Balanced or Unbalanced Connections?

Within Pro Audio, recording and PA applications there is only one standard protocol for passing un-amplified or pre-amplified analogue signals, which is referred to as ‘Line Level’. However, Line Level comes in one of two varieties, namely Balanced or Unbalanced.

UnBalanced

A single core screened cable generally carries an unbalanced line level connection. The screening around the core, which carries the signal, provides the earth connection and protects the core from unwanted interference or noise. However, within long cable throws it is possible for noise to penetrate the screen and to become superimposed upon the signal, carried by the core.

Unbalance line level operates at a signal strength of -10dBu. Typical connectors are ¼” Jack or Phono connections.

Balanced

To counter the issue broached above, wherein noise may be superimposed upon signals carried by long unbalanced cabling, one may use balanced connections providing the products within a particular system support this protocol.

Balanced cabling uses a twin core screened cable. As in an unbalanced lead the screen offers a certain degree of protection against unwanted noise, which may be superimposed upon the signal carried by the core. However, within a balanced signal there are two component parts that carry the signal, a positive connection and a negative connection, which are precisely 180 degrees out of phase.

Upon transmission within a balanced system the signal is split into two components, one remains untouched (positive) whereas the other (negative) is phase shifted by 180 degrees. Upon receipt, the negative component receives another 180-degree phase shift and at this point is recombined with the positive signal. As a result any noise, which may have been superimposed upon both the positive and negative components of the signal within the cable, becomes completely phase cancelled leaving a ‘clean’ signal with a far higher Signal to Noise Ratio than would otherwise be the case if using unbalanced connections.

Balanced signals also have a higher signal strength, at +4dBu, than unbalanced signals, which operate at a standard –10dBu. Typical connections are either XLR or ¼” TRS (Tip, Ring, Sleeve) Jacks. Note that within XLR’s, pin one is the screen, pin 2 positive and pin 3 negative whereas on a TRS Jack the sleeve connects to the screen, the tip is positive and the ring negative.

Examples of mixers that have balanced outputs:

Mackie 1202 VLZ3

Mackie FX12 MKII

Yamaha-MG32-14FX

Examples or power amplifiers or active speaker cabs that have balanced inputs:

Yamaha P7000S

RCF-ART-322

It is therefore apparent that is far more preferable to use balanced connections, particularly over long cable throws, to unbalanced providing the products used within a given system support this protocol.

Note: Screened cabling must never be used as speaker cabling, since it extremely inefficient at carrying the high power levels generally delivered by power amplifies. The effect of using screened cables for speakers is normally twofold, firstly reduced output due to the resistivity of the cabling and secondly cables failing as they burn out – speaker cables use much thicker wiring designed to efficiently pass high power, unlike screened cabling.

About these ads
This entry was posted in Recording, Setup advice. Bookmark the permalink.

2 Responses to Balanced or Unbalanced Connections?

  1. headrot says:

    Hello there,
    I have a query regarding balanced\unbalanced connections, being an ametuer producer in my room..
    I (will very soon) have a compressor mic (balanced XLR) going into my small mixer (balanced connection) that outputs to (unbalanced RCA) phono jacks into my pc sound card (unbalanced conncection) for recording.
    Is this mix of balanced\unbalanced that occurs during the mix stage a bad thing? Should I, for example, keep the RCA cables as short as possible?

    • Dave Cochrane says:

      It’s not a bad thing at all. Sending a line-level signal over a short distance unbalanced from mixer to recorder is absolutely fine – there shouldn’t be significant noise over short distances (a metre or two). Balanced connections are more necessary for longer, low-level connections (e.g. microphone cables).

      Further, the use of line-level balanced cables to connect home stereo audio components may be psychologically pleasing (like using gold fuses and other such nonsense) but will have no appreciable effect on the sound.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s