Audio Cables and Connections

Last month we began a two-part series on connectivity with a look at video cables. This month, we’ll look at audio cables and connectors, since choosing the right audio connection can be just as important as your video signal path. The discussion below puts the choices in order from best to only so-so.

FireWire

As we discovered last month, FireWire is the gold standard for high-quality desktop video connectivity. Not surprisingly, it’s also ideal for moving digital audio from tape to your editing system and then back again. Formally (and formerly) known as the IEEE-1394 protocol and marketed by Sony and other electronics companies as i.LINK, FireWire was invented in the mid-1990s by Apple Computer.

How It Works

  • Carries a bi-directional audio/video data stream with time code and machine control between devices that understand the IEEE-1394 protocol.
  • Provides a fully digital pathway; signal degradation and other problems common to analog connections aren’t an issue.
  • Better-than-CD quality 16-bit, 48kHz stereo audio playback from the camcorder.

How It Connects

  • Ports are built into most digital camcorders and many new computers; accessory cards are also available.
  • Connectors are four-pin or six-pin. The tiny u-shaped four-pin connectors are found on camcorders; the larger rectangular six-pin connectors are used at the receiving end on computers and internal cards.
  • Cables are four-pin to four-pin, four-pin to six-pin, or six-pin to six-pin. The first can connect one camcorder to another for digital dubbing; the second connects a camcorder to a computer or hub; and the third connects two powered hub devices.

How to Use It

  • Connect a camcorder to a computer with a FireWire cable and then power on the camera (“hot-plugging”) to activate the bi-directional DV stream.
  • Playback and print your project to tape from your editing system with fully digital, lossless audio fidelity.

How the Cable Measures Up

  • Four-pin connectors are extremely small and fragile, leaving them vulnerable to early failure.
  • Ultimately, as a data protocol, quality is unlimited and perfect and depends on system software and audio/video applications to function.

XLR

XLR cables and connectors are the top of the line for making analog audio connections. Also known as Cannon connectors, these devices provide a balanced transmission between high-end audio devices, like microphones and DAT decks, to ensure pristine audio reproduction without electronic interference.

How It Works

  • Two-wire balanced cables (the most common type of XLR connection) feature a 3-pin connector linked to a 2-wire twisted copper pair and a ground lead.
  • Each of the wires in the twisted pair – the “high” and the “low” – carries an audio signal that’s identical to the other, but 180-degrees out of phase, providing a fail-safe that’s known as a balanced signal. This ensures you get maximum signal fidelity.
  • Available on some consumer and many professional camcorders.


How It Connects

  • Three-pin connector. Male connectors are used for audio output and female connectors accept input.
  • Spring-loaded locking tab ensures a solid connection.

How to Use It

  • Connect a quality microphone to a high-end audio deck.
  • Connect an audio or video deck with XLR outputs directly to a PC interface card for digitizing and final output.

How the Cable Measures Up

  • Extremely durable metal connector and robust cable.
  • Heavily shielded to ensure interference is kept to a minimum.
  • Balanced signal path allows long cable runs and high signal fidelity.
  • XLR connectors available only on expensive pro-audio and video devices and analog-to-digital interface cards.
  • Can be tricky to adapt to other equipment (see this month’s Tech Support).

RCA

RCA cables and connectors are found on televisions, VCRs, stereos and camcorders so they’ll allow you to connect almost anything to almost anything else. Though not nearly as robust as XLR, RCA connections clearly win in the convenience category.

How It Works

  • Cables feature a single wire and a ground lead.
  • Carries analog audio signal in the form of a sine wave.

How It Connects

  • Pin-and-cuff design – male cable ends plug into the female device sockets.
  • Look for stereo connectors marked in white (left) and red (right – although you can connect them however you want) on the back panels of many consumer devices, as well as on camcorders. Some VCRs and camcorders feature mono audio with a single connector.
  • Many of today’s small camcorders have a small adaptor cable that goes out from the camcorder and terminates in three RCA connections: yellow for the video and white and red for the audio.

How to Use It

  • Use to monitor audio output from a camcorder or nonlinear editing system; connect RCA jacks to a powered speaker system, television or VCR.
  • Connect two decks or camcorders to make tape copies.
  • Use to pass analog audio from a FireWire device to a VCR or television.

How the Cable Measures Up

  • Cables vary widely in quality, length and best use.
  • Heavier shielding yields a cleaner signal.

1/4″ Phone (6.3mm)

Though less and less common in a world of FireWire and USB, 1/4″ phone connectors can still provide a robust signal path for some audio devices. These cables send a mono or stereo signal along a single path, making them a fine connectivity choice when other options aren’t available.

How It Works

  • Cables use two or three conductors to transmit mono or stereo signals.
  • Carries audio as sine wave.

How It Connects

  • For mono audio, male connector uses tip and sleeve conductors and plugs into female socket; for stereo, male end has tip, ring and sleeve conductors to send left and right signals.
  • Most frequently seen on powered speakers, microphone and instrument cables, mixers and headphones.


How to Use It

  • Use to connect a microphone or instrument to an audio input device like a recorder or mixer.
  • Connect high-quality headphones to a headphone jack.

How the Cable Measures Up

  • Long runs can make cable vulnerable to high levels of radio frequency and magnetic interference.
  • Heavy shielding and high-quality connectors are a must.

1/8″ Mini (3.5mm)

Tiny 1/8″ mini connectors have virtually replaced the 1/4″ connection in the world of consumer audio. Though neither as robust nor as capable as 1/4″ cables, 1/8″ mini connections are an essential piece of any system that uses consumer audio and video equipment.

How It Works

  • Two, three or four conductors transmit mono or stereo audio or stereo audio with video in the case of the special 1/8″ audio/video connector used on many smaller camcorders.
  • Single wire carries audio as sine wave.

How It Connects

  • For stereo audio, male connector has tip, ring and sleeve conductors; special A/V connector has tip, sleeve and two ring conductors for an added video signal path.
  • Find these used for computer audio output, camcorder headphone connections and camcorder analog audio and video output.

How to Use It

  • Connect audio output from a PC to powered speakers or a VCR (adapter required – see below) to monitor and record audio from a nonlinear system or other application.
  • Connect a camcorder’s analog audio/video outputs to a VCR or television for monitoring and dubbing.
  • Connect headphones to a camcorder or PC for close listening and preliminary audio mixing.

How the Cable Measures Up

  • Connectors, especially female sockets, are extremely fragile and notorious for failing; look for good construction and be gentle.
  • Cable is thin and very lightly shielded; heavier construction is best.

[Sidebar: The Long and Short of Cables]

Shorter cables are always better. Since all connecting cables, including FireWire, are subject to some degree of electrical and magnetic interference, it’s important to use the shortest cables you can; the longer the cable, the more the signal deteriorates and the more chances there are that your audio will pick up interference.

[Sidebar: USB Audio Transfer]



You may have seen devices on the market that let you capture analog audio via an interface box with a USB connection to your computer. It’s a great idea, since USB is economical and even more common than FireWire, but it’s not for everyone. All of these “breakout boxes” must perform their own analog-to-digital conversion and some devices are better at that than others.

[Sidebar: Are All Cables Made the Same?]


There are wide variations between cables made by different manufacturers and it’s undeniable that some are better than others. You’ll often see an emphasis placed on gold connectors; these can be helpful in avoiding corrosion at the contacts, but we’ve never seen a corroded cable in our living room. With thinner-gauge (20-gauge is thinner than 12-gauge) cables like RCA and 1/8″ mini, heavier construction can mean better sound and longer life-span. And whatever the connector, look for plenty of shielding – some manufacturers use almost none and it definitely makes a difference.


[Sidebar: The Adaptor Puzzle]


Many of us have used adapters and adaptor cables to get from one analog connector type to another. Adaptors can be lifesavers: they can help make the leap from, for example, the 1/8″ stereo mini audio out from your computer to the double RCAs on your VCR. But they can also cause problems. They add another potential source of interference and signal loss to your system.

[Sidebar: Line vs. Microphone]

Watch out: there are a few different voltage levels that might be used for analog audio connections. The higher voltage line level outputs can damage microphone level inputs, so make sure you check the type of connection before you power up. For example, camcorders typically have microphone (level) inputs while mixers often output a line level signal.

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