In this guide, I hope to cover the role a microphone preamplifier plays in the audio signal chain as well as how to choose one, and what to look for. Before you read on, I’d just like to preface this guide by pointing out that, for most of you, a simple phantom power unit will suffice. If you’re using a condenser mic and need to power the capacitor before the microphone enters the compressor on your signal chain, then going with something like the Behringer Micropower PS400 is more than enough. Many compressor models don’t carry the phantom signal from an interface or mixer, so this unit will serve to supply your microphone with the 48v it needs to function.
If you’re using a dynamic microphone, or are an audiophile and would like a quality preamp to “color” your audio tone then read on! I will cover the advantages to acquiring a quality preamp as well the conveniences of channel strips. Depending on your streaming setup, multiple mics and inputs may or may not be relevant to you, so it’s up to you to decide how best to use all this information.
As I mentioned in the first installment of this guide series, my plan is to also include some gear recommendations so that these guides are informational as well as practical. However, if you have questions about specific gear, please PM me rather than comment below. I’d like to keep the comments section devoted to questions about the guide and gear-related inquiries can quickly take over with a plethora of specific questions and nuances.
Why a Preamp?
Along with the microphone, your choice of preamp will play a significant role in the final sound of your audio signal. While a basic purpose of the mic preamp is utilitarian, there are many other aspects to take note of in order to get the most out of your microphone. A mic preamp takes the low output from a microphone and amplifies the signal to a higher line level. The preamps built into most audio interfaces will do just that, but low cost on-board preamps are typically limited in tone and flexibility. They can add unwanted tonal coloration that produces a sound you don’t like or, even worse, introduce noise. A high quality microphone preamp, however, will do much more than making your mic level louder. The ideal preamp delivers a cleaner, more accurate signal with higher gain, lower noise, less distortion, and more head room between your signal and the noise floor.
In most instances, the goal of a quality preamp is to capture the source as transparently as possible. Most budget preamps inherently introduce some degree of hiss and background noise to your signal. A good mic pre will allow you to actually have a quieter signal (and avoid clipping before reaching the compressor) without any added noise or distortion.
On the other hand, certain preamps are famous for adding their own unique quality to an audio signal. Experienced audio engineers will use different preamps much like painters use different brushes for various colors or textures. These types of coloration are usually referred to as sounding “thin/fat” or “cool/warm”. Preamps that feature transformers or discrete amplifiers in their circuit (like the Neve 1073 or the UA 2108) add varying degrees of character to an otherwise transparent signal. The same goes for tube-based designs, which are famous for adding “warmth” and saturation to signals – hence why many companies like to slap the word “tube” somewhere in their advertising to attract novices who have heard of the legendary “tube” quality.
Conversely, many transformerless designs (also called Solid State) are lauded for their crystal-clear transparency and fantastic rendering of source signal. Ultimately, it is up to you to decide how you would like your signal to sound and I hope this guide will help you make a more informed, artistic decision.
Inputs and Outputs
Any microphone preamplifier will have (at least) one microphone input and one line-level output. While that will certainly get the job done, you may want more functionality out of your preamp. Some mic pres have a hi-Z direct input (DI) as well, which streamers may find useful for ¼ inch cable inputs. It’s not uncommon to see an XLR output and a ¼ inch TRS output on the same preamp to offer more connectivity options. Some preamps with multiple outputs will allow you to use the pre as a signal splitter (you could run one line-level output to your mixer and another to an interface for separate processing). Depending on what you have connected, preamps with multiple outputs can be a huge asset.
Some preamps have a built-in A/D converter, which outputs a digital signal from the preamp directly to your recording device. This typically achieves a lower noise floor than running an analog connection and is also a great way to take advantage of an unused digital input on your interface, thus saving an analog input for a different application.
There are three basic flavors to preamps: standard 19 inch rackmounts, 500 Series modules, or desktop units. Depending on your streaming space, you may want to focus on the smaller units to reduce their footprint. Some manufacturers make their more popular models available in multiple form factors, so be sure to extensively search.
Even if you don’t currently stream with more than one microphone, that may change in the future. In addition to looking at single or dual channel preamps, multichannel preamps allow for many inputs as well as many kinds of inputs (XLR and TRS). There’s investment value to consider, too. Compare the per-channel cost of a high-end, multichannel preamp to a single or even dual channel pre. Sometimes, you may actually pay less per channel for a higher quality preamp. Yes, the initial investment is higher, but you’ll be glad you have the extra inputs once you expand.
Channel strips are basically preamp and processing in a single box. The channel strip is comprised of signal processing tools starting with a preamp usually followed by compressor, EQ, and, in some cases, de-esser. For a streamer, this offers every processing tool you’ll need for a professional vocal sound in one convenient and cost-effective module. Since all the electronics are housed inside the same unit – as opposed to being patched from separate preamp to compressor to EQ to etc. – the chances for noise are diminished.
For the streamer using only one or two microphones at a time, a couple of channel strips could serve much better than working with separate preamps and processors. Not only will this simplify the signal flow, but you won’t have to manage multiple pieces of gear to get the sound you want – all with great results!
Besides the gain control, some mic pres have added controls and functions that may be helpful. One common feature is the low-cut (also called highpass) filter, usually around 100Hz and below. This is a great way to cut out low-end rumble and useless sonic noise that is just eating up your volume headroom and not adding any useful information to your audio signal. If your microphone doesn’t have an on-board low-cut switch built in, then you’ll definitely want a preamp with this feature. This will also cut out desk-bumping or other unwanted low-end noise and clean up your overall sound.
One final thing to consider is stereo recording for dual-channel preamps. Some units have a mode that allows the adjustment of gain equally across both channels with just a single knob. This makes it easier to record a balanced stereo signal from two mics. If you run a two-person stream or want to have guests, definitely keep an eye out for two-channel preamps with channel linking capabilities.
What to Look For
In summary, here are some points to ask yourself when looking for a microphone preamp:
- What will you be connecting the preamp to and how will it fit into your existing workflow?
- How many channels of preamplification do you need?
- Do you want addition sound-shaping controls on the preamp or just mic gain boost?
- Would a channel strip with built-in compression and EQ be a more efficient way to get the sound you want?
This covers the preamp, this first step in your signal chain that will, hopefully, take you through the rest of the guides in this series. If you’re reading this before the other parts, then follow the links below in order to locate the rest of the installations. If you’re reading this as the guides come out, then you’re already at the end of the line looking back and hopefully this has cleared up any questions you may have had. Either way, I hope this was helpful, informative, or in some way useful to y’all! Happy streaming <3