How to pick a mic pre - Audio Media International

How to pick a mic pre

How to pick a mic pre
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If you’ve heard more than one microphone in your life you’ll be familiar with how much of a difference your microphone choice makes, both in terms of model and placement (one inch of movement can make or break a guitar cab mic sound). We all recognise the recording industry adage ‘garbage in, garbage out’, and it does you no end of favours when it comes to mixing to start with a quality recording. But of course, that recording chain only begins with the microphone. What the microphone is plugged into has an impact too, and depending on the mic itself, a potentially huge one.

A microphone is often just a light membrane being vibrated to create a small electrical current. By itself, it creates only a tiny, weak signal. That whisper must be amplified enormously to be loudly and clearly recorded, and the manner in which it gets up to that volume can have an enormous cumulative effect on your recording. A microphone needs a microphone preamplifer, and they’re not all the same either.

Microphone preamplifiers all have inherent noise levels, added by their circuitry and by the microphone itself. Noise, or hiss, is just a part of analogue recording, ever present in the background. Put the microphone too far from the subject and you’ll need to amplify the signal more than usual to get it to an acceptable level. The more you beef up the signal, the more noise you beef up with it – they cannot be separated. You can counter this introduced hiss with careful filtering or clever and expensive plug-ins, but there is only so much that can be done without affecting the sound you want to keep.

Sometimes you don’t get a choice where you place the mic. A microphone preamplifier with low self-noise can help get you an acceptable recording, and it’s often desirable to have one with in excess of 60dB of gain. Ribbon microphones – sensitive, frequency restricted, but wonderful on sources like drum overheads and guitar cabinets – need plenty of gain. Here your choice of pre-amplifier should be made carefully.

The ‘ultimate’ mic pre is ‘wire with gain’ – which is to say, the signal that goes down the wire has gain applied and nothing else whatsoever. Of course, this does not exist in the real world, and we must accept and embrace some of the tonal colour, noise, and change in frequency response that ends up in our recording. “Embrace” is definitely the word, as of course many microphone preamplifiers deliberately aim to colour the signal, but in pleasant ways. There are many vacuum tube-based amplifiers that are celebrated for the harmonic distortion they introduce – the grit, bite, and sonic ‘dirt’ imparted, which is characteristic of microphone preamps of yesteryear. But after all, this is music, not science, and short of the precision often required for classical music recording, a touch of colour is half the point.

We’re the UK distributors for a number of quite well-known music technology brands, and among them a number of mic preamps. Let’s have a little look through some, covering the gamut of price, and see how they relate to the factors we’ve been exploring.

PreSonus of Baton Rouge, Louisiana, will be known to many as makers of quality yet affordable gear. The company’s standard microphone preamp is the XMAX. ‘Standard’, however, does it a disservice – it’s an affordable, excellent sounding, and quiet (self noise) pre with little signal colour. XMAX is the preamp included 33 times in the flagship PreSonus StudioLive 32.4.2AI digital mixing console as well as its lower cost audio interfaces such as the AudioBox 22VSL. Supplied with 48V phantom power but with enough gain (65dB in the 32.4.2) to satisfy quiet ribbon mics, these are workhorse preamps that really do provide great results.

PreSonus also offers two low-cost standalone mic pres: the TubePre V2, which is a tube-based XMAX variant able to impart a warmer, grittier sound than its standard counterpart, and the BlueTube V2, which features dual clean XMAX and a tube stage which can be blended for the best of both worlds.

Universal Audio (UA) produces some of the best-known and most well loved studio gear in history. UA’s SOLO/610 mic preamplifier is based on the modular 610 tube-based console built by founder Bill Putnam and used to record luminaries such as Frank Sinatra, Nat King Cole, and the Beach Boys. Capable of up to 60dB of gain, full frequency range, it nonetheless imparts a degree of warmth and sonic character to the recording (though not overpoweringly so), due to dual tubes inside the unit. UA also produces a 710 mic preamp, which has the novel ability to blend between two tonal colours – a tube-based preamplifier side and a grittier, more ‘modern’ sounding transistor-based side. It does so in a phase-coherent manner, so you can smoothly blend between the sides without strange phasing artifacts.

API, a highly celebrated American studio brand, is the go-to choice for a punchy rock and roll sound. A huge part of its business has come from selling large-format studio mixing consoles, and, like PreSonus, its flagship mic pre that is present in its biggest desks, is also available in smaller forms – namely as a 500 series ‘Lunchbox’ module called the 512c, which offers 65dB of microphone gain with the characteristic API sound, and the 3124, which is effectively four 512s in one 19in rack, with power supply included.

Expert witness
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