Transparent or colored, transistor or tube, rack or 500 series... Mic preamps are an indispensable tool in any recording studio, but we are often overwhelmed by the sheer number of options on the market today.
In this article we'll try to give you the keys to choosing the right preamp for each situation, without getting bogged down in complicated technical explanations, and drawing on the experience of our own studio.
What Does a Preamp Do?
The most important thing when delving into the vast universe of mic preamps is understanding their function and their place in the recording chain. To do that, let's go back a few links in the chain and look at the sound source. It could be a voice, a trumpet or a drum kit: anything we want to record that alters the properties of the medium (in this case, air) through waves. Those waves will interact, to a greater or lesser degree, with the objects they encounter along the way.
As a rule, they won't carry enough energy to produce significant changes in our walls, floors or furniture... unless they strike something truly sensitive and light: the diaphragm (or ribbon) of a microphone. Microphones are designed to respond even to the faintest whisper, with some of their components vibrating to generate a tiny electrical current, or microvoltage, that travels down our cables.
This is where the first “change of state” of the sound takes place, as we go from tiny oscillations in the air (pressure, temperature...) to a minuscule electrical signal.
That signal is so small that it's impossible to work with. We couldn't EQ it, compress it or convert it to a digital signal, because it doesn't have enough energy to be considered usable. So how can we amplify that signal and bring it up to the right levels? Exactly, as you've probably guessed by now, that's the job of a mic preamp.
Altering the Sound
Carrying out that amplification is no easy task. It takes a lot of wires, transistors, resistors and little screws. In the process, our original signal can undergo serious alterations, such as the appearance of harmonics or the boosting or loss of certain frequencies. The first preamp makers surely tried to avoid these distortions as much as possible, until, surprise! they realized that in some cases they “enriched” the sound, making it more pleasing to our ears.
That's the case with Neve preamps, which naturally “color” the sound by subtly compressing it and slightly taking the edge off its harshness, making them an indispensable element in rock, pop, funk and soul recordings.
Other manufacturers (Millenia, DAV Electronics, etc.), however, have managed to keep those distortions to a minimum, offering very transparent preamps that are faithful to the original signal. They tend to be used on recordings that demand a high level of sensitivity in capturing nuance, such as string quartets and symphony orchestras, although they work beautifully in any other setting too.
The “speed” at which a preamp amplifies the electrical signal also lends certain characteristics to the resulting sound. Some preamps are very fast at this job, such as those made by API.
That trait makes them ideal for translating the transients of percussion instruments, adding a touch of aggression and punch that is highly prized in certain styles. By contrast, Neve's circuitry subtly slows down the attack of the signal, which in turn brings a warmth that can be a great fit for some recordings.
To each his own! In our drum recording studio we have twelve API preamps, four Neve preamps and four DAV Electronics preamps so we can cater to our clients' preferences.
Format
Most mixing consoles have their own preamps built into each channel. So do some AD/DA converters, which makes things easier and cuts costs for anyone getting started in the exciting world of recording. But if you're thinking about buying preamps separately, you'll have to choose between two different formats: rack or 500 series.
What's the difference between them? According to the sources we consulted, there is no difference in sound, but there is in price and in configuration options. 500 series racks offer a set of slots where you can insert the different preamps as you acquire them. You can buy them one at a time, whereas in rack format they are usually only available in pairs or sets of four.
The module that houses the 500 series slots has a single power supply for all the units, which cuts costs considerably.
You'll find a surprising range of prices on the market, depending on the brand and the quality of the chassis. In principle, since it's basically a power supply that has to deliver a given voltage, there shouldn't be any difference in sound, but there will be in durability and reliability.
Applications
So is there an ideal preamp for each instrument, or will any of them do the job? According to the engineers we consulted, it all comes down to taste. What are we looking for on each occasion? It's true that the aesthetics of some styles may lead us to lean toward specific preamps. Recording rock drums with API can be a very good decision. But so is doing it with Neve. It all depends on the nuance we want (or are able) to give it.
Why a Good Preamp Matters
As the saying goes, a chain is only as strong as its weakest link. In the recording process we have to be careful with every element, because we'll be limited by the one with the lowest quality. In my view, there are two major phases in the recording process, with the turning point being the change of state I mentioned earlier.
We could call these phases “emission” and “capture.” In the emission phase we have to look at the acoustic factors of the process, where the sound is still a disturbance of the properties of the medium that carries it.
Here we're affected by the room acoustics, the tuning of the instrument, the performance of the musician, and even other psychological and emotional nuances of the people involved, subtle but certainly perceptible. In my opinion, and based on my own experience, I'd say the musician's performance is the defining element of this phase.
The sound capture phase begins with the microphones and continues through the cables, preamps and the analog-to-digital converter (where the second change of state of our signal takes place: from electrical microvoltage to zeros and ones). All the steps, as we said, are very important, but in my view the choice of microphones (dynamic/condenser/ribbon), their polar pattern (cardioid, omni, figure-8, etc.), and their placement in front of the signal source are the most audible of all.
Of course, everything will be processed and amplified by our preamp, but when choosing the “color” or “character” of the resulting sound, we're getting into the realm of subtleties. The choice of AD/DA converter would come third in terms of how noticeable the differences are, with cables in last place (absolutely imperceptible if they work properly).
In our online drum recording studio we've been able to run countless tests to determine how important each link in the chain is. We could conclude that all the elements in the “emission” phase are far more noticeable than those in “capture,” and within the latter, the choice of preamp would rank second out of four.
In a blind test published on our YouTube channel, we put several sound engineers to the test, inviting them to download some drum tracks that had been recorded with API and NEVE at the same time. They had to work out which preamps had been used in each case. Only 50% got it right.
So should we invest in good preamps? Absolutely and unreservedly, yes. As we said, it's important for every link in the recording chain to be of the highest possible quality.
Keep in mind that all of our work will sooner or later pass through a preamp, and it shouldn't ruin the musician's performance. It's also true that a preamp can't work miracles: you won't be able to improve anything that's happening “on the other side of the microphone.”
Conclusion
What do preamps contribute to our recording from a musical standpoint? The answer is a nuance, a tone, subtle but perceptible. Imagine you're painting a picture: you'll need different colors. Just any blue or any green won't do... You'll want to capture on the canvas what you have in your head, and for that you'll need a broad palette that lets you express what you feel. Often a drop of red mixed with yellow will be enough to add that touch of warmth. Other times you'll darken a tone with a pinch of gray...
Our musical canvas is made up of small details, and every one of them matters. Welcome to the world of music, where the sum of infinite nuances makes for big differences.
