MIX FIELD TEST: Solid State Logic Avant
Video Post and Film-Dubbing Digital Console
Reviewed by Mel Lambert
Coincident with its introduction at the Fall 1994 AES Convention in San Francisco, SSL quickly pointed out that the original Axiom Digital Production System was intended to be the first in a range of application-specific topologies that would come to comprise the A-Series. And that is exactly what has since come to pass; the original Axiom "serving suggestion"- a post-production and broadcast version- was soon joined by Aysis Air, a 48-channel console designed specifically for live broadcasting, and Avant, a system tailored to meet the specific demands of film re-recording and high-end video post. The result is a flexible, remarkably powerful yet simple to use system that's attracting a great deal of attention from a growing number of facilities around the world. [SSL recently unveiled Axiom MT, a "multitrack" version for music recording studios. In essence, MT is the digital equivalent of an in-line SL-4000 G-Series rendered in silicon - ML.]
In essence, Avant features the same Hub Router and HiWay structure as Axiom, but with some twists. Avant's Master Processor supports a total of 96-times-two channel paths via a quad-layer topology. In this way, a 48-channel strip system, for example, can simultaneously address a maximum of 96 input sources with EQ and dynamics, plus 96 pre-dub returns. With access to more hardware channels, of course- up to maximum hardware configuration of 96 channel strips- inputs/predubs can be permanently assigned to on-surface controls, with a simple toggle to reach additional layers. The Avant mainframe accepts between 16 and 96 channel strips, in blocks of eight. The system includes a 64-into-8 digital monitor matrix, and up to three recorder control/monitor panels.
As always, SSL has managed to dramatically upset the cost/performance ratio with its latest application-specific offering. And a non-scalable architecture means that the engineering crew will not be forced to make a choice between using a processing resource for, let's say, an EQ function on a particular channel, instead of using the same resource to create an additional channel. The company's Real Time Resource processing, based on 32-bit floating-point math, means that EQ, dynamics and routing are always available to every channel, regardless of console size.
In look and feel, Avant retains the overall appearance of a conventional analog console, with dedicated controls for a number of functions, but with total automation and recall of every on-surface knob and switch settings against timecode. Channel functions can be dynamically automated or reset from snapshot memories, either globally or selectively. Again, SSL has emphasized the philosophy of "One control per function; One function per control;" this results in a panel layout that's extremely easy to follow, with few assignment panels to call up to change system parameters. All user controls are totally re-settable, with circular LED displays around the skirt to show current settings of all knobs. As with other A-Series offerings, color schemes and channel strip layouts closely mimic that of SSL's analog consoles.
Unlike its cousins, Axiom, Aysis Air and Altimix (which adds onboard editing functions), SSL is currently downplaying the role of DiskTrack as part of Avant; apparently, the firm's marketing department has concluded that the majority of potential film and high-end post customers will be using some form of tape- or disk-based replay of source and premixed elements, and will lay off finals and stems to similar media. So, until the firm finalizes development of various file-transfer utilities and related functions, it is advising users to work conventionally. (Which, of course does not preclude an update in the near future; watch these pages!) The optional DiskTrack provides up to 128 tracks of random access record and playback, with random-access editing.
Dynamic automation of surround panning on all channels is provided, with pan automation being written with conventional panpots or central joysticks. Flexible routing is provided across 32 busses, which can be configured as multiple stereo, four, six or eight channel stems, with stem mixing that complements simultaneous master outputs and multitrack busses. A familiar Bus/Tape Panel enables Avant to accommodate a variety of two/three-operator configurations, with individual motion control, joystick panning, PEC/Direct switching and group masters at dedicated music, effects and dialog sections. An array of eight assignable pairs of bi-directional paddles provide bus/tape monitoring and Record In/Out switching of up to 64 tracks on single or multiple recorders. Programmable Bus/Stem re-assignment and control of up to 96 predub returns are also available.
A dedicated Surround Sound/Monitor Select Panel provides selection of surround-monitoring formats, speaker muting and other functions, in addition to monitoring of individual channel sources and stems. External pre-mixes can also be monitored individually, or within a soundtrack mix for "Mix-in-Context." Dubber and machine control is provide through a third-party biphase interface, in addition to a quartet of RS-422 nine-pin for direct control of VTRs, ATRs, DA-88s, workstations, etc. Options include SSL's VisionTrack digital video system that provides full random access to digitized picture.
In terms of I/O hardware, Avant bristles with flexibility. The Hub Router communicates with the Avant engine, and a variety of input/output units, via HiWay Links that carry 95 sends plus 95 returns; a separate Ethernet link handles system control. Up to 24 HiWay Links may be connected to the Hub Router, four being used for connection to the Avant engine. (Work out the math: 95 channels times 20 HiWays provides a theoretical capacity of 1,900 inputs and 1,900 outputs!)
Via these HiWay Links, a user can access a number of analog and/or digital sources, and route outputs to recorders via Remote Input/Output units (RIOs). Analog RIOs provide between eight and 48 16/20-bit line-level inputs and outputs, expandable in increments of eight I/Os. Digital RIOs provide between 24 and 94 inputs and outputs (in 24-bit AES/EBU-format pairs), expandable in increments of 24 I/Os, and are normally fitted with between one and four 24-channel Sample Rate Converter cards that will accept any sample rate from 25-55 kHz and output at 32, 44.1 or 48 kHz, or any external clock frequency in the range 22-55 kHz. (One 24-channel SRC card is fitted as standard in the main processor.)
Connection to a digital multitrack via SDIF-2 is handled with a converter box that offers 48 inputs and outputs (available both with or without SRC). A remote mic amplifier handles 12 mic/line-level inputs; multiple units provide clusters of up to 72 inputs via a single HiWay Link, with remote control of various functions from the channel strip.
For example, one HiWay might provide access to 72 mic-line analog sources; a second HiWay might provide 48 channels of SDIF-2 Digital I/O (with or without sample-rate conversion, plus GPIs for track arming, for example, a PCM-3348 digital multitrack); a third HiWay 96 channels of AES/EBU-format I/O (again, with or without sample-rate conversion); and a fourth HiWay for 48 channels of 16/20-bit line-level analog I/O.
Eight, 20-bit I/O ports are also provided for interfacing with a six/eight-way monitor rig - to handle DTS, SDDS, Dolby Digital, HDTV and related formats - in addition to 24 AES/EBU-format outputs with sample-rate conversion for connecting to digital dubbers, etc.
Outputs can be locked to any input, to the system's video reference (48 kHz), or to an on-board reference (32 kHz or 44.1 kHz). The entire console runs at a sampling rate of 48.0 kHz, with the usual film- and video-based pull/down ratios; sample-rate converters are available on various inputs to accommodate 44.1 kHz and other frequencies. A dedicated processor design ensures that processing delay through the core is just few samples, and remains constant.
Each Avant channel strip includes dedicated controls for a four-band parametric digital EQ section; eight auxiliary sends; a digital dynamics section; digital effects processing; plus direct assignment to 32 multitrack/recorder busses; an additional 24 assignable predub busses with automated panning and routing are also available. Currently, the four-band EQ section is only available on the main input; in the near future, additional DSP will be added to Avant to provide comprehensive EQ on the predub returns.
Being fully digital, the current EQ functions include a user selection of 10 equalization types that can be modified and stored/recalled from a master library. To simplify system setup, upon system boot the four-band EQ defaults to a number of factory-set parameters that limit the bands to "typical" settings. By assigning film-specific center frequencies and ranges to each of the four bands, less time is taken in re-adjusting them once the session begins. (While all four bands can be extended from 20 Hz to 20 kHz, most of us will prefer to set LF, low-mid, high-mid and HF bands that provide a reasonable range of adjustment per controller, rather than end up with coarse controls with wide sweep ranges.)
Input sources to and output destinations from Avant are controlled via the system's crosspoint router- or Resource Management System, to use the jargon- which tags a physical port to the input, insert point or send of an assignable channel path. Once the physical cross points have been selected, that path can be assigned to the control surface, either in default locations- 1 thru N across the user controls, then Layer #2, extending to designated predub returns on subsequent layers- or mapped to other bays of the console. In addition, Avant offers the familiar bay-swap function from Axiom, whereby a bank of eight on-surface control strips can be swapped to a "Golden Section" close to the operator's central location. And, being a film-dubbing system, multiple operators can be simultaneously using Avant; additional master sections, complete with PEC/DIRECT paddles and monitor switching can be added anywhere across the control surface.
In many respects, Avant looks more like the SL-5000 analog film console than the music series. Which might not be too much of a surprise, given the 5K's success in the film and post market. Unlike Axiom, input sections are laid out in a way that reduces the front-to-back dimensions by several inches, and allows all controls to be reached from a seated position. Citing the need to provide fast, unconfused access to routing and control functions, Avant's designers have provide a layout that is more defined than Axiom, for example, and which places controls in locations that will reflect their importance during the predub and re-recording process. These channel controls are complemented by an extremely powerful center section that offers the high degrees of flexibility and user selection that make film mixing such a function-intensive operation.
Working from the top of the input channel strip, below the peak/VU channel meters, a new assignable Routing Tile provides access from inputs to 32 mix busses (instead of the four-by-eight matrix provided on Axiom), plus 24 pre-dub outputs. Source selection and output routing has been dramatically streamlined, with the result that users can access sources and destinations (busses plus relevant pan laws) very quickly from the surface by category, rather than having to move over to the center section and use the Project Management screens, (Although it is still possible to set I/O that way, it's a great deal more intuitive to call up a source by name, and then assign it to a channel.)
Below the Routing Tile comes a Dynamics Section (gate, expander and compressor-limiter, with a feed-forward operation to delay the main signal path by up to 20 mS); four Aux Send controls (selectable from a total of eight buss outputs, pre/post fader and in mono or stereo mode); a four-band EQ Section; Channel Insert; a Panning Section with dedicated Left-Right and Front-Back controls (usefully, the latter knob is rotated 90 degrees so that front is up and back is down; it's the little things that count!); and, finally, the motorized channel fader (with VCA-style master/slave subgrouping or from a central bank of master faders).
The Panning Section provides access to eight Modes, ranging from mono through discrete LCRS, to discrete 7.1 channel mixing. These same controls can also be remapped to provide Gain Trims (pre- or and post-dynamics controls) and Microphone Source utilities (peak limiters, 48V phantom, Hi/Lo-Z, 20 dB pad and highpass filter, plus gain trim).
All of the dedicated sections have been very well thought out in terms of functionality and accessibility. All controls are easy to see and operate; a useful "Hold-down" mode zeros out any selected function, and resets it to a factory value (normally flat response for EQ and 1:1 dynamics). In addition, Load buttons enable stored parameters to be recalled from a library; values can also be copied across multiple channels.
In the "Typical" mode preset by SSL, the four EQ sections map to values that match the on-surface legends. (Overall response and individual gain/frequency settings are also displayed on the central color VDU.) In this mode, the LF band extends from 30 Hz to 45 Hz, the LoMid from 200 Hz to 2.5 kHz; HiMid from 600 Hz to 7 kHz, and the HF from 1.6 kHz thru 16 kHz. Useful values, and a good starting point for most applications. Each band can be set to low-pass filter, high-pass filer, LF Shelf, HF Shelf or parametric with bandwidth variable from 0.9 to 10.5.
And yes, the EQ sounds extremely sweet and smooth in operation; never a protest from the circuitry, even when asked to deliver outrageous amounts of boost at narrow notches.
Channel Banking enables individual channels to swap out on-surface controls between active audio paths. Controls can be flipped individually- Layer A or B, Input or PreDub- or by using master switches. Channel numbers are displayed on the meter bridge to provide additional operational feedback. Bay Swapping enables any channel to be accessed from the sweet spot, by bringing a selected bank of eight channels to a master location in front of the operator. The new channel positions are also displayed clearly on the meter bridge, making this powerful feature very simple to utilize. Predub sources can be accessed by pushing just two buttons.
Built-in effects processing can provide either 48 delay (up to 1.3S per path), 24 reverb algorithms, or an intermediate combination of the two, freely assignable to any channel. Input to the processor is post-EQ and dynamics; its output feeds the channel fader. Echo and reverb parameters include room size, RT60, and reverb filter. A unique "3D Room" display allows values to be adjusted while viewing a color representation of the resultant environment; neat stuff. Shape and size of the environment can be adjusted via the graphics tablet. User presets may also be stored/recalled from a presets library.
Bays can also handle stereo operations in place of the normal mono channels, with matched EQ, Effects and Dynamics processing, Stereo channels normally feed Aux Sends with a mono sum of both channels; in addition to L/R and F/B panning, stereo width can be adjusted, or the stereo image reversed. (MS decoding is also available on both mono and stereo channels.)
Extensive machine control facilities are provided on Avant for synchronization with ATRs, VTRs, mag dubber and projectors. While an Ethernet-based control network handles internal DiskTrack, VisionTrack and any other installed SSL systems (such as the APS or other A-Series consoles), external machine control is provided via four independent RS-422 serial ports. Serial track arming for multiple digital tracks, plus analog VTR tracks, is also available. Machines that require a control interface or synchronizer can be handled via TimeLine Lynx II, Audio Kinetics or Motionworker units driven directly from one of Avant's serial ports. (Biphase busses for film machines can be driven using CB Electronics' Film Master Unit., or other third-party interfaces.)
The Center Section handles output routing to the eight analog and 24 digital signals connected directly to the processor, plus those connected via the HubRouter, and which are provided for local applications such as control-room monitoring. (Of course, many more outputs can be accessed via the Hub Router for distribution around a studio complex.). Each output can be assigned any source, including main mixes, monitor mixes and aux sends; in addition, any system input may be routed directly to an output, effectively bypassing the console. Eight master bargraphs in each center section can be programmed to display any source signal or mix, including post-Bus/Tape signals.
The monitor system comprises a dedicated control panel with Bus/Tape and Record On/Off paddles (plus switches for monitor and, meter selection, fold downs and inserts, plus solo and cut); a programmable 64-by-8 monitor matrix, controlled both from on-screen or from the panel itself; and an eight-channel insert point and stems fold-down mixer. A calibrated monitor level control features Dim and Cut buttons.
The current monitor setup can be saved in one of two presets that may be independently saved and recalled. All crosspoint selections, input-trim levels and monitor assignments are memorized as Monitor Formats. Record Presets hold source, record and paddle selections. Up to 50 monitor formats and 50 record presets can be named and saved per project.
Given a few minutes practice, and a glance at the User Manual, all functions are easy to comprehend. Avant's Dynamic Automation is extensive, to say the least. In addition to faders, EQ dynamics, gain trims, effects processing, panning and auxiliary sends and group master faders can be also be automated. For added flexibility, each group of controls (faders, EQ, panning, and so on) is treated as a separate entity. This means, for example, that faders can be updated while EQ and dynamics are in a safe mode. Other modes include real time and clip-based automation; the familiar protect, static, overwrite, rollback, clip fill, clip end, cycle fill and cycle end modes are available for all controls, as well as snap with autoglide (up to 10 seconds). EQ, Aux Sends, Pan and Faders can also be grouped in automation.
Usefully, there is no need to define a start and end time for dubbing mixes; all data runs from zero to midnight, with start/end times being the first and last points at which a change occurs. The last six mix passes are held in memory; any one can be held indefinitely as a reference. Mix can also be stored permanently as part of a Project, and tagged to individual or all operator sections across the console. A total of 64 snapshot memories will store static topologies of all automated controls that can then be recalled, globally or selectively. Separate structures exist for storing channel source and output routing.
A comprehensive array of programmable macros keys on the Motion Control panel is stored in the Default Project that forms part of the console's factory-set configuration. Macro can be used, for example, to store/recall combinations of snapshots and input-routing presets. Or to control bay swapping and channel banking. An Events List manages sequences of time-based events.
Project are stored on Avant's internal hard disk or MO drive via a directory in which individual files are held for every element of the system. As SSL reasons, separating a project into different elements means that they can be saved or loaded individually, thereby reducing setup time on dubbing sessions with common settings.
In a Nutshell: SSL Digital Quality, Dedicated/Assignable Controls and Application-Specific Topology
Without a doubt, the SSL Avant Digital Film Console represents a high-water mark for a company that knows more than a little about DSP-based systems. Designed to address both the specific needs of large film-dubbing stages and the more compact requirements of video post, Avant can be configured to accommodate single or multiple operators, with up to three motion-control panels, three monitor panels and joystick panners. Full compatibility with other SSL digital products enables Avant to share resources with Aysis Air, Axiom, Altimix or SL-9000 J Series systems in multiroom facilities.
It is obvious that SSL has listened to what the film and post community wants from an all-digital console. A careful blend of dedicated and assigned controls allows the best advantages to be gained from digital technology (compact designs plus total reset of all functions), without forcing engineers to re-define their current paradigm. Layering is only used where it makes sense, and without compromising the clean, uncluttered lines of the console. The monitor/recorder section is powerful yet simple to grasp in operation. Comprehensive dynamic and snapshot automation of all functions rounds out the Avant package.
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