In this post, we’ll talk about what a microphone preamp is and if you need one. Short answer: if you already have an audio interface, you probably don’t. 🙂
Let’s dive in.
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What is a microphone preamp and what does it do?
A microphone preamplifier (mic preamp) is an electronic device that amplifies the signal from a microphone. Mic preamps are used in a wide variety of audio applications, including recording studios, live sound reinforcement systems, and broadcast television.
Mic preamps boost the signal from the microphone to a level that is appropriate for the next stage in the audio chain. For example, if you are recording to a digital audio interface (DAW), the mic preamp will raise the signal to a level that is compatible with the input of the interface.
Mic preamps typically have controls for gain, impedance, and phantom power. Gain adjusts the overall level of the signal, while impedance matching ensures that the microphone and preamp are working optimally together. Phantom power is used to power condenser microphones.
How analog to digital conversion works
Before we go any further, let’s pause to talk about exactly what happens when you speak or sing into a microphone, and how that signal gets converted to something usable inside your DAW.
Simply put, when you speak or sing into a microphone, your voice vibrates the air around the mic diaphragm. This vibration is converted into an electrical signal by the microphone capsule.
However, that signal is so quiet that it needs to be amplified before it can be used. That’s where the mic preamp comes in. The preamp takes that tiny signal and amplifies it to a level that is compatible with the next stage in the audio chain.
In most cases, that next stage is an analog to digital converter (ADC). The ADC converts the analog signal from the mic preamp into a digital signal that can be used inside your DAW.
What are the different types of mic preamps?
There are two main types of mic preamps: tube and solid state. Tube preamps use vacuum tubes to amplify the signal, while solid state preamps use transistors. Each type has its own unique sound character.
Tube preamps are known for their warm, smooth sound. They tend to add a bit of harmonic distortion to the signal, which many engineers feel gives it a more natural quality.
Solid state preamps are known for their clean, clear sound. They tend to be more accurate and have less distortion than tube preamps.
There is no right or wrong answer when it comes to choosing a type of mic preamp. It really comes down to personal preference and the sonic character you are trying to achieve.
How do you know if you need a mic preamp?
In most cases, you will need a microphone preamp if you are trying to record anything other than a very simple audio signal. For example, if you are recording a band with multiple instruments, you will need a mic preamp for each microphone you are using.
If you are using a digital audio interface (DAW) to record your audio, you will need a mic preamp that is compatible with the input of your interface. Most interfaces have built-in mic preamps, but in some cases you may need an outboard mic preamp.
This is one of the main reasons I recommend the Focusrite Scarlett series for a starter audio interface. They’re one of the few brands that don’t skimp on their mic preamps even in their budget-friendly interfaces.
Finally, if you are using a condenser microphone, you will need to use a mic preamp that provides phantom power. Phantom power is a DC voltage that is used to power the capsule of a condenser microphone.
If you are using a dynamic microphone, you do not need phantom power. However, many mic preamps provide it as an option, so it’s something to look for if you think you may want to use a condenser mic in the future.
Why would anyone buy an outboard mic preamp?
So let’s address the elephant in the room. If most audio interfaces come with perfectly sufficient built-in mic preamps, why would anyone need to spend the money on physical outboard preamp hardware?
The main reason is that outboard preamps generally offer higher quality than the mic preamps that are built into audio interfaces. They often provide more headroom, better noise performance, and more features.
Granted, most producers (including myself) will tell you that outboard preamp hardware is probably the last thing you should upgrade in your studio.
For the untrained ear, the difference will likely be imperceptible.
Another reason is that some people simply prefer the sound of a particular outboard preamp. As we’ve already discussed, each type of mic preamp (tube, solid state, etc) has its own sonic character.
Some people prefer the warmer sound of a tube preamp, while others prefer the cleaner sound of a solid state preamp. Ultimately, it comes down to personal preference.
Finally, some outboard preamps offer features that you may not find in built-in preamps. For example, the Universal Audio 610 is a very popular mic preamp that offers a unique feature called “tube saturation.” This gives the signal a warm, fuzzy quality that can be very effective on certain types of sources.
Not all outboard preamps offer this type of feature, but it’s something to keep in mind if you are looking for a specific sound.
Do you need an outboard mic preamp?
The answer to this question is, unfortunately, “it depends.”
If you are just starting out and are on a tight budget, I would recommend using the built-in mic preamps on your audio interface.
As your needs grow and you start to invest more in your studio, you may find that upgrading to an outboard mic preamp (or two) is a worthwhile investment.
But ultimately, the decision comes down to personal preference and the type of sound you are trying to achieve.
Thanks for reading, and check out these related posts for more production advice: