unit to any other BSS distributor in the European Union.
You should include a statement listing the faults found. The unit’s serial number
must be quoted in all correspondence relating to a claim.
We recommend that you record your purchase information here for future
Dealer Name:
Dealer Address:
Post/Zip Code:
Dealer Phone No.:
Dealer Contact Name:
Invoice/Receipt No.:
Date of Purchase:
Unit Serial Number:
In keeping with our policy of continued improvement, BSS Audio reserves the right
to alter specifications without prior notice.
The DPR-504 was designed and developed by BSS Audio, Hertfordshire, England.
Phone (+44) (0)1707 660667. Fax (+44) (0)1707 660755.
World Wide Web address: http://www.bss.co.uk
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10 Specifications
10.1 Input section
Balanced 12k ohm differential
>-50dB 20Hz-20kHz
XLR3-31 or equivalent style
10.2 Output section
Balanced and floating to drive 600 ohm loads
+20dBv into 600 ohm load
+/-1dB 20Hz to 20kHz. Ultrasonic low pass filter
-3dB at 32kHz
Measured to CCIR 468-2
Zero attenuation <-86dBv
Maximum attenuation <-90dBv
Distortion THD <0.05% 20Hz to 20kHz
SMPTE IM <0.02%
Connector XLR3-32 or equivalent style
10.3 Operating controls
Key filter
Key width
Key source
EXT Socket
Variable between 100Hz and 20kHz centre frequency
Variable between 0.5 and 10 octaves
Switchable internal or EXTernal via 1/4" RTS jack
Variable between +20dBv and -50dBv
Audio attack switchable FAST (20uS) or AUTO (40uS 5mS) program dependant
Combined Hold/Release function variable 1mS to 4S
Hold period tracks proportionally with release
Release has custom audio taper
Switchable attenuation between -70dB and -20dB
Stereo linkable in pairs; channel 1/2 and channel 3/4
Channel 1 and 3 become masters
3 pole 1/4" RTS jack socket to provide unbalanced
access into key side chain
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10.4 Metering
Key level Simultaneous average and peak reading 12 point LED
display showing 28dB range of Key side-chain signal
Gate open Single triangular LED showing exact gate status
Mimics response profile as set by attack and release
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