What is a mic preamp?
What is a Mic Preamp? Today it seems like every sound engineer talks about microphone preamps and how they improve the sound. It’s definitely a piece of studio equipment that is nice to have but not critical if you’re just getting into music production. You might have asked yourself:
“Can’t I just plug my microphone into my audio interface?”
The answer to that is both yes and no. After reading this guide you’ll know what a mic preamp is and if you need one in your studio setup!
So let’s dive in!
What is a preamp?
A while back I bought a Shure SM7B microphone because of all it’s accolades (it’s one of the best vocal microphones available). I went home and plugged it into my audio interface and started recording. The audio signal was weak and I had to boost the gain to max to even make it audible in the mix. If you just crank the gain you’ll also get annoying hiss noise in the recordings. I didn’t do my research before buying a dynamic microphone and thought it was plug-n-play. Microphones usually need 30-60 dB gain-increase and built-in preamps in budget audio interfaces usually don’t handle that very well.
There is a lot of on-going hype about preamplifiers but the truth is they only have one job: To boost weak audio signals (mic-levels) up to a line-level signal. All of your external recording gear from equalizers, compressors and A/D converters all expects line-level signals to work properly. Line-level signals come from electric guitars and keyboards – not microphones. Line-level signals have a much higher voltage than a moving coil in a dynamic microphone.
Different types of preamps
There are many different preamps available but simply put they all fall into one of two categories:
- Transparent microphone preamplifiers
- Colored microphone preamplifiers
Depending on what you want out of a preamp and what kind of FX-plugins you are using you might want to choose the first over the other and vice versa.
Clean mic preamplifiers
Transparent microphone preamps are ideal if you want an uncolored sound without any harmonic distortion. This is probably the best choice if you’re doing additional processing with plugins in your DAW. Transparent microphone preamps take the incoming signal and boost it up to 75dB without or with minimal colorization. You will probably have to do a little bit of more manual mixing when you send an uncolored signal into your DAW. In my experience it’s a headache and nearly impossible to remove the harmonic distortions from your recordings so you’ll end up with more possibilities with clean signals. Pretty straight forward right?
Great examples of clean preamplifiers are Grace m101 and Millennia HV-3C.
Colored mic preamplifiers
If you want to process the input signal and add some characteristics to it you’ll want to consider a colored mic preamp. These preamps have electronics or transformers that alter the sound before it enters your DAW. These harmonic distortions usually add some clarity and smoothness to the sound so it stands out in the mix more easily. This pre-colorization of the sound will get you limited in terms of post-processing but you can’t deny that these preamplifiers sound great!
A couple of famous colored mic preamplifiers are BAE 1073MP and Universal Audio SOLO/610.
Transformers vs transformerless
Speaking of transparent/colored preamps:
Whether to go for a preamplifier with transformers or without is a topic hotly debated in audio engineering forums all around the world.
Transformers are a common ingredient in audio components and can lower or increase the audio signal. It’s the transformers in preamplifiers that add color to the sound, give it warmth and that vintage sound that we all love! The transformerless preamplifiers create a more transparent and clean sound without any harmonic distortion.
The more you know is better!
Tube vs solid state preamps
So another common debate about mic preamps is Tube preamps VS Solid State preamps. I’m not gonna bore you out with the technical differences and how they work but there are some pros and cons to consider before buying a microphone preamplifier. A tube preamp usually has a warm and smooth sound that Solid State preamps lacks.
- Warm and smooth tonality
- Create beautiful harmonic distortions
- Suitable for acoustic guitars, vocals, violins etc.
- Tubes require more maintenance and are very fragile.
- Not suitable for instruments with powerful transients like drums
- Tonality and sound characteristics can change over time
Solid state preamps
- Uncolored sound
- Can handle high gain signals better than tube preamps
- Cheaper than tube preamps
- You may need to invest in a more expensive solid state preamp for decent audio quality
- Sometimes it can produce odd harmonics that sounds bad
So the concept of hybrid microphone preamps is to create the best of two worlds. Hybrids are usually Solid State Preamps with a separate tube stage for warmth and color.
Built-in preamps or external preamps?
If you are a beginner on recording I would recommend you to spend a little more on your audio interface with better mic preamps built in. You’ll also save up some space on your studio desk when you have one piece of studio equipment that can handle the same job as two. However, the built-in preamplifier in your audio interface probably won’t give you the same result as a decent standalone.
An external microphone preamplifier is a great improvement of your home studio when you’ve learned the basics of home recording and want to take your audio quality to another level. With external hardware you can easily get to signal level-input with low output microphones like dynamic and ribbon.
Built-in preamp or external preamp, it’s important to point out that your recording quality only gets as good as your recording environment!
Mic preamp formats
Microphone preamps are available in three different formats:
Rackmount preamps are studio standards and are designed to fit in studio racks. Many rackmount preamps are single-space units (1U) but some are 2U (double-space units) I would say rackmount preamplifiers are most common in professional recording studios and usually take up too much space in a home studio environment. They look cool and professional but the design is not very smooth or flexible if you only use a couple of inputs or outputs.
Desktop models are portable and can be placed on your studio desk. This format is most common in home studios and when it’s placed on your you’ll have all your controls within a hand’s reach. The ability to record and at the same time have the ability to adjust settings on your preamp is a great advantage!
Lunchbox-models cas commercialized by pro audio pioneer API. Lunchbox preamps fit in a 500 series rack, also known as lunchboxes. I wouldn’t say that they are portable but let’s say they are something in between a desktop-model and a rackmount-model. You can also place other modules like EQs and compressors in your lunchbox chassi.
How many channels?
The most basic mic preamps have one channel which means you can only record with one microphone at the time. These will work fint if you are recording a single vocalist or guitarist. If you want the ability to record both vocals and guitar from two different microphones simultaneously or record in stereo you’ll need a dual preamp (2 channels). Dual preamps are obviously more expensive than single preamps. You can also buy a multi-channel preamp with more than 2 channels if you’re going to record a whole session!
Phantom power is recording 101 and a key feature in all preamps and audio interfaces. Phantom power boosts the signal from microphones and it’s a basic feature in all preamps. Dynamic microphones don’t need it but condenser microphones won’t work if you don’t have phantom power. When you buy a preamp you have to make sure that it supplies a 48v of phantom power so you properly can power your condenser mic. If it’s any lower than 48v it might not be enough.
Which mic preamp should I buy?
By now you should have a solid understanding on what mic preamps are, what options you have and how they can improve your existing studio setup. So which mic preamp should you buy? Here are some important features that you’ll need to put into consideration.
Your desired sound
Before you go and buy a microphone preamplifier you should think about what you are going to record on it. As mentioned above, preamps have tonal differences and some works better than others on different sound sources.
If you are recording a thin sound like a violin or a vocalist you probably want a preamp that will fatten up the sound. Consider buying a tube preamp!
If you want to add warmth and “analog feel” to your recordings you should also go for a tube preamp. These harmonic distortions can sound beautiful on an acoustic guitar but many sound engineers want to record the instrument’s natural sound and add processing later. Then you should go for a solid state preamp that doesn’t color the sound. There are no rights and wrongs here, one man’s meat is another man’s poison!
What about drums? A tube preamp will fatten the sound and compress the attacks. If you want those attacks you should go for a solid state preamp.
Think about future needs
So if you are going to buy a microphone preamp you should think about your future needs. The normal progression is usually to start with a single channel preamp. I did just that but I quickly grew out of it and bought a dual channel preamp. Would it be cheaper if I bought it right away?
Planning ahead could save you some money. If you’re really into recording your own stuff you probably will outgrow your single channel preamp quickly when you can’t record in stereo. Buying a dual channel preamp is probably the best choice. If you’re just going to record yourself singing or podcasting you will be just fine with a single channel mic preamplifier.
There are many preamps in the market that will cost under $100. Unfortunately, they are not very good. For a good decent preamp you will have to spend at least $300 per channel. If you choose budget preamps you will have issues with noise, gain and overall sound quality. Quality will always win over quantity. You will have no use of owning multiple preamps that all sounds bad. Like everything else here in life, you get what you pay for. Always go for the best microphone preamplifier you can afford!