In our Understanding Audio – Part 1: The basic things you need to know post, we discuss the dynamics of sound, terminology and what you need to achieve great sound in your recordings. In Understanding Audio – Part 2, we go over balanced vs. unbalanced audio levels and the types of cables and connections you will need to work with both.
Unbalanced Audio
Unbalanced audio was developed primarily for its ease of use and cost effectiveness for consumer audio equipment although it’s cost effectiveness and ease of use see it also implemented today in a variety of Professional and semi pro equipment applications.
Unbalanced audio runs at higher “level” or loudness than a mic level, so the first rule to note here is that Mic and Line are not the same, so a mic won’t go into a line level input as it’s too low, and because some equipment allows you to select what level its sending, if you try to run line level through a mic input it will distort badly, because it’s level is too high (loud).
Unbalanced line level is still a lower level than Pro Balanced levels and therefore is more susceptible to noise etc. so it’s really designed for shorter cable runs like ideally less than 30 feet. It moves on two conductors (+)(-) although today, because Stereo Left & Right channel sound is so common, you will often see the cables married or even combined. Unbalanced Line level typically has a peak level of -18dB.
You can use also unbalanced cable for connect consumer or prosumer microphones, but here because of the extremely low mic level be sure to keep runs very short, ideally less than 10 feet or much shorter is better.
Unbalanced cables come commonly with two types of connections, Phono (commonly called RCA) type and Jack (normally a 3.5mm plug liked you would see on your phoned headphones). The phono or RCA type has a centre (+) plug and a ring (-), the negative conductor is typically a shield or woven conductor that wraps around the insulated centre positive conductor wire.
Often they will be Right and left (Red and white) bonded together. The Jack type can be mono or stereo, and even Mic, Line and Head Phone together, arranged in either TS/TRS or TRRS configuration on the jack –Tip/Sleeve – Tip/Ring/Sleeve or Tip/Ring/Ring/Sleeve. With the Tip normally the Right (+) the Ring Left (+) and the Sleeve a common (-). The TRRS standard can vary from vendor to vendor so you always have to check what’s what!
Balanced Audio
Balanced Professional audio cables have 3 conductors as standard, and run at much higher Line levels than unbalanced (so again they cannot be directly connected together), which is designed to keep the Signal to Noise ratio down (lower noise) as well as eliminate cable induced noise by providing the signal two out of phase conductor paths inside the equipment these out of phase signals get compared so that any induced signal or noise is eliminated. The connection is most commonly called an XLR or (Cannon, the inventor’s name, or Nutrik, popular connector vendor) XLR stands for eXternal Line Return.
Balanced cables are much more robust, and have better noise rejection, and can also run up to several hundreds of feet, and that is why you will see balanced deployed in most professional facilities or at minimum in the front line connection of microphones.
Obviously the cost of the associated products themselves varies with the implementation of Balanced vs Unbalanced audio and so does the cost of the cable itself.
With an XLR cable Pin 1 is the common or earth connection which is also the wrapped shield of the cable designed to stop external noise from leaking into the main conductors and it is designed to connect first. The other pins 2 and 3 are both hot, just 180 degrees out of phase with each other. Any induced noise is therefore cancelled out in the end when the two phases are put back together.
Because of the excellent noise cancellation features of the XLR cable you will also often see it used with Professional grade microphones to move the low mic level without inducing noise.
XLR and RCA Line levels can only be matched by feeding it into corresponding equipment, or by separate passive or powered adapter boxes.
¼” jack is another common cable and connector that comes more from the Pro MI (Music Industry). You can even find what are called “Combi” connections on some equipment which integrates both a centre female ¼” Jack receiver and a XLR plug female receiver into one. So you can plug in either ¼” or XLR.
¼” jack can be either unbalanced (mono TS) often found in speaker or line connections (one for Left and one for Right), or balanced (TRS) or even stereo (TRS), as in a Pro ¼” Jack Headphone (HP) connection. You can often see a XLR female connection, to plug in to a Microphone at one end, and a ¼” jack, to plug into a mixer at the other end for example. The great thing about ¼ jack is that they are typically much higher gauge cable with thicker shields similar to XLR cables and so they have better noise rejection and cancelation characteristics overall that allow for much longer cable runs, as you would find in a typical live stage setup.
Other Audio Interfaces
Of course there are other types of audio cable and connections, audio can travel over the lightning connector of your phone or tablet or via the USB interface of your computer, Midi connections for musical instruments and devices, S/PDIF optical for consumer audio devices, or Professional Serial Digital which can run through SDI video cables, or even digital audio audio over Ethernet connections. As the world become increasingly more digital these connections grow but the core of audio will always the analogue balanced and unbalanced types described above since sources like microphones are analogue.
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