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Allen & Heath Spectrum

With on-board midi mute automation, six auxiliaries, 16 inputs and 16 monitors, Allen & Heath's new pint-sized Saber looks set to emulate the success of its larger brethren. Dave Lockwood checks it out.

Allen & Heath's Saber mixing console has proved to be one of the most popular 'personal multitrack' desks on the market over the last year or so. Now their latest model, the Spectrum (called the Saber 8 outside the UK), looks set to extend the Saber range down to a significantly lower price level. Although only an 8-group console, it features 16 monitors — all with EQ and auxiliaries — and is thus well suited to any configuration of small multitrack, whilst the large number of sources that can be controlled on mixdown should appeal to those who run MIDI devices as additional 'virtual tracks'. Also included is the highly effective MIDI Mute Processor from the Saber, which has been further enhanced in this latest system.

The Spectrum is semi-modular in construction, with input channels in blocks of eight, and a single large group/master module. Three different frame sizes are available, accommodating 16, 24, or 32 input channels. However, the two smaller configurations of the desk can be extended by the addition of an 8-input expander module, allowing a large system to be built up without the need to purchase an oversize frame at the outset (a 16-input system can eventually be fully expanded to 32 by using two additional modules, but a 32-input version cannot be expanded to 40, presumably due to PSU capacity)

The traditional 'split' layout is both simple to understand and operate, with input channels located to the left, outputs/monitors to the right, and the master section in the centre. Construction and finish appear to be to the same high standard as the Saber, and will disappoint no-one. All connections are made to the vertical rear panel of the wedge-profiled console, and a meter pod attaches to the rear edge, featuring 12-segment bargraph displays for the 16 group outputs and a pair of moving-coil VUs for the stereo bus (all VUs is an option). DC power input is from an external 3U rack-mount case with supply monitoring LEDs. Thoughtfully, expander blocks are supplied with a replacement full-length armrest, and it is also possible to relocate the meter bridge to the new centre of the desk, thus neatly avoiding the 'DIY' look of some expanded consoles.


Input channels have a choice of three signal sources: Mic, Line or Tape, with a 16dB Pad available on the mic input. Individual 48V phantom power switching is available, but only via recessed rear panel switches (the same type of switch is used to set the nominal level of the system for +4dBu or -10dBV operation). Tape inputs 1-16 are paralleled to the tape returns on the monitor channels, as expected. The Phase Reverse facility present on the Saber has been omitted, and at this price one cannot really mourn its absence, but the wide-ranging Gain control, calibrated merely in arbitrary 0-10 units, remains active on all sources.

Multitrack routing is achieved via the Pan control, operating in conjunction with four switches that select the eight groups in pairs. Each group is also paralleled into a pair of tape sends (1 with 9, 2 with 10, etc.) making interfacing with a 16-track recorder very simple, via a standard loom. Inputs can also be routed directly to the mix bus via dedicated L-R switches, or lifted from the bussing system entirely by means of the direct out facility (post-fade, post-EQ). This obviously makes it possible for the desk to record more than eight separate tracks in one pass. Indeed, with a little creative patchbay work, extra groups can be formed without difficulty, for direct outs seem quite content to be paralleled. The signal path on individual signals may also be minimised by bypassing the group summing amps.

Allen & Heath continue to follow their own convention on this series of consoles, for like the Saber and its up-market companion the Sigma, the Spectrum places the aux sends above the EQ in the channel layout. There are six auxiliary busses in total, accessible via four pots. Aux 1 and 2 are governed by a Cue/Aux switch, determining Stereo/Mono and Pre/Post-fade operation. The Cue position sets up a stereo, pre-fade mode for foldback use, with Aux 2's pot acting as a Pan control, whilst the Aux position allows the pair to function as separate mono auxiliaries.

Auxiliaries 3 to 6 are all post-fade for effects use, and are accessed via a switch which throws both pots, as a pair, to either 3 and 4 or 5 and 6. This is never as satisfactory as truly separate auxiliaries, but it is easily accommodated with a little forward planning of your effects system. Indeed, in a console of this price, it should be viewed as a little extra flexibility, rather than the limitation that would have been imposed by providing just four auxiliaries.


The Spectrum offers a basic 3-band EQ, with shelving high and low sections, and just a single swept mid band. All three stages offer 12dB of cut or boost, with the fixed bands offering a choice of frequency. HF can be switched to operate at either 8kHz or 16kHz, with LF at 50Hz or 100Hz (which is what the Saber should have had, in my view!). The LF band is complemented by an independent low-pass filter rolling off 12dB/octave at 80Hz. HF and LF pots are centre-detented for easy zeroing, as is the gain stage of the mid section, which covers the range 250Hz to 6kHz. The bandwidth selected for the mid stage seems a fair compromise between precise selectivity and 'musicality' — high 'Q' filters may be preferable when cutting, but they can often sound harsh or coloured when boosting. An EQ In/Out switch facilitates instant comparison between flat and equalised signals — so often this is the first thing to be omitted on a down-market version of a console, and operation is always significantly poorer as a result.

Channel faders, like the group and master faders, are the ever-popular 100mm Alps units, which means they are very smooth and noise-free in operation. Infinity attenuation is not specified, but there is the usual 10dB of gain above the unity position. Below the faders is a scribble strip, without channel divisions, and the narrow, lightly padded armrest. Signal level within the channel is monitored by a pair of LEDs at the top of the fader, one displaying signal presence and basic level indication (via brightness), the other acting as a clip indicator. The peak detection circuit monitors the signal at three places (after the input stage, after the EQ, after the fader), detecting potential overload anywhere within the channel.

As on the Saber, the channel isolating facility is designated 'Check', covering the fact that it can function either as a normal PFL or a true Solo-In-Place (SIP), according to the status selector on the master module. During Solo-In-Place operation, the programmable mute bus is used to turn off all channels which are not soloed, thus making this a 'destructive' operation when recording, whereas PFL only affects the monitoring of signals. SIP muting, quite correctly, includes the monitor channels but the dedicated effects returns are inherently Solo-safe, allowing a proper solo-with-effects to take place.


All input channels, monitors, and auxiliary masters are equipped with a large non-latching Mute switch (with status LED), which can be operated manually or under the control of the MIDI automation system. The FET switching arrangement used in this range of desks is most impressively silent in operation, and can even be used on a relatively exposed signal. The system is controlled from a small panel of eight membrane switches located next to the master faders. Although, inevitably, some switches multifunction between Patch operations, Song operations, MIDI and console configuration, the system is very easily mastered, especially as the documentation of this aspect is exemplary.

The MIDI Mute Processor (MMP) on the Spectrum has been significantly enhanced in comparison with the Saber version, for it now includes its own 'virtual sequencer' to record real-time mute data internally. In a combined tape and MIDI system, a timecode-to-MIDI convertor simply needs to be configured to feed MIDI clocks to the desk, as well as any synchronised MIDI equipment. The MMP then uses MIDI Song Position Pointers to record the time position of any mute activity, relative to the incoming clocks — at 384 clocks per quarter note, the internal timing resolution proved to be more than sufficient for precise work, even at a very slow tempo.

'Snapshots' of the mute status of the whole desk can be stored and recalled as Patches — 33 can be stored on-board (with battery backup) with Patch 0 reserved for initialising the desk on power-up, and as the default for starting each 'song' under synchronisation. Patches can be recalled either manually or via MIDI Program Change commands — one small but helpful change from the MMP on the Sigma desk I have previously used is that the Patch number is now incremented automatically when you store (termed 'Update') a Patch, which saves you having to remember to advance it manually when entering a series of consecutive 'snapshots'. Patches can also be recorded as part of the automated 'song' data. Indeed, the configuration of all the Patches used within a song is incorporated within its data, both in internal memory and when dumped via System Exclusive.


Using the internal 'sequencer' is simplicity itself — pressing the Record button and sending the system MIDI clocks is all that is required. Playback is automatic, provided some mute data has been recorded, and the system is always in Overdub mode whenever you are in Record, so you can easily build up the information a little at a time. Recording the mute data internally allows the system to employ its own method of 'chasing' data (ie. being able to employ the correct configuration of mutes even if the tape or sequencer is started from a point just after what should be the current setup), rather than having to rely on an external system. The Spectrum system is specified to chase up to date within half a second, and seems able to do so irrespective of the amount of data recorded.

Individual mute events on any channel can easily be erased, using the system's Erase Last or Erase Forward facility, which gives you a choice of procedure depending on whether you find it easier to think ahead or react to events that have just happened. When Erase Last has been used, the preceding event in the list then becomes the next 'target', and so on, until you reach the start — simple and intuitive to operate. Editing is still semi-real-time, however, for any off-line editing must be done by dumping the data out to a MIDI sequencer, employing its graphic editing facilities, and then reloading it. The Spectrum's MMP, with its simple two-digit LED display, is simply not capable of showing enough information to allow on-board step-time editing.

Channels can easily be detached from the internal mute automation system and temporarily returned to manual control, by means of the Isolate facility. Thus you do not need to disable the entire system just to utilise a single channel for a last minute overdub. An isolated channel will still allow direct activation of its mute button, and will also respond to a channel-specific mute command via MIDI.


Having completed a set of mutes to your satisfaction, it is necessary to transfer the data from the scratch-pad memory (referred to as the Working Song) into one of the 32 non-volatile on-board Song Memories. This clears the Working Song for new data. Like the Patch data, stored Songs can be dumped to, and reloaded from, any MIDI storage device that can handle System Exclusive information. Songs in internal memory can be recalled via MIDI Song Select messages, which — whilst it may not seem important in normal studio usage — could certainly be of value for live performance applications.

If the number of on-board patch locations should prove insufficient, as they perhaps might for a particularly complicated piece of work, the total can be increased by employing 'Virtual Patches', saved to an external sequencer as Sys Ex data in real time. Inevitably, the Chase facility will be compromised by this mode of operation, unless the sequencer has a chase function of its own, of course. Better still, you can save individual patches as Sys Ex data, returning them to the MMP only when required, thus giving an effectively unlimited number of mute configurations.

The Spectrum MMP defaults to using MIDI Note-On messages to control muting, although the option to employ Controller codes, as used by earlier versions of the system, is still present. The Velocity byte actually determines the mute status (above 64 = Mute On, below 64 = Mute Off), whilst the Note Number decides which channel is being addressed. The familiarity and simplicity of this type of data makes editing via a sequencer very easy, should you feel the need to indulge in off-line editing, which is probably why it has gained favour over the Controller-based system. Earlier implementations of the Note-based system used to occasionally fall foul of the fact that some sequencers automatically turn off any notes that they think are sounding when the system is stopped (in order to prevent 'droning' notes). This otherwise very welcome facility used to have the unfortunate effect of also turning off all the mutes, but I am happy to report that the problem does not seem to arise with the Spectrum.


The master controls, the eight groups and 16 monitors are all contained within a single large module, which forms the right-hand side of the console. The six Aux masters all feature MIDI muting, and there is a generous number of effects returns provided. Two stereo returns are featured, again each with programmable muting, and a further four mono inputs. Returns 1 and 2 (both stereo) are routable to all busses, for convenient recording of effects to tape without repatching, and can also be fed to 'cues' 1 and 2, in order to send effects, like reverb, to the foldback mix.

Other useful master module facilities include an integral, flush-mounted talkback microphone, activated by a non-latching switch conveniently mounted low down in the module. Cleverly, and typical of the cost-efficiency of the design, this shares destination switching and level control facilities with the simple oscillator provided. There may be only a single frequency (1 kHz), but it is useful nonetheless, and there is always the option of plugging in a more sophisticated unit when necessary, via a dedicated socket at the back.

A comprehensive source selector is provided for the Studio output, from which foldback mixes can be taken. Auxs 1 and 2 (stereo aux pair), the Left and Right busses, and the control room monitor mix can all be combined, or selected individually, according to need. This is a very flexible arrangement, saving you the bother of building an entirely new mix on the auxiliaries, by allowing you to use the existing monitor mix as the basis for the feed. You can then additionally lift anything that needs to be highlighted, from the individual source 'cues' — a powerful facility, well implemented, and not normally found on a console in this price range.

Control room source switching allows for two stereo machines to be selected, in addition to the normal L-R bus (in stereo or mono), plus the ability to listen to the Studio feed. 'Alternate' output switching is provided, allowing convenient selection of a secondary monitor system (for nearfield speakers), if connected. A large control room listening level knob is provided, complete with Dim facility and manual mute, to kill the monitors altogether. A front panel headphone socket is also featured, with its own level control — this is never the most convenient location for headphones connection, in my experience, but the facility is welcome nonetheless. Master facilities are rounded off with the MMP panel, and the separate Left and Right stereo bus master faders.


Finally, there are the eight group outputs, with their associated 16 monitor channels (eight upper, eight lower), which are all identical except for the additional facility of Fader Reverse on the lower set. Source selection is between Tape/Group or additional Line inputs, with metering following the Tape/Group switching even when 'Line' is selected, in addition to the rotary Level and Pan controls, the monitors are equipped with a simple 2-band fixed EQ, providing 12dB of cut/boost at 100Hz and 10kHz.

Four of the auxiliaries are accessible from the monitors: auxs 1 and 2, forming the stereo cue send, plus 3 and 4. Auxs 1 and 2 on the monitor channels still retain their switched option to function as two separate mono postfade auxiliaries, which is preferable for normal effects usage. Monitors have the same Check (PFL/Solo-In-Place) facility and Mute switching as the input channels, which enables them to fully participate in automated muting when used as extra inputs during mixdown.

Finally, Fader Reverse enables the functions of group fader and monitor pot to be swapped over — in mixdown this allows eight more sources to be controlled on-long-throw faders. If the number of inputs is not so large as to require the use of the monitors as extra channels, sub-grouping can be employed, with groups assignable directly to the mix bus (odd numbers Left, even numbers Right). In this mode, the monitor pots function as additional feeds into the sub-groups.


In use the Spectrum proved to be more than competent, with acceptably low noise and no obvious vices on the audio side. Crosstalk is the big enemy of most budget consoles which employ unbalanced internal busses, but the Spectrum proved no worse than its competitors in this respect. The EQ seems to do most things that might reasonably be asked of it, and the electronically balanced mic amps perform well enough, especially with higher output mics that demand less gain.

Even if one overlooks the MIDI Mute Processor altogether, the Spectrum still looks a good buy; when you do take into consideration the extremely powerful production facility which the MMP represents, this desk begins to look like a real winner. The budget end of the 'personal multitrack' console market is a particularly congested area at the moment, with little to choose between units on sound quality alone. It is therefore primarily on the range of facilities on offer that the potential buyer has to be attracted, and on that score it is difficult to find fault with this model. The Spectrum is an attractive, comprehensively equipped console at a remarkably low price, and looks certain to extend the success of the current Allen & Heath range into a new market area.


Spectrum 16-8-16 £3449 inc VAT.

Thatched Cottage Audio, (Contact Details).

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Roland MV30 Studio-M

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Bill Nelson

Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Mar 1991

Donated by: Bert Jansch / Adam Jansch

Gear in this article:

Mixer > Allen & Heath > Spectrum

Review by Dave Lockwood

Previous article in this issue:

> Roland MV30 Studio-M

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> Bill Nelson

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