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Effective Automators

Akai MB76 Programmable Mix Bay, PEQ6 Programmable Equaliser

Used together, the Akai MB76 Mix Bay and PEQ6 Equaliser can bring a limited but useful degree of automation to the MIDI-based home studio. Ian Gilby explains how.



If your music is predominantly sequencer-based and you wish to automate certain mixer operations, then you should be interested in two new budget-priced, MIDI-controlled processors from Akai: the PEQ6 Programmable Equaliser and the MB76 Programmable Mix Bay. Let's begin with a look at the MB76 unit. . .

You probably know that by the use of Program Change commands, MIDI can instantly recall parameter information stored in computer memory. In the recording studio, this ability allows MIDI to be applied to a growing number of tasks where some degree of automatic switching or selection is envisaged, the most obvious application being an audio patchbay or jackfield.

Although Akai's MB76 Programmable Mix Bay can be used as a straightforward 7x6 patchbay, it also has applications as an audio submixer in a MIDI set-up, as we shall see.


MB76 MIX BAY



The MB76 is aptly named. Basically, it allows you to route up to seven different audio signals connected to its inputs directly to any combination of its six outputs and/or to vary the levels of the seven sources and thus mix them.

The rear panel houses MIDI In, Out and Thru connections along with 13 quarter-inch jack sockets, which are unbalanced. The seven inputs are designed for connecting instrument sources such as keyboards and guitar, though they could be used with high impedance microphones (typically those fitted with jack plugs as opposed to XLRs). The six outputs operate at line level (OdBm, 600 ohms) and are thus suitable for connection to pro gear as well as home studio equipment.

What sort of things would you use it for? Well, imagine you don't own a mixing desk but have three instruments you would like to add reverb to. Problem is, your reverb unit only has one input socket, which means you can only connect one instrument at a time. What you need is some way of combining the output of each instrument into one overall output which you can then connect to the input of the reverb unit. Using the Akai MB76 you can do exactly that, by assigning inputs 1, 2 and 3 (say) to output 1, and connecting output 1 of the MB76 to your reverb unit. However, if your reverb unit has no direct/effect mix control of its own, you would hear the reverberated signal only-not much use. There is a simple way around this with the MB76-you could either assign the same three instruments to a second output as well, if you wanted a combined direct ('dry only') signal for instance, or you could assign each instrument its own dedicated output as well as routing it to the combined output that feeds the reverb, thus retaining maximum flexibility. In this way, up to seven different instruments could be routed to up to five different effects processors, keeping the sixth output of the MB76 to carry a dry mix of the seven instruments. Pretty useful stuff.

So how is this feat of ingenuity possible? On the front panel, each input source has its own Input Trim rotary control and an associated red LED. These controls actually attenuate (reduce) the levels of the input signals and when turned fully anticlockwise to the 'Off' position, effectively mute the input. If you intend using the MB76 purely as an audio patchbay, to route inputs to outputs in the conventional manner, then obviously there will be no need to vary the levels and so the Trim controls should be set fully clockwise for unity gain. Those inputs that are not required as part of a particular routing patch or mix can be turned off using their Trim control, or simply not included when defining the program. Turning the Trim control off is a fast way of temporarily cancelling a signal from the mix/patch rather than forcing you to modify the stored program. If you do wish to vary the levels however, to produce a 'mix' of the inputs, simply adjust the rotary controls to suit just as you would set the faders on a mixer. Obviously there was no way Akai could fit faders on a 1U high box, but the MB76 is not intended to be a replacement for a mixer, it is designed for those occasions when several levels need to be balanced and then left.

Having done this, you then assign the inputs to a chosen output which you select by incrementing the Output button until the required number is shown in the main LED display. You can then press the Copy/ Write button to copy this same mix to a different output if desired.

In this way, you can build up six different mono mixes of the seven inputs (one mix per output), and these can be stored in any one of the Akai's 32 battery-backed memory locations simply by incrementing the Bank number with the Up/Down nudge buttons then pressing Copy/Write twice. When you recall an already programmed Bank from memory, naturally you need some way of knowing which combination of inputs have been used. This is where the red LEDs above the Trim controls come in; when lit the corresponding input channel is active. The problem is, there is no means by which you can tell what the recalled volume level is. The front panel knobs will still be set to their previous positions whenever a new Bank is selected.

There are three ways in which to recall a mix from memory: you can manually select a Bank with the nudge buttons; increment the Bank number with a footswitch connected to the front panel Bank Up jack socket; or send the MB76 a Program Change number on whatever MIDI channel you are using. Any one of the 16 channels can be used.

Choosing the latter option allows for a certain degree of automation, where MIDI Program Changes can be recorded on a sequencer track at appropriate points in the music and sent to the Mix Bay to select a program Bank. In this manner it is possible to call up one mix setting for use during a verse, for example, then switch instantaneously to another for the song chorus, then to another for the solo, and so on. Obviously, you are restricted to a snapshot style of mixing, which is of limited use, but you could theoretically programme slight level adjustments and store each new setting in successive Banks, then recall those Banks in very quick succession with a sequencer to simulate a fade-in or fade-out. I tried this but it proved difficult to produce a satisfactorily smooth change - 32 successive snapshots (one per Bank) is too few to produce anything other than a very noticeable, stepped level change, however close together they occurred. Having said that, you could just about get away with this technique on certain types of non-dynamic music, where gradual level changes were not demanded, and a snapshot style of mixing could still be a handy tool in the right situation.

There appear to be plenty of potential applications for a unit of this nature. It would make a handy little submixer for anyone with several keyboards/expanders, particularly on-stage where its diminutive 1U size would take up little space in a rack, and there is less requirement for constant tweaking of levels. (Incidentally, when Bank 00 is selected, the level controls can be manually adjusted in real time, thus acting as rotary faders.) The MB76 could likewise be used to provide seven additional inputs on a conventional mixing desk, or indeed increase routing flexibility when connected to the send/return of a desk with only one or two auxiliaries. Anyone still using unbalanced, high impedance microphones could try connecting them to the MB76 and, by careful planning and programming, control the MB76 from a MIDI sequencer and have it mute those mic channels that are not in use, thus reducing unwanted pickup of extraneous noise.

Like all of their products, the Akai MB76 is well-built and pleasing on the eye (I far prefer Akai's pale grey panels to morbid black ones, any day!!). It appeared to add no noise of its own to the signal chain arid when switching from one Bank to another remotely via MIDI, there were no audible clicks or pops, which was comforting. All in all, the MB76 represents fair value for money and should prove a useful addition to most recording/stage set-ups. You could even disregard the MIDI control and level adjustment and use it purely as a conventional patchbay, but with the added benefits that programmability brings.

Price £249 inc VAT.


PEQ6 EQUALISER



The companion to the MB76 Mix Bay is the PEQ Programmable Equaliser, which looks virtually identical and shares many of the same programming characteristics. It too has 32 non-volatile memory locations (Banks) which can be recalled manually from the front panel, incremented by a footswitch, or selected automatically over MIDI on receipt of Program Change numbers in the range 1-32.

The PEQ6 is a seven-band graphic equaliser - or rather, six seven-band graphic equalisers in one box! The rear panel sports 12 paired input/output sockets, which are all of the unbalanced, jack variety with the output impedance being 600 ohms. These can be used to connect the PEQ6 to the insert points of any suitable mixing desk; alternatively, the unit can be connected in-line with up to six of the mixer's input channels, or subgroups, or at a push across the main stereo outputs of the desk. MIDI In, Out and Thru sockets are also provided. (The inclusion of an Out and Thru means the PEQ6 could be used as a two-way 'splitter box' for MIDI signals - 1 in, 2 out - and it does not recognise Program Change numbers above 32, so these may be sent from a keyboard without updating the PEQ6.)

Rotary controls are used to vary the amount of boost/cut of each equalisation band in place of the sliders found on most graphic equalisers. These offer a maximum of 12dB of signal gain or attenuation, which is not over-generous but sufficient for most jobs. An LED indicator above each control shows red when boosting signals, green when cutting, and is extinguished when set central to the 'flat' (no boost or cut) position.

Although seven bands of equalisation is pretty restrictive as far as graphic equalisers go, at least Akai have done their homework and chosen an excellent range of frequencies for the bands they do provide - 63Hz, 160Hz, 400Hz, 1kHz, 2.5kHz, 6.3kHz, and 16kHz. These are well positioned to provide control over most of the useful and troublesome frequency spots people encounter when recording, though the scope is obviously nowhere near as flexible as a good parametric. Although each band acts over a fairly broad range, above and below the quoted centre frequencies, there are inevitable gaps in the frequency spectrum not covered by the PEQ6, so it is best used in conjunction with a secondary source of equalisation like a multi-band parametric (this is true of any graphic EQ which offers only a handful of bands). Still, seven bands is considerably more than most budget mixing desks, portastudios or keyboard amplifiers are blessed with and for the budget-conscious the PEQ6 could prove extremely valuable when patched into channels or effects send/returns which have no EQ of their own. I suspect this is where the PEQ6 will be used most.

As the PEQ6 is effectively six independent equalisers combined, you can connect up to six different sources and equalise them individually, storing the settings of all six equalisers in one memory Bank. Each EQ has a number and you select it with the Line button. The programmable nature of the device is very appealing - there's nothing worse than having to arduously reset the EQ controls by hand on multiple mixer channels, in readiness for a mix. It's even worse than writing down the control settings of an analogue modular synth on a patch sheet!! (Anyone remember them?) Far better to simply call up the necessary Bank from memory. Trouble is, there are only 32 Banks and no external data storage is possible. It would be nice if it were possible to save/load the contents of all 32 Banks to and from a floppy disk using a System Exclusive dump via a computer, or to a sequencer. How about it Akai?

As with the MB76, the PEQ6 works fine provided you don't wish to make frequent changes to the control knobs. Altering programmed settings is a bit of a pain because you have to turn the knob past its centre position before the PEQ6's internal processor recognises that you wish to manually override the stored EQ setting. This takes you (and the equalisation) back to square one, ie. flat, and you have to waste time trying to set the right amount of cut or boost again instead of just being able to tweak the amount of EQ a modicum. If you can live with this way of working, fine; if you can't then I'm afraid you'll have to look elsewhere at other, more expensive, programmable equalisers - or stick with what you've got.

Price £299 inc VAT.

Contact Akai UK, (Contact Details).



Previous Article in this issue

Korg 707 Performing Synthesizer

Next article in this issue

How It Works: Multitrack


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 1988

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Gear in this article:

Mixer > Akai > MB76 Mix Bay

Studio FX > Akai > PEQ6 Equalizer


Gear Tags:

EQ
Graphic EQ

Review by Ian Gilby

Previous article in this issue:

> Korg 707 Performing Synthesi...

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> How It Works: Multitrack


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