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Mixer & Control Surface
Published November 2005
By Hugh Robjohns

SSL AWS900Photo: Mark Ewing

With their latest Superanalogue console, SSL bring the sonics and functionality of their flagship SL9000K to studios with smaller rooms and budgets. In the process, they've incorporated comprehensive control-surface facilities for driving computer DAWs remotely. But can the AWS900 really live up to its pedigree?

The acronym SSL is likely to be recognised immediately by everyone reading this review. The Oxfordshire-based manufacturer Solid State Logic redefined the art of the large-format analogue mixing console some thirty years ago when it launched the original SL4000 desk. This console became a must-have for almost every high-end recording studio around the world, and it has maintained that position — albeit with various updates and improvements over the years — virtually right up to the present day. While the SL9000 series Superanalogue console took over as the flagship product nearly a decade ago, the popularity of the venerable SL4000 has continued, and I noticed a brand-new SL4000 being readied for delivery during my recent factory visit.

SSL recently passed through a rocky patch in the company's long history, but with new management and funding now in place the future is looking bright once again, with four main product lines. The flagship product remains the SL9000K Superanalogue console for music recording and production, and is accompanied by a new generation of digital consoles aimed primarily at the broadcast and post-production sectors: the C100, C200, and brand-new C300.

The other two product lines are closely related to each other, and are both derived directly from the SL9000: the XLogic rackmount equipment, including the Superanalogue Channel which I reviewed back in SOS February 2004; and the AWS900 console, the subject of this review. In order to make the console commercially viable, a way had to be found of reducing the production costs while retaining the Superanalogue sound quality — and that meant moving to surfacemount technology and automated circuit board production. In the process of redeveloping the SL9000 circuitry for the AWS900, it became apparent that surfacemount circuit boards would also lend themselves nicely to rackmounting applications, which led to the development of the XLogic series.

What Exactly Is The AWS900?

The clearest way to look at the AWS900 is as a Superanalogue console in miniature, combined with a bespoke HUI-compatible control-surface interface. It was designed as a high-quality tracking console for use with Pro Tools DAW rigs and the like, but also serves as a superb analogue mixdown desk. It features twenty-four highly specified input channels with switchable E/G-series EQ, in-line functionality, and motorised faders. Unlike the SL9000K desks, which incorporate dynamics in every channel, the AWS is equipped with just two dynamics processors, but these can be assigned to any two channels or outputs. The classic G-series buss compressor is also included, along with very comprehensive 5.1 surround monitoring facilities. Bar-graph metering is built in for all the inputs and outputs, while the two main outputs are displayed on large-format VU meters. In addition to the 24 input channels, there are four stereo effects returns and a pair of main buss direct (cascade) inputs, allowing up to 34 input sources at mixdown. Full snapshot recall and fader/mute automation of the console are available as cost options.

The very elegantly designed and fully integrated hardware control element of the console surface is compatible with any system that supports multiple HUI-compatible surfaces, allowing the console to appear as a continuous 24-fader surface to the DAW. A similar approach is used by Yamaha with their DM2000, DM1000, and 02R96 consoles, and the necessary multi-port interfacing is currently supported by Pro Tools, Logic, Pyramix, SADiE, and Soundscape. At the present time Nuendo and some other DAWs only support a single HUI-compatible interface, and the AWS900 can only provide eight control faders with these systems.

The desk and DAW are linked via multiple MIDI connections, a decision which initially seemed odd — why not use a fast USB interface? However, it was explained that MIDI is an established interface format to which the majority of DAW manufacturers conform (thus maximising compatibility), and using multiple interfaces allows data transfer rates much faster than actually required by the desk. MIDI can also be used over greater distances than USB (up to 15m instead of 5m), which is very useful when the DAW computer is located in a machine room away from the console.

The motorised Alps channel faders and the associated assignable rotary encoders can be switched globally between controlling the console's analogue signal paths and various DAW parameters, allowing a kind of virtual in-line working practice to be set up, building up a monitor mix on the channel faders by remotely controlling the DAW's internal mixer channels.

The AWS900 looks like a 'proper' SSL in every way. It works and sounds like an SSL, and the bespoke DAW interface is extremely ergonomic and very cleverly engineered so that controlling the DAW's signal-processing facilities becomes a natural extension of the console, with the same immediacy and control resolution. Of course, none of this comes cheap in the absolute sense, but it is certainly a lot more cost effective than a fully featured traditional SSL console, and represents an ideal solution for many 'tapeless' studios and smaller post houses. In fact, some of the leading studios around the world have already re-equipped tracking rooms with AWS900 consoles.

Superanalogue Circuitry

The AWS900 console is a single-box product which can be either built into the studio furniture or supported with an optional floor stand. The internal mains power supply has heat sinks running across the rear of the meterbridge, so there are no noisy fans. Borrowing an idea from long-established telecommunications technology, the incoming mains is converted to a high-voltage (400V) low-current supply for internal distribution, with local conversion and regulation on each circuit board. Although unusual in the professional audio world, this approach is reliable, efficient, and extremely cost effective — although it does mean that service engineers have to be as careful working on live AWS900 boards as anyone working with traditional valve equipment!

With the exception of dual engineer's headphone sockets, all of the console's I/O is arranged along the back panel. Channel inputs and outputs are provided on XLR or TRS sockets, as are most of the main outputs, while the monitoring section, buss outputs, and cue/effects sends are accessed via 25-pin D-Subs in the familiar Tascam format. This enables the console to be quickly and easily installed, and also allows it to be used without a patchbay, should this be necessary.

SSL AWS900Photo: Mark Ewing

The audio circuitry is derived directly from the SL9000K series, but redesigned to use mainly surfacemount components. SSL claim that the sound quality has not been compromised in any way during this redesign, and in some cases it has actually brought extra benefits thanks to the easier introduction of ground planes and the shorter circuit track paths. It uses the same DC-servo technique throughout to avoid coupling capacitors in the main audio path, and provides the same wide bandwidth and uncoloured signal quality as the flagship console. The specifications claim a response that is 3dB down at 135kHz and 4dB down at 200kHz, so 'wide bandwidth' is definitely an appropriate phrase here! The desk also boasts headroom of +27dBu, distortion of 0.002 percent at +24dBu, and noise below -90dBu (providing more than a 110dB dynamic range when feeding professional A-D converters).

Channel Facilities

Each channel has three inputs: mic, line, and instrument — the first two on XLR and the last via a quarter-inch socket. The mic/line selection can be controlled globally from the console's master section, or overridden locally with a Flip switch. The mic input is essentially the same as that used in the SL9000K-series consoles and XLogic channel strip, and provides continuously variable gain from +15dB to +75dB. A 20dB pad accommodates loud sources, and phantom power and polarity are switchable on each channel. The line input has a separate ±20dB gain control, and the FET-based instrument input — something no other SSL console can offer — provides a very high impedance to suit electric guitars and the like.SSL AWS900Photo: Mark Ewing

The EQ section is, again, derived from the K-series console's four-band equaliser, including a separate variable high-pass filter. The top and bottom bands are shelving types, independently switchable to a bell shape, while the two middle bands are fully parametric. The EQ section also features switchable characteristics corresponding to the original E-series and G-series designs. The default mode provides the E-series response, featuring standard 6dB/octave filter slopes, while the G-series mode provides steeper slopes with an inverted gain region immediately before the turnover frequency. For example, dialling in a high-frequency boost to give 'air' also results in a modest level dip over the frequency region below the turnover frequency — a combination that often works very well and certainly gives a different flavour to more conventional EQ designs.

Located in the centre of the EQ panel section are three buttons which switch the entire EQ section in or out, switch the insert point in and out (with separate balanced TRS sockets for send and return), and reorder the signal path so that the insert point is before or after the equaliser.

Cues & Auxes

The AWS900 has flexible aux and cue-send facilities, derived once again from the SL9000K consoles. Each channel can access one of two stereo cue busses, with level and pan control and pre- or post-fade selection. The send is turned on and off by pressing the level knob. There are also two aux send controls — labelled FX1 and FX2 — each being post-fade and switchable between two effect busses, giving up to four aux-buss outputs in total. Again, each send is turned on and off by pressing the level knob.

All these cue and aux sends can also be switched into an EFX mode, in which the relevant send output is isolated from its normal buss and routed instead to the Track Buss routing matrix (of which more in a moment) in place of the normal channel output signal (the Cue signal is routed in mono when switched to the EFX mode). Obviously, only one send control per channel can access this EFX mode at a time, but the idea — borrowed from the SL9000 console — is to allow a lot of flexibility in signal routing and output destinations while using a small control set. As an example, you could hook up the eight Track Bus outputs to eight headphone amplifiers, and thus use the system to generate an additional eight separate mono headphone feeds. Equally, you could use the Track outputs to feed additional effects processors, extending the number of effect sends.

The channel's Direct output socket normally carries a post-fade signal, although it can be switched pre-fade using a button at the top of the sends section of the channel strip. However, if the EFX mode is activated on any of the Cue or FX sends, the corresponding signal is routed to the channel direct output instead. This whole EFX scheme may appear a little complicated at first sight, but it allows for some extremely versatile signal routing possibilities.

The last of the channel strip's analogue controls is the main stereo routing section, which provides a pan pot and buttons to access the independent stereo Record and Mix busses. The Record buss is intended to feed the DAW while overdubbing, with the Mix buss allowing simultaneous and independent audition of the complete mix — another example of the flexibility of the desk's design.

Meters & Routing Options

The meterbridge above the main channel strips carries a pair of bar-graph meters and indicators for each channel, along with various routing buttons. The console's eight Track Busses can be selected individually and are normally fed with a post-fade channel signal. However, additional buttons allow pairs of Track Busses to be fed with a post-pan (stereo) signal, or with a mono pre-fade signal. If the EFX mode is active, then the Track Busses are fed from the appropriate Cue/FX control as previously described.

Underneath each channel's multi-function meter are a matrix of routing buttons, below which are the switches which are used to assign the two mono dynamics sections for individual channel processing.Underneath each channel's multi-function meter are a matrix of routing buttons, below which are the switches which are used to assign the two mono dynamics sections for individual channel processing.Photo: Mark Ewing

The bar-graph meters show either the analogue channel signal or the corresponding DAW channel, depending on the mode of the desk. Normally, only the left meter is active, but when a stereo DAW channel is being controlled, both left and right channels are displayed. Above the meters are a pair of tally lights which illuminate when the relevant DAW track is armed to record, or is currently being addressed by the plug-in editor.

Four more buttons here allow one of the two assignable dynamics processors located in the master section of the console to be inserted in the channel, with options to insert the dynamics pre-EQ (after the channel input) or post-EQ (at the channel output). Combined with the insert point routing facility incorporated within the EQ section, these switches enable the channel signal path through the EQ, insert, and dynamics blocks to be configured in six different ways.

Channel Fader & Rotary Encoder

The remaining portion of the channel strip comprises an encoder knob, the motorised fader, two four-character electronic scribble strips, and separate Solo and Cut buttons for the analogue channel and DAW channel. There is also a Select button to access the appropriate DAW channels for track arming, plug-in editing, and so on.

An Auto button near the top of the fader is used to activate the various console and DAW automation modes, with adjacent red and green LEDs to show the current read and write status. The electronic scribble strips are used to show DAW track or channel names, the assigned encoder control function, DAW I/O allocations, fader and automation trim levels, and various other useful things, depending on the console mode.

The default mode is for the fader to control the analogue channel level, while the rotary encoder controls the corresponding DAW channel's virtual fader. However, a Master Flip control in the master section swaps these controls, allowing a monitor mix to be built up on the faders while the console channel 'record' levels are set on the rotary encoders — the latter then being akin to the small fader on a traditional in-line console.

It probably won't come as a surprise to learn that audio is not routed through the fader or encoder. Instead, both generate high-resolution control signals that are routed either to the DAW or to the channel MDAC (Multiplying D-A Converter) which essentially uses switched resistors to provide the required degree of signal attenuation. The MDAC technology was adopted because it provides better sonic performance than traditional VCAs for the console signal path.

The fader and rotary-encoder data is transmitted to the DAW as a pair of Continuous Controller messages, allowing excellent 14-bit resolution, and every button sends separate control messages to indicate when it is both pressed and released. Clearly, this means there is a lot of data passing between console and DAW, but there is no perceptible control or tally-light lag at all. Everything works exactly as you would expect it to, as one perfectly integrated system with no difference in response between using a control to address a console signal path or a DAW channel.

Master Section

The master section of the console occupies the right-hand side and cannot be relocated to the centre of the desk, but this is not a problem, since the entire console can be reached easily from a central position, and hence there is no need to leave the monitoring sweet spot while working. The master section incorporates all the traditional analogue console facilities: main fader, buss compressor, FX and Cue send masters, monitoring controls, and so on. But there is also a full set of transport controls (with auto-locator), a comprehensive array of dedicated DAW control keys, and a colour TFT screen, of which more in a moment.

Above the display screen is a panel section which includes a line-up oscillator providing one of six selectable tone frequencies or pink noise (with both preset and variable level options), routable to the Track, Record, and Mix busses. There is also a built-in talkback mic with separate output-level controls for Slate, Foldback, and Direct output, plus an input-level control for the studio Listen mic, which is processed with SSL's infamous Listen Mic Compressor. An external talkback mic can be used instead of the internal mic, if required. A quartet of LEDs indicate the presence of the critical power-supply voltages.

To the right of the screen is a section devoted to the four stereo returns and the two foldback outputs. The stereo returns are usefully equipped with Width, Balance, and Level controls, in addition to separate left and right cuts, AFL, and independent routing to the Record and Mix busses. There are also facilities to send these return signals to the two Foldback outputs, with an independent Studio level control, making it easy to set up reverb in the headphones when recording vocal takes.

Each foldback output is provided with Level control, cut and AFL facilities, and six source-selection buttons, allowing contributions from the two stereo Cue busses, the Record and Mix busses, the four stereo returns, and the control-room monitor outputs — all of which makes it easy to arrange zero-latency headphone monitoring for performers. The engineer's headphone outputs can be fed with the control-room stereo monitoring signal or either of the foldback signals.

Assignable Dynamics Processors

Above and to the right of the TFT display are the dynamics facilities: a pair of mono multi-function processors and the stereo buss compressor. The two mono units can be linked for stereo operation and allocated to any pair of input channels (using the appropriate buttons in each channel's routing section) or to the Record or Mix busses using a clever matrix arrangement.

The mono dynamics processors provide both compressor and expander/gate facilities, sharing a common gain-reduction element. The compressor section follows SSL's usual practice of providing variable Ratio, Threshold, and Release controls with fully automatic gain make-up.

SSL AWS900Photo: Mark Ewing

By default the side-chain is RMS-sensing with a soft-knee transition, but the Peak button switches the response to peak-sensing and hard-knee, which is generally more appropriate for transient-rich signals. The attack time is normally programme dependent (varying between 3ms and 30ms), but a Fast Attack button fixes the attack time at 3ms if necessary.

A column of yellow and red LEDs shows the compressor's gain reduction, while an adjacent column of green LEDs shows the gain reduction applied by the gate section. The gate has four rotary controls — Range, Threshold, Release, and Hold — plus another Fast Attack button and an Exp switch to change the mode to a 1:2 expander instead of a hard gate. The gate can be triggered by an external key signal (input via a rear-panel connector and shared by both dynamics channels).

The stereo buss compressor is derived from the G-series quad compressor, and uses the same dual-VCA feed-forward topology. It can be switched into either the Record or Mix busses (but not both at the same time), and is equipped with a full set of controls: Threshold, Ratio, Attack, Release, and Make Up Gain, plus a bypass switch and a traditional white-on-black moving-coil gain-reduction meter.

The main buss matrix allows any of six separate functions to be introduced into either the Record or Mix busses. Both stereo busses have their own balanced insert points which can be switched in or out using this matrix, and unusually the insert return can either replace or be summed with the main buss signal — a facility that allows an external mixer output to be combined with the main busses, or for the Record buss output to be summed back into the Mix buss, for example.

The two dynamics processors and/or the buss compressor can also be inserted using the matrix, and the master stereo fader can be assigned to control either buss. By default the master fader operates with unity gain at the top of its travel (which makes fade-ins and fade-outs a lot easier), but an additional 10dB of gain can be introduced if required, so that it works like the channel faders, with gain in hand.

In the top right-hand corner of the master section are rotary level controls and associated AFL buttons for the eight Track Busses, and a section concerned with the master outputs for the two stereo Cue busses and four mono FX busses. The level controls all have centre detents which correspond to unity gain, with an additional 10dB of gain available if required. Each output has its own AFL button, and a set of bar-graph meters above these controls shows the output levels for the Cue, FX, and Foldback busses.


The monitoring section is surprisingly well equipped, with comprehensive facilities to drive two sets of 5.1 monitors and two sets of stereo monitors, complete with automatic downmix to stereo or mono. There's also individual-speaker level calibration, bass management, and encode/decode processor inserts. Further clever facilities make it easy to integrate a visiting engineer's preferred front monitors while retaining the 'house' rear channels.

The Solid State Logic web site already has an extensive library of FAQs and detailed tutorials, and there are even things like track sheets to download.The Solid State Logic web site already has an extensive library of FAQs and detailed tutorials, and there are even things like track sheets to download.External monitor inputs are provided for four 5.1 sources and a further four stereo sources — all of which can be mixed together and/or routed to the main monitors, studio foldback, or headphones. The first six Track Busses are also available to the surround monitoring (to accommodate a 5.1 stem) and there is even a dedicated 5.1 output facility to feed a multi-channel metering system like DK Audio's MSD range.

The monitoring facilities are further enhanced with an elaborate solo system, again derived from the SL9000K console. Destructive in-place solo, stereo AFL, and mono PFL modes are all available, with a separate PFL output to feed a dedicated PFL speaker if required. There is also a useful in-front solo mode, which is essentially stereo AFL, but with a user-configurable level of the entire mix added back in, allowing the soloed channels to be heard more clearly, but in context.

The master volume control has an associated numeric display to show the relative level either of the entire selected monitoring system, or of individual channels in calibration mode, or of the current dim levels when configuring the Solo modes. A bank of six buttons is used to assign the volume knob to adjust the default levels of various monitoring signals including the AFL, PFL, and solo-in-place feeds. Three large white buttons switch the monitoring between the alternate 5.1 system, and the two stereo 'mini' systems. Additional arrays of buttons serve to mute or solo the individual monitoring speakers; select 5.1, 5-into-2 downmix, or mono modes; and select the monitoring source, with an option to mix the selections together if required. Its all very intuitive and flexible, and just what you would expect of a thoroughbred console from the SSL stable.

DAW Control

As already mentioned, the multiple-HUI aspect of the desk enables the 24-channel fader, mute, solo, encoder, and channel-selection controls to be assigned to operate the desk's analogue path, the corresponding DAW channels, or both, in banks of eight. The faders assigned to the DAW can be scrolled individually or in banks to access any number of DAW tracks.

However, it is in the master section that the majority of DAW facilities are to be found. The basic transport functions are supplemented with auto-locate features, including Return To Zero, End, Loop, Pre/Post-roll, Punch In/Out, and so on. There is also a numeric keypad, a jog/shuttle wheel, and a set of navigation cursor buttons. Particularly thoughtful additions are the Undo, Save, Shift, Alt, Control, Option, Escape, and Enter buttons, which allow access to all the context-sensitive alternate functions which proliferate in every DAW's menu architecture. This renders the keyboard all but redundant for normal operations.

The small colour TFT screen has a relatively low resolution, but provides clear graphical and textual information relating to both the console automation and the recall facilities, as well as various DAW functions including effects plug-ins. The question many will ask is, can the display be output to an external screen, as on the big SSL consoles? The answer is no; the display resolution is much too low, and there really is no need because its wide viewing angle allows it to be seen clearly from whichever end of the console you happen to be sitting.

The various menus and graphical displays are controlled using an array of soft keys and four rotary encoders below the screen. The encoders (with a press switch action) and associated soft keys are used mainly to control graphical plug-in parameters, while two more buttons scroll forwards or backwards through any additional parameter options or menu pages. Two rows of eight buttons below these access the various console and DAW global options and commands, as shown with neat labels running across the bottom of the screen. This arrangement is very clear and intuitive, although some familiarity is required to manage these functions at speed.

Finally, to the right of the jog/shuttle wheel are an array of talkback buttons which fall easily to hand, and there is even a button to switch on the studio's red light — how thoughtful!

On Session With The AWS900

The sonic and ergonomic pedigree of this console was immediately evident from the outset. It is very easy to find your way around the channel strips, and the flexibility of signal routing allows the desk to do far more complex things than you would have thought possible. The mic preamps and EQ are classic Superanalogue designs and do exactly what you need them to do.

The monitoring section is surprisingly comprehensive (and future-proof too with its 5.1 support), and all the tools are provided for easy communication with the talent. After only a few minutes familiarisation I felt completely at home with the analogue aspects of the console, and controlling the primary DAW functions — arming tracks, recording, overdubbing, adjusting channels, tweaking plug-in settings — came just as easily. Overall this desk is Intuitive, ergonomic, and professional.

However, there are a few aspects that restrict the ultimate flexibility of the console and highlight the fact that it was conceived mainly as a tracking desk, before analogue mixing again became more fashionable. The first clue is the absence of any groups or VCAs, although you can link faders.

Perhaps a more obvious clue is the lack of dynamics on every channel — a pair of assignable dynamics processors may well be sufficient when tracking, but a lot more are usually required for mixdown. Of course, you could use DAW plug-ins, but that defeats some of the advantages of an analogue mixdown. Fortunately, SSL have addressed this issue by announcing the XRack range, the first unit of which will provide up to eight dynamics processors (the same as those in the console) which can be patched into the required channel insert points. The rack also incorporates Total Recall facilities which integrate fully with the console's system.

The second element is the lack of surround panning facilities in the channels, making surround mixdowns rather tricky. Again, there are various workarounds, but a lot of reliance must inherently be placed on the DAW's facilities. Fortunately, again, the monitoring section is sufficiently flexible to allow several 5:1 stems to be combined from the internal Track Busses and external inputs.

Having said all that, these compromises are not likely to be particularly significant to most users, and are easily outweighed by the numerous highlights of the console — a Superanalogue mixer with 'big desk' sound, features, and flexibility, for a remarkably modest UK price. You can really see where the money has been spent on this console, and it constitutes a truly professional high-end console for the mid-market studio or post house. Throw in the perfectly executed DAW interface and console integration and this has to be my product of the year!

Published November 2005

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