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Audio Toyes #12 - Following the Signal

Brian Toye
March 08, 2011

A break down of the recording chain. (Front end signal flow)

Signal flow is the term given to the path a sound source takes through the recording chain. For instance, when you speak into a microphone your sound source will follow this general path:

Vocal chords – Air – Microphone capsule – XLR cable – Microphone Preamp – XLR or TRS Cable (TRS is tip ring sleeve its a 1/4 inch cable that looks like a guitar cable but it's balanced) - A/D Converter – toslink (ADAT is an optical cable for digital data) or AES digital cable (XLR cable but it transfers digital audio) - Interface - USB/Firewire or PCI card – Computer Software.

Lets look at each step a little bit closer to understand why all these steps are necessary in order to get your voice into your digital recording software. The sound starts off as a wave moving air molecules causing locations of high and low pressure. The capsule of the microphone vibrates due to this pressure change and converts the vibrations into small electrical signals. We touched on this last week. This small electrical signal will travel down the XLR cable into a microphone pre amp. This will take the small electrical signal and boost it, otherwise its so small we would not hear a signal (or see one in our digital recording track). The output of most microphone pre amps include XLR or Ό inch TRS. So the amplified signal travels out of the microphone pre amp through such a cable and into an analog to digital converter (A/D converter). This is a device that measures the electrical signal and converts it into computer language. For every second of passing electrical signal the A/D converter will take 44, 100 samples by measuring its amplitude thus drawing a hypothetical wave form. This data is sent to an audio interface via ADAT cable or AES or S/PDIF digital connections. The audio interface ultimately sends this information into your computer via USB/FIREWIRE or PCI card which communicates with your recording software. You then see the sound wave drawn in the track you have armed in your software.

The above example assumes that each stage of the recording chain is contained in a separate “box” or product. There are many products out there that contain all these steps inside the same box. Such as the Avid Mbox or the RME FIREFACE UFX. Such audio interfaces as they are called contain a mic preamp an analog to digital converter and an output to your computer. These are convenient for home recording and when used properly can result in fantastic quality audio. Most high end studios will use separate high end “boxes” for each step in the recording chain to have more control over their sound.

So if your a home recording enthusiast using an Mbox or an m-audio interface of sorts and you want a bigger sound you can start by using a different microphone preamp. For instance a great vocal combination is a Shure SM7 microphone into a Golden Age 73 mic pre that you then output into your audio interface thus not using the mic pres in your Mbox or m-audio interface, just using its A/D converters and digital sends to the computer. The Golden Age 73 mic pre will be of higher quality than the mic pre's in your Mbox.

If your still confused feel free to email me with your setup and I can suggest ways to upgrade. Also, check out these pics of products to help you piece it all together:

Microphone Pre Amp

A/D converters

-Brian Toye-