Key takeaways

• Preamps are intended to boost the gain of a signal before they are amplified, i.e., reproduced through monitors, PA speakers, or headphones
• They’re built to amplify mainly microphone or instrument-level signals to line level, making them easier to mix and giving you more consistency
• Preamps can either be clean or coloured; most more affordable preamps will be cleaner gain-boosters, whilst higher-end units offer more features for colouration
• Preamps come as default with some audio gear, like audio interfaces or DJ mixers, but also come as standalone pieces of outboard gear

What is a preamp?

At its core, a preamp – short for preamplifier – is an audio circuit designed to boost the gain of a signal. Preamps boost quieter microphone or instrument-level signals so that they sit alongside other elements or line-level signals in a mix (signals straight from microphones tend to be significantly quieter by comparison).

This makes them essential for all kinds of audio – but especially recording, as they can help you get consistent levels for multiple microphones, like when mic’ing a drum kit, for example.

Preamps are needed in both studio and live performances as compressors, studio monitors, equalisers, and PA speakers all anticipate receiving line-level signals.

This is why you’ll also see preamps in DJ mixers. They help boost the level of your mixer’s signal to one with enough power to come through the PA speakers as punchy, loud, and clear as you want it to.

However, the main way in which we’ll usually see outboard preamps used is in studio recording.

You’ll often hear discussions of specific, dedicated vocal chains in the case of high-end audio production, and a key part of this is the preamp. This chain usually comprises a dedicated vocal microphone, a preamp, and analog outboard gear before going into the DAW. Let’s take this example to look at the signal chain of a preamp and where you want it to go.

Example: Studio recording signal chain

Vocalist > Microphone > Preamp > Outboard Gear > Analog-to-Digital Converter (often audio Interface) > DAW > Digital-to-Analog Converter (also often an audio interface) > Studio Monitors

This sequence fully tracks the flow of sound from its original source to how you would later hear it. Without the preamp, the signal in the DAW and from the monitors would be way quieter than it should be, and wouldn’t be able to hit any outboard processing, if that was desired.

Do I need a preamp?

If you want to record with microphones at any stage, yes, you will need a preamp. If you’re an instrumentalist recording bass or guitars at home using amp modelling or amps with direct outputs, you might never need to worry about preamps.

However, for the rest of us, from engineers and producers to vocalists, streamers, and podcasters, you will need a preamp.

If you’re reading this, you probably already have an audio interface with one or two preamps on there that you use for recording, as they’re almost always included in interfaces. If you don’t, you should probably start looking for an interface first!

There are even some microphones, such as the Aston Stealth or Shure SM7dB that have built-in preamps to boost their output. The SM7dB especially is a big leap forward for Shure, given that the SM7B is extremely famous for requiring a preamp to boost it. This new version has it all in one recording solution.

There are also devices like the Shure MVX2U, which converts XLR signals to USB for recording directly to your computer with just the microphone of your choice, and has a gain boost in it as well.

Universal Audio’s Volt audio interfaces are perfect centrepieces for your setup if you’re after the sonic character of vintage tube preamps. These audio interfaces come with a Vintage Mic Preamp Mode which adds the richness and warmth of the vintage UA 610 tube preamplifier – used by the likes of Ray Charles and Van Halen – to your recording signal. 

However, the real question is what kind of preamp do you need? And the answer to that question is entirely dependent on what and how you want to record.

Types of preamps

Clean

Clean preamps come in two main forms: in-line preamps and audio interfaces. These boost signals completely transparently, with zero colouration and maximum headroom, so that you have the flexibility to process your signals however you want to.

This is common in the current era of digital recording. Squeaky-clean recordings allow you to use plugins to sculpt the sound you want. However, it’s not the only way to go!

Coloured

Preamps don’t always end up clean, however. Input and output transformers within the circuitry can create a pleasant harmonic distortion when the signal’s input or output volume is pushed hard enough, resulting in a colourful, complex sound. This can be extremely aggressive or subtle and pleasing.

A top tip from me, if you have a two-channel preamp, this can double as a nice warming unit for stereo buses like drums, providing everything from a subtly enhanced sound or an extremely aggressive character. You can even place them on your mix bus to add gentle harmonic distortion.

The issue with coloured preamps, of course, is that they limit flexibility – a signal recorded with a colourful or pushed preamp can’t have that effect removed, so you’re committed to that sound. This can be a benefit that saves on mixing time, but it can also limit your options for future processing.

Choosing the right preamp for you

Number of channels

How many things are you looking to record at once? Professional recording studios are full of preamps because they work with a large number of microphones and may want the range of subtle sound and colouration options they offer. If you’re strictly a vocalist, you might only need one good preamp.

Whether you’re happy with your interface’s built-in preamps or want something more bespoke is down to your preference. If you’re an engineer or producer who works with bands and runs multiple mics at once, needs eight microphones at once for drum kits, or carries out orchestral recordings, you may need a lot of preamps.

If you’re working with outboard gear, you might need a larger number of preamps for converting signals to line level.

Type

There’s a wide range of preamps available, from in-line preamps to exclusive microphone preamps to preamps with DIs built-in for instrument recording. So, another main consideration is the preamp circuitry.

If you’re looking for vintage colour, character, and weight that harks back to the age of massive tape machines, a tube preamp will fit your needs, imparting warm harmonic distortion even at low volumes. However, it can easily get heavily distorted as you increase its level for more creative effects.

FET circuitry tends to be characterful too, even though it’s transistor-based. A lot of classic designs use it to add a different kind of distortion character than vacuum tubes.

Solid-state circuitry tends to be clean, transparent, and have high headroom. However, it’s not always that simple. A lot of famous preamps like the Neve 1073 and API 512, which are both famous for their colour, were solid-state designs.

When it comes to solid-state preamps, look for input or output transformers. If it has them, you can expect something that’s cleaner but that can be pushed into distortion, imparting a much gentler colour than tube circuits at low levels. If it doesn’t have transformers, you’re looking at a clean, transparent boost from the preamp.

Maximum gain

Since you’re boosting the gain of a microphone, it’s important to think about what range and maximum level of gain you want to be able to achieve.

Some preamps on the lower end can offer around 30 dB of gain. This can be good for many standard condenser mics but isn’t sufficient for some lower-output mics.

Shure quote the necessary gain of a preamp for boosting the SM7B to desirable levels as 60 dB minimum, which is not an amount to be taken lightly! The maximum gain range of most preamps tends to be near 70 or 80 dB, giving you all the volume you need.

Another thing to keep in mind is that cheaper preamps like the ones on entry-level audio interfaces will have louder noise floors when cranked this high, so even if it has the gain you need, you’ll want to make sure you have something of good quality.

In-line processing

This element is important for compact setups, plugging directly into your microphone. It can also be used to boost volumes over long cable runs. If you need easy, direct volume boosting with no added frills, this is the way to go. This one’s a common choice for podcasters using famously low-output microphones like the Shure SM7B.

Whilst Shure have now addressed this combination themselves with the SM7dB, some people might have a preference in form factor or want a more coloured in-line preamp that they’ve personally chosen. Either way, whether it’s built into the microphone or external, in-line is one of the least intrusive ways to boost a mic signal.

Connectivity

What do you need to record? Microphones? Guitars? Bass? Multiple microphones at once? Preamps can allow for any or all of these, but you’ll have to consider this to see what best fits your needs.

The quality of DI in outboard preamps can really add to your instrument recordings, with preamps like the Universal Audio 610 tube preamp being extremely popular not only for microphone recording but also for specifically bass guitar DI, thanks to its deep bass response.

Preamp vs. power amp

So, now that we’ve established what a preamp is, there can be some confusion between this and power amps. What’s the difference? Purpose and connectivity.

Power amps come much later in the signal chain, usually just before PA speakers or studio monitors. They exist to boost line-level signals for further projection afterwards. Preamps tend to have more complexity in connectivity, potential features, and boosting low amplitude signals.

Our preamp recommendations

G4M 500 Series Preamp

Designed with producers in mind, the G4M 500 Series Preamp is a compact powerhouse. Its gain range of up to 70dB ensures precise amplification and crystal-clear sound, whilst Mic/Line input switches make it compatible with multiple audio sources. LED indicators provide simple monitoring, and you can maintain signal integrity in multi-microphone setups thanks to a Polarity/Air switch. The preamp also includes a pad function for attenuation control, making it a versatile and reliable tool for any producer.

FAQs

Do I need a preamp if I have an amp?

If you want to work with microphones, you will need a preamp. Power amps and guitar amps serve very different functions to preamps, but if you want to record your guitar amp or cab with a microphone, you’ll need a preamp of some kind. Usually, an audio interface’s preamps should be sufficient, but a higher-grade preamp can further improve your recording quality.

Does a preamp improve sound quality?

Preamps do, technically, improve sound quality. However, if you really want to improve your sound quality, it all starts with the right microphone. If you have a high-end microphone that you’re well and truly happy with, then a new preamp is worth considering, but always consider upgrading your mic to that of a better quality first if you’re unhappy with your recordings.

How do I know if I need a preamp?

Ask yourself a few simple questions to determine if you need a preamp: “Am I happy with my microphone?”, “Does my microphone need more gain?”, “Do I want new or different tonal options for my recordings?”, “Do I feel unable to record everything I want to record simultaneously?”. If your answer to all or most of these questions is yes, then it might be time for a new preamp.

Final thoughts

Preamps are a dense topic, and there’s a lot of information to consider when looking to buy one or even just understand these pieces of gear. So, hopefully, you come away from this article feeling more confident in what preamps are and how they’ll help your sound.