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Mix Amp Headroom

That Brand X mixer sounds OK at the music store when the salesperson demos just two channels with a CD player. But then you take the mixer home and connect all 16 channels to a pair of sizzlingly high-output ADATs or DA-88s – when you start mixing down it sounds like a Buick hitting a row of empty garbage cans. You're out of mix-amp headroom.

Headroom– the ability to handle multiple, intense signals without distortion – has always been what sets pro consoles apart from hobby toys. Our mixers have headroom to spare, even when you've loaded every channel with hot inputs. In fact, our compact mixers are the Number 1 choice of professional electronic percussionists for just that reason.

The bottleneck in any mixer is the mix amplifier, where all signals come together. If it can't handle the full force of a dozen or so simultaneous inputs plus aux returns, you hear some very gnarly distortion. Basically, as more and more signals are summed together by a console mix amp, its output level invariably rises toward the maximum operating level. As you can see in the top figure, each time the number of input signals is doubled, the output level goes up by as much as 3dB. It doesn't take long to overload a conventional mix amp. And backing down the main faders doesn't get you out of the red, since the bottleneck problem occurs before this point.

All Mackie mixers have main mix amps that use our distinctive negative gain mix amplifier architecture. Instead of mixing channels together at unity gain where headroom is quickly exhausted, our mixers get more headroom by mixing at -6dB (second figure). At this negative gain level, they are capable of summing four times the number of hot signals before clipping (last figure). That nets out at double the amount of mix amp headroom available with many other compact mixers.

You'll notice the difference whether you're mixing keyboards, drums and vocals live or mixing down digital multitrack recorder outputs in the studio.

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