Do Dynamic Microphones Need A Preamp? 2-Minute Read

A good preamp is one of the most important tools in a studio and perhaps one of the most important in the recording input chain. Without a decent preamp, you will never get a decent recording since you will start out with a bad signal. 

But, do dynamic microphones need a preamp?

Dynamic microphones need a preamp in both live and studio (recording) situations because they produce weak signals (mic level) which must be boosted up to line level. This is what a preamp does when it is either integrated into the mic or the mixer or the audio interface or as a stand-alone unit.

In this article, I will explain further why you need a preamp for a dynamic microphone, and we will also talk about external preamps and how important they are to get good recordings.

Dynamic Microphones & Preamps

Before we talk about why a dynamic microphone needs a preamp, first let’s understand what a dynamic microphone is and what a preamp is.

After we have understood how they both function, then we will be in a better position to understand why I highly recommend using a preamp not just with a dynamic mic, but with any microphone.

What is a Dynamic Microphone?

Dynamic microphones turn sound waves into a voltage with the use of a magnet. So basically they convert sound into an electrical signal by means of electromagnetism. 

They essentially work like speakers but in reverse. In a speaker, electricity vibrates the diaphragm, which creates sound waves. 

Dynamic microphones on the other hand use sound waves that vibrate the diaphragm and create electricity.

A typical dynamic microphone has the following components:

A magnetic structure that provides a magnetic field.

A conductive element in which an electric potential difference (voltage) can be taken via lead wires.

A mechanism that allows relative movement between the conductive element and the magnetic field.

Although dynamic microphones are very tough, and they are straightforward to use, they generally tend to produce a low-level signal, which means the sound level produced is kind of soft.

If you’re wondering why that happens, then here is your answer:

Why do dynamic mics produce low-volume sounds?

Dynamic microphones are not usually powered microphones, and so they do not need to have phantom power sent to them.

Condenser microphones, on the other hand, are powered by phantom power and that is why they are capable of producing a louder sound using tier built-in preamplifiers. 

Typically, 48 volts of phantom power is essential for a condenser mic to work.

Since dynamic microphones do not need phantom power to work, this means that they are not very sensitive, which is usually a good thing, as these microphones are best suited for use in live situations when the microphone should be as quiet as possible. 

But, due to the lack of sensitivity in dynamic microphones, (because they don’t need phantom power to work) the mic-level signal they produce is generally very low.

This is where a preamp comes in which helps in bringing the audio signal up to line level for use in professional equipment.

What is a Preamp?

A microphone preamplifier is an active electronic device designed primarily to supply gain to a mic signal and output the signal at line level.

Here’s an easier explanation:

The signal that is produced by a dynamic microphone is weak and soft, this signal is called – mic-level

Now, all of our recording gear from compressors, equalizers, analog-to-digital converters, etc, expects a line-level signal

A line-level signal is at a much higher voltage, which is to say a louder volume. This is the type of signal coming out of electric guitars and keyboards for instance.

This is where a microphone preamp comes in – it raises a mic-level or instrument-level signal up to a line-level signal

Audio equipment designed for recordings, such as mixing desks and audio interfaces, have good built-in preamplifiers that are more than capable of boosting your dynamic microphone to a sufficient level.

The Focusrite Scarlett 2i2 (3rd Gen) USB Audio Interface is the best bang-for-your-buck audio interface for home recording musicians who only need to record 1 or 2 audio sources at a time.

What are external stand-alone preamps?

We also have external preamps that are designed to take the incoming signal and boost it dramatically, while introducing as little coloration (harmonic distortion) as possible. 

Basically, you get the input source sound, and it’s loud enough to work well with the rest of your outboard gear or drive the line input of your interface. 

External preamps are better designed and offer more in the way of versatility than built-in preamps.

If you’re wondering what makes a good external preamp and what are the factors that you should consider when looking for one, then here’s your answer.

What to look for in an external preamp?

Here are a few factors that you should consider when shopping for an external preamp.

How many channels? — do you need one, two, eight, or more channels? Be sure to get as many as you need

Type of preamp — tube and FET preamps tend to be highly colorful, while many solid-state models (particularly transformerless ones) are cleaner and less colored

What’s the maximum gain? — while condenser mics may be fine with 30dB–50dB of gain, low-output/high-impedance mics such as old dynamics and ribbon mics typically require lots of gain (50dB–70dB)

In-line processing — the onboard EQ and compression you typically get from channel strips can be really handy

I/O — of course, you need to be sure you can hook up your gear, but things like onboard digital conversion can be really handy, especially for 8-channel preamps that connect via ADAT optical

Why do you need a preamp with a dynamic microphone?

Till now we have understood that a dynamic microphone turns mechanical waves (sound) into electric signals which are generally very are weak. 

These weak (mic-level) signals need to be boosted up to the line level for use with professional equipment.

This is what a preamp does, it adds power (gain) to the signal so that it can be recorded properly. 

Basically, dynamic microphones output mic level signals and need preamps if they are to be used with mixing consoles, recording devices, or digital audio workstations.

Moreover, as I mentioned at the beginning of this article, you will require a preamp with a dynamic microphone in both live and studio (recording) situations.

Do Condenser mics also need a preamp?

Yes. You need a preamplifier for a condenser as well as a dynamic microphone but not for a ceramic mic.

A preamp amplifies the electrical signal from the microphone to a usable level. It also provides phantom power which is required for a condenser microphone to work. 

So, a condenser mic doesn’t need a preamp by definition, but a preamp is usually the source of power for this kind of microphone. 

Condenser microphones, unlike dynamic mics, need a separate power source to run, this power source is called phantom power.

A preamp provides the charge for phantom power, causing the condenser microphone to record sounds. The preamp also brings the sound levels of the microphone up to the proper levels for recording. 

Conclusion

Given the low-level signals produced by dynamic microphones, they will need a preamp to boost the mic level signals to line level.

A microphone preamplifier is designed to take a microphone signal at its input; apply an appropriate amount of gain (typically adjustable), and output a line-level signal.

Preamps work the same way for other instruments as well. Depending on the preamp, they’ll adjust the line levels of the sound for various microphones and instruments and add color and tone to a recording. 

The line-level is the lowest level of sound that a line input can take in. Anything lower than 0 DBV (one volt of sound) is impossible to pick up with the line inputs from the microphone to the mixing board. 

Dynamic microphones naturally give out about one-tenth of the necessary volume to register and record. 

Preamplifiers bring up the volume of the sound waves before they get to the mixing board. 

The preamp performs an essential function in the recording setup because of the inherent difference in microphone level and standard line level. 

For any microphone, a preamp of some kind is necessary. 

Written by:
Amit Gupta
Amit Gupta

Hi, my name is Amit Gupta, and I am the owner and contributor at Radaudio. My passions include guitar, bass, and piano, as well as a range of classical instruments that I have been playing since school.

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