Preamps, which boost the signal of microphones so they can work with mixers and audio interfaces, can be the most important gear in your studio. Here's the lowdown on how to choose and employ the right preamp for any recording situation.
Bicoastal Music LTD., Ossining, NY, Control Room
Photo by Sean Smith
Portico 5012, designed by Rupert Neve
The Solid State X-Rack can hold mic preamps and other signal processors.
ART Pro Channel
Universal Audio Solo/610
With the popularity of today's Digital Audio Workstations (DAWs),more composers, songwriters, and musicians than ever are taking matters into their own hands and recording at home. While these home studios can offer the creative freedom of working on your own time, they often lack the quality gear of the big rooms. That in turn can yield results that, well, can make your productions sound like they were done at home. But one investment that can help take your personal audio quality to the next level is the purchase of a good microphone preamp. In this article, we'll explore why you might want one, see how it can help improve your sound and examine a few of those popular all-in-one channel strips.
So just what does a microphone preamp do? Technically, it amplifies the low voltage from a microphone and creates an output level (usually +4dB) that audio devices such as recorders and consoles can utilize. Many preamps not only have balanced +4 dB ins and outs for mics, but also have 1/4" unbalanced line I/Os to accommodate such things as keyboards, guitars, and basses.
The objective of any good preamp is to amplify the input signal with high amounts of gain without adding additional distortion and noise. But that is something easier said than done. However, there are countless types and styles of preamp available, with budgets ranging from around a hundred dollars to several thousand. You'll find single-channel, dual-channel, eight-channel, instrument preamps, and full-blown channel strips. Some have analog outputs only; others have built-in A/D converters and can plug directly into the digital inputs of your recorder.
Do I Need a Pre?
Most mixing consoles already have preamps built into them. Think about all the Mackie 1202 and 1604 consoles out there&they have preamp channels neatly packaged into them already! What about gear like Digidesign's MBox and 003, Tascam's 2488 hard disk workstation, and Korg D3200 digital recorders? Yes, they all have preamps built into them, as well. Just plug in your mic or keyboard, adjust the level, and get to work. I know what you're saying: Why should I spend more money on something I already have?
The quick answer is quality. If you think in terms of economics, preamps that are built into most consoles or recording devices must compromise on quality in order to keep the price at a reasonable level. It's a trade off of function and quality versus price. Now this certainly may not apply for those five- or six-figure consoles, but for the most part, you get what you pay for.
That's not to say you can't get a good result from a built-in preamp: You certainly can. Many engineers, in fact, would prefer to use one in a Neve, SSL, or API console. But few people have those in there home studios. So for those of you without such toys, one of the best ways to upgrade your signal path is by use of an external preamp unit.
For many, the vocal track is all-important. This is where it's often best not to skimp and use a mediocre preamp. Or, if you're doing a live recording and have only one good preamp, you can run the vocal through it and have everything else go through the others. But if the tracks can be done separately, one good preamp can be used to record parts over and over. You don't need a rack of gear, just start with a single good investment, and build your collection from there.
A good mic preamp can capture more detail from any microphone, and therefore can improve the tone, depth, and clarity to your recordings. Sonic character can vary widely from model to model, but if you're choosing just one to be a workhorse, it should be able to handle just about any type of microphone, from a classic Neumann U-67 to a Royer 122-V ribbon to a workhorse Shure SM57. It should also be able to take in any of those keyboards, basses, and samplers. A good preamp should be flexible enough to handle all the tasks you ask of it.
Typical features to look for include +48v phantom power; a 1/4" instrument jack (hopefully on the front panel); some form of either analog or digital metering; an overload LED light; a pad switch, which attenuates input level to help prevent that overload light from firing; a high pass filter to eliminate mic-stand rumble; and of course, lots of gain! Some will also offer variable impedance&a feature that lets you best match the output impedance of a microphone to the input impedance of a preamp.
Most will of course have +4dB XLR balanced (and/or -10B unbalanced) outputs that can plug directly into the line inputs of your console, or even directly into your DAW or recorder. Other models include such things as inserts, where you can plug in your favorite outboard compressor or equalizer. Some models also feature digital outputs, either in the form of optical, S/PDIF, or AES/EBU connections. This lets you bypass the D/A (digital-to-analog) conversion of your recorder and instead use that of the preamp itself. This also may help eliminate any noise incurred by long analog cable runs from your preamp to the recorder. While there is no right or wrong choice between analog or digital outputs, it is nice to connect two or more channels to your recorder with a single digital cable!
Add Some Color, Or Not
The next consideration is a little more subjective: Do you want a preamp that will influence the sound or do you want something more transparent? Some producers look for preamps that typically add no coloration to the signal coming from the mic, such as the popular Avalon AD2022, Earthworks 1022, or Grace Design m201. The signal path of these preamps is pristine enough that they pass your audio virtually untouched to the amplifier and onto your recorder.
Other producers seek to impart a "character" from the preamp. Neve and Universal Audio preamps are revered for their midrange grit and growl, as are those from companies like Manley, Tube-Tech, and Groove Tubes. Plugging into each type of preamp will yield a slightly different sonic result, and the way you set the gain control can really impact the sound. When shopping, seek out professional engineers and see what they recommend. Of course, opinions will vary widely, but one thing for sure is that you'll get one!
In my own work, Imix and match depending on the application. When recording acoustic guitars, for example, I will run an Earthworks QTC-1 microphone into a Focusrite ISA 428 with the impedance set to its highest setting. Then I will also use a Royer 121 ribbon mic through a PreSonus ADL 600 to impart extra warmth and low end with some tube flavor. For vocals, I use a good vocal mic with a Demeter VTMP-2b, which also provides tube warmth. For bass direct recording and miking guitar cabinet, I opt for a Groove Tubes ViPRE. Each preamp has its own character and flavor and fits each application differently. I've invested in a few choice hi-end preamps, and they get used on a daily basis.
Should You Tube?
So what is that mystique about old-school tubes technology and preamps? Generally speaking, tube preamps are thought of as "warm" or "smooth" sounding compared to solid-state equipment. Tube circuitry distorts and overloads in amore natural way than transistors do¬ that you should be overloading your preamp in the first place. But tubes generate harmonic distortion that creates a sonic character prized by engineers. Yet solid-state premps are just as viable and often sound better than tube preamps&especially when the tubes aren't functioning at their best. They can be the first choice for many applications. It boils down to a matter of personal taste, but if you have the budget, you'll probably want at least one of each type.
When you sit in a studio and look at each channel of a high-end mixing console, you'll see an input at the top, then maybe a few bands of equalization, some compression and gating. Keeps it simple, right? Everything you need is right there in that strip, multiplied by however many channels on the console itself. What if you could separate a strip from the console and maybe own one or two channels for yourself?
Many manufacturers now produce outboard "channel strips" that combine several components into a single, easy-to use package. While the features included in each model may vary, in general, a channel strip would allow you to not only amplify your mic, but also add some equalization and a little compression before it gets to the mixer or recorder.
The Avalon VT-737sp offers a Class A preamp, an opto-compressor and a sweepable EQ. Console makers Solid State Logic now offers the XLogic Alpha Channel with an SSL preamp, EQ and limiter/ filtering section, as well as an X-Rack component system. Focusrite's VoiceMaster Pro features a Class A preamp, a "Vintage Harmonics" processor, voice-optimized EQ, and an optional A/D card. ART has an all-in-one Pro Channel, which has a tube mic pre, switchable optical/ variable mu compressor and tube EQ.
Whether you choose to go with a separate channel strip or just a simple mic preamp, thinking outside the console can help you achieve better results in your next recording. Sure, it may cost you a few dollars but the investment in yourself and your music will be well worth it.