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Using a Mixer: Rehearsals

    Before you’re ready for arenas and stadiums, where you’d no doubt call on the services of an experienced sound technician, you need to rehearse. And as long as you’re rehearsing you might as well do it in the right conditions: where everybody can hear themselves and in turn be heard. This means adequately controlling sound levels and using your sound system correctly. And most of the times this means: understanding and using a mixer...

    Before you’re ready for arenas and stadiums, where you’d no doubt call on the services of an experienced sound technician, you need to rehearse. And as long as you’re rehearsing you might as well do it in the right conditions: where everybody can hear themselves and in turn be heard. This means adequately controlling sound levels and using your sound system correctly. And most of the times this means: understanding and using a mixer...

    Even though the "Garage Band" setup, with everything plugged into guitar amps at full volume (including mics and keyboards), has helped many musicians progress and go from amateurs to experienced amateurs, even professionals, it’s relatively easy to rehearse in a more practical way that’s more consistent with professional standards. It would be a good idea to stop the "do it yourself" method as soon as possible, which, even though it lets you set up relatively quickly without having to carry heavy PA equipment, won’t suffice for many situations and won’t correspond to the real world of sound technicians and live gigs in bigger venues. Rehearsal rooms often have equipment that lets you practice in a more professional manner and which won’t damage your ears. For a reasonable budget, it’s also possible to set the same thing up "at home" ...

    How many inputs do I need?

    Plan de groupeFig.1

    Our group "example". There are three singers, an alto saxophone, electronic drums, keyboards, and the sound module going into the mixer. Four microphones, and five inputs from electronic sources. Only inputs are shown.

    The first question to ask yourself is whether everything will be sent through the sound system, which is usually the case on a real stage, or if only certain sources will be amplified by the sound system. In most cases, due to lack of equipment, the second option is chosen, at the expense of a real sound check, to prepare for a show ... So you try to get the most out of what you’ve got, depending on the situation. Singers will of course be the first on the list to go into the sound system, as well as any keyboards and/or wind instruments in the band. Let’s say that the guitars and drums won’t be using the sound system. Fig. 1 shows a group with: 2 singer-guitarists, another singer, a bassist, a keyboardist using two instruments, a saxophonist and a drummer using electronic drums. They’ll need a mixer with at least eight channels, assuming the keyboards use "mono" connections... When choosing a mixer, you should choose one with at least one third "more" channels than what you usually use. In this case, a twelve channel mixer would be a reasonable minimum and sixteen channels a comfortable investment for the future! One tends to feel like their over-sizing this type of equipment ... but things could get very tight as soon as more musicians join the band or if you want to connect the whole group (including guitar/bass amps) into the mixer as you would do in a large venue.








    How many outputs?

    The choice among 16-input mixers is fairly wide and it won’t be difficult to find the right one for you. However, you also need to decide how many outputs you’ll be needing. A pair of stereo outputs is of course the minimum. But the singer will probably appreciate having a monitor, same for the drummer, whose electronic drums don’t produce much of an acoustic sound without amplification. The keyboardist would also probably like one too since he probably doesn’t want to haul around a keyboard amp just to hear himself better. If you want to eventually be able to add some effects to vocals, it’s a good idea if the console has an auxiliary out, post-fader. To sum up: a main stereo output, at least two independent monitors, ideally three, in aux out, pre-fader, and an aux out post-fader. So 6 outputs that will be controlled with your mixer. To illustrate these examples we’ll use a Yamaha MG166CX. This small analog mixer has 8 mono channels, six of which have a small compressor on the "mic" input, and four pairs of stereo inputs, two of which are equipped with an XLR input for "mics" and two with RCA inputs. There’s a switchable global phantom power for any condenser mics or DI boxes. Finally, the MG166CX also has integrated digital effects with reverb, chorus, flanger, and delay. Being within range of an average budget, rackable and particularly light to carry, it’s one of the ideal rehearsal mixers.



    Where do I plug in?


    Entrée 1Fig.2

    A close up of the connection section of the Yamaha. Note the XLR "mic" inputs and jack "line" inputs, and on channels 1 to 8, insert jacks to connect dynamic effects.


    Let’s take a more detailed look at the connections of your equipment. Microphones will of course be connected into the XLR inputs of the channels. For "line" sources, use the asymmetric "Jack" inputs (Fig.2). Note that the insert inputs on channels 1 to 8, allow the use of an external dynamic effect (compressor, limiter, noise-gate ...). Channels 9/10 and the rest are stereo (Fig.3). So you’ll be connecting the electronic drums output to one of these, and why not, the keyboard outputs . However, Yamaha has also foreseen the possibility or necessity of connecting an additional XLR microphone. But in this case, the "stereo" channels become "mono"! The Yamaha MG166 is not a "real" 16 channel mixer, but ... A 12 mic channel + 4-line-level channel mixer. You’ll need to take this into account when making your choice!

    Entrée 2Fig.3

    Stereo inputs. Channels 9/10, and 11/12 are for connecting stereo equipment, or using an XLR microphone (on 9 and 11 only). Channels 13/14 and 15/16, also stereo, don’t have XLR inputs, but the jack inputs are coupled with RCA inputs. Also note the "2 track in", allowing the connection of an additional source connected directly to the "Mix" bus but without any settings.


    There is no set order to cabling channels on a mixer since they’re interchangeable. But in a live setting, it’s sometimes conventional to find from left to right, drum channels, bass, guitar, and then all the others depending on their location on the stage, to make it easier for the technician know what is where. In rehearsal, this of course doesn’t make any sense. In our case, all channels are not identical. It’s probably wiser to keep the channels with compressors for singers and why not also the drums, via "line" or XLR (Fig.4). In the latter case you’d need to use two DI boxes whose function is to balance the signal, adapt impedance, and match levels (Fig.5), as we did, at the end of the example, for keyboard outputs. In the case of a rehearsal room, where cables and cable-length are often quite limited, the use of a direct box is not necessary and may even be regarded as a luxury. However, in case of "humming" and "buzzing" problems, our little "magic box" is likely to solve the problem ...

    connectique entréeFig.4

    Connecting your equipment (inputs). The "instrument" sources are all here connected (via jack) to the line inputs.

    Boite de directFig.5

    A direct box (DI) is a small box used to adapt an unbalanced high impedance line level to a low-impedance balanced mic level. From a purely "practical" standpoint, a direct box adapts a (line level) jack output of an instrument to the XLR input (mic level) of the mixer. Its use on stage is essential in order to limit risks of signal perturbations due to long cable lengths. In rehearsal, it could be considered a luxury ...




    Gestion auxiliairesFig.6

    Extract from the Block and Level diagram. Two auxiliaries are directly accessible (the 3rd one is assigned to the integrated effects). The first is pre-fader, the second is switchable to pre or post.



    The pre/post switch for an auxiliary must be switched to "pre" for use with monitors.

    The number of outputs needed in our example are five or six, as mentioned above: two stereo outputs, and three monitor circuits. There’s a snag ... the mixer only has two auxiliaries (Fig.6). On the other hand it has an integrated multi-effects. The first auxiliary is systematically pre-fader, and the second is switchable pre or post. We must therefore set it to pre-fader. Since we need three monitors, it would be wise to combine two of them. The most sensible thing to do would be to group keyboard and drums and keep the vocal monitor isolated. (Fig.7). The stereo outs of the mixer are doubled, XLR or jack. Given the likely short distances in a rehearsal room, between mixer and amp, the wiring could easily be done using jacks. For monitors, connect the two inputs of the amplifier (or each amplified speaker) to "Aux Send" 1 and 2, and don’t forget to switch aux 2 to pre-fader (Fig.8). If it’s absolutely necessary to separate both keyboard and drum monitors, there’s an alternative, less "pro", but functional, solution: you can use a group out for the drum monitors after allocating the channels to the "Group 1" bus for example (Fig.9). It won’t be possible, in this case, to mix track levels of this group any differently from what is "sent" to the main outs. Last solution: when all groups are already used or when there aren’t any on the mixer: you can use the monitor outs, which are controlled by a knob and for which, again, the "mix" is the same as what’s sent to the main mix ...



    Keyboard and drum monitors will be linked on the same channel, and the vocal monitor will be isolated.

    Affectation busFig.9

    You can, within certain limits, use group outs to serve as monitor outs. You need to assign the channel to the group with the appropriate switch. The output level of monitors will be adjusted with the group out fader.

    Connectique sortiesFig. 10a

    Output connections. They are all made here via jack connections. Note the send to a third monitor, coming from a group.

    Sorties consoleFig. 10b









    The integrated multi-effects of the mixer. The big knob lets you select the effect, while the white button below that adjusts the parameters of the effect. Note that you can assign the effect to the auxiliaries: singers will appreciate it in their monitors ...


    The MG166CX has a multi-effects, which features 16 presets corresponding to most basic needs (Fig.11). It appears on the bottom of the mixer like an additional channel called Effect Return. The bottom looks like a normal channel strip with a fader and switches and the top has the parameter settings. There are 8 reverb programs that can be applied to sources connected to the mixer. The voices of the three singers will of course benefit from this processing. Each channel has a send towards the effect placed under the auxiliary and identified by a white knob. (Fig.12). The setting of this button will specify the amount of signal sent to the effect which also receives the sum of all "sends" of each channel. The Fader will mix the effect (after processing all tracks assigned to it) into the main mix output. This is handy for reverb, since you can globally process voices which will even out the sound, but dangerous when we you want to use a flanger, auto-wha or distortion which is better reserved for a single instrument ... It should also be noted that the reverb can also be sent to the monitors, thanks to the aux 1 and 2 sends in the effects channel. Singers will appreciate this, because they’ll hear themselves with the reverb which will of course (in most cases) make their voices sound better...

    Départ effetFig.12

    Every channel has an effects level knob (under the auxiliaries) that determines how much signal is sent to the mixer’s multi-effects.



    The compressor. It would be difficult to find a more basic one! A single knob for channels 1 through 6. The knob adjusts the compression ratio while output gain is automatically adjusted, that’s all!













    The three band EQ on the mixer. The mid is semi-parametric (frequency & gain) and lets you effectively adjust the sound of vocals.


    The use of the compressor (Fig.13) will also be valuable for the vocals. This compressor doesn’t represent state of the art compression, but it can serve to instruct you on the uses and effects of compression. The compression ratio is fixed, and the single knob effects both the gain and the threshold. You’ll need to make several tests depending on the of style of the group: levels won’t be the same for lounge music or thrash metal ... It could also be interesting to apply it to the electronic drums, which explains why we connected it to channels 1 and 2. By the way, don’t forget to pan extreme left and right so as to get a good stereo image.

    The "mono" channels have a three band equalizer, with a semi-parametric mid (Fig.14). This may be valuable for enhancing the singers’ tone and refining the saxophone sound. But note, we’re talking about correction and not EQing! This means that their use should be limited to compensating and correcting a bad mic and/or the venue and not a bad singer! On the whole, for voice, you tend to reduce low-mids a little bit.





    Tips & Tricks

    2 tracksFig.15

    The "2 tracks In" setting lets you connect, via RCA, a cd player or any "other line" source.



    We’ve described a "normal" situation for a mixer. But ... a rehearsal might occasionally require some additional needs. First possible scenario, the sudden arrival of new musicians: of course you’ll connect the new instruments to the "line" inputs of channel 13 and other free channels. If there aren’t anymore channels, two additional hidden line inputs are still available: a stereo return, sent to the mix or to both auxiliaries, which have no settings, and the "2 tracks in" (Fig.15) sent to the mix via RCA connectors, which can connect a stereo line level. For example, you can connect DJ hardware or a stereo instrument using jack/RCA adapters.




    The assignment selector of the channel. The routing is done to both an even channel (right) and odd (left). By completely panning to one side or the other you can opt to send the signal to only one of the two.


    So the rehearsal was successful and you’d like to record it the next time around? If, like in this case, the mixer has Record Out connections, there’s no problem. You can record the main Mix in stereo by connecting, via the RCA connectors, a Mini-Disc, CD recorder or directly into a computer soundcard. By the way: if you opted for the 166-USB, you could connect the mixer directly to one of your computer's USB ports and record your Mix directly into Cubase 4 (included with the mixer)! This of course requires that you install an extra pair of microphones, to globally capture all instruments not directly connected to the mixer - the guitars and bass, in this example - or that you record each of them separately. It would be better, in the latter case, to use a DI box on the bass inserted directly between the instrument and the amp on the one hand and the console on the other, rather than use a microphone. Caution: you’ll have to reduce the general volume level to the minimum needed to ensure that the mics don’t start feeding back ...



    Ok, but ... the computer’s audio interface has eight inputs and you’d like to record everything at the same time! It would be a shame not to take advantage of this while also using the compressor and EQ of the mixer ... There’s a trick that will probably make the "pros" shudder with horror but in rehearsal ... you sometimes do what you can! If you accept in this case, to reduce monitoring to a single monitor and not use effects that can be added with your computer, you can get exactly eight outputs! The four groups are individually selectable through switches (fig.16) and you can, by panning, choose to "route" the signal to an individual output. The main outputs will behave in exactly the same way, so there’s two more! You could, on the mixer, use the bus used by the effects: by inserting a jack into the "Effect" connector (Fig.10), it bypasses the internal multi-effects and you can use this output to send a signal. It’ll be a post-fader send, but "you do what you can"! That’s one more... Then use the two pre-fader sends to get your eight outputs. All are fully autonomous and will let you record 8 tracks simultaneously. It’s almost ... (but not quite) as easy as using a mixer with a FireWire interface ... But that's another story ...

    Even if technical requirements are not as demanding in rehearsal as a live show (unless your preparing for the tour of the century), it is still important that everything go well, without major problems getting in the way of the quality of your music and protecting everyone’s ears! A good rehearsal isn’t necessarily one in which you played as loud as possible. It would be wise to prepare a little before in order to avoid wasting time later. It may not be such a big deal when rehearsing at home where time is plentiful, but in a rehearsal studio time is money and there’s usually people after you waiting for the same room. So plan in advance how you’ll be using your equipment, even if you won’t be doing things in such a "conventional" way: don‘t wait until the last second to get to know your gear!

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