george.shilling.com

Prism Sound Maselec Master Series MLA-2 Compressor and MEA-2 Equalizer

Review by George Shilling

Prism Sound is well known for its A/D and D/A converters, widely used in CD mastering, classical recording and higher-quality studio recording. Its key engineering staff have been developing DSP audio products since the late 1970s. The company has also developed sophisticated measuring equipment to assess the performance of its digital converters. These devices are now widely used by recording studios, manufacturers and broadcast facilities world-wide. Meanwhile, producer and engineer Leif Masses, known for his work with such giants as Led Zeppelin, Jeff Beck and Black Sabbath, has also been involved in equipment design for some years. He started off setting up and modifying equipment at Abba's Polar Studios in Sweden. Masses is widely known for his development of an 'alternative' equalizer circuit for the SSL E Series desk, known as the Maselec. He also designed a 'brick wall' Limiter for broadcast use which became popular with mastering engineers. In recent years Masses has recorded new bands, but lately scaled down recording commitments to concentrate on equipment design. This is a lengthy procedure as equipment is tested extensively by trusted colleagues in 'real' situations during the development stage. Maselec equipment was once marketed by the now defunct SSE Marketing. Masses subsequently co-produced an album with Carey Taylor, founder of Metropolis Studios, London, and Taylor introduced him to Prism. In this collaboration, the Maselec and Prism names both grace these two imposing units. The Compressor has the appearance of test equipment. This 2U stereo unit has a front panel dominated by two huge VU meters. These look as if they belong in a school science lab, with black on white legending instead of the usual red and black on cream. The weighty (9lb) case is no-nonsense bare steel; the (perhaps slightly thin) front panel is finished in a durable matt grey, with very clear white legending. The two channels are arranged side by side and between them there are small toggle switches for Power On/Off and Link On/Off. Each channel features huge stepped rotary gain controls for input and output levels. Smaller rotary controls adjust Ratio, and Attack and Release times, each of which have six switched positions. The VU meters are accompanied by VU/GR and compressor In/Out toggle switches. On the rear panel, inputs and outputs appear on well-spaced XLR connectors. Mains is supplied via an IEC socket with a fuse, and there is a primary power switch on the rear with a built-in light. An external switch allows voltage selection. There is also a large binding post with a screw-top for earthing, and, unusually, a toggle switch labelled Normal/High Threshold. When you turn the unit on, there is a disappointing lack of flashing lights. If the compressor channels are switched in, you will see a green light glowing on each channel, and, well, that's all. The VU meters are not illuminated, which I found a little disappointing. However, the meters are so huge that even in fairly low light they are still visible. Not only that, but the green lights on each channel turn red when the compression threshold is crossed. The Input gains have a range from -20dB to 0dB in 1dB switched steps. The Output gains are similar and range from 0dB to +20dB. Every single position is labelled, and with such large knobs there is no chance of confusion when recalling previously noted settings. The compressor works optically rather than the more commonly used VCA method. This provides a smooth transition across the threshold as the compression starts to work. Like the Urei 1176, the MLA-2 has a fixed threshold: increased compression is obtained by increasing the input gain. The advantage of this is that when increasing the input gain to increase compression, the output level remains fairly constant (depending on the chosen ratio). You do not have to alternate adjusting threshold lower then turning up the output to compensate, as you would on other designs. Unlike the Urei, the Input and Output gain knobs have no effect if the compressor is switched out, which helps when matching compressed and uncompressed levels. This unit has a much more refined character to it than many of its competitors. The Maselec is no slouch if you want heavy compression, but it is harder to make it pump than most. The Maselec has a very 'musical' sound to it, allowing the signal to breathe, yet smoothing the level in a very pleasing way. Nominal attack times range from 0.005 to 1.5 ms/dB, which represent average attack times for typical audio programme. Similarly, the Release times can be set from 0.02 to 1.0 sec/dB which represent the maximum release times. One of the key features of the MLA-2 is the ability of the circuitry to vary these times according to program content. Short duration peaks will cause shorter release times. This enables more transparent operation than can be obtained with less sophisticated units, and I thought it sounded great on a variety of program material. The Ratio can be set between 1.4:1 and 8:1 (six positions). Changing this setting also adjusts the threshold to cleverly maintain output level for small (i.e. less than 6dB) amounts of gain reduction. This system works well, and enables the user to hear the difference between different ratios without the usual corresponding jumps in gain. It is at this point I should explain the rear-panel Threshold switch. The manual suggests setting this to High for mastering applications and Low for recording. Actually, the legending on the unit indicates High and Normal rather than Low. As a recording engineer I would agree with that - we are much more 'normal' than mastering engineers(!) The large toggle switch locks into place and has to be pulled outwards to change its position. The Normal (Low) setting puts the threshold about 9dB lower than in the High position. (The actual threshold depends on the other settings.) This philosophy assumes that you want substantially more compression when recording as opposed to mastering. That is mostly true, and even when not the case, the 20dB ranges of the input and output controls allow you to set a wide variety of compression amounts. However, I have a natural aversion to switches placed on the back panel of any unit, as you inevitably want to change them at some point. This is obviously a nuisance when the unit is in a rack. The Link does what you expect, but again features enhanced circuitry. The "ImageLink" intelligent dynamic stereo linking system is program dependent. Momentary gain-reduction due to short duration peaks will not be linked. This means that the integrity of the stereo image is maintained, but obvious pumping effects from short peaks on one channel are avoided. This system works beautifully, and enables a clarity and smoothness which you just cannot obtain from most stereo units. The manual states that the ImageLink system is independent of all other controls, i.e. different ratio, attack and release can be set on each channel. I cannot imagine wanting asymmetrical stereo compression very often though... The manual examines every detail of the unit's functions and contains many charts of test results, no doubt obtained with Prism test equipment. All the theory has been put into practice impeccably. The audio performance is exceptional: the manufacturers' figures quote huge dynamic range and a flat frequency plot over a huge range below and above the generally acknowledged range of human hearing. I am a great believer in the importance of this extended range. I am really sold on this unit. It is by no means cheap, but I believe the right combination of scientific practice and recording engineers' desires have come together in this unit. Less fully featured than some similarly priced competitors, it nevertheless delivers in the important area: it sounds superb. It worked well on vocals, but would not necessarily be my first choice for that particular application. However, on stereo program material it really comes into its own. Internally the construction of both machines is similar, and most impressive. In each, two circuit boards are linked via ribbon cable. The main board mounted behind the front panel includes a huge number of resistors, including one for each position of the knobs - no continuous pots are used. At the rear, another board is mounted horizontally and connected to the inputs and outputs, next to a huge encased torroidal mains transformer. The MEA-2 is a two channel equalizer. It is housed in a bulky 3U case, with similar build to the MLA-2. I really feel that a thicker front panel would be more appropriate, as lazy people often bolt units into racks with just two bolts. I predict there might be a few warped front panels on some of these units before too long. Apart from that criticism, the unit feels very solid, although at this high end of the market you might expect a more 'snazzy' finish. However, the important practical aspects have all been thoroughly satisfied. The legending is large and clear, and the array of large switched knobs all feel very solid. They are easy to set, clicking positively into place. The back panel features inputs and outputs on XLRs, an earthing binding post, a fused IEC mains socket with voltage selector and a primary mains switch with a light. In the centre of the front panel, a small toggle is provided as a secondary mains switch. There is no indicator of the presence of mains power on the front panel. However if power is switched on and present, the two large EQ bypass switches glow dimly green when pushed in and EQ is on. These are centrally mounted and usefully adjacent to each other. Each channel comprises four bands of EQ, but when you look at the legending you will realise that this box is something out of the ordinary. For a start, each band's gain control can boost or cut the following amounts: 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0 and 8.0dB. This suggests a mastering rather than recording application, with the stepped rather than continuous controls, and the seemingly small amount of maximum boost/cut. However, a look at the frequency selector knobs reveals an unusual approach here, too. The two low frequency bands and the two high frequency bands of each channel are 'paired' thus: each control has 21 frequency settings; LF1 ranges from 19 to 530Hz, while LF2 ranges from 21 to 572Hz, filling in the gaps. Similarly, HF1 ranges from 617Hz to 24kHz, while HF2 ranges from 665Hz to 27kHz. This gives a complete set of an astonishing 84 frequencies to select from for each channel, about 8 per octave. The overlapping of the paired bands means you never have the problem of running out of frequencies having started with the 'wrong' band. A corresponding set of controls adjust bandwidth or set shelving characteristics for each band. The two LF bands can be set to a low frequency shelf and the two HF bands to a high frequency shelf. The bandwidth control has five bell-curve settings labelled 4, 6, 9, 14 and 20. The curves are asymmetrical to give a more useful and musical EQ, so without diagrams it is difficult to explain the exact settings. Suffice to say they work well in practice for a broad range of applications. The limit of only 8dB cut/boost may preclude the use of this unit in some recording applications. However, at the cost of losing one frequency band, you can set two bands to adjacent frequencies and by overlapping them virtually obtain +/-16dB cut/boost at any frequency. Boosting two adjacent narrow bands gives a pleasing spread of coloration. The superb design of this unit means that such gains can be applied without fear of distortion or nasty phase shifts. Like the MLA-2 this unit boasts astonishing audio performance figures and I would love to have one of these strapped across my mix, whether in the studio or in the mastering room, where I am sure their use will be popular despite the high price tag.