MTA Intermix

We've all heard of modular mixing desks — but perhaps not where all the modules are rackmounting and can be mixed and matched to form a custom console, or used alone. Hugh Robjohns makes all the right connections.

Malcolm Toft Associates (MTA) is a relatively young company formed only a few years ago, yet it has an impressive pedigree in the mixing console business, which goes back much further. Malcolm Toft was the man behind Trident — a company he sold in 1988 — which was possibly best known for its large multitrack consoles, such as the Series 80, an enormously popular desk in its day.

Malcolm is still designing and building large multitrack consoles at MTA, but the subject of this review is on a rather different scale and, as far as I am aware, is unique in the console market.

The Intermix

The Intermix is a modular 16‑channel multitrack mixing console. Big deal — most of us have seen modular mixers before. In this case, though, the modules are not individual channel strips, but 16 channels worth of signal processing — 16 channels of mic amps, 16 4‑band EQs, 16 channels of 8‑output aux sends, and so on. The Intermix module design allows the construction of up to 48‑channel desks, and MTA's literature suggests a number of standard configurations, from a simple 16:2 mixer, up to a 48:16:2 with EQ and aux sends in both channel and monitor paths. The possibilities are extensive, and the modules' design lends itself to all manner of configurations.

All the Intermix modules are rackmounting units, and each module is only about three inches deep, so table‑top mounting is quite feasible. MTA are planning a conventional console case to house the units in the future. Power is supplied by a separate mains unit, capable of driving up to three modules (possibly more, depending on their current demands) and almost all the audio connections are electronically balanced on standard jacks (XLRs for the microphone inputs). They're also paralleled on multi‑pin ribbon cable connectors for fuss‑free module linking. The circuit design of each module is directly derived from MTA's flagship 980 console. The only differences are in the provision of each section's inputs and outputs, and the fact that the mix busses are unbalanced, to keep the costs down.

The Intermix concept is rather novel — even elegant — and should appeal to a very wide range of potential users. The beauty of the system is that each module can be used as a stand‑alone device, or to enhance an existing console — by replacing the mic amps, or providing more powerful EQ, for example. They can also be combined to construct a console to meet virtually any requirements, either in terms of facilities, or layout, or even as money becomes available to extend the desk! The quality and flexibility of the design would make the Intermix worthy of consideration for just about any application: studio or location recording, mobile setups, front‑of‑house band rigs, monitor desks, theatre sound — the list is almost endless.

To appreciate the scope of the system, perhaps we should investigate each module individually.

The Power Unit

Power supplies are not the most enthralling part of a mixing desk, but they are a vital component and I feel obliged to give you a brief description of the Intermix PSU, for completeness, if nothing else! It's housed in a 1U‑high box with a mains on/off switch and three fuses on the front panel. Each fuse has an associated LED to confirm the presence of the power rails (plus and minus 18V, and a 48V phantom supply).

The rear panel features a standard IEC mains connector, a small (quiet) fan, binding posts for chassis and audio earths, and three 16‑way multi‑pin connectors that provide power for the audio modules via ribbon cables fitted with IDC connectors.

Mic/Line Module

The 16‑channel mic/line input processor occupies a 3U chassis, is clearly laid out, and is gloriously simple. A rotary gain control covers the range 20 to 65dB for the microphone input, and 0 to +40dB for the line input. A push button introduces a 20dB pad for both inputs, and other buttons provide a phase‑reverse facility and phantom power (a red LED indicates when it's active).

You may be wondering how to select between mic and line inputs. Well, the input connector for each channel is a Neutrik combi‑jack — an XLR socket (the mic input) with a jack socket (for line‑level inputs) built into its centre. It's physically impossible to connect both inputs at once, so there's no need for a selector switch. As mentioned earlier, both inputs are electronically balanced.

The output for each channel is on a jack socket, also electronically balanced and operating at the professional +4dBu level. The output circuitry is 'ground sensing', and if it detects an unbalanced destination, it increases the output level on the active wire to compensate.

At the bottom of the rear panel are two multi‑pin IDC connectors — a small power socket, and a large output connector. The latter provides a very convenient means of linking all 16 channel outputs directly to another Intermix module, and is wired in parallel with the main output sockets for each channel. Although it's perfectly possible to use the separate balanced outputs from each channel as direct recording feeds, whilst using the Intermix connector to pass the channel signals to another module, care should be taken to avoid loading the outputs unduly.

The entire system is incredibly versatile and flexible, and the whole concept is absolutely excellent.

The quoted specifications for this module are all very respectable, with distortion better than 0.05%, headroom of 20dB or more, noise around ‑80dBu for the line input and ‑128dBu for the mic, and a frequency response completely flat between 20Hz and 20kHz. More importantly, it actually sounds good too! The mic inputs are pretty quiet, and certainly much quieter than those of some well known 'state‑of‑the‑art' desks I can think of. They also sound very clean and natural, having no discernible character of their own: they simply amplify the mic signal to line level, with minimal effect on the original quality — which is exactly what I want from my mic amps! There might be one or two better‑sounding mic‑amps around, in top‑flight boxes costing not much more than this module. But they only have two channels, whereas this has 16, so on a cost‑per‑input basis, this module is excellent value for money, as well as being very hard to fault on sonic quality.

The line inputs are as up to the task as the mic inputs, with gain range and impedance perfectly suited for DI‑ing keyboards and guitars (although some guitar pickups might prefer a higher impedance than is provided by the Intermix).

Equaliser

The equaliser module is amongst the largest in the collection, occupying four units of rack space — but it does have more knobs to accommodate!

Connections to and from this module are via two rows of balanced jack sockets, plus a pair of inter‑module IDC multi‑pin connectors (wired in parallel with the jacks). The output jack sockets may be used as direct feeds if required, but the inputs should not be used at the same time as the Interlink connections, because of unpredictable loading conditions, which could damage the modules or connected equipment. Module power is provided through a third IDC connector, and this may be 'daisy‑chained' with those of other modules (up to the maximum current capability of the PSU).

Each of the 16 channels has four independent, sweepable, overlapping bands. Each band has one control to select the centre frequency, and one to set the required cut or boost (up to 15dB). There's a bypass switch for the entire equaliser at the bottom of each channel strip. For the record, the four bands cover the following ranges: 40‑650Hz; 150Hz‑2kHz; 700Hz‑10kHz; and 1‑15kHz. As you can see, the bands overlap nicely and seem to work well together. I was able to achieve all the creative and corrective equalisation effects I needed with no trouble at all, often with very small amounts of boost or cut in each section. The four sections are truly independent of each other, and I couldn't detect any interaction between adjacent bands with moderate gain settings.

Some (all?) equaliser designs have a distinct character: the Intermix EQ sounds very 'musical', working well with everything I pushed through it. It was usually very easy to find settings which enhanced each instrument and pulled out the qualities I was seeking, without damaging or distorting other parts of the spectrum.

Channel Faders & Routing

The track routing and panning module takes up another four units of rack space, and provides precisely those functions — plus a fader for each channel (always a handy thing to have!). Routing is provided for 16 groups (assigned in stereo pairs by eight buttons at the top of the strip).

A pan pot separates the group routing buttons from a block of four buttons which provide routing to a master stereo mix buss, AFL, PFL and mute (the latter with an LED indicator). At the bottom of the strip is a short‑throw (60mm) channel fader, calibrated with the usual 10dB of gain in hand, and a peak overload LED. The AFL signal is derived post‑pan pot, so it provides 'in‑place' monitoring.

Rear‑panel connections are plentiful, with three rows of 16 jack sockets catering for balanced inputs to each channel strip, post‑fader direct outputs from each channel, and all 16 group outputs. At the bottom of the rear panel are six IDC connectors in various sizes: a power connector; a pair of 'interlink' input and output connectors; another pair, each carrying eight of the 16 channels of pre‑ and post‑fader sends (intended to feed an auxiliary sends module); and a connector carrying the stereo mix and group busses, together with the PFL/AFL signals. This is intended for connection to a master monitor and output module.

This unit is most likely to be used as part of the complete Intermix mixer, rather than alone, though there are a number of applications where a 16‑input, 16‑output selectable matrix could be useful. The tech specs match those of the other modules, but I have to say that I don't like the faders very much. Being short throw (their size is limited by rack space), it's difficult to mix with any degree of accuracy or finesse, and the fader action is far too light. I'd like to see a module with decent 100mm faders, possibly as a table‑top box with an umbilical to a faderless version of the routing module.

Channel Monitor & Tape Returns

This 4U‑high module provides a means of listening to the group sends or pluggable tape track returns at the press of a button, for each of the 16 tracks. It also provides 16 60mm group faders, a monitoring level control for each group or return (on a rotary knob), an associated pan pot which feeds the stereo mix buss, a mute button (and LED), and an AFL button. There's also a fader reverse button which swaps the signal paths of the rotary control and the fader.

The busy rear panel hosts three rows of 16 balanced jacks, providing group insert points (the group side of the Tape/Group button), tape returns and group outputs. Below these are IDC connectors catering for power, pre and post auxiliary take‑off points, and interlink module inputs and outputs. Further IDC connectors provide input and output links to an optional second EQ module, the stereo mix, group, PFL and AFL busses connector, and a final connector to a metering module (available shortly).

A nice design feature is dedicated connections for an equaliser module, providing EQ in the monitor path. Similarly, the module provides feeds for connecting an auxiliary module, allowing effects and cues to be derived from the groups and/or tape returns.

Like the routing module, this unit is let down by the faders, but is otherwise a well designed and flexible part of the Intermix system, whose inclusion allows quite sophisticated multitrack mixers to be created

Auxiliary Sends

The 3U auxiliary sends module provides 16 channels worth of eight sends each. Auxes 1&2 are mono, with pre/post selection, mute buttons and independent rotary level controls. Auxes 3&4 are a stereo pair, again with pre/post and mute buttons, level control and a pan pot. Auxes 5&6 and 7&8 are stereo pairs with the same facilities, but these share one set of controls and an extra button to determine which pair is in use.

On the rear panel, two rows of 16 (unbalanced) jack sockets provide the pre‑ and post‑fade inputs for each channel. A third row of sockets provides the eight auxiliary outputs. The usual IDC sockets for power, pre and post inputs, auxiliary sends and the auxiliary mix busses complete the line‑up. The latter allows multiple auxiliary modules to be linked together: one module might provide aux sends from the channel routing unit, whilst a second does the same for the monitor section.

Master Control Unit

The master control unit is really dedicated to the complete Intermix system: I can't imagine any stand‑alone applications for it, although I'm sure someone will come up with one!

This module provides front‑panel controls to tie up all the loose ends from the other modules, making a fully‑functioning multitrack desk, albeit with relatively basic facilities. On the left are master output controls for the eight aux sends, each with an AFL button. Next to these are six 'aux' returns (a possibly confusing label — effects returns might have been better) with level controls, pan pots and mute buttons.

The central section contains a built‑in electret mic with level control, for talkback. Push buttons send talkback to all the group outputs, aux 7&8 (nominally the headphone cue mix), or the studio loudspeakers. The control room loudspeakers are automatically dimmed whenever a talkback button is depressed.

Monitoring facilities include a dedicated Studio speaker section, with a volume control, an On button, and selection for auxiliaries 5&6 or 7&8. I would have liked another button here which mirrored the control room selector (or at least a 2‑track replay machine) for instant playback to performers.

A Solo Master level control determines the monitoring volume of signals selected by the AFL or PFL buttons; an associated lamp shows that a solo selection has been made on the desk. To the right of this is the control room monitoring selector. Aside from the main monitoring level control, there are six buttons selecting between three 2‑track recorder returns, the stereo mix buss, mono and mute. This seems a rather basic provision, and a Dim control might have been useful, as well as a second loudspeaker output.

The picture is completed by a 100mm fader controlling the main stereo output, plus an LED bargraph meter calibrated from ‑21 to +12dB.

The rear panel has an assortment of connectors, starting with four jack sockets, providing a stereo insert point for the main mix buss. Below these are the three 2‑track monitoring inputs, and three pairs of XLR connectors provide outputs for the control room and studio monitoring systems, plus the main stereo mix buss. Jack sockets are provided for the six aux (effects) returns, as are two blocks of eight jacks for the auxiliary master inputs and outputs (the former being in parallel with the IDC auxiliary module connector at the bottom of the panel). IDC connectors are provided for power, the auxiliary mix busses (for talkback purposes), the auxiliary master outputs, and the group, stereo mix buss, AFL and PFL connector.

Impressions

My only criticism of the Intermix design actually applies to all of the Intermix modules. Their physical construction does not appear to be particularly rugged, and there are plenty of cheaper desks around that feel a lot more substantial than these modules. For example, the shafts of the control knobs are not supported through the front panel, so they tend to wobble about as they are rotated. Also, the front panels are not particularly thick and have no bracing across their width, so pressure around the centre causes flexing, which may stress the PCBs, increasing the likelihood of failure.

These points are clearly linked to the overall cost of the Intermix modules: in trying to keep the cost down, it's always difficult to strike a balance between the excellence of the electronics and the module's physical attributes. MTA have decided to place greater emphasis on the parts that affect sound quality rather than the mechanical components — an approach which is certain to win favour with many users. At the end of the day, personal perceptions and the requirements of the working environment will define how suitable these modules will be.

Some desks are specifically designed to survive being stood on: this isn't one of them! On the other hand, some desks are made to look and feel extremely solid, belying the fact that their electronics sound dreadful: the Intermix is certainly not one of those!

Despite my slight misgivings over some of the mechanical aspects of these modules, my overall impression is that the good points far outweigh the bad. The sound quality of every module is beyond reproach, the facilities are generally well judged, module interconnection is child's play, the entire system is incredibly versatile and flexible, and the whole concept is absolutely excellent. The mic/line and EQ units would be very useful as part of a large keyboard system, at home or on the stage. Equally, they would be an excellent way of improving the capabilities of existing recording equipment. In the same way, the auxiliary and routing modules could be used to extend the facilities of mixing desks which might otherwise become redundant, perhaps adding multitrack capability, or matrix outputs for monitor mixer duties. To sum up, I'm convinced that these modules will prove to be very popular, both as stand‑alone units and as elements of custom mixer configurations.