Too many outputs and not enough inputs? Ian Gilby investigates this compact, versatile 16 channel submixer.

MIDI may have removed most of the headaches of interfacing different manufacturers' equipment but it has generated some interconnection problems of its own. The recording musician with even the most modest collection of MIDI instruments continually faces the problem of not having enough audio inputs on their mixer to allow them to make the most of their instrument set-up. The chief protagonist, of course, has traditionally been the drum machine with its eight or more separate audio outputs, but more and more instruments are being released with separate outputs - samplers, synth expanders (eg. Roland's forthcoming rack-mount version of the MT32 - the D110), etc. It's our own fault really: we complain if a new sampler does not offer separate outputs for each voice, but when the instrument manufacturers give us what we ask for, we complain that we've used up all the spare inputs on our desk and thus can't actually take advantage of these wonderous facilities to individually process each drum sound or sampled instrument! It's a growing dilemma too, made worse by the fact that few of us are in the financial position to keep on trading-in our old mixer for one with more inputs, as soon as we add another multitimbral expander to our MIDI network. (And, as the price of such expanders continues to fall, more and more users will eventually be confronted with this problem.)

So what is the solution? We could, of course, simply forget about using the separate outputs fitted to our equipment and use only the main stereo audio outputs which we can route to two channel inputs on the mixer - after all, a growing number of stereo devices include the facility to set individual voice levels and pan positions internally, so why duplicate the effort on the mixer? The answer is that it is simply far easier, faster and more intuitive to move a channel fader or tweak a pan pot during a mix than it is to access the internal settings of a drum machine in order to pan the hi-hat slightly more to the left.

The sensible purchasers amongst us, of course, would have anticipated the problem and would have chosen a modular mixer in the first place - one which could be expanded when required by adding, say, an extra block of eight input channels. The problem here is that most of the 'starter' ranges of audio mixer are not modular in concept, so musicians new to recording will invariably face at least one change of mixer as their instrumentation grows, unless they can afford a modular mixer at the outset. Few can, but it's definitely worth thinking about.

If you do require more input channels but are otherwise happy with your present mixer, or simply cannot afford to upgrade, there is one other potential solution and that is to make use of one or more submixers. Enter the Roland M160, stage left...

SUBMIXER CONCEPT

A submixer works very much like the subgroups on a multitrack mixer, in that it enables you to configure a mix of the individual volume levels of several sound sources and to control their overall balance from one or two 'master' faders. The individual outputs of a drum machine are the obvious candidate for this sort of treatment - you can feed each drum sound into its own submixer channel, add effects and equalisation if required, position each sound in the stereo image, then take the main submixer left/right outputs and feed the composite stereo drum mix into two input channels of your main mixer, remembering to pan one input hard left and the other hard right to preserve the original stereo positioning. Those two channels can then be treated just like any other single input source, although their faders actually act as subgroups controlling the level of the stereo drum mix within your main mix.

It is for this type of application that Roland have developed their M160 Line Mixer. It offers 16 input channels, and both balanced and unbalanced stereo outputs, all in an extremely compact, 4U high, rack-mounting black box. It has obvious applications as a drum or keyboard submixer for both live and studio use, and could massively enhance the creative scope of the home recordist who owns plenty of sound generating/processing devices but prefers to demo songs on a 4-track cassette recorder instead of a full-blown multitrack reel-to-reel system. After all, with today's sequencer technology, you just need a mixer with plenty of inputs, plenty of effects sends/auxiliaries for adding external effects processing of the sounds, and some means of balancing levels - there's no need to put everything down on tape if the majority of your sound sources are electronic in nature. You can make do with fewer tape tracks as these can be left for recording acoustic sources, such as vocals, and a sync code. With these needs in mind, let's take a look at the M160.

FEATURES

The M160 adheres to tried and proven mixer design with the channel inputs laid out on the left, master outputs to the middle/right, and auxiliary send/return controls on the far right. Two peak-reading LED bar meters are provided above the master faders, which indicate the left and right output signal levels. Monitoring of input signals before the master faders is taken care of by two small pre-fader LEDs located just below the meters. These glow green when channel signals are above —20dB and red at the onset of clipping (—6dB). The same system is employed on each of the 16 input channels to monitor the input signal peaks and is used in conjunction with the input channel Sensitivity control to set the optimum signal level.

Channels 1 and 2, incidentally, are primarily designed for microphone inputs, being rated at -50 to -10dBm. Channels 3 to 16 are intended for line level signal sources, such as direct feeds from synthesizers, drum machines etc, and are nominally rated at between -20 and +4dBm. However, all channel input connections are via quarter-inch unbalanced jack sockets on the rear panel, which means you can't use quality microphones fitted with XLR connectors - cheap dynamic mics only, I'm afraid.

Each input has its own pan pot and short-throw (30mm) channel fader, which is nonetheless pretty smooth in operation and perfectly adequate for the job. Accompanying these are three independent Effect Send level controls (all post-fader) and one Auxiliary Send control. Pressing the Aux Select pushbutton on the far right, the circuit can be switched so that all 16 channel Auxiliaries are either post-fader-ie. they function as a fourth Effects Send - or pre-fader, in which case they can be used to set up a mono foldback mix for monitoring purposes.

Rather unusual for this price range is the fact that each of the three dedicated Effects Send busses has its own pair of stereo Return jacks on the rear panel (the Left socket can be employed as a mono Return provided the Right jack is left unconnected). In this age of inexpensive stereo signal processors like the Alesis Micro Effects range, far too many budget mixers still fall down by offering only mono effects returns. Thank you Roland, this is precisely what we want to see! All we need now are stereo Sends to take advantage of the stereo inputs you find on many of today's digital reverb units - still, we can't expect everything for this price can we.

The Aux Return is mono but it does have its own pan pot for positioning the Return signal in the stereo mix, and there are 'master' Send and Return level controls located on the far right of the front panel for each of the four auxiliaries. There is also a very handy slider switch on the rear which lets you select either -20 or +4dBm input levels for Effect Returns 1 & 2 only; Returns 3 & 4 are permanently set for +4dBm operation. This makes it easier to accommodate both professional and budget signal processing gear on the one mixer, particularly those effects units which have no output level control of their own. As it stands, the Effects/Aux configuration of the M160 mixer works very well and offers a welcome degree of flexibility.

PHONES MIX

As well as the obligatory stereo headphone socket and level control mounted on the front panel, one very clever bit of design is the inclusion of a direct Phones Mix In jack on the rear. There is no means of controlling the input level at this socket (other than on the source unit) but it has several useful functions. For example, when using the M160 as a submixer, by connecting the monitor mix output from your main mixer to the Phones Mix In jack, it is possible to hear that mix on the headphones - signals fed to the Phones Mix In socket are not routed to the master outputs by the way, only to the headphones. For the record, the headphones monitor the channel signals after the channel faders but before the master left/right faders.

More useful, however, is the recommendation by Roland that this Phones Mix In socket be used for the connection of an external metronome or click-track. This means that you could monitor the metronome output from a sequencer or drum machine on headphones, without tying up a valuable input channel but ensuring that the metronome sound is kept out of your main stereo mix, which is just what you want if you are a drummer or keyboard player playing along with a pre-programmed drum pattern or sequence.

If 16 channels is not sufficient for your mixing needs and you aren't short of a few bob, you could always buy two M160 mixers. The reason I mention this is that the M160 features four dedicated Bus In jacks on its rear panel. These are designed to be used when you wish to cascade two or more M160s together to extend the number of available channels but still wish to route the additional channel signals to the same group of effects processors. To do this you connect the Effect/Aux Sends of the slave mixer to the Bus Ins of the master mixer, and connect the effects devices to the Send/Return circuits of the master M160 in the normal fashion. The Effect/Aux level controls on each slave channel are then set up in the same way, but the tapped signals are fed through to the master mixer's Effects loop instead and then out to the connected peripherals for processing. Although I could not test this facility myself (I only had one M160 for review), I shall assume that it works.

The remaining connections on the rear panel are the master left and right outputs. Roland have been generous here and provided two sets of stereo outputs: an unbalanced pair of jacks, and a balanced pair of rugged XLR connectors (with pin 3 wired 'hot'). Both sets of outputs function simultaneously, thus allowing the XLRs to feed a stereo power amplifier and pair of monitor speakers, say, whilst the jacks may be used to feed a main PA mixer, in a live performance situation, or a suitable tape recorder for home or studio recording applications.

At this point let me put in a good word for Roland's well-designed rotary controls. With 16 sets of channel controls to fit into the limited space of a 19-inch box, I was pleasantly surprised at how easy it was to manipulate things on the M160. Although smaller than conventional mixer controls, the control knobs are nicely tapered and large enough to grasp easily without scraping your fingers on adjacent pots. Their positions are also easy to identify from a distance, thanks to the use of coloured pointers on the knob caps. The pan pots all have detents at their centre positions, as well.

TRANSPARENT

So how does the unit sound? Actually, it has no identifiable 'sound' of its own, it is almost an electronically transparent device. This is due in part to the fact that the M160 has no onboard equalisation facilities. Roland felt it unnecessary, in the light of its intended application as a keyboard submixer, to add EQ as it would have made the unit prohibitively expensive to manufacture and therefore unviable. I don't see the lack of EQ as too much of a problem myself, provided the M160 is not the sole provider of mixing facilities in your system. Although synthesizers are capable of much more varied tonal modification than most mixer equalisation circuits, and you could argue that synth sounds can be better modified at source, there would undoubtedly be a need for channel EQ were the M160 being used to submix individual drum machine outputs, for example.

In fact, the lack of EQ proves a big bonus as far as noise generation is concerned, for the M160 is very quiet - the equivalent input noise level is quoted at -124dBm and channel crosstalk is good at -70dBm (@ 1 kHz), and reality seemed to bear these figures out.

CONCLUSION

There are plenty of possible uses for the Roland M160 mixer - both live and in the studio - and you won't find many competitors that can offer 16 channels of quiet, almost noise-free mixing, and four auxiliaries (three of them with stereo returns) for this sort of money. The unit is well-built and beautifully compact, without the controls being at all cramped. And the logical layout means that you can get on with the important business of making music instead of playing at being a studio engineer.

My only criticism, apart from possibly the lack of EQ, is that there is no scribble strip provided for identifying the sound source in each channel - a necessary requirement I would have thought. Although free space is at a premium on this device, it would be possible to include such a strip across the top of the front panel in place of the channel identification numbers, which could be re-positioned below the channel faders where they would be of more immediate use. This may seem like unnecessary bickering on my part, but some means of identifying signals is an absolute must on any mixer, especially a 16 channel version. I only wish more manufacturers would wake up to this fact and not expect users to rely on pen and paper!

Price £725 inc VAT.

Contact Roland (UK), (Contact Details).