The MLA-2 Precision Stereo Compressor is
designed for recording, mixing and mastering applications where ultimate sonic performance
The MLA-2 employs state-of-the art analogue circuits to provide a perfect
solution for recording and mastering, especially used in conjunction with Prism
Sound A/D and D/A converters.
The MLA-2 was developed in association with engineer/producer Leif Mases. Leif's work
with a diverse range of artists including Abba, Led Zeppelin and Black Sabbath is
demonstrated by the MLA-2's design with the engineer in mind:
- 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 gain reduction or signal level (VU) metering
- Low noise
- Extended headroom with maximum input amplitude of +28dBu
- Extended frequency response
- Low distortion
- Electronically balanced inputs and outputs
CONCEPT AND CAPABILITIES
The MLA-2 Precision Stereo 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, to provide a natural and warm sound and to offer a greater degree of
transparency in the presence of compression. The MLA-2 has precise controls to enable
exact re-creation of previous configurations.
Early compressors or limiting amplifiers had few controls and were simple to operate.
Many such devices are still popular today, despite (or perhaps as a result of) the
limitations of their early technology.
Such devices often employed a 'drive' control which provided progressively more
compression (depth) and input gain when increased.
Some later devices split this function into two controls, which had 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, so peak level can vary only slightly, determined by the 'ratio' which sets the
severity of compression.
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 dramatically.
The MLA-2 reduces this effect, particularly for moderate amounts of gain reduction, by
making small adjustments to the threshold, depending on the ratio setting. This results in
less variation of output amplitude for a given input range, as the ratio is varied.
For larger amounts of gain reduction (more than about 4-6dB), as 'ratio' is increased,
it is necessary to compensate by increasing 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.
The gain element of the MLA-2 is an optical device rather than the more conventional
VCA. This provides a smooth transition between linear and compressed operation with a low
level of noise.
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; 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 pumping distortion so noticeable in
less sophisticated designs.
- The analog inputs are on a three pin XLR connector with positive and negative signal
polarities on pins 2 and 3 respectively, and ground on pin 1. Pins 2 & 3 have a
high impedance path to the chassis earth.
- Differential input impedance: 27kR (pin 2 to pin 3)
- Single-ended input impedance: 27kR (pin 1 to 2 or 3)
- Coupling impedance to chassis: 1.0MR (chassis/pin 1 to 2 or 3)
- Common-mode range: 10 Vrms (note: I/P is not floating)
- The analog outputs are on a three pin XLR connector with positive and negative signal
polarities on pins 2 and 3 respectively, and ground on pin 1.
- Differential output impedance: 62R (pin 2 to pin 3, balanced)
- Single-ended output impedance: 31R (pin 1 to 2 or 3, unbalanced)
Specifications quoted are to AES17-1991 (ANSI S4.51-1991), with input level set
For 'Compressor in' measurements, the in/out switches are illuminated and other
Input Gain : -10dB, Output Gain : +10dB, Threshold : High,
Ratio : 2:1, Attack : 0.100ms/dB, Release : 0.10sec/dB
- Maximum input amplitude : +28dBu
- Output noise:
Compressor out: <-100dBu
Compressor in: <-90dBu
- Frequency response : + 0.1, -0.4dB, <1Hz to > 50kHz
- -3dB points: 0.03Hz to >350kHz
- Crosstalk : less than -100 dB, 20 Hz to 20 kHz (undriven input terminated 150R)
- Dynamic range : (measured at -32dBu)
Compressor out: >125dB
Compressor in: >107dB