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:

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 gain reduction or signal level (VU) metering

Technical:

• 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.

DYNAMIC BEHAVIOUR

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.

SPECIFICATIONS

Analogue inputs:

• 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)

Analogue outputs:

• 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)

Performance:

Specifications quoted are to AES17-1991 (ANSI S4.51-1991), with input level set to +22dBu.

For 'Compressor in' measurements, the 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 : +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