Reducing Electrical Interference: Balanced v. Unbalanced Connection - DJBooth

Reducing Electrical Interference: Balanced v. Unbalanced Connection

A look into electrical interference, balanced and unbalanced connections?
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Whether you’re an audio tech geek or live sound engineer, the love of music was probably the initial reason for you entering the music industry. However, as time goes on, musicians and engineers realize that things aren’t so simple. Our music careers can become riddled with road-blocks. Technical processes, complex music theory, gear troubleshooting, and an infinite number of other issues find their way into our lives.

The internet is chock-full of blogs that troubleshoot musical and technical issues. It seems like there are always problems to be solved.

Today, we embark on bringing light to yet another issue. It plagues everyone on the stage and in the studio: electrical noise and interference. This article will cover some of the ways one can reduce electrical interference, and we will observe what balanced and unbalanced connections are and how to use them to your advantage.

What is electrical interference?

Electrical Interference happens when your audio signal is interrupted, altered, and/or bombarded in any way by an outside electrical source. For the sake of being articulate, we will stray from expounding too much on RF (radio frequency) interference and intermodulation (though they will be briefly covered). This article focuses more on wiring and how balanced or imbalanced cabling can reduce electrical interference.

Here are a few different types and causes of electrical noise:

Parasitic Capacitance:

Also called “stray capacitance”, parasitic capacitance is noise generated when electrical units, cabling, or circuits that are in close proximity to one another. If the electrical conductors in these electronic systems vary in any way, parasitic capacitance can be a result.

Since every component in a circuit has internal capacitance (amount of charge an individual component can hold), noise created by parasitic capacitance is a serious issue. Manufacturers and engineers are constantly trying to narrow the capacitance gap between circuit components.

Noise Generated By Computers and Digital Signal Processors:

Digital interference and digital artifacts can cause electrical and RF interference. DSPs (digital signal processors) can easily affect wireless units, and other digital devices can generate interference that travels through AC power and audio wiring.

*RF interference is caused by radio frequencies or digital artifacts that interrupt and interfere with wireless technology. If you’re unfamiliar with this concept, understand that audio can be transmitted via wireless radio frequency (RF). Unfortunately, this RF channel can be interrupted by other radio frequencies if they exist on a similar frequency in the electromagnetic spectrum.

Interference From Natural Sources:

Lightning and other natural, electric phenomena can interfere with audio components. This can also occur from the natural magnetic charge of a particular area, but you won’t have to worry too much about natural interference in your daily life.

Balanced and Unbalanced Cables

There are many misconceptions when it comes to balanced and unbalanced cables. While balanced cables are indeed the standard for live and studio applications, they aren’t used for everything. Many people believe that balanced cables mean “no buzzing noise”, and that unbalanced cables mean “lots of buzzing noise”. This isn’t exactly true. It depends on application.

Balanced Signal

This form of connection is designed to reject outside noise and contiguous crosstalk (undesired parasitic capacitance between devices). A true, balanced signal is formed by a three-wired connection.

Here’s how it works:

The audio signal is sent along an in-phase (hot) wire and an out of phase (cold) wire. Because the polarity of the signals is opposite, both signals will be canceled out. Sounds weird right? This is where it gets cool.

The receiving balanced channel will flip the inverted signal back into phase. Now, it seems like this did nothing...but actually it canceled out electrical noise traveling along the cable! See, both signal wires picked up the same noise during the signal transfer process (the electrical noise in each signal being IN PHASE with each other - even though the audio signal is out of phase). When the receiving balanced channel inverted the phase on the cold signal, electrical noise in this signal was also inverted. This means that the noise in each signal is now in opposite phase. So the noise is gone and the signal survives. This process is known as common mode rejection.

Not mentioned is the ground. Balanced cables incorporate the ground in different ways. In many cases, the ground is wrapped around the signal wires in a shielded mesh. This helps deter parasitic capacitance.

Uses

  • Connecting high-end studio and live gear. Most instruments incorporate the use of unbalanced connections. However, these connections are usually converted (with a DI or transformer of some sort) so that a balanced connection can be used. Balanced cables are especially used for monitors.

Other advantages

  • Allows for around 6dB more signal level!
  • Can run longer lines (than unbalanced signals) without severe audio degradation or electrical interference.

*Please note: Not all studio monitors are created equal. Some monitors will still suffer from some electrical interference even when using a balanced connection

Unbalanced Signal

There is no common mode rejection when it comes to unbalanced cables. While an unbalanced connection isn’t “bad”, it can induce excess noise if not used correctly.

Here’s how it works:

Inside the wire, there is a signal and a ground. Like in a balanced cable, the ground is usually in the form of a mesh shield that surrounds the signal wire.

In an unbalanced connection, the ground completes the circuit and protects the cable from electrical interference.

If the cable is too long - usually over 15 feet - the wire can act like an antenna, picking up RF frequencies and excess electrical interference. This is why musicians keep their standard guitar cables short. If the cable is of superior quality, the grounded shielding does an excellent job at deterring electrical interference.

Uses

  • Used for many audio applications, but mainly used for electrical instruments.

Other Advantages

  • If the shielding and length are good, this cable will serve you well. It’s not as pricey as many balanced cables, and it has many applications.

Observe the schematics of your gear to see what cables you need. You may find that you can incorporate balanced cables to take your rig to the next level!

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