How to Mike a Guitar Amplifier for Recording

03.15.2013 Gibson GA amp

Miking an amplifier to get great guitar sounds in the studio seems like a simple proposition. Get a great guitar sound, a good reliable microphone, and let it rip, right?
Well, yes and no. It is possible to get credible guitar tracks just that simply, but what about ambient mics? Those were the key to Jimmy Page’s incredible sound on the first few Led Zeppelin albums. And if you do begin using an array of mics — or even amps — issue like phasing come into play. And what exactly constitutes an adequate or awesome microphone for cutting guitar tracks?
Let’s consider some major points.
• Amp selection: If you’re serious about playing and recording guitars, you’ll have several amps available for sessions. Keep in mind that a 4x12 cabinet is going to sound different than a single-speaker driven by the same head. Ideally you’ll want to raise multi-speaker cabinets off the ground to reduce potential phase cancellation. And bigger cabinets should have more space around them so they have room to open up harmonically. Also remember that small speakers will break up when turned up, and big speakers will yield a more defined, trim sound.
• Single-mic, single-amp recording: For the home recordist, this is a common technique and it works perfectly well. The three factors involved — beyond the quality of your amp tone — are microphone selection and positioning, and amp placement. Unless you’re going for a crazy reverb sound, you want a space that’s sufficiently open for the amp to sound good. If you are going for crazy reverb, than by all means place your amp in a large trashcan or a tiled bathroom and let ’er rip.
• Microphone placement for one speaker: A microphone placed dead center in a speaker gets the brightest, most highly defined sound. There’s no debating that. The tone gets darker and warmer as you move off-axis. And as you move further away from the amp, the bass gets less accented. Experiment a bit to see what makes your ears happiest, which may vary from song to song, depending on the vibe you’re seeking.
• Microphone selection: The mic you use for recording guitar is also a matter of taste, provided finances do not limit you. A workhorse SM-57 will often do the trick — especially for demos. That’s a type of dynamic microphone. If you’re ambitious about recoding, you should also own a good, versatile condenser mic. These work grandly for guitar, bass and acoustic recordings, from vocals to drum cymbal overheads. And if you’re looking for bottom-rich, gutty electric guitar tones, your go-to could also be a ribbon mic, which tend to accent the richness of the low frequencies.  
• Get good monitors: Now’s a good time to mention that you should get the best monitors you can afford. A $4,000 microphone is going to sound like crap if you’re listening through terrible speakers at the board. Shop around and see what fits your ears best. Monitors are typical the gear that gets the least care in selection from home studio owner, and they affect every step of the recording process.
• Recording multiple amps: If you’ve got the space, the microphones and the inputs, running your guitar through multiple amps simultaneously is a great way to generate fresh tones and have a adjustable sonic palette for mixing. So if you opt for this technique, be sure your amp tones are varied — clean, dirty, trebly, low. Different amps can be bought to the fore of the mix to underscore certain sections of the song you’ve cut. The vocal line in the verses might call for clean guitar support. Then you might want to dirty it up more for the choruses, and just go all-out on the solos. For a good example of multi-amp recording and mixing in action, check out Nashville blues-rock guitarist Bart Walker’s sophisticated version of the Allman Brothers’ “Whipping Post.” Producer Jim Gaines had at least five amps simmering at all times during the sessions for Walker’s new Waiting On Daylight album. And you can hear the tones move from ultra-sweet to gritty in this performance. Of course, to pull this off you’ll need a bay or port that allows multiple outs to the amps or a good, quiet A/B box or two.  

• Recording with multiple close mics: Individual microphones of the same make nonetheless have subtle difference in sound. So placing two mics on the same speaker can have interesting results. Placing one dead center and another at the edge of a speaker gives broad tonal coverage, and cutting two tracks with the same or different microphone allows for varying EQ options in the mix.
• Employing ambient microphones: Unless you count the old days of one-, two- or three-microphone recording for the entire band, ala Chess Records, the Brits invented ambient miking as we know it today during the last 1960s and early ’70s. Jimmy Page and Alan Parsons jumped on this concept, placing a close mic on a speaker cone and then one or more mics at various points around the room holding the cabinet. Good spots to consider are behind the cab, to get a darker, reflected sound; at elevation eight to 15 feet away, to pick up the open ends of the soundwaves being produced; or at near-ground level at six-feet or more to pick up powerful lows. Like using multiple mics on a single speaker, this yields a rich variety of tones that can enliven the mix and it makes for big guitar sounds, even from little amps.
Having multiple tracks from a single amp also opens up an array of options for phasing, EQ and panning in the final mix. But mixing multiple guitar tracks is fodder for an entire article on its own.