Audio basics for streamers part 2: preamps, mixers, and interfaces

Last time, we took a look at the different types of microphones and some specific models you might use. We’re going to gloss over cables (because you should always get a quality one) and skip to the next part of the signal chain: preamps, mixers, and interfaces. I’m grouping these all together because a lot of people get them confused and because they are actually somewhat related. Let’s dive in.

Preamps

There are three basic signal levels in the audio world: mic, instrument, and line. Line level is the standard, so the goal of a preamplifier is to increase a mic or instrument level signal to line level. It’s a pretty simple objective, but the quality can vary wildly from one to the next. For example, your computer’s sound card, as long as it has a mic input, has a preamp, but it may be noisy or generally not sound very good. Most audio interfaces these days have decent preamps in them, so that can be a nice upgrade if your computer’s sound card isn’t very good. And you can also buy standalone preamps like the UA Solo 610 I have if you really want an improvement (though that would be extreme overkill for streaming).

Long story short, preamps are necessary, but you don’t really need to think about them as separate from other pieces of gear you need to use with your mic. It’s just helpful to know what they do so you can troubleshoot your signal quality later.

Mixers

One of the biggest misconceptions people have when they are just starting out is that they need a mixer. They saw a picture of a studio somewhere with a big mixer and though, “Wow, I need that!” The thing is, you don’t. Before computer recording was a thing, albums were mixed on enormous analog studio consoles, but these days, most of those are just control surfaces that move digital faders in a computer. They don’t actually process any sound. Similarly, the only real reason to use a mixer these days is for mixing a live show – a concert, for example. With streaming, mixing is done in the computer. If you mix everything with an external mixer before it gets to your computer, you actually end up losing functionality because everything is on a single audio track. You can no longer apply filters to individual elements or split them to multiple tracks in your video file.

The one potential use of a mixer is to take several external analog sources, like retro game consoles, and condense them down to a single output. A lot of old consoles output at different volumes, so this would allow you to balance them to get consistent levels from one console to the next. Of course, if you’re converting their signals to digital anyway, then there’s not much reason to do this, especially since you could just set up different scenes in OBS for the different volume levels. Basically what I am saying is don’t buy a mixer. You don’t need it.

Audio interfaces

Think of an audio interface as a fancy sound card because, well, it is. We just like to use fancy words to distinguish professional audio gear from regular PC components. The core function of an audio interface is to take your analog audio signal and convert it to a digital one (and vice versa). This is where the term AD/DA converter comes from: analog to digital/digital to analog. Most will also have a preamp built in so that you can record your mic or instrument. These days, there aren’t many “bad” choices for audio interfaces, but you may find that some fit your needs better than others. You’ll generally want to find one with low noise and low latency. If you might also use it for recording music, then sure, invest in a better quality one. But for streaming, where you are just talking, the quality differences are going to be negligible.

The one thing to keep in mind with interfaces is that generally the inputs come in pairs. In recording software, you can record each input to its own track, but in OBS, these are typically seen as stereo pairs. So, for example, if I have an interface with two inputs, OBS will see these as a single input with input 1 being the left channel and input 2 being the right channel. So if you need to capture multiple mics, you may want an interface that has two inputs per microphone (with the mics plugged into every other input) so that you can apply different filters and effects to each mic. We’ll talk more about why that happens when we get to the software side of things.

Sound cards

I’m mentioning these separately because I talked in part 1 about using your computer’s 3.5 mm input for headset and shotgun mics. Despite the fact that I have significantly nicer options for getting audio into my computer, that’s what I’m doing now. Shotgun mic with a 3.5 mm cable into my computer. Nothing fancy about it. Your mileage may vary here, but in my case, my motherboard came with a pretty nice sound card that isn’t very noisy and sounds halfway decent. If you are also going with a headset or shotgun mic, that may be all you need. There are also aftermarket sound cards you can buy (including USB ones) that may offer improvements over your built-in card.

However, if you’re using a mic with an XLR jack (which is most other non-USB mics), you’ll want to get an audio interface instead.

Final thoughts

Ultimately, you will need to consider your entire signal chain (not just your mic) when getting set up for streaming. For example, if you buy a USB mic (like the Yeti), you’ve already got a preamp and an audio interface built into the mic. If you buy a headset mic or a camera-mount shotgun mic, you might be fine with just using your computer’s sound card. If you get an SM7B even though I said not to (it’s okay, I understand), you’ll want to make sure to get an audio interface with lots of gain available. And if you get an XLR condenser mic (you really don’t listen, huh?), your interface will need phantom power, too.

Now that you’ve got signal going into your computer, what do you do with it? Next time, we’ll look at filters and effects to really maximize your sound quality. And I guess we’ll also touch on figuring out the proper levels so you can be heard without distorting.

Part 3: levels, filters, and effects

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