Exploring the audio signal path

- Now let's talk about the gear you'll need in order to get audio into your computer or other recording device. We'll start with the audio signal path. In nearly all cases, the path audio follows from the sound source to your computer is essentially the same. So you'll need some basic types of gear regardless of what you're recording. The basic audio signal path looks like this. A sound source, like a vocal, is captured by a microphone and converted from acoustical energy to a low level electrical, or analog, signal. That signal is then amplified to a higher level with a mic pre-amplifier. It's then converted from analog to digital data and recorded into your computer onto a hard drive. When played back from your computer, the digital data is converted back into an analog electrical signal. Then your speakers convert, or transduce, the electrical signal into acoustical energy and you hear your sound. This might seem kind of complicated, so let's break down each of these steps a bit as well as discuss some of the variations to the signal path and gear involved. First, to capture acoustic sounds, you need a microphone. An acoustic sound is any sound you can hear in the air like a vocal, an acoustic guitar, or drums. Acoustic sounds are created from vibrations in the air in the form of sound waves, and sound waves are changes in air pressure. To record these changes in air pressure, we use microphones. All types of mics have a diaphragm that moves in response to sound waves and create a low level electrical current that mimics the acoustical energy. However, on their own, microphones don't provide a strong enough signal to allow you to work effectively with the audio that's being captured. The signal needs to be amplified. A mic pre-amp takes the signal from the mic and boosts its level, or its gain, to an optimal input level before it reaches your recording device. Hence the name pre-amp, it's a pre-amplifier. The pre-amp itself might be a standalone device or it may be built into an audio interface connected to your computer. Regardless, in order to get the signal into your computer, you'll need an interface that converts the electrical analog signal into digital data for use in your computer. These days, it's most common for an audio interface to connect to your computer via USB, fire wire, or thunderbolt. And some may require you to install a special card into your computer before you can connect the device. The interfaces have analog to digital and digital to analog converters in them that do exactly that. They convert analog electrical signals into digital data and vice versa. The configuration of an audio interface varies greatly. Some are basic devices that allow you to plug in one microphone, while others can accept anywhere from two to two dozen simultaneous inputs. Also, most audio interfaces allow you to directly plug in instruments that don't create acoustic sounds, like a bass guitar or a synthesizer. Electric guitars and basses output what are referred to as instrument-level signals. Synthesizers, digital pianos, and drum machines have what are called line-level outputs. Most audio interfaces can accept all of these input level types. But if not, then you may need a direct box. Direct boxes are designed to take an instrument-level output signal and basically convert it into a signal that mimics the output of a low voltage microphone output. And that also needs to be amplified, as well, through a pre-amp. Mic signals, line-level signals, and instrument-level signals all have to be routed through the audio interface and converted to a digital signal. All of these signals are then routed through your computer, running a digital audio workstation, to a hard drive to be recorded. Now while there is a possibility that you may be recording to tape or another medium, the most common recording device is a digital audio workstation, or DAW. DAWs allow you to record, edit, and mix multiple audio signals and output a final stereo or multi-channel track. There are many DAWs on the market today and we'll take a look at many of the options in a different movie in this course. And you'll also find training on many of the most popular DAWs. And we'll discuss learning paths for those DAWs later in this course. Now, after getting the audio into your computer, DAW, and hard drive, of course, you'll want to be able to hear it. For this to happen, the digital signal is converted back into analog in the audio interface and then converted from an electrical signal into acoustical energy via headphones or monitors. Headphones are the easiest solution. Just plug them into your audio interface or directly into your computer. But if you're planning on doing music production, you'll want to have a decent set of speakers, commonly referred to in audio production as monitors, so you can hear what the sound is like outside of the close confines of headphones. Monitors need power to reproduce sound. Many monitors have built-in amplifiers. These are often referred to as powered monitors and they usually have on/off buttons and volume dials built into them. Non-powered monitors, the kind you might have connected to your home stereo, require an external amplifier. In those cases, you'll run a line out of your computer or audio interface into the amplifier, which then amplifies the signal and sends it to the monitors so you can hear the audio. So that's a run down of the basic audio signal path. Again, you start with the source of your audio. If it's an acoustic sound, you'll need a microphone. If it's not an acoustic sound, you'll need a direct box. The signal then goes into a pre-amp that's either a freestanding device or built into your audio input device. From there, the signal goes into your DAW and is stored on your hard drive. When you play back the audio, it's routed to your headphones or speakers. Now you may have other devices in your signal path but this represents the most basic path that almost all audio signals will follow from the source to the recording device and back out to your ears.