Setting Up Input Gain—In Conclusion...


For the last few posts, I’ve been delving into the topic of setting input gain. Apparently that struck a nerve, as it’s generated some great conversations on Twitter. I’m all for this, as we can always learn from others. 

Some people (cough…Jake Cody…cough)* took issue with the concept of the Fader Unity approach. That’s fine; I’m not married to a particular method, but I think his issue is the result of a fundamental lack of understanding of what I was saying. To be clear:

In all cases, the input gain still needs to be set properly. That is to say, you should be within 6-12 dB of optimum input gain across the board. Some seemed to think I was implying it was OK to run your inputs at −40 so long as the faders stay at unity. That is not correct. If you find your inputs are consistently that low with your faders at unity (and with the output somewhere near unity as well), you have a an overall system gain issue, and it needs to be addressed. 

When I set my faders up at unity, I find my inputs are generally within 6-8 dB of each other—and are in the ballpark of being where I think they sound the best (in my console’s case, about −12 dBfs). And while I could sweat those lost dBs, I don’t. Mainly because it’s not that big of a deal. 

In the interest of clarity, I’ll rephrase this again:

If you input levels are consistently way too low or way too high, you need to look at system gain. Find out where your preamps sound the best, and strive to get close to that level on most of your channels. Then adjust the overall system levels to achieve proper volume in the room. At that point, you can decide between Maximized Preamp Gain and Fader Unity, and it honestly won’t make a huge difference in the overall sound. 

Then there is the digital bits argument. Others (cough…Lee Fields…cough)* argued that you have to run every input to the maximum level to achieve the maximum resolution. While that is theoretically true, I would argue that it’s practically not a major issue in this century. Back when digital audio was in it’s infancy, there wasn’t that much resolution to begin with. Now that we’re using 24-bit and higher Analog to Digital Converters (ADCs) and 40-bit floating point internal processing on modern digital desks, the practical difference between 0 dBfs (full scale) and −12 dBfs is pretty minimal. And by practical I mean what you can actually hear in an actual live mix.

Again, I’m NOT saying run your inputs at −40 dBfs. I’m saying don’t stress out about trying to use up every last bit in the digital process. It just doesn’t matter that much in practice. In fact, if you try to use up all the bits, you may make things worse. Musicians tend to play louder in front of a crowd, so if you max out your gain during soundcheck, you’ll likely be into distortion come service time. And digital distortion is not so pretty; though again, through modern trickery, it’s not nearly as bad as it used to be.

Also, if you have some time to kill and want to hear some interesting examples of this, head over to Ethan Winer’s site and look through his tests on dither and bit depth. Fair warning; once you get started there, you’ll find hours go by pretty quickly. 

The reality is this: there is way more going on in live sound that simply maximizing preamps or bits. In 99.5% of live music venues, there are way bigger problems than absolutely ideal input gain. And based on many of the mixes I’ve heard at various events this year, the biggest problem is not the gear at all. But that’s a different post. This is not to say that gain structure is not important. It most certainly is. I said as much at the beginning of the series. However, once you’re in the ballpark of proper input levels, there are dozens of other factors that will make far more significant impacts on your sound quality. Not the least of which are the musicians on stage, the PA and the room acoustics. 

Settle on a method that works for you. You need to choose a process that works well for you, your team and your church, is repeatable and delivers consistently good results. Do that, and don’t worry about the rest. Remember, if you ask 10 sound guys how to best set up input gain, you’ll get 11 answers.  And for every one who insists that preamps always sound better when cranked up as much as possible, you’ll find another who believes preamps sound better when dialed back a little bit. And there’s always another who doesn’t believe you can hear the difference anyway (check out Ethan’s listening tests…).

In conclusion, relax…deep breaths…and focus on putting up a great mix. And enjoy the process.

*Notes: Both Jake and Lee are good friends of mine and I’m just giving them a hard time. Mainly Jake, because he blew up my Twitter feed last week. Which did help my “engagement” scores on Klout. So thanks for that! In fact, I wanted to start off this post with, "Jake doesn't know what he's talking about..." and I told him that Friday. He laughed and said I totally should, but I thought it could be interpreted wrong. So we're just having fun here, OK?

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