CAUTION - MAINS FUSE
TO REDUCE THE RISK OF FIRE REPLACE THE MAINS FUSE ONLY WITH THE
SAME TYPE, WHICH MUST BE A CLASS 3, 230 VOLT, TIME DELAY TYPE, RATED AT
80mA WHERE THE MAINS INPUT VOLTAGE SWITCH IS SET TO 230 VOLTS AC. AND
160mA WHERE THE MAINS INPUT VOLTAGE IS 115 VOLTS AC. ALL FUSES MUST COMPLY
WITH BS EN 60127-2:1991, SHEET III. THE FUSE BODY SIZE IS 20mm x 5mm.
CAUTION - MAINS CABLE
DO NOT ATTEMPT TO CHANGE OR TAMPER WITH THE SUPPLIED MAINS CABLE.
CAUTION - SERVICING
DO NOT PERFORM ANY SERVICING. REFER ALL SERVICING TO QUALIFIED
TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK DO NOT EXPOSE THIS
EQUIPMENT TO RAIN OR MOISTURE.
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The DL441 is a quad channel compressor / limiter designed to
meet the needs of professional studio and live sound applications. It may
be used in balanced or unbalanced systems and each channel is
independently switchable between +4dBu and -10dBv operating levels by
means of a rear panel button. In addition to the compressor / limiter,
each channel also contains an independent, fast-acting peak limiter.
The compressor section features a highly developed, auto attack/release
system which adapts itself to the programme material being processed and
is equally effective on individual sounds or complex mixes.
To maximise flexibility, each channel of the DL441 is switchable between
traditional ratio (hard knee) and soft-knee operation; in the soft-knee
mode, the transition from unity gain to gain reduction at the selected
ratio is progressive and occurs over a nominal 15dB input level range. The
four channels may be operated independently or linked in pairs for true
Traditionally, soft-knee compressors are preferable for unobtrusive level
control or for the control of finished mixes, whereas ratio type
compressors are generally considered more successful in creative
applications or where large amounts of gain reduction are required. By
offering a choice of both modes, the DL441 is capable of outstanding
results in a very wide range of studio and live sound situations.
Also included in each channel of the DL441 is a peak limiter which allows
the user to set an absolute output signal level that will not be exceeded.
If the peak limiter threshold is exceeded for more than a few
milliseconds, additional gain reduction will be applied to reduce the
overall signal level to within accepted limits without distortion. Once
the peak has passed, the system gain will return to normal after a period
of about one second. This facility is extremely valuable both in live
sound applications, for driver protection, and in digital recording where
an absolute maximum recording level exists. Furthermore, when deliberately
overdriven, it can be used creatively to produce level "pumping"
effects which can be useful on electric guitar or rock vocal sounds.
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The DL441 is designed for standard 19" rack mounting and occupies 1U
of rack space. Avoid mounting the unit directly above power amplifiers or
power supplies that radiate significant amounts of heat and always connect
the mains earth to the unit. Fibre or plastic washers may be used to
prevent the front panel becoming marked by the mounting bolts.
INPUTS and OUTPUTS: Both the input and output XLRs may be used either
balanced or unbalanced, the wiring convention being: pin 1 Ground, pin 2
Hot and pin 3 Cold. The rear panel push buttons should be released (out)
for +4dBu operation or depressed (in) for -10dBV operation in order to
optimise the internal gain structure of the unit. For use with unbalanced
systems, the Cold pin (3) must be grounded at both input and output XLRs.
If earth loop hum problems are encountered, don't disconnect the mains
earth but instead, try disconnecting the signal screen inside the XLR
connector at one end of the cable connecting the DL441 to the patchbay. If
such measures are necessary, balanced operation is recommended.
The unit will have been supplied with a power cable suitable for domestic
power outlets in your country. For your own safety it is important that
you use this cable. The unit should always be connected to the mains
supply earth using this cable.
If for some reason the unit is to be used at a mains input operating
voltage which is different to that as supplied, the following procedure
must be carried out.
- Disconnect the unit from the mains.
- Using a number 1 size pozidrive
screwdriver, remove the two self-tapping screws holding the voltage
selection switch cover plate on the rear panel.
- Remove the cover plate and slide the
switch fully to its opposite end.
- Rotate the cover plate one half turn,
(180 ) and refit the two screws.
- Replace with a correctly rated fuse for
the selected operation voltage.
- Re-connect to mains power source.
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All four channels of the DL441 are identical and may be used completely
independently or linked for stereo operation. Separate linking switches
are provided to link channels 1 and 2 or channels 3 and 4. In the linked
mode, only the left hand channel controls are functional and serve as
master controls, though the channel bypass switches remain independent. In
linked mode, the compressor/limiters and peak limiters of the two linked
channels track together to avoid the inevitable image shifting that occurs
if the two channels of a stereo signal are treated independently.
Threshold: Determines the input level above which gain
reduction will be applied and may be set in the range -40 to +20dB. When
Soft Knee compression is selected, the onset of compression is progressive
over an input range of approximately 15dB, above which level conventional
ratio compression is applied. For this reason, the signal level may appear
to fall when the compressor is switched from Hard to Soft Knee operation
and some readjustment of the threshold setting may be required.
Hard/Soft: Selects Hard or Soft Knee
operation. In general, the Soft Knee mode provides the least obtrusive
gain control and is often the preferred setting when treating finished
Ratio: Sets the final compression
ratio that will be applied once the threshold level is exceeded. The ratio
may be continuously adjusted from 1.2:1 to infinity:1 allowing the
possibility of true hard limiting.
Gain: During compression, the signal
is attenuated depending on the dynamics of the signal. As a result, gain
may need to be applied in order to produce the desired output level. The
GAIN control has a range of -20dB to +20dB. If the limiter is in
operation, only increase GAIN until the limiter operates on signal peaks.
Any further GAIN will just cause excessive limiting, thus reducing the
effect of the compressor.
Bypass: This switch will disable the
functioning of the Compressor section and the Peak Limiter. If operating
in Stereo Linked mode, both linked channels will be bypassed
The DL441 Bypass is a 'hard bypass' which directly links the input sockets
to the output sockets whenever Bypass is active. The adjacent red LED
indicates the Bypass status.
Gain Reduction Meter: An eight segment
LED bargraph meter continuously monitors the gain reduction applied by the
compressor/limiter over the range 0 to 30dB.
Output Level Meter: This is a
5-segment LED bargraph level meter that monitors the level of the output
signal over the range -10dB to +10dB with reference to the selected
(-10dBu or +4dBu) operating level.
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Level: This control sets an absolute
limit to the level that the output signal will not be permitted to exceed.
This limiter is very fast acting enabling it to control any peaks without
audible distortion. If the output signal is so high as to cause the
limiter to operate for more than 20mS, the system gain is automatically
reduced to bring the signal back within range. The system gain is then
returned to normal over a period of approximately one second.
The compressor Gain control should be used to ensure that the peak limiter
operates only rarely if at all if the limiter is to be used purely for
peak protection. Alternatively, the unit may be deliberately driven into
limiting to produce creative effects.
Stereo Link: These two switches configure channels 1,2 or 3,4 for stereo
operation where the left hand channel/s controls act as masters for both
audio channels. The same degree of gain reduction is applied to both audio
channels to prevent image shifting which would otherwise occur whenever
the left and right signal dynamics varied from each other by any
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The unit should be connected in-line with the signal to be processed via
suitable insert points. Ensure that the insert send and return level on
your console matches the operating level set up using the rear panel
push-buttons on the DL441. If not, select the appropriate operating level
on the DL441.
For mono use, each channel may be considered as being completely
independent and set up accordingly. For use with stereo signals such as
complete mixes or submixes, the appropriate pair of channels should be
switched to Stereo ink mode and all setting up done using the left hand
Setting up is simplified by the auto attack and release system which
continually optimises the attack and release times to suit the dynamics of
the material being processed. The ratio setting depends on how firmly the
signal dynamics need controlling; as a rule, higher ratios provide a
higher degree of control but also tend to be more audibly apparent in
operation when high levels of gain reduction are required. In general, a
higher compression ratio may be used when in Soft Knee mode without
compromising the subjective sound quality.
Having selected Hard or Soft Knee and set a suitable Ratio, setting up is
simply a matter of adjusting the Threshold control until the desired
amount of gain reduction occurs. This is judged partly by ear and partly
by observing the gain reduction meter. Normally a maximum gain reduction
of between 8dB and 12dB will be adequate. If more gain reduction appears
necessary, it is worth considering applying a conservative degree of
compression during recording and then further compression while mixing.
Compressing during a mix does increase the subjective level of tape and
other background noises during pauses and quiet passages as maximum gain
is applied when the signal level is minimum. For this reason, it is unwise
to use more compression than is strictly necessary.
Finally, the Gain control may be set to provide the required output level
using the level meter as a guide. Avoid running at very high output levels
as this reduces the available amount of signal headroom and could lead to
distortion in extreme cases. Once the gain is correct, the Peak limiter
Level control should be adjusted so that the limiter LED only lights
briefly on extreme signal peaks. Alternatively, the Peak limiter Level may
first be set to the desired value and then the compressor Gain control
adjusted to ensure minimum limiter activity.
The Peak limiter has no bypass control, but turning the Level control
fully clockwise will effectively prevent the limiter from operating.
Compressors are often accused of dulling the sound being processed, but
the auto circuitry in the DL441 has been designed to allow transient
sounds to pass through cleanly, thus maintaining the clarity and
transparency of the original source. Soft Knee operation is usually
preferable when unobtrusive gain control is required.
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INPUT IMPEDANCE 20KOhm
MAXIMUM INPUT LEVEL +21dBu (+17dB ref. +4dBu)
OUTPUT IMPEDANCE 50 Ohm
MAXIMUM OUTPUT LEVEL +20dBu
BANDWIDTH <12Hz to 35KHz -1dB
CROSSTALK @10kHz Better than -80dB
@20kHz Better than -75dB
OUTPUT BALANCE Better than 40dB 20Hz to 10kHz
Better than 40dB 20Hz to 10kHz
NOISE AT UNITY GAIN reference +4dBu
Wideband 22Hz -
A Q-Pk CCIR
Unity Gain, +4dBu Input <
< 0.015% < 0.035%
+14dBu Input, 10dB G.R. <
< 0.1% <
POWER REQUIREMENTS 115Volt or 230Volt at 50-60Hz, 13 Watts
FUSE RATING 80mA for 230Volt, 160mA for 115Volt
CONFORMING TO BS EN 60127-2:1991 SHEETIII
FUSE TYPE 20mm x 5mm, Class 3 Slo-Blo, 250Volt working
CASE SIZE 482mm (w) x 44mm (h) x 200mm (d)
WEIGHT (incl packaging) 3.4 Kgs