Learning to create high-quality recordings is a central technique in computer/electroacoustic music. The core skills learned here will translate directly into recording studio environments, field recording, and almost any other situation which requires audio input.
The core principle is to maximize signal quality on the way in. As a rule of thumb, this means recording the maximum amplitude without going over the limit while deferring effects like reverb, equalization (EQ), and other environmental effects to later. The last part of this is important to note: if one were to record sounds with reverb or EQ that, in the end, sounded unflattering, there is no way to get back the original signal. Think of it like taking a picture, if a shot you took turned out blurry (or the camera’s cap was on!), all the sharpening or lighting effects in the world will never get back the original shot. One could, however, easily manipulate a clear, high-quality shot–blurring or applying other effects–to achieve almost any look.
In seeking the highest quality signal there are a number of important concepts to understand. Each of these will be discussed in detail in the following sections.
Signal to Noise Ratio
One of the first and most important concept to understand for recording is signal-to-noise ratio. In analog systems, this refers to the available bandwidth for the signal relative to the noise inherent in its physical system (circuits, recording medium).
In the digital realm there is no inherent physical noise (except where it interfaces with the analog realm) except during the process of quantization. Our goal in the digital world is to maximize the signal relative to this quantization noise, a value determined by the number of bits the recording system is using. We want to excite as many of these available bits as possible, filling them with signal to overcome the quantization noise. To do so is a matter of signal resolution, not of volume.
A “gain stage” is any point in the signal path where a gain boost or attenuation is available. In other words, it’s any place in the chain where you have amplitude control, such as the output knob on an electric guitar, or the input level on an amplifier, etc.
Let’s use the hypothetical guitar/amplifier signal-path scenario to illustrate the importance of gain staging. Say our guitar player turns the volume/output knob on his instrument almost all the way down, while turning the amplifier input all the way up. In this case, the amplifier is being taxed to compensate for the guitar’s weak signal. The result will be a very thin sound for the guitar as well as an unpleasant amplification of circuit noise inherent in the amplifier. We are not maximizing our signal at all…and may in fact be harming our amplifier.
Now let’s reverse the scenario, the guitar level is “cranked” while the amplifier input is almost to nothing. Here again the problems are both timbral/aural and physical. The amplifier is not taking advantage of the incoming signal, acting as a barrier to the guitar rather than a support. Regardless, the overfed guitar signal might be overloading the amplifier input, causing physical damage.
The above is a simple case. Yours will be more complex including 3 and 4 gain stages. You will need to understand your signal path fully in order to get the best results.
Again to repeat a rule of thumb: the shorter the path, fewer signal traps along the way. You will have gain stages where the signal must be raised or lowered while the ideal of many gain stages is to be transparent, to simply pass along the signal without impacting it, without boosting or attenuating.