Recording Chain Stages. Digital.

Analog-Digital Converter IC

Yes, that’s how analog-digital converter really looks.

Until that moment we were dealing with analog signal in our chain. Analog signal means, that the sound is represented by the amplitude changes of an AC voltage. When voltage is low, the signal is quiet, when voltage is high, the signal is loud, something like that, but our recording device is most likely to be digital (if You are not using an analog tape machine, but they are quiet exotic nowadays). Digital devices are discrete – based on byte system where each byte should contain a defined number, therefor digital recorders cannot record uninterrupted waveform (as it is in the air and as analog devices do), so it has to be split in some kind of small pieces with defined values to have the ability to store it as a table. Yes, basically, audio files are just huge tables of numbers. This process is called discretization and that is exactly what ADCs do – they measure the level of a signal with a certain frequency (for example, at 44.1 kHz – forty-four thousand and one hundred times per second) and round that natural value to the nearest possible defined end value each single fraction of a second.

Be advised, don’t start searching the catalogues for analog processing devices right away and don’t think that if You purchase them Your recordings will start sounding great. They won’t – until You are sure that You know exactly what these types of processing do and how to use them. Begin with Your DAW and learn devices as software plugins, use Your ears, change parameters and listen carefully to what is going on with sound. It might take some time until You really begin to hear differences, so don’t worry if You don’t right away. I haven’t worked with any single person who wouldn’t be able to define even subtle audible changes sooner or later, assuming that the person was motivated and willing. The ability will come in time if You work hand enough. And don’t stick to numbers! Don’t look – listen. I know it is difficult, but try to remember about it and to control Yourself.

After a while the ability will turn into a sense – You will just start feeling what exactly You have to do to match the sound in the monitors to a reference idea, that is inside Your head. When You have this sense You can finally switch to hardware analog processing devices, then You will be ready and able to appreciate the major sonic differences they will bring. Still, it is a bit confusing in the beginning, as You don’t see Your graphs and precise values anymore (that’s why I advised You not to stick to numbers) – now You are left with Your ears only. Again, don’t worry, You’ll get used to it soon.

ADC / DAC device with USB computer interface.

ADC / DAC device with USB computer interface.

You should understand, that there is no way back after discretization. There is an opposite device, called DAC (digital to analog converter), that I have mentioned before, that will restore the waveform out of the tabled values, but it will be the closest possible copy of original signal – not the original anymore. It is the same, as with graphics – You can take a digital picture of a scenery, load it into computer and even print out, but it is not the scenery anymore, it is just a snapshot and its scalability is limited by the resolution of a camera. In this case the frequency and resolution of an ADC is the same as resolution of a camera – as more often ADC measures the level of a signal and as more end values it has to round it to, as more detailed and precise will be the copy and as closer to the original waveform will restored signal be, but never the same.

World class FireWire audio interface from Apogee, a manufacturer well known for the quality of their analog-digital converters.

World class FireWire audio interface from Apogee, a manufacturer well known for the quality of their analog-digital converters.

The other thing to remember – when Your signal is digitalized You don’t have any headroom anymore. This is the best possible quality you can have from now. Further, any kind of processing will degrade the signal. Remember – it is not “might”, it is “will”. Getting back to comparison with graphics – when You reduce the level of digital audio (make it quitter), it it same as “shrinking” the image. Imagine that You have a digital picture, then You take it and shrink to one third of original size. Now You have one third of graphics and two thirds of white background and while the size of file remains the same (assuming, that we are talking about uncompressed graphics), the resolution of the actual image is reduced trice. But it is still the “same” image. Sounds funny? The same is about the digital audio. Understand, what does the increasing of signal level mean now? Right – stretching! Remember, digital amplification is the same as digital zoom in a camera. Do You know any professional photographer who uses it?

Of course, I have overemphasized the issue and it is certainly not possible to avoid digital processing in most cases, but I just want You to have the clear idea of what You are actually doing. Getting back to analog processing – all the analog devices You use before the discretization (e.g. before ADC) are the optical lenses of Your camera! Get what I mean?.. Ok, ok, getting back to audio, I promise – no more photography!

Typical window of a digital audio workstation. Apple Logic in this example.

Typical window of a digital audio workstation. Apple Logic in this example.

Digital Audio Workstations (DAW)

Digital Audio Workstation is a common way to call the system You use to store, edit and process the recorded material. In almost all the cases it is going to be a computer with an audio editing software installed.

Let me note, that the purpose of this course is to teach You to understand the music production and audio recording processes, to employ Your creativity and to make You able to work and to make decisions of Your own, not just following some kind of step-by-step manual. That’s why I never teach “how to use the software” – sessions can easily turn into lessons of mouse-clicking this way instead of being dedicated to understanding the reasons and essential concepts of every action involved. You should understand, that DAW is nothing more, then a tape recorder for You at the moment. Would You need to study the detailed manual of a tape recorder? I suppose You would just figure out how to put the tape on and then push the record button. Try doing the same with a software – it is just a little bit more complicated!

In fact, watching the students of my local music production courses I have concluded, that it takes an average person few days to get very comfortable with a DAW, while, again, I never teach how to. When the practical sessions begin I quickly show where are all of the main function located and just let students work. Usually people stop asking questions about locating different functions and effect settings in three to four lessons. The rest of the time of my three month course is dedicated to understanding the nature of audio processing and sound itself.

Finally, all the information about particular software functions is available in software manuals and on the web. As You’ve understood, I am not a software nerd – if I need to drill a hole in a wall to put the picture, I just take any drilling machine which is nearby and drill; I don’t dig the manual to learn all the functions of the device and to check if the particular drilling machine is capable of producing the kind of hole I require. Trust me – it is, so I advice You to do the same.

The window of the Steinberg Cubase SX digital audio workstation with an open project.

The window of the Steinberg Cubase SX digital audio workstation with an open project.

The most common type of software is a multitrack editor. It is used to create projects with numerous tracks involved and to mix the result down into one file. Nowadays all of them have major editing, processing and often also midi sequencing functions. The big three of names are certainly ProTools, Cubase and their modern, but quickly gaining in popularity competitor – Logic. Certainly, there are many more of them, like Audition, Samplitude, Nuendo, You name… I have to stress – almost any of them are quite usable now, especially in a home studio. Of course, function allocations are a bit different, audial performance and processing quality of native plug-in packages vary, ergonomics might be questionable sometimes, but they all do work!

Believe me, You can make a very reasonable production using any of commercial software available, as it is not the program, that shapes the sound, it is You. Program just performs what You command it to. As I’ve told, aspects do differ, but the basic idea and signal routing principles are almost the same everywhere – those that originate from good old hardware analog mixing console designs. That means, while consoles are usually not required in home or projects studios, it is very important to understand how they operate, just because DAW programs follow exactly the same logics. We’ll talk about mixing consoles later.

Very specific "state-of-the-art" audiophile headphone amplifier. Consider trice if You need something like that in Your home recording setup :)

Very specific “state-of-the-art” audiophile headphone amplifier. Consider trice if You need something like that in Your home recording setup :)

Monitoring Section

All of the devices we have discussed so far are the elements of a recording strip and provide necessary functions for signal would be able to go all the way from the air onto the physical recording medium (hard disk). They all directly pass the signal through and each link of the chain affects the signal some way, so the quality of a material, that You are going to have recorded is directly dependent on the quality of each device You use.

Now we’ve come to a separate branch of the setup – the monitoring section. It is used for simultaneous listening to Yourself (whatever You do – sing or play any instrument) and to the tracks that are already recorded. So, the idea of monitoring section is to mix at least two sources – recorded material with a realtime performance – and to feed the resulting signal to a headphone amplifier or to studio monitors (in case if You don’t use a microphone in the same room). As You might understand, the quality of this stage is not critical to the quality of signal that gets recorded, as it is branched from the main recording strip and terminates in the headphones or monitors, so that is the part where You can cut the budget to release funds for recording critical devices. Most of monitoring devices I have worked with were reasonable. Quality varies, but the majority of models on the market are up for the task.

The important thing about monitoring in a computer based studio is that the monitoring can be direct and indirect. Direct monitoring means that Your monitoring mixer receives the actual signal directly from microphone preamp and mixes it with the sound of tracks that are played back from DAW. Note, that many of computer audio interfaces offer direct monitoring as a built-in feature, but You should be aware, that it is not default, check out the specs of each device!

The block-diagram represents the routing of a standard audio interface. Red lines represent the signal being recorded at the moment, green lines represent pre-recorded material, played back by DAW. Solid lines represent analog parts of the circuitry and dashed lines - digital. The switch in the middle toggles between direct (B) and indirect (A) monitoring. The dashed black line represents the software command, that controls the switch.

The block-diagram represents the routing of a standard audio interface. Red lines represent the signal being recorded at the moment, green lines represent pre-recorded material, played back by DAW. Solid lines represent analog parts of the circuitry and dashed lines – digital. The switch in the middle toggles between direct (B) and indirect (A) monitoring. The dashed black line represents the software command, that controls the switch.

So, what does indirect monitoring mean? Indirect monitoring is a setup when Your monitoring stage does not receive the signal from a microphone preamp directly and the signal, that You are recording at the moment, gets mixed with the rest of tracks inside the DAW and then the whole mix together gets returned to a monitoring mixer via DAC (digital to analog converter, remember? – it restores the waveform out of the table of numerical values). The main disadvantage here is usually a latency – a delay caused by the processing time of particular computer. If You have a very modern and powerful machine, than maybe it wouldn’t matter, but for most people it is going to be a problem, as even the latency of 5 – 7 milliseconds can be very disturbing. Anyway – the stability of monitoring, even in the case with a powerful computer, depends on how strongly the computer is loaded with processing at the moment. So, whatever You do, think about spending few more currency units (whatever they are in Your location) and going for the direct monitoring. This way You will save Yourself a couple of nerve cells.

Regarding myself – I am a conservative kind and prefer to have a hardware device to control monitoring. They are not expensive, but much more convenient and flexible, than switching between programs all the time, looking for needed window, and finding a button to click. If You are good at computers, You might know the way how to do it easily, but I kinda like to rotate real knobs!

Note, that built-in monitoring of audio interfaces sometimes seems confusing, as this function is almost always operated via software! You should pay attention, that in this case direct monitoring is switched not using the DAW, but using the software supplied with Your device. In spite this function is software operated, the signal is not routed through computer and consequently does not get affected by latency. Think of it this way – when You click a software button that engages the direct monitoring function, the software sends a command to Your audio interface to route the output of a built-in microphone preamp to a built-in headphone amplifier, take a look at schematic – position A of a switch is indirect monitoring here, while position B is direct monitoring (it is simplified, of course). So, if Your audio interface has direct monitoring function, don’t get messed up and don’t monitor via DAW – use the native software of Your device.

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