Choosing Between Internal and External Microphone Preamps

1. Even a super-inexpensive mic preamp like the $39 Behringer Tube Ultragain MIC100 can provide useful coloration in the studio. 2. A channel strip—like the Joemeek threeQ—offers a one-stop recording solution that connects directly to your DAW. 3. The PreSonus DigiMax D8 provides eight mic preamps that can be fed digitally into your DAW, instantly expanding the number of tracks you can record at once.

In my June 2012 column, “Delving Deeper into the Audio Interface,” we discussed audio interfaces and how some have built-in microphone preamps—just plug in your mic and get recording. So why would you want to have one or more separate mic preamps?

First of all, most audio interfaces have a limited number of mic preamp inputs. Interfaces with two mic preamp inputs are common, some offer four, and some have as many as eight. But if you’re trying to record a full band, that may not be enough. Fortunately, many audio interfaces offer line-level inputs along with their built-in mic preamps. By using these line level inputs to route signals from external preamps into the interface, you can run more mics simultaneously.

The second reason to use external mic preamps is for the tonal colorations they can provide. In most cases, the microphone preamps that are built into audio interfaces are designed to be clean and transparent. But if you want a different tonal coloration, external mic preamps can help. Some are designed for clean and transparent operation, while others are designed to provide a specific “color” to the signals they process. Some offer thick mids, others offer warm top end, and so on.

In the “clean” category, you’ll find preamps from Grace Designs, Millennia Media, GML, and others. “Colored” preamps include Chandler Limited, Universal Audio, and A Designs. “Classic” mic pres include those designed by the legendary Rupert Neve, who has made preamps for Neve, Focusrite, Amek, and his current company, Rupert Neve Designs. You can also find Neve preamp clones, such as those from Great River, Vintech, and Brent Averill. Many engineers love API preamps for drums and electric guitar because of their thick, punchy midrange response.

In my opinion, the contribution a preamp makes to a recorded sound is often subtle compared to the contribution made by the microphone and mic placement. And certainly, getting the sound right at the source before it ever goes into a mic makes the biggest contribution to the final sound. My advice is to go for the best preamp you can get with your resources. These days, even an inexpensive preamp can give you great sound quality.

External microphone preamps can provide features beyond boosting mic-level signals into line-level signals. Some offer built-in analog-to-digital converters so you can route your microphone into the digital inputs on your audio interface. Some preamps include built-in equalizers so you can adjust the tone of your signals as they pass through the box. And some have built-in compressors for controlling dynamics as you record signals. Some even go further with built-in de-essers, gating, and other processing. Such preamps are usually referred to as “channel strips,” because they resemble a channel from a full-featured mixer. Whether these additional features are worth having depends on how you like to work.

There are basically two camps of recording engineers. One camp likes to commit to a sound as they are recording. They’re happy to use EQ and compression as they are tracking to fine-tune the signal on the way into the recorder. Someone in this camp would find built-in processing in a microphone preamp to be very useful.

The other camp likes to track “dry,” with no EQ, compression, or other processing. The idea is to capture a robust, unaltered signal that can be processed during mixdown to adjust the tone or dynamics as required. The advantage to this approach is that you hear each signal in context of the overall mix and are free to do what is necessary without having to work around EQ or compression that was applied during recording. Someone in this camp would prefer to have their microphone preamps unadorned with additional features.

Which method is better? It comes down to what you are doing, the types of signals you are recording, and how you like to progress through a project. Personally, I prefer to have a mix of preamps available and I work with external preamps most of the time for maximum flexibility and for additional options while tracking. I like to have clean, transparent preamps for acoustic guitars and for capturing pristine electric tones. Then I like to have a colored preamp or two, including a tube preamp that can thicken and “punch up” electric tones. A channel strip (transparent and colored types of these are available too) is useful for tweaking the tone and smoothing out dynamics a bit on the way into the audio interface.

External preamps are useful for the color and features they can provide, but they are not essential. You can capture great sounding tracks using the preamps that are in your mixer or audio interface.

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Mitch Gallagher is the former editor in chief of EQ magazine. He’s written more than 1000 articles and six books on recording and music technology, and has released an instructional DVD on mastering. His upcoming book is entitled Guitar Tone: Pursuing the Ultimate Electric Guitar Sound. To learn more, visit mitchgallagher.com.