How to Choose the Best Mic Preamp For You
This is a guest post by Rajiv Agarwal of Audioshapers.
A microphone preamplifier (or mic preamp) is one of the many things you’ll need to equip yourself with before recording anything with a microphone.
Simply put, a mic preamp amplifies the weak signal from the microphone and boosts it to line level, so the audio can be recorded onto your recording device.
The sounds you record via the microphone won’t be distorted and will be loud enough to register on most recording devices.
What Exactly do Mic Preamps do?
In essence, a mic preamp increases the line-level while providing a stable gain.
Using a microphone without a preamp and then trying to record will result in either very low recording levels or nothing at all. The signal is too weak to be usable and might distort the sound so much that it becomes unrecognizable.
Most mixing consoles and recording devices won’t produce an adequate return if the mic is not connected to a preamp. But finding the best mic preamp that is right for your particular mic is not always a simple task.
Choosing the Best Mic Preamp
Choosing a mic preamp really comes down to compatibility and what kind of sound you want to get out of your mic. You have three options at your disposal:
- Tube
- Solid State
- Hybrid
Tube mic preamps are based on vacuum tube technology and have been around since the beginning of recording technology. Even though they represent old technology, they are still preferred by various musicians. These preamps have a built in tube which amplifies the signal.
Solid state preamps are newer pieces of technology and are transformer-based. They add less character/colour to the recorded sound and are more accurate. The major difference between the mic preamps is the distortion they add to the recorded signals.
Obviously, hybrid preamps are a combination of the two technologies.
Distortion can be a key issue in determining what preamp is right for you.
If you run out of headroom on the circuit (a condition in which the output voltage extends beyond the power supply voltage), you will encounter some distortion. For the most part, the distortion with solid-state preamps will not be pretty. Indeed, it is a highly unpleasant sound that can ruin a recording if you’re not careful.
On the flip side, the distortion that tube preamps cause is actually quite pleasant to the ear. It adds a natural character to the sound. It’s a big reason why many people gravitate to the older style because it’s been proven to deliver high-quality sound even at high voltages.
That being said, many musicians have certain preferences, especially if they choose between two high-quality options. For the most part, vocalists prefer tube preamps because the sound produced is much richer and fuller. There is also increased clarity. By contrast, solid-state preamps might tend to make vocals sound thin and flat.
Musicians who play instruments like the drums or the guitar often prefer solid-state preamps because they can catch each individual snare hit or guitar pluck in rapid succession. Although tube distortion can be pleasing with vocals, it often garbles the sound of any speedy instrumental playing.
Other Technical Considerations
Channels
This might sound like a television question, but, in fact, it describes the ability to record a certain amount of tracks.
Each preamp will have a set amount of channels and each channel will correlate to the amount of tracks one can record simultaneously. Obviously, a single-channel preamp allows you to record only one track at a time. This is ideal for those one-man bands that need to record everything separately.
There are dual-channel and multi-channel preamps that provide exactly what their names imply. But, some preamps come with a device referred to as a channel strip which provides a number of different features on top of the ability to record multiple tracks.
Impedance
You’ll also need to take into account something called impedance.
This is basically a holistic measure of the restriction in alternating circuits (AC). Every microphone has its own range of impedances generally ranging from around 50 ohms to 2,000 ohms. You’ll want to find a preamp that “harmonizes” with your microphone in this sense.
You’ll probably want to look elsewhere if the preamp has a limited range (or the microphone’s ideal impedance output is somewhere outside that range). As a rule of thumb, the mic preamp’s input impedance should be around 10 times greater than the microphone’s output impedance. So, if the mic’s output impedance is 100 ohms, then the preamp should be able to accommodate up to 1,000 ohms.
Phantom Power:
If you are going to use a condenser microphone, make sure the preamp has Phantom power to power up the mic. Condenser mics will not work without Phantom power.
Noise levels:
How much noise is the preamp adding to the overall sound? It is very important to check this, not on the paper, but by actually recording a test audio. The preamp should be quiet and have no noticeable noise, even at very high gain.
As a rule of thumb, high-quality preamps will always outperform lower-quality preamps. For example, if you’re using a mediocre solid-state preamp and can switch to a better tube preamp, you should probably do it. The same is true for the opposite. A cheap tube preamp will sound worse than a better-designed solid state preamp.
Overall, finding the best mic preamp involves tweaking it and discovering the right settings for your particular microphone.
Happy Recording!
Rajiv Agarwal is sound designer, music composer and mastering engineer. His studio Audioshapers delivers professional audio mixing, mastering and audio post production solutions.
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