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This article was originally published in issue #38
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Now that mixer manufacturers have discovered that you can pack a powerful digital mixer into quite a small form factor and remote control it from a wi-fi enabled tablet, the floodgates have opened. UK Manufacturer Allen and Heath has extensive experience in digital mixing technology and the Qu-24 benefits from this experience.
Physically, the Qu-24 has a striking appearance with a sloping front panel that carries all the unit’s switches, encoders, moving faders and the 800x480 touchscreen - plus a place to put your iPad. The rear connector panel sits at ninety degrees behind the front panel and the designers have added a return that not only acts as a support, but also leaves a U-shaped space through the centre of the Qu-24 which helps in heat dissipation and the separation of digital and analogue electronics.
The rear panel carries the Qu-24’s inputs - 24 microphone XLR, 24 line level ¼” jacks and another four ¼” jacks for the two stereo inputs (there’s a third stereo input on a front panel mini jack). There are two stereo matrix outputs, four group outputs, four mono and three stereo Mix outputs on XLR with two separate XLRs for the main L/R output. Four ¼” jacks carry an alternate stereo out and an analogue 2-track stereo out.
Digital and computer connections comprise an AES-3 output on XLR, a dSnake Ethercon port to connect an A&H AudioRack (which allows you to have I/O on stage and to run an Ethernet cable to the mix position instead of a multicore), a USB connector that lets you attach the Qu-24s 32-out, 30-in interface to a computer (you can also map the faders to your DAW) and a network port which is where you’ll connect your wi-fi access point. Finally, you’ll find a 5-pin XLR lamp connector and the XLR connector for a talkback microphone.
Audio mixing, FX and system control are the responsibility of five ARM DSP chips. Mixing functions can be accessed not only via the faders, switches and encoders but also through, or in conjunction with, the front panel touchscreen and its associated switches and encoder. The touchscreen switches give you access to set up and essential operating screens such as those for Processing, Routing, Channel, FX and Scenes. Four additional buttons sit below the screen selecting Function, Copy, Paste and Reset.
Finally, on the extreme right of the front panel is a section that carries the third line input mini jack, the Qu-Drive USB input where you can attach either a USB stick or a hard drive for live multitrack recording, the socket and level control for a set of headphones and a physical level control for the alternate output.
The gain on all 24 AnalogIQ pre-amps is remotely adjustable and recallable in 1dB steps. The most essential channel controls sit in the so-called Superstrip block, which is complemented by the touchscreen interface that carries those channel facilities - for example, compressor attack/release that you’d normally set up at soundcheck - that don’t often need to be accessed speedily. Controls are analogue/USB input switching, gain trim, polarity reverse, high-pass filter, insert/ducker, 4-band parametric EQ, compressor and delay.
Routing-wise, you’ve got four stereo groups, four DCA (Digitally Controlled Attenuator) groups, four mute groups and four matrix outputs to play with. DCA groups channel faders whose levels are controlled as a group by one of the DCA faders. Unlike a conventional subgroup, no audio passes through a DCA fader - the audio remains entirely in the individual channels.
As mentioned previously, the rear panel mix outputs are configured as a main stereo mix, four mono mixes and three stereo mixes. A four-band parametric EQ, compressor and delay are available on all the main mix outputs.The Qu-24 is also compatible with A&H’s ME monitor system which individual band members can control via the Qu-You iOS app - assuming that they have iPhones, iPads or iPod Touches!
The Qu-24’s effects selection is taken from the iLive and is quite extensive, with four sends feeding four separate, stereo FX engines running a range of reverbs, delays and other time domain programs. All four stereo FX returns are equipped with four-band parametric EQ.
Finally, to aid you in setting up your entire PA system, there’s an onboard signal generator, a real-time analyser with peak frequency detection and a spectrogram display to help you in dealing with room acoustics and to spot potential feedback frequencies.
Since the dawn of time, bands have wanted to record their gigs and have hated soundchecks, and the Qu-24 is ideally equipped to help as its onboard USB recorder is able to record and replay up to 18 tracks at 48kHz either on a connected computer DAW or directly to a suitable USB hard drive. This means that the band can be recorded at rehearsal so that the sound engineer can get a soundcheck in before the gig without the band having to do anything more than just turning up and playing.
The Qu-24 is a pretty complex beast and you’re going to need to get yourself familiar with it before you go anywhere near a live gig. The quickstart guide is 22 pages long and the full manual extends to 91 pages. This is not a mixer you’re to try to wing it on.
Once you’ve got it up and running, sound quality is absolutely excellent and latency (specified at 1.2ms) is a total non-issue. The user interface, once you’ve got the basics under your belt, is highly intuitive and the interaction between the Superstrip and the touchscreen means that you can work quickly when necessary. The iPad mixing app sets up quickly, works smoothly and is again fairly intuitive to use - once you’ve studied the manual.
There are a couple of unusual features that aren’t overly common on any live mixing console. The “ducker” function reduces the level of any channel, group of channels or output and is used to give single or multiple microphones priority over others - for example if you have background music playing and want to make an announcement without having to pull faders down all over the place, or for an emergency announcement override.
The automatic microphone mixer is almost essential in conference situations where you want all mics live but you don’t want any open when the user isn’t talking. This function also comes in useful if the panel has a moderator (or important members) who need priority over all other microphones in order to maintain control or make their points unhindered.
To make life even easier, the settings for the entire mixer can be saved onboard in up to 100 scenes so that you could have, for example, one scene for when a singer/guitarist is singing with a guitar (amp mic and vocal mic on) and another when he/she moves across stage to sing at the piano (amp and guitar vocal mics off/piano and piano vocal mics on) and switch between them with one button press. The 100 scenes can also be saved onto a USB stick as a show file, allowing you to store settings for a number of different bands, duos or solo artists and recall any of them at the touch of a button - ideal for festivals or open mic nights.
Being able to add inputs via A&H’s AudioRacks allows you to operate more conventionally by placing an AudioRack on stage and running a dSnake Ethercon cable out to a conventional mix and lighting position. This means that you could have (for example) an AR618 stagebox and have eight local analogue inputs for things like radio mics that need to be monitored or controlled manually during the show. During the soundcheck, the sound engineer can also take advantage of the mobility that the iPad app gives him - providing that he’s got a wireless talkback mic (think about it).
The Allen & Heath Qu-24 is a very fine, professional-level mixer, with comprehensive facilities and a level of performance that makes it suitable not only for live gigs, but also for use in conferences and fixed installations. And, of course, if you don't happen to need this 30 in/24 out version, there are other models to choose from, including the 22in/12 out Qu-16 and 38 in/ 28 out Qu-32. It's also worth adding that this is an expanding series from Allen and Heath, now including accessories and software updates.
The Qu-24 isn’t the least expensive mixer of its type but, as far as I’m concerned, it has everything that you’d need to cope with any gig. It’s not all that long ago that I happily paid more than the price of a Qu-24 for a digital mixer that did considerably less, so I happen to think that it’s extremely good value for money.