Recording Chain Stages. Analog.

000_060-1
We will be discussing all the stages Your signal goes through between a real sound in the air and the final numerical table on Your hard disk, so let’s briefly pass through the processes in a recording channel strip step-by-step:

1) The air motivated by the sound source passes the motion energy to the diaphragm of a microphone.
2) The motion of a diaphragm generates an AC electrical signal, a “copy” of a sound wave. The low voltage (few millivolts) signal gets fed to a microphone preamp.
3) The preamp amplifies the signal with ratios of hundreds of times up to a “line” level usable by further stages (few hundreds of millivolts).
4) If processing is used, the signal follows to an EQ, compressor or both of them, where the frequency response or/and dynamics are shaped.
5) After processing or right after the preamp if processing is not used, the signal moves on to ADC (analog to digital converter) and turns from AC voltage into a stream of numerical values closely (but not exactly) corresponding to original electrical signal.
6) The stream of values gets passed to DAW, that operates them and allocates data in files.
7) Simultaneously the copy of a signal gets routed from the microphone preamp (assuming direct monitoring) to a monitoring mixer, mixes with the signal returning from DAW via DAC and gets fed into headphone amplifier or monitors.

Generic audio recording studio equipment rack

Looks confusing, huh? I felt the same way in the beginning. Don’t worry, everything is quite straight forward here.

Analog Chain Stage Basics

Combinations of recording equipment in every studio are unique and individual and mainly depend on two factors – a taste and preferences of a person who runs the facility and, of course, a budget and the main purpose of the particular studio. There are countless models of different audio devices available on the market today and this fact contributes to the huge diversity of subjective sound characteristics of final audible results from different recording and production facilities. Every person engaged in audio recording has personal preferences in gear and, taking into account that there are several types of audio devices with different functions in a signal chain and probably thousands of models to choose from in each type, it is easy to understand that there can be almost endless amount of device combinations in one random studio. Truly, out of all the studios I have been to – from small individual home studios to big commercial recording facilities – I have never seen two with a same setup. There weren’t even fairly similar ones.

From my own experience I can say that because of such a huge amount of options the overall concept of a recording chain might seem quiet confusing to a beginner. But I would like to encourage You here – it is not! After many times of explaining the basics to different people I have found out that the easiest way to understand is to split the whole chain into it’s links and then the one would see, that in spite of endless variations of each link on the market the amount and types of links themselves are very limited.

Block-diagram of recording chain stages.

Block-diagram of recording chain stages.

Take a look at the block diagram on the right side. There can be six types of functional parts in any recording setup, with five of them used exactly for recording (1 – 5) and one for monitoring (6), with five of them being technically mandatory (1 – 2, 4 – 6) and one optional (3). We will not talk about DAC (digital to analog converter) separately at the moment (that’s why I haven’t given this block a number), as it is not engaged in the recording process (at least, directly), we will threat DAC as just a functional part of monitoring stage for now.

All the parts in the diagram do not change no matter if we talk about big recording studios or home setups – they are always the same in spite they might look and perform very differently. Let me note, that each block in the diagram does not necessarily represent a single physical device. In most cases few of functional blocks (and sometimes all of them) are represented in one case. There is a description of usual block combinations in real commercial devices in the end of the chapter.

Now back to the idea – explanation of every block and its functions. I am not going to explain the applications of each device at the moment, wait until specialized articles on each of them, it is just an overview of their basics now.

Rode NT1-A

The typical appearance of a large diaphragm studio microphone. Rode NT1-A as an example.

Microphones

This part is quiet strait forward. The stage usually consist on one single device, but sometimes there are two in one body, known as stereo microphones. A microphone is a transducer that transforms the kinetic energy of a sound wave into an electric energy of an alternating current signal. There are few types of microphones, that will be discussed in details in the microphone chapter.

Different types of microphones are intended for various purposes, but don’t get tempted to listen to marketing guys, who declare, that “this microphone is a vocal microphone, this one is a kick drum microphone and the other one is a snare drum microphone”, remember – microphone is just a device for transformation of one energy into another, it doesn’t care what is an acoustic source of air bouncing, it just transforms the pressure changes into an electric signal. Any microphone can record anything. It is up to You to decide what to use it for.

Of course, there are known types and usage patterns, but just be aware of putting labels without personal research and judgment. And last thing, which cannot be stressed well enough and was written countless times – in the world of microphones the price range is not the final instance. Microphone is the most subjective device ever. I have worked with some cheaper microphones that sounded very appealing to me and with very expensive ones that I personally didn’t like at all. Leave the final judgement to Your ears.

Shure SM-58 dynamic microphone, classical model for stage applications.

Shure SM-58 dynamic microphone, classical model for stage applications.

The microphone is the first stage in Your recording chain, and together with a microphone preamplifier it defines the character of the signal. All other stages might add some character of their own or to affect the signal in different ways, but they are not likely to change it dramatically if they are quality ones and used the right way (assuming we are talking about the “clean” sound without the intention of strong artistic processing, at least during the recording process). Selection of a microphone might take a major time during the session (if You own more then one), especially when recording a vocalist, as audial performance of different microphones even of the same price range may alter obviously.

Another thing to note, is that the signal produced by any microphone is very dependent on the angle of element to the source, so the accurate positioning of a microphone is as important as choosing the microphone itself. The importance of microphone positioning is multiplied by the fact, that the sound of any instrument varies dramatically depending on the listening position in the space, so be sure You do listen carefully where to put the microphone.

True Systems P-Solo

High quality stand-alone studio microphone preamplifier by True Systems. Single channel.

Microphone Preamplifiers

Microphone preamplifier is a device, that amplifies a low voltage signal coming from a microphone (down to 5 mV or even less for specific models) up to a “line level” (around 300 – 500 mV) usable for further stages of a signal chain. Note, that this is the stage with the highest gain (relation of an output amplitude to an input amplitude of a signal) in the whole system! Devices with such levels of amplification – hundreds of times – are very critical to the quality of design and manufacturing and usually vary in performance very much.

As I’ve told, a microphone together with a microphone preamplifier (further just preamp) form the first stage of a signal chain. In general, these parts of a system cannot be judged separately, as when a microphone gets connected to a preamp, they start to interact with each other. It is a misconcept to consider that a microphone just “feeds” the signal to preamp. It does, but in reality preamp has a significant affect on a microphone too. This “reverse” interaction is unwanted, but it cannot be totally eliminated. Usually, as higher is the quality (and consequently the price) of a preamp as less it affects the performance of a microphone, except for cases when specific modes are included (and engaged) on quality preamps with intention to have an option for a special “signature” sound. Most of manufacturers have some special know-how features in preamps and each of them understands the concept their own way, so You have plenty of options to choose from.

Opposite to microphones it is rather fare to say that in the case of preamps statement “what You pay is what You get” is most often true. As I’ve told, these devices are very critical to the quality of manufacturing and consequently to the quality of electronic components they are made from. You cannot make a high-end device using cheap parts, but quality components cost much, consider it an axiom.

Chandler Germanium

Preamp by Chandler. It features circuitry, based on very seldom used, but very audio-friendly Germanium transistors.

I would even say, that preamps have higher emphasis on the quality of sound then microphones. It is not a statement, just a subjective conclusion based on personal experience. While a good preamp would make almost any of microphones sound better, the poor preamp would usually ruin the sound of major ones.

Microphones together with preamps form the main shape and coloration of a sound. Same microphone coupled with different preamps is almost guaranteed to sound differently. This difference can vary from subtle to major depending on kinds of both – microphone and preamp. Preamps are usually produced with one of two primary intentions – either to be “transparent”, intended to keep the signal as close to an authentic signal source as possible, or to be “with a character”, intended to add some amount of specific coloration (wanted and controllable types of distortion) into the signal. Again – it is up to You what to use, but most people prefer to have both kinds in a studio for wider possibilities.

Preamps can exist as onboard and outboard devices. Onboard means that a preamp is an inner part of a bigger device, for example, of a mixing console or a computer audio interface. Outboard means that a preamp is a single physical device in its own case with its own power supply. Outboard preamps can include from one to several channels, usually up to eight.

Semi-parametric equalizer module for 500-series equipment racks by Alta Moda.

Semi-parametric equalizer module for 500-series equipment racks by Alta Moda.

Processing. EQs and Compressors

This part is optional, as nowadays most of processing is done digitally on a computer after You have all of the material recorded – during the mixing (production) stage, – but processing in a recording chain (pre-recording processing) is still widely used by experienced engineers and producers. It can include equalizer (EQ), compressor or both of them. There might be other choices of analog devices and creative solutions, but in general, these are two most widespread types of processing to be used before the recording machine (computer in most cases). So, what do they do?

You may ask – why one might need analog processing in the recording chain when everybody knows, that You can do any processing You want afterwards using the software? – it is easier, You can experiment and undo if You don’t like the result, You can choose from thousands of plugins… That’s right, but just read on – in the next block (Analog-Digital Converters – ADC) and You should have Your answer.

EQ. Equalizer is a device, that shapes the frequency response of a signal. It means, that You can control the proportion of certain frequency ranges in relation to other frequency ranges. In other words, You can add some “highs” or attenuate “bass” or shape the tonal response of a signal any way You want. There are two major types of equalizers – graphic EQ and parametric EQ. On graphic EQ all the frequencies are fixed and You can just amplify of attenuate them (“boost” or “cut”). On the other hand, parametric EQ allows You to edit all the parameters (that’s why it is called that way) – to select the center frequency (it is called “center” frequency because it represents the center of the range You are going to play around), the width of a frequency range (“band”) and the gain, that can be positive or negative (again, “boost” or “cut”).

Both types are widely used for different purposes. Equalizing seems very tempting in the beginning, but I have to warn, that wise EQ is when You have it as little, as possible. Always remember one thing – cutting is in high priority to the boosting, as boosting can make Your signal sound unnatural very easily, but cutting is more forgiving. It is because human ear is much more sensitive to the over-exposure of any frequency bands (especially narrow ones) rather then to their absence.

High-End tube stereo compressor by Gyraf Audio.

High-End tube stereo compressor by Gyraf Audio.

While EQ shapes the frequency response of a signal, compressor shapes its dynamics. The main idea of a compressor is the reduction of a dynamic range. Dynamic range is a difference between the quietest and the loudest moments in a distinct sound piece. There are few types of compressors, but they all share the basic concept – they reduce the amplitude of loudest moments following a specific algorithm set by operator and then evenly amplify all the signal. As a result we get quiet moments to become louder and loud moments – quieter, while the average level of the whole piece turns higher and it sounds louder and more even.

Compressors and their settings will be discussed in details in an individual chapter, but I would like to note now, that while they are usually the most confusing out of all the devices, the way You use compressors defines the character of Your production further more then any other kind of processing. Compressing is not that straight forward and visual as equalizing and is usually difficult to understand right away (but don’t worry, it is almost the same story with everybody) and audio signal compression is an art in itself.

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