Microphone Preamps: Outboard Or Plug-Ins?

Microphone preamps are very simple. The basic function is to boost the low level signal from a microphone to a more robust line level. The signal can then be used for broadcasting, editing, recording or sound reinforcement.

In an earlier era, all mic preamps were outboard, standalone hardware devices. These preamps either sounded good or bad, depending on the quality of the components used in the signal chain.

It should be remembered that when using the combination of a microphone and preamp, the tonal quality of the sound is somewhat altered. This can be where the magic happens.

Focusrite ISA One Mic Preamp.

Focusrite ISA One Mic Preamp.

In the analog era, many preamps used vacuum tubes to amplify the signal and produce a signature warm sound. This warmth in analog audio is coveted and has created a modern industry trying to emulate it in the ultra-clean and often sterile digital era.

Though expensive outboard preamps are still widely used, time has moved ahead. Today, software plug-ins can emulate the “warm” sound of hardware mic preamps. Now, a quality audio interface with built-in preamps and software plug-ins can do the trick with far less investment cost.

Audient iD22 Interface.

Audient iD22 Interface.

Most modern top-of-the-line interfaces with numerous channels are moving toward a USB-C connection — the replacement for fast Firewire and Thunderbolt connections. USB 1.0 is considered too slow, while USB 2.0 can handle basic audio tasks. However, a faster connection is needed to avoid latency issues.

Today, channel count is the most important way to differentiate audio interfaces for buyers. A rule of thumb: price says a lot about quality. Expensive brand name interfaces with a low channel count probably means the device has a better-quality signal path.

As with all recording, it depends on the function, work flow and budget as to the right equipment to purchase. A home studio is far different from a commercial studio installation. A simple podcast is different from recording music groups. With today’s technology, all can sound great — if the right gear for the job is chosen.

High-quality interface devices with low channel counts and good plug-ins offer the best sound quality for the dollar. In fact, top name interfaces are remarkably good and offer the best signal quality in the entire history of recorded music.

So, for sound excellence, does one need an outboard microphone preamplifier or a plug-in? This is a difficult question to answer since sound quality is subjective and perceived differently by each individual. What sounds good to one person may not to another.

However, generally, a dedicated outboard preamp will usually translate into better audio quality when properly matched with the microphone. (There are often mismatches with even the best quality gear. Consider what to pick carefully.)

UA Apollo X4.

UA Apollo X4.

That said, plug-ins have dramatically improved and are getting better. For example, Universal Audio’s Unison technology starts right at the input stage of the preamp allowing it to sound and behave like the plug-in's tube and solid-state designs.

By capturing the impedance, gain stage “sweet spots” and component-level circuit behaviors, Unison gives the interfaces the tone and feel of legendary mic preamps from a range of classic preamp manufacturers. This is very powerful technology that can blur the line between hardware and software. Most ears can no longer tell the difference.

Neve 1290 Preamp Plug-in.

Neve 1290 Preamp Plug-in.

If one has the money and wants an outboard preamp, the key decision is a choice between a tube or solid state model. Tube models tend to have a vintage, fat signature sound. Solid-state models are audibly crisper and more defined. Again, the channel count, as with audio interfaces, usually determines the price. Even good single channel preamps can be quite expensive.

The ultimate decision of the type of preamp one chooses, whether hardware or software, comes down to achieving a personal signature sound. If you have identified that special sound and know the gear needed to achieve it, go for it. You have found recording's sonic Holy Grail.

Sennheiser MK4 Microphone.

Sennheiser MK4 Microphone.

Since most of us don’t yet know our signature sound and don’t have a vast budget, it is best to start with plug-ins. They are much more cost effective and offer far greater possibilities for experimentation in determining the right choice of sound.

Even though the cost of high-quality recording is lower than ever, it still can add up. For beginners doing self financing, chose a microphone and a small name brand interface with included plug-ins and dive in.

Then experiment and learn. Once the craft is mastered, it is time to concentrate on the nuances of the sound. This is when it may be time to choose and purchase a more expensive preamp.

The limitations of the work helps develop skills and fuel creativity. At some point, you will know which preamp you really need.  

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