Maselec MLA-2 User manual

MASELEC MLA-2
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MLA-2
precision
stereo compressor

MASELEC MLA-2
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1. INTRODUCTION
The MLA-2 Precision 2-Channel Compressor is intended for professional audio use in
recording, mixing and mastering applications where high performance is required.
The MLA-2 provides a unique set of tools, carefully crafted to provide a compressor whose
sonic character was the most important design objective.
The unique character of the device is evident in the technical description of the behaviour of
the device.
2. SUMMARY OF MLA-2 FEATURES
Operational:
• Easy to operate with input gain controlling compression depth (drive)
• Minimal gain adjustment needed when changing ratio
• Optical gain element for smoothness and freedom from noise
• Dynamically-controlled attack and release to minimize pumping
• Precision stepped controls
• “ImageLink” Intelligent dynamic stereo linking system
• Output gain make-up
• Switchable metering (VU): gain reduction or signal level
Technical:
• Low noise
• Extended headroom with maximum input amplitude of +28dBu
• Extended frequency response
• Low distortion
• Electronically balanced inputs and outputs

MASELEC MLA-2
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3. GETTING STARTED
It is not necessary to read the entire manual before being able to use the MLA-2. This section
contains all the information required for you to get going.
3.1. Unpacking your MLA-2
Check that the slide switch mounted on the rear panel is set to the correct mains voltage
range.
115V setting: 90V-130V ac 50-60Hz
230V setting: 180-260Vac 50-60Hz
The plug fitted to the mains lead must be of the correct type.
If not, DO NOT CONNECT THE MAINS SUPPLY.
Please keep the packaging for re-use in the event that the unit should be shipped to another
location or if it ever needs to be returned to the retailer
or distributor.
3.2. Using the MLA-2 for the first time
Refer to section 21 for wiring details of connecting leads.
• Connect a source of balanced audio to the input connectors on the MLA-2.
• Connect the output of the MLA-2 to a balanced audio input.
• Connect the mains supply to the MLA-2 unit.
There is a main power switch on the rear of the unit and an auxiliary (standby) switch on the
front, which is more convenient to use if the equipment is rack mounted and the rear panel is
inaccessible
The indicator lamp in the rear-mounted mains switch should illuminate when switched on.
If it fails to light the power may be absent or the unit may be faulty.
Check the fuse and replace if it is blown. (315mAT, slow blow).
If the problem is still evident contact your retailer or distributor.
Set the rear-panel Threshold switch to:
• ‘Low’ for recording or
• ‘High’ for mastering or for working on a stereo mix.
Switch the secondary power switch on the front of the MEA-2 to 'ON'.
Set the meter function switch to ‘G.R.’ (Gain Reduction).
Set the Compressor In/Out switch to ‘In’.
By momentarily muting or disconnecting the inputs, check that the meter indication is 0dB.
Re-connect or un-mute the inputs.
A suggested starting point for control settings is:
• Ratio: 2
• Attack: 0.100
• Release: 0.10
• Input Gain: -10dB
• Output Gain: +10dB
(all controls set to 12 o’clock position)
The unit is now ready to use.

MASELEC MLA-2
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3.3. MLA-2 product concept and capabilities
The MLA-2 Precision 2-Channel Compressor is designed to provide very high quality signal
processing for the most demanding professional applications.
It has been carefully developed in conjunction with balance engineers, producers and
mastering engineers to be easy to use, and to provide a natural and warm sound and to offer
a greater degree of transparency in the presence of compression.
The MLA-2 also offers precision controls, which enable exact
re-creation of previously used configurations.
3.4. Driving the compressor
Early compressors or limiting amplifiers had few controls and were simple to operate.
Many such devices are still popular today, despite the limitations of their early technology.
Such devices often employed a ‘drive’ control, which provided progressively more
compression (depth) and input gain when rotated.
Some later devices split this function into two controls, which would have to be operated
together to achieve the same progressive effect without marked shifts in signal amplitude.
The MLA-2 uses the ‘drive’ principle and the control is called ‘Input Gain’. The compression
threshold is left unchanged while the input gain is adjusted to alter compression depth.
This has the advantage that gain and compression depth are adjusted together and so peak
level will only vary by a small amount, determined by the ‘ratio’, which sets the severity of
compression.
Therefore to increase the depth of compression, or to bring the quieter parts of the mix or
instrument dynamics forward, simply rotate the input gain control clockwise until the desired
effect is obtained.
Another problem with less sophisticated designs is that as the ‘ratio’ is increased the output
level drops.
The MLA-2 reduces this effect, particularly for moderate amounts of gain reduction, by
making automatic adjustments to the threshold, depending on the ratio setting.
This results in less variation on output level, for a given input range, when the ratio is varied.
For larger amounts of gain reduction it might be necessary to compensate by adjusting the
‘output gain’.
In general, for mastering applications use the 'High' threshold setting
(switch on the rear of the MLA-2)
And for recording applications (such as for an instrument, in an insert point)
use the 'Low' threshold setting.
Please note: ‘High’ setting changes the 0 VU setting to +10dBu (6dB higher)

MASELEC MLA-2
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3.5. Dynamic behaviour
The gain element of the MLA-2 is an optical device.
This provides a smooth transition between linear and compressed operation with a low level
of noise and distortion.
One of the main problems for compressors is recovery after loud transients, often called
‘pumping’.
To avoid this the attack and release times of the MLA-2 are dynamically
controlled - i.e. program dependent.
In short, the nominal attack and release times set by the controls are modified according to
the program content. This is a key feature of the MLA-2 and one which enables the device to
operate effectively and transparently on the
most difficult signals without introducing the excessive distortion or pumping.
4. OPERATION
The unit is designed for either stereo or 2-channel operation and each channel is controlled
independently by an identical set of controls.
A linking facility is provided that enables tracking of the two channels for stereo operation.
When selected, stereo linking is intelligently controlled by the “ImageLink” system described
below.
Each channel has controls for:
• Compressor in/out
• Input gain
• Output gain
• Ratio
• Attack
• Release
Some of these parameters are dynamically controlled. More detailed descriptions are
provided below.
Metering is provided for each channel and meter function may be signal amplitude (VU
dynamic characteristic) or gain reduction (GR) according to the ‘meter’ function switch. The
meter scale is in dB units.
There is a global threshold selection, provided by a toggle switch on the rear of the unit. This
is designed to be set at installation and should not require changing afterwards.
See section 20 for details of the threshold range switch.
The Threshold toggle switch affects the meter in VU mode:
• Normal Threshold setting (on the back): 0 VU = +4dBu
• High Threshold setting: 0 VU = +10dBu
The MLA-2 is galvanically bypassed (inputs and outputs) when the power is off.

MASELEC MLA-2
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4.1. Input gain
This control attenuates the input audio signal before the gain-reduction (compressor) circuit,
over the range 0dB to -20dB in 1dB steps.
Increasing the input gain (or reducing attenuation) will drive the compressor harder. The
depth of compression will be increased.
Output level will also increase, subject to other settings including the compression ratio and
attack and release times and the audio signal
amplitude and dynamics.
Increasing the input gain can not cause overload.
4.2. Output gain
This control increases the output audio amplitude after the gain-reduction circuit, over the
range 0dB to +20dB in 1dB steps.
The Output gain control does not affect the amount of gain-reduction (compression).
[Note: Refer to section 3.3 for a brief overview of MLA-2 operation]
4.3. Ratio
This control adjusts the severity of the compression applied to loud signals (i.e. those which
exceed the compression threshold).
The MLA-2 automatically adjusts the threshold to maintain output level for small amounts of
gain-reduction (< 4dB GR).
Ratios available: 1.4:1 , 1.7:1 , 2:1 , 3:1 , 5:1 , 8:1
4.4. Attack time
Setting of this control will determine the attack-time. For real audio programme with complex
waveforms the setting will indicate the average attack-time.
[Note: Refer to section 3.3 for a brief overview of MLA-2 operation]
Nominal attack times (ms/dB) are: 0.005 , 0.020 , 0.100 , 0.500 , 1.0 , 1.5
4.5. Release time
Setting of this control will determine the release-time. For real audio programme with complex
waveforms the setting indicates the maximum release-time caused.
Short duration peaks will not cause long release times.
[Note: Refer to section 3.3 for a brief overview of MLA-2 operation]
Nominal release rates (sec/dB) are: 0.02 , 0.05 , 0.10 , 0.20 , 0.40 , 1.0

MASELEC MLA-2
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4.6. VU / GR
This control switches the meter reading between:
vu Meter displays the output level.
g.r. Meter displays the average gain-reduction (dB).
4.7. Compressor in/out
This control switches the compressor, including input gain and output gain controls, in and out
of circuit.
out: Compressor by-passed. Meter displays input amplitude in VU mode.
in: Gain-reduction (compressor) circuit is active.
4.8. Compressor indicator lamp
This bi-colour indicator indicates if the compressor’s gain reduction circuit is active:
Green Indicates that the compressor is in circuit (on).
Red The colour changes to red when the input signal causes gain reduction.
This is particularly useful when the two channels are stereo linked, as the VU meters
will not show which channel is causing the gain reduction (dominating).
The light will also assist when the unit is located at a greater distance from the user.
4.9. Stereo linking
This switch enables the intelligent "Image-Link" system that matches the gain reduction
applied to both channels. The linking is programme dependant.
Momentary gain-reduction due to short duration peaks will not be linked.
This technique maintains the integrity of the stereo image, while avoiding obvious pumping
effects resulting from momentary transients on one channel.
The ImageLink system is independent of all other controls. Different ratio, attack and release
can be set to either channel.
4.10. Threshold range
This control is located on the rear panel and is designed to be pre-set at the time of
installation. It selects between two ranges, ‘Normal’ for studio use and ‘High’ for Mastering
use.
In the ‘High’ setting, for a given audio programme the depth of compression will be less.
The compression threshold is modified dynamically within these ranges by the MLA-2 control
circuitry, according to programme content.
Normal Threshold: Threshold range -10.5 dBu to +14.5dBu
High Threshold: Threshold range -1.5dBu to +23.5dBu

MASELEC MLA-2
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5. CONNECTORS
The MLA-2 has symmetrical input and output amplifiers with no impedance or loading
difference between pin 2 and pin 3.
Some users and equipment use pin as ‘hot’ and pin 3 as ‘cold’, others implement the
opposite.
The MLA-2 works perfectly in both cases.
Balanced analogue audio connections should use a good-quality screened twisted-pair lead.
Unbalanced connections must also be screened.
The inputs are ‘ground floating’, and both pin 2 and pin 3 must be connected.
5.1. Output connections
The outputs are electronically balanced and both pin 2 and pin 3 must be connected.
The level remains unchanged when an output is driving an unbalanced input.
Note: When driving unbalanced loads with the MLA-2 the maximum output level is reduced by
approximately 6dB from the nominal +28dBu.
5.2. Rear panel connectors
A. Audio I/O
• Left Channel Input
• Left Channel Output
• Right Channel Input
• Right Channel Output
B. Earthing Stud – Connected to mains earth and the case
C. IEC Mains Inlet (fused).

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6. SPECIFICATION
6.1. Analogue inputs
The analogue inputs are on three pin gold plated Neutrik XLR connectors with
signal on pins 2 and 3 respectively, and screen on pin 1.
Pins 2 & 3 have a very high impedance path to earth.
Differential input impedance: 100kohm (pin 2 to pin 3)
Unbalanced input impedance: 100kohm (pin 1 to 2 or 3)
6.2. Analogue outputs
The analogue outputs are on three pin gold plated Neutrik XLR connectors with
signal on pins 2 and 3 respectively, and the screen on pin 1.
Output impedance: 33ohm (pin 2 to pin 3, balanced)
Unbalanced output impedance: 33ohm (pin 1 to 2 or 3)
6.3. Performance specification
in/out switches are illuminated and other settings are:
• Input Gain: -10dB
• Output Gain: +10dB
• Threshold: High
• Ratio: 2:1
• Attack: 0.100ms/dB
• Release: 0.10sec/dB
Maximum input amplitude: +29dBu
Output noise: Compressor out < -99dBu
Compressor in < -93dBu
Frequency response: + 0.1, -0.4dB, <1Hz to > 50 kHz
Crosstalk: less than -100 dB, 20 Hz to 20 kHz
Dynamic range: Compressor out > 128dB
Compressor in > 110dB
6.4. Servicing and repair
There are no user serviceable parts inside this unit.
Repairs should only be undertaken by qualified electronics technicians or engineers.

MASELEC MLA-2
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6.5. Mains transformer voltage selection
The mains transformer has a tapped primary to allow operation at nominal voltages of 115V
or 230V. Ensure that the correct voltage range is selected before using the MLA-2.
6.6. Fuse
There is one mains fuse, accessible externally in the IEC320 mains inlet. If this fuse is blown
it should be replaced by a similar value and type.
20x5mm 250V 315mAT (antisurge, slow)
6.7. Earthing
The unit has an internal link connecting the audio ground to the chassis.
A chassis earth stud is provided on the rear of the unit.
6.8. Physical dimensions
Weight: (10lb) (5kg)
Width: 19 inch (483mm) rack-mountable
Height: 2U (90mm)
Depth: 10.25 inches (260mm) add clearance for connectors
7. ELECTROMAGNETIC COMPATIBILITY
This equipment is intended for use in an electromagnetically controlled environment.
To maintain the performance specification it should not be subject to strong magnetic fields
(such as in the immediate vicinity of a power amplifier or cathode ray tube)
This equipment does not include digital circuitry or generate high frequencies that could be
radiated or conducted from the unit.