Mic Preamp - What is it and how to choose one that suits your needs : Magroove Blog

Mic Preamp – What is it and how to choose one that suits your needs

October 08, 2019 • 10 min read

At some point, while you were setting up your home recording studio, you’ve probably heard about or read about this somewhere. Even if you’re still in the process of planning the studio, that’s probably something that crossed your mind at some point. What is a mic preamp? Why should I get one? Do I really need one and which is best suited for me? Isn’t my audio interface enough? If those are questions you’d like to get answered, I’m glad to say that you’re in the right place. Stick with me and let’s find out what exactly it is and how to choose one that suits your needs.

What a is a mic preamp anyways?

In short, a microphone preamp is a device that boosts a weaker signal to line level. It’s any input expecting microphones that has a trim/ gain potentiometer. It’s found on interface mic-ins, recording console mic-ins and sometimes it’s an external, dedicated, mic preamp hardware.

Why do I need a mic preamp?

Let’s see first why do you need it. For that we have to understand what an amplifier is.

Basically, an amplifier is a device that allows us to increase the amount of electronic signal that is present in an electronic device. Allow me to explain how it works. The microphone captures the sound and it turns it into an electric signal. That signal goes to an amplifier, which will boost that signal. That is necessary because you must have a signal strong enough so that it can sound properly on a speaker, for instance.

But here is where we have a problem. Have you ever tried to plug a microphone directly into a power amplifier? If you already did, you’ll know that it will not only sound not loud enough, but will also have unnecessary noise.  That’s because the amplifier’s input is expecting a line level signal. Unfortunately, most microphone’s signal are too low. So in order to the amplifier to receive a usable signal, it has to be boosted from mic-level to line-level first.

That’s simple enough to understand, right?

Pretty much every audio device operates at line level. From amplifiers to devices like compressors and reverbs, to your DAW.

Which cases I don’t need a mic preamp?

Setting up a home recording studio could be expensive. That’s why you don’t always have to buy everything you heard or have seen in a pro studio or a guide somewhere. For instance, there are a few devices that won’t require a mic preamp. Ones like recording interfaces, USB mics and some mixing consoles are examples. But let me be clear, those devices don’t need mic preamp because they have it already integrated. In order words, although in some cases you don’t have to use an external mic preamp, you’ll always be using one (built-in). If you don’t, the signal level will be too low and you’ll notice something is missing.

Audio interfaces have a built in mic preamp in every mic input

Does my audio interface have a mic preamp integrated?

Before we dive into the topic, if you don’t know what is an audio interface, you might want to check this article of ours to understand.

That’s a tricky question. Although the answer is usually “yes”, it doesn’t mean that all audio interfaces will have a great mic preamp. In some situations, some of them will have mic preamp integrated mostly because they need it. Pro tip: Keep your eye on price range and device specs, should tell you a lot about its quality.

“Mic Ins” in audio interfaces contain mic preamps. The difference from external mic preamps is that mic ins are embed in one container, in line with the A/D Converter. External mic preamps work only on the analog realm, as the mic signal goes directly to it, and from it, to the interface. If that’s the case, it must be connected to the line in (as it’s not a mic-level signal anymore. It was amplified to a line signal).

Types of mic preamp

Pretty much like microphones, there are types of mic preamps as well.

So far we have covered a lot of relevant information in regards of the mic preamp topic. Now I think it’s necessary to understand also the different types of mic preamps and for what microphones they are best suited.

Tube mic preamp

Tube mics work using one or more vacuum tubes to amplify the mic signal. They are best known for its warm, open, “fat” sound.

Tube preamp with high THD (Distortion)? Fear not. Actually, if you ever find one like that, consider yourself lucky.

Tubes bring their best when they distort. You’ll probably notice that a mild distortion brings a nice touch. THD is often seen bad in solid states/ transistors when they distort the sound. But that doesn’t happen with tubes, trust me, they sound great. Unfortunately, they end up suffering the same judgement, so the companies produce tube equipment with low THD. As a result they end up doing nothing, just amplifying linearly. Right, “nothing” is a strong word here, as musical information is very dynamic, let’s just say they are probably doing something around the peaks. If you want full tube power, you won’t (can’t) get it. Sad, I know. As an alternative, some producers have been filling that need with hand crafted preamps (with absurdly high THDs). And it works pristine. If you ever get it touch with one of those hand-mades, be sure to have fun.

Solid state preamps

Those don’t use tubes. Solid-state mic preamps use transistors to amplify a mic’s signal.

The amplification comes from its design, its amplifier components and circuitry (op-amps and transistors), and its transformers (if it is transformer-based).

The main features of solid state preamps are that they offer a clean, transparent sound, with minimal distortion. In other hand, they often have the ability to handle higher gain levels without distorting.

Just a quick side note here regarding distortion: It will be added to the recording anyway (via saturation plugins). If you don’t add it, you should consider adding that to your vocal mixes.

So, go boldly and confident and add some distortion while you’re recording. That way your base recording will get a little distorted. Conservative people would say to record it all 100% clean and re-amp to distort out of the box when (or if) needed. But the best recordings are the ones “juicy” from the beginning, wouldn’t you agree with me? (And hey, they always did that till a decade ago or so. They also had no choice, so they had to be good and bold from day 01).

Hybrid preamps

Hybrid mic preamps are a combination of tube and solid-state designs.

You may not see those as appealing as the tube and solid state options, but I can ensure you, the idea to combine the best of both worlds is amazing. To accomplish that they are usually designed as solid-state mic preamps with a separate tube stage for warmth and color.

Typically speaking, solid-state components drive the input stage, and a tube drives the output stage.

Channel Strip preamps

A channel strip is a microphone preamp combined with other signal processing circuitry all in the same enclosure. The idea here is to provide everything you need to record, all in one convenient package. Some if its main features may include having EQ and compression/limiting.

If you’re asking yourself what are the benefits of using channel strip preamps, the answer is simple: If you get one, you get a complete signal chain, in a single enclosure. For you, as a musician, that translates into less noise from connecting separate units. It’s a lot easier to use too, we can’t argue with that.

Which mic preamp type do I choose?

The two first are the most popular ones, and if you did some research you’ve probably stumbled into one of these. The thing is, you may find some other options, so, for starts, do your research. Try to understand as much as you can about each option. Make sure you have in mind what kind of recordings you want to do. How you want your recordings to sound? Clear, transparent, want to add some vintage warmth? And of course, do always prioritize quality over quantity. Just make sure it stays within your budget margin and you should be fine.

Is it worth to have an external mic preamp?

As we have mentioned before, some audio devices will offer a built-in mic preamp. If you’re just getting started setting up your home recording studio, I would recommend you to opt for a slightly better (more expensive) audio interface with decent built-in preamps. That definitely should do the trick for you.

But you should always keep a mic preamp in your wish list, below I’ll show you a few compelling reasons why.

Better sound quality

You might not notice that in lower levels, but If you use higher gain settings, you’ll hear a significantly improvement on quality. That happens because they are equipped with more sophisticated circuitry that retains full transparency even at their highest gain settings.

More gain

Some mics, with low output dynamics, like ribbons, may require up to 70 dB gain. You’re hardly getting that using a built-in preamp of an audio interface. Maybe if you’re lucky you’re going to get 60 dB gain or so.

A special sound character

That’s probably one of the main reasons why people decide to opt for an external mic preamp over any built-in in the first place. For instance, let’s assume you’re trying to get a smooth “vintage” sound of an 70s style transistor device. You’ll only be able to get that from a mic preamp. In other words, if you’re looking (and if you’re ok) with a clean and transparent sound, built-in mic preamps should do the trick for you. On the other hand, if you like a specific sound quality or feature, opt for an external mic preamp.

At the top of that, an external mic preamp should give you considerably less noise. That’s definitely something that sounds appealing, right?

There are more things you have to consider, besides the ones listed above. Like versatility and consistency, which is the ability to know where you want to get with a certain preamp configuration. In addition, built-in mic preamps often lack phase reverse, low cut or pad switches. So, if you’re looking for those features, you may want to find a good external mic preamp that fits your needs.

External mic preamp adds a special sound character

Pricing

Almost there with our article, but now that I’m here I’m wondering if I shouldn’t have brought this topic before. That’s because, as mentioned somewhere above, one of the things you must consider, whether or not to buy a mic preamp in the first place, is your budget. Actually, it wouldn’t be so hard to decide if the price range were not so madly mismatch. Why there are so many models? Let’s see if I can answer some of these recurrent questions.

If I think about it, I could write a whole article just to discuss that, but let me try focus on what matters the most.

It basically comes down to two things:

Operational options

If we’re talking about operational options it could mean tons of different features. For instance, the number of channels, whether it provides digital outputs, and so on. Besides that, there are other features that make a lot of difference, like if it has phantom power, high-pass, polarity reverse, and the list goes on.

Sound quality

That’s probably the one that makes the most difference, sound quality. Pretty much like anything we have ever discussed in this blog, the sound quality will always be crucial. From the price range, to choosing a device, to que quality of the sound you get, there are tons of things to consider. When it comes to mic preamps, it’s the same. Well, there is a whole article you’ve just read covering almost all the variables. Which means, that from a certain sound character to its specs and configuration, pretty much everything counts and adds to its final price.

In conclusion

Many musicians and audio engineers like to experiment with different mic and mic preamp combinations. So, my suggestion is that you do the same, if possible, of course.

Visit studios, put your listener qualities to good use. Do your research, and obviously, make sure all other pieces are in place in your studio, from the acoustic treatment home studio, to the audio cable types, to your microphone. It just doesn’t make sense having a $300 dollars mic preamp if you have a crappy acoustic or a bad quality microphone. In other words, your top notch mic preamp won’t solve all your recording problems nor will it take your music to the next level the way you intend to.

Hopefully this article will help you and answer (most of) your questions. Keep up the great work!