While I’ve written about gain structure before, I continue to run across people who don’t fully understand it. And that means one thing; I need to keep writing about it. I actually understand why many people have a limited understanding of proper gain structure. It’s not glamorous like plug-ins or digital consoles, and there is really nothing new to discuss. However, if you’ve never gotten a good handle on how to properly set gains on your console, there is no time like the present to learn.
If your gain structure is whack, no amount of EQ, plug-ins or compression will fix it. For this post, I will focus primarily on input channel gain structure (overall system gain structure is another post, but I’ll mention it briefly).
To Hit the Pre's Hard Or Not?
It has often been debated whether it is better to hit the pre-amps hard then turn down at the main output, or run the mains up around unity and dial back input gain to get the SPL you want out of the system. As a general rule (there is an exception, which I’ll detail in a minute), I would argue the former is the correct (or at least better) method, and here’s why. Most pre-amps sound best when you hit them pretty hard—at least up to the point of clipping, which is too hard. By running your pre-amps hard—and by hard I mean within 6-12 dB below full-scale on a digital board, or within 6-12 dB of clipping on an analog board—you are maximizing your signal to noise ratio. Typically, preamps just sound better when you keep the levels up. Keep in mind, that’s a general rule, your mileage may vary. Now, it’s quite possible that if you dial your input gains up so that all your pre-amps are running high, your overall system level will be too high. That’s when you would lower your main level to compensate. This method will keep the signal to noise ratio high throughout the mixing chain, and will attenuate the signal at the last possible moment.
Goals of Proper Input Gain Structure
Before we get to setting up the gain structure, let me lay out my goals in for the process. First, I want to maximize S/N ratio. Keeping the input level high means I won’t be boosting it later, which adds noise. Second, I like to mix with my faders around unity. Mixing with faders at unity is another key ingredient to good mixing.
The fader resolution is highest right around unity, so you can easily make small adjustments. If you try to mix with your faders at -20, a slight change in fader position might yield a 3-5 dB change rather than the 1-2 you actually desire. Finally, I want to be sending a very solid signal out of my mixer to the processors to again maximize signal to noise.
Using All the Bits?
At one point, I believed that if we were mixing in the digital world, we wanted to try to use up as many bits as possible to keep S/N high. And that may have been true at one point, but now that even inexpensive consoles are using 24, 36, 40 and higher floating point resolution internally, we effectively have unlimited dynamic range and high S/N ratios. Modern digital consoles are very quite and have great dynamic range. So the point of running the input gain high is really to extract the best tone out of the pre’s.
So now that we have some understanding of the goals of the process, we need to consider how to properly set up the gain on the console. And that will be the focus of the next post.