What Is A Preamp & What Does A Preamp Do?
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In this article, we’ll be talking about preamps. What they are, what they do, and different types of them that will help you choose the right one for your purposes. Before we dive in, you should know that The Sound & Light Hire Company is not only a great resource for information about sound, lighting, staging or LED screen equipment, but also that we’ve got hundreds of thousands of products available in our hire stock at any given time, with sound engineers like myself waiting to help you out. So visit us today at The Sound & Light Hire Company at https://truesoundhire.co.uk/ Let’s get started.
So, what is a preamp? Preamp is short for preamplifier.
A preamp is a kind of amplifier that’s designed specifically to take really weak signals and, well, make them louder. Think about like a microphone. When you plug it into something like a mixer or a recording interface. What it’s going into is a kind of preamp. You might wonder why you might be presenting your preamp with a weak signal to begin with.
So, to better understand this, we’ve gotta talk about microphones as a kind of electrical device called a transducer. A transducer, at, at its most basic form is any kind of device that takes one form of energy, in this case the vibrations of molecules in the air that we perceive as sound, and trans, uh, transduce it into something that, uh an electrical device like a mixer or a recording interface can use, a voltage.
If you think about what a microphone is doing, the diaphragm inside is responding to really, really tiny vibrations of those air molecules. So, when that energy gets tra- transduced into an electrical signal, it’s a really, really tiny signal at the level of millivolts. But our devices, like mixers or recording interfaces or speakers, can’t really use that signal, it’s too low. So that’s why that microphone has to first go into a preamp that can give it the amount of gain necessary without inducing a lot of distortion or noise into the signal. This is why preamps are a kind of specialty amplifier, because they have to take that really weak signal and make it louder without inducing a lot of noise.
Preamps do this in different ways. There are different circuits, there’s, uh, different components that are used in different types of preamps to make this happen. Some use technologies like, uh, tubes, that you might be familiar with. Some use transistors. Regardless of the kind of preamp, at the end of the day, it’s still taking your microphone signal and essentially making it louder in a clean or coloured way, so that the devices further down the chain can use that signal.
Let’s talk about different scenarios in which you might need a preamp.
Let’s say you’re performing, uh, live with your band, and you’re singing into a microphone. Chances are you’re going into a mixer like this one. The microphone input on this mixer is a kind of preamp. It takes the signal coming off of that microphone, and helps you add gain to it so that the rest of the mixer can use that signal, so that it can be mixed with other signals, and then eventually be sent on to a recording device, or, uh, monitors, or your main PA speaker system.
Same thing if you’re using preamps in a recording environment. Let’s say you’re at home, in your project studio, recording a microphone on vocals or an instrument. Chances are you might be going through an interface like this one, which microphone input on that interface would also be your preamp. Or you might be going through an outboard preamp like this one here, which is more of a specialty piece that would still need to go into a different kind of device, like a converter, downstream.
In any case in any of these situations, you’re still using a preamp, which is helping to take your microphone signal and add gain to it, so that devices down the chain can use that signal.
Any electrical device, just by its very nature, is going to add a little bit of noise to your signal, right. But preamps have to be designed in a specific way so that they can minimize that while giving you what you really want, which is the sound of your microphone, so that you can get a bunch of clean gain without adding that extra distortion or noise.
You’ll see these things in technical specifications for preamps when you’re picking them. You’ll see distortion listed as THD, which stand for total harmonic distortion, or, uh, the noise floor spec, which refers to, uh, when no signal is passing through that preamp, what is that idle noise floor?
Both of these are important specs to keep in mind, but at the end of the day, we also need to remember that preamps are, uh, different flavours in our recording or live sound setups like this Live Sound Package. Some preamps might colour our sound, or add character to our sound in a way that’s pleasing to our ears. Others are designed to be very clean or transparent, meaning that they don’t add a lot of color or extra harmonic saturation to your signal, but allow you to get a bunch of clean gain from that signal so that it can be processed however you like later on.
Whether we’re using a clean preamp or a coloured, or character preamp, it’s important to know the different types that are available.
They’re all ultimately different tools that we can use in our musical setups, whether you’re performing live or recording in the studio. Another important thing to consider when choosing your preamp is the type of microphone that you’re gonna be using with it. Because different types of microphones output different signal strengths, this is something to keep in mind when choosing that preamp.
So, for example, a condenser microphone, which typically gets power, uh, over phantom power, is gonna output a hotter signal. It’s more sensitive, and it might not need as much gain as a low-gain microphone like a Shure SM7B, for example, or an Electro-Voice RE20 would need. These types of dynamic microphones are low-gain microphones because they need more gain from the preamp. The signal coming off of that microphone is a little bit lower, so it needs a little bit more help before it can go on to the rest of your signal path.
Consider ribbon microphones as well. By their very nature, because of how the transducing mechanism works, they also output a much lower signal. In fact, there are preamps that are designed specifically for ribbon microphones to help you get a bunch of gain in a really clean way to preserve the character of the ribbon microphone, while also getting you the amount of signal you need for the rest of your path.
As you can see, there’s lots of factors to consider when selecting a preamp, and we’re just starting to scratch the surface. The Sound & Light Hire Company audio engineers are here to help you pick. We’ll talk to you about what’s in your setup, and what might be the right addition moving forward. Be sure to like this blog if you want to see more like it, and leave us a comment below. Thanks for reading .
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