The next step is getting sound into the recording device. Sound gets into a recorder either by being plugged directly into the recorder with a cable, or by using a microphone to pick up the sound.
If you play an acoustic instrument, a microphone is necessary to convert the sound waves into electrical signals that can be recorded. What makes any microphone different from any other microphone? This is more important than just hearing “use an SM-57 on guitars,” or “use a beta-58 on vocals.” As a budding sound engineer, you should understand why engineers choose different microphones for different purposes.
The simplest answer is that every microphone hears sound differently. Some microphones only hear what's directly in front of them (unidirectional). Other microphones pick up everything from all sides (omnidirectional). And others hear sound on two distinct sides (called figure eight). If you were trying to use one microphone to record a room full of sound coming from all sides, you would choose a microphone that hears sounds from all sides (the omnidirectional microphone). If you were trying to zero in on just one instrument, and trying hard not to pick up other sounds, you would want to use a unidirectional microphone pointed right at the sound source.
Knowing what direction a microphone hears is usually the determining factor in choosing which microphone to use. You must choose the one that works best for what you're trying to record.
Some microphones also hear certain frequencies of sound better than others. This is called frequency response. You wouldn't want to use a microphone that can't hear very high signals clearly on a high-pitched instrument, or low signals on a low-pitched one. Microphones also color the sound they transmit; this is tied into frequency response. These colorations are what give microphones their distinct sound — “warm,” “clean,” or “clear” are terms commonly used to describe sound colorations. Because of construction differences between microphone manufacturers, every model sounds unique. With some training and experience, you'll be able to pick the right microphone(s) for your setup. Getting the right type of microphone is more important than buying a particular brand. Chapter 9 gets into all the nitty-gritty details of microphones.
Microphones don't produce much signal by themselves. If you plugged one directly into a recorder, the sound level wouldn't be very high. You could try to compensate by turning up the entire track, but unfortunately you'd turn everything up, including the noise. What you need is a preamplifier. The preamplifier raises the output of the microphone loud enough to make the signal clear and strong.
How many microphone preamps will I need?
You will need one preamp for each microphone you record at the same time. If you don't need to record live groups, you might need only a few microphones, recording one or two tracks at a time.
Commonly, preamps are built into mixing boards, studios-in-a-box, and computer interfaces, so you might not need to purchase these separately. You can also buy individual microphone preamps if your device has none or you need more. The number of microphone preamps that your mixer or other recording device has is a critical factor in determining if the gear is right for you. This is the time for you to evaluate how many microphones you plan to use at once.
Any instrument that plugs directly into the recorder is called a direct input. No microphones are necessary in these cases. Keyboards, synthesizers, drum machines, and certain guitar and bass amplifiers are equipped with “line outs” that can be plugged directly into a mixer or a recording device. A guitar or bass plugged in directly via a cable won't be “line level”; that is, its signal won't have enough “juice” to be heard. It also has the wrong impedance, which is an electronics term referring to how much “force” the signal has due to how it impedes the flow of electricity out. Guitar and bass are very high impedance sources and generate very low output levels. Even though guitars and basses appear to have line outs, you'll need a direct box, or a “DI,” if you want to record a guitar or bass directly without an amp. A direct box simply takes a signal that is too low, is too loud, has the wrong impedance, or is an unbalanced signal, and converts it to a perfectly balanced line-level output.
Direct boxes come in two flavors: passive and active. Passive DIs don't require extra power to run; active DIs do. Active direct boxes can offer additional signal strength for very low output instruments. In most cases, passive direct boxes will do just fine. Every studio should have at least one direct box.
Another nice benefit of a direct box is that it can isolate nasty buzzes that studios encounter from time to time via a button called a ground lift. Even if your amplifier or keyboard has a line out, if you are getting buzzing that's driving you crazy, try a direct box between the output and the recorder's input, and flip the ground switch. Many times this will do the trick. Anyone who has played on stage has encountered a direct box; it's indispensable. If you plan to record bass, guitar, or certain keyboards that aren't line level, you will need a few direct boxes.