Paul White looks at the easy way to turn a great guitar performance into a great recording.

Despite the miraculous advances in technology that have brought us synthesis, sampling and realistic drum machines, the electric guitar stands alone as a bastion of low technology that refuses to be replaced by progress. Nobody invented the electric guitar sound — it just evolved, based on the inadequacies of amplification and speaker technology, and all those subtle (and some not so subtle) imperfections have become inexorably bound up in the sound that we now take so much for granted. Solid state amplifier designers have been trying for years to unravel the mystery of the valve amplifier but, despite various claims of success, few are completely satisfied by the imitations.

The sound of the electric guitar depends on a combination of the instrument itself, the amplification and loudspeaker system used, the room acoustics and, most importantly, the way in which the instrument is played. The amplifier makes a profound contribution to the sound, which is why so many people still mic up guitar combos and stacks, rather than relying on speaker simulators or guitar multi-effects preamps. That's not to decry simulators or preamps in any way, but very few, with the possible exception of those that have resorted to valve circuitry, capture the spirit of real valves and real loudspeakers being driven to the edge of destruction by an enthusiastic performer.

Guitar speaker systems tend to comprise 10-inch or 12-inch drivers, either singly or in multiples, mounted in cabinets which may be fully sealed or open backed. The distinctive overdrive sound is caused by harmonic distortion added in the amplifier and then filtered by the tonal character of the speaker and the cabinet. The very limited audio bandwidth of a typical guitar speaker removes most of the upper harmonics introduced by overdrive circuitry — without this filtering effect, the result would be thin, buzzy, and very unmusical. Most players still uphold that valve amplifiers sound better than solid state models, especially for rock music, and for recording work, a low-power valve model will produce results which are just as good as a full-sized stage rig. I use a little Fender Champ in my own studio and it can sound huge, even though it's only rated at 15 watts!

Microphones

Dynamic microphones are the most common choice when recording the electric guitar, and even a modest general-purpose cardioid will usually give quite adequate results. Because guitar amplifiers are loud and have a limited audio bandwidth, it isn't necessary to use a very sophisticated microphone, and most dynamic mics used for live vocals will work perfectly well. Professionals tend to use popular dynamic models such as the Sennheiser 421, the Shure SM57 and suchlike, but try all the mics you can get hold of because they'll all produce a slightly different sound.

Some American engineers still prefer to use a capacitor microphone on the electric guitar, which helps to produce the typical American rock sound — not so fat as the British sound, with a tendency to be brighter. You could also experiment with the Tandy PZM mic, as these can produce surprisingly good results. In this case, place them flat on the floor in front of the speaker cabinet, rather than mounting them on a stand.

Guitar cabinets can either be miked close, miked from a distance or, using two or more mics, with a combination of the two methods. You really have to treat a guitar cabinet like an instrument in its own right, because different sounds come from different parts of it. Even with a sealed cabinet, a surprising amount of sound comes from the back and sides of the box. With an open-backed cabinet, as much sound comes from the back as from the front.

Stacks

To get a live sound, you can't beat setting up the full stack and then miking it from ten feet or more. This way, you capture the direct sound from the speakers, including any phase cancellation effects caused by multiple drivers, and you also get the sound reflected from the floor which, because of the longer path length, creates further comb filtering or phasing effects. Figure 1 illustrates this point. A distant mic 'hears' the performance much as an audience would, but few home studios have the space to work in this way, especially when several members of the band are playing together. Furthermore, in a session where several players are working together, separation becomes a major problem unless the microphones are placed as close to the guitar amps as possible.

Miking at a distance produces a warm, powerful sound quality, but it doesn't sound as bright as a close-miked amp and may not cut through a busy mix so well. For close miking, position a single mic between two and six inches from the centre of one of the speakers in the cabinet — many engineers work with the mic right up against the speaker cloth. If the resulting sound is too bright, it can be mellowed by moving the mic towards the edge of the speaker. If you're working with 4x12 cabinets, it's worth listening to the individual speakers and then miking up the best-sounding one.

A fuller sound may be obtained by miking the rear or side of the cabinet and then adding this sound to the direct-miked sound. Strictly speaking, the phase of the rear mic should be inverted (using the phase button on the mixing console) so that its output is in-phase with that of the front mic, but try both options and pick which sounds best. If you don't have a phase inverting button, you can make up a phase inverting lead by swapping the wires going to pins 2 and 3 inside the XLR plug that plugs into the microphone. If you do this, ensure that the lead is prominently marked!

It can be interesting to use an additional ambience mic, usually a capacitor model or PZM, several feet from the cabinet, and then add this to the close-miked sound. A direct comparison of the two sounds in isolation will reveal that the close-miked sound is more clinical and noticeably brighter. The ambience mic will have a softer tone and will include a degree of room ambience, making the tone thicker and less immediate. By balancing the two mic levels, you can achieve a useful range of tonal difference, and to create a stereo effect, you could pan the close mic to one side and the distant mic to the other.

Treatment

Some additional EQ may be needed to achieve the desired tone, because the sound you hear in the studio is rarely exactly the same as the sound you get on tape. Even so, try to get the best sound you can by moving the mics before you worry about EQ, and try compensating with the tone controls on the amplifier before you resort to the EQ on the desk.

In the case of the guitar any effects, such as pedals, are modified by the character of the amplification system itself, so it might be wise to record these 'live' rather than try to duplicate them while mixing. Also, the player responds to the sound of his or her playing; effects are an integral part of the sound, particularly overdrive or delay. The moral is — don't compromise the performance for the sake of some slight technical advantage by insisting that you use your own studio effects.

Once recorded, the guitar can be processed just like any other sound source — close-miked guitars tend to need a little reverb to provide a sense of space. Short, bright settings do the trick without muddying the sound, but the only real rule is: if it works for you, it's OK. Gated reverb is also useful for creating a raw, punchy sound and it has the advantage that it leaves plenty of space between notes and phrases, even when a lot of the effect is added.

Separation

If two guitars are used on the same track and seem to be conflicting, you can pan them left and right to try to keep them apart, but it also helps to EQ the sounds to make them a little different. Ideally, choose two guitars with fundamentally different sounds, such as one with single-coil pickups and one with humbuckers. If you have no choice in the matter, then try getting the players to rearrange the song so that they aren't both playing at the same time all the way through, especially with heavily overdriven sounds.

EQ can help by removing excess bass from sounds and also by peaking them up in slightly different areas of the audio spectrum to create different character. For example, one guitar could be given a little EQ boost between 2.5 and 3kHz, while the other might be peaked up at 4kHz or so. Miking the two guitar amps from different distances can also help to keep the sounds sufficiently different.

Though this might sound obvious, before you start, make sure the guitars have decent strings fitted and that they are set up properly. All the points brought up last month concerning acoustic guitars also apply to electric guitars, except that with electric guitars you also have to worry about faulty leads, hum and interference. If there is too much noise from the guitar, it is OK to use a gate when mixing to keep the thing quiet during pauses or between phrases. However, set the gate attack to its fastest setting and ensure the release time is long enough so as not to chop off the end of sustained notes before they've been given a chance to die away. Also ensure that the gate's threshold is set as low as is possible without the noise breaking through; this way the gate is less likely to chop out wanted parts of the sound such as quiet notes. I don't like using a gate during recording, as a perfect take can be ruined by incorrect settings. If you make a mistake while mixing, at least you can reset the gate and try again.

Finally, be absolutely ruthless when it comes to tuning. Always use the same tuner for all members of the band and check the tuning regularly, as it tends to drift throughout the day. No matter how well you play, if the take is out of tune, there's nothing you can do to save it.