Audiovisual receivers buying guide

AV receivers sell the idea of turning your living room into a cinema. How much should you spend?
 
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01 .AV receivers

AV receiver

An AV receiver is the hub of any home-theatre system. Its job is to take the sound and video information from your DVD, CD player or set-top-box and, if necessary, convert it to an appropriate output – then send it through to your screen and speakers.

Our buying guide explains:

  • Controls you should look for
  • Which types of connections are necessary
  • How much power you need for good sound quality
  • Some of the jargon associated with audio equipment

For more information about Home theatre, see Home entertainment.

When you buy a 'home theatre in a box' the AV receiver and DVD/CD player are often combined into one unit, which you connect to the speakers and TV. However, there are two good reasons to buy separate components: you get more control over the quality of each and, should one component break down, you don't have to replace the whole system. The former is by far the most important.

Sound quality

The main purpose of a home theatre set-up is to provide surround sound. The AV receiver includes the amplifiers necessary to drive your speakers.

At the cheaper end you’re likely to get a 5.1 system, which means it has five speaker connections (three front and two back) and a sub-woofer connection. This is the most common format for DVD movies.

More expensive systems tend to be 6.1, with three at the front, two back and one back centre, or 7.1, which has an extra back centre speaker. You don’t necessarily get better sound with a 6.1 or 7.1.

Their aim is to try to increase the sensation of sounds coming from different directions by using more speakers, as you’d expect in a movie theatre.

CHOICE verdict

For most consumers a mid-priced AV receiver (around $1,000) should provide enough power, connections and quality of sound. Extra connections often come with more power, but that's no guarantee of sound quality – always check the specs, especially total harmonic distortion.

 
 

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Front panel

The front panel controls should allow you to perform all the basic functions necessary to set up and use the receiver. You can expect the volume control to be the largest dial, but different manufacturers will design other controls in different ways.

Cheaper models may have no on-screen menu function, so the display on the front of the device is the only way of knowing what it's doing. This front panel display is very important for all AV receivers because it's your primary source of information on the receiver's settings.

On-screen menu

On-screen menus (sometimes called a graphic user interface or GUI) appear on your TV. These make it easier to do more complicated setting up because you can see all the options at once, rather than having to cycle through them on the front panel display. However, most of these settings are unlikely to be used often, so a GUI is handy but not essential.

Remote controls

Remote controls

The remote control is very important. Its design has to allow you to control all the receiver's functions. Some come with a basic remote that can control the receiver and some other devices, such as a DVD or video player.

The more expensive models allow you to use the remote to control other brands' devices as well, but none would be as versatile as the best of the universal remote controls we tested in CHOICE July 2008. 

Some also come with a second remote control which is smaller and easier to use than the main one. However, these usually can only perform basic functions.

The receiver needs enough ins and outs to cover all the home-theatre devices you have, or are likely to have in the near future. In general, the more you pay the more connections you get.

As you can see, the back of these receivers can look daunting, but you only need to connect the devices you have, so you can ignore the rest of the connectors. It's really just a matter of knowing which ones attach to what.

Inputs

  • HDMI is a digital connection via a single cord that does everything for both sound and vision. It's very handy, provides excellent quality sound and vision, and saves clutter.
  • However, both the receiver and the device connected via HDMI need to 'talk' to each other. Problems can occur if the HDMI standard is not implemented exactly. Also, HDMI includes a copy-protection component that can interfere with signals under some conditions.
  • Digital sound can be either via an optical (TOSLINK) or a coaxial cable, if you don't use HDMI. It doesn't matter which you use, so long as the receiver and the device to be attached have the same type of connector. Having both optical and coaxial connections is handy for attaching a new device in the future.
  • Analogue sound can be stereo or multi-channel depending on the connections available. Cheaper models may only have stereo analogue inputs. Multi-channel connections are only useful if you want to use your DVD or CDs on-board DAC (see Jargon buster).
  • Analogue video comes in three types: composite, s-video or component. The latter is the best quality and probably the one you'll want to use to connect your main video devices (DVD or set-top box), if you're not using HDMI. However, if you want to connect a DVD, set-top-box and VCR via component, you'll have to look around because most connection are via HDMI these days.

Picture quality

Cheaper receivers may only accept analogue video signals and pass them out to your screen. More expensive ones will accept both analogue and digital (HDMI) video inputs and then send them out via HDMI. They may even have up-scaling technology to increase the resolution of the video output to 720p or 1080p. 

There's a lot of emphasis on power in the marketing material for AV receivers, because selling them on their technical specifications for sound quality is difficult. The amount of power you need is determined by your listening distance, desired volume and speaker requirements.

The power rating of the amplifier tells you the maximum power available for the loudspeakers, and the power to each speaker is referred to as a 'channel'. The technical term for it is the Root Mean Square (RMS) power measured in Watts (W).

For typical domestic listening, power ratings between 50 W and 100 W RMS per channel should be sufficient. You don't have to use all that power, you just need to have sufficient in reserve to avoid distortion in the loud sections. This is sometimes called 'head room' or 'dynamic power'.

To make an undistorted 50 W RMS system sound twice as loud you don't need 100 W, you need more than 500 W - and you also need speakers that can handle the power without distortion. Most domestic speakers require only about 50 W or less and even more expensive models may be rated at only 120 W per channel at 8 ohm.

What to look for in the specs

A good receiver spec might look something like:

  • Minimum per-channel power 100 W RMS
  • 8 ohm, 20 Hz-20 kHz
  • 0.04% Total Harmonic Distortion (THD)

It may appear daunting, but it's just a shorthand way of describing the amplifier's ability to produce a given amount of power without introducing sound distortion.

8 ohm

An amplifier is like a miniature power station supplying electrical power to the loudspeaker. Ohms are a measure of the load a speaker puts on the amplifier. Domestic equipment commonly quotes a load of 8 ohms. Some manufacturers also quote power available for four, six or 16 ohms. The higher the number the more power is needed to drive the speaker.

If an amp has a power output of 55 W at 6 ohm, when recalculated at 8 ohms it's reduced to 41.25 W.

20 Hz-20 kHz

Humans can hear a wide range of frequencies - from very low, below 20 Hz, to very high, around 20 kHz. The amplifier needs to state the range of frequencies for which full power is available. This is usually described as the power bandwidth.

Unlike the mains power supply that maintains a constant voltage, the amplifier output voltage continuously changes in response to audio signals. As the volume and frequency changes, so does the amount of power needed to drive the speaker.

0.04% Total Harmonic Distortion (THD)

This is a measure of the change introduced by the system to the original input. THD figures below 0.1% for amplifiers are achievable and are generally inaudible for all but the most trained ears. We can hear low levels of distortion in audio signals and therefore can hear when the amplifier starts to overload.

So it's important to know the maximum power output at a given and low (ideally inaudible) level of distortion.

The major contributor to distortion when playing loud sounds is usually the speakers, not the amplifier.

For a more detailed (and technical) explanation of how amplifiers work we suggest you read Making sense of amplifier and receiver specifications by Graeme Huon.

AIR Studios

Originally set up by George Martin, of Beatles fame, and is now a recording studio which provides certification to a set of quality standards for some audio products. Similar to THX (see below) in that regard.

Audio delay

Allows for the difference in video and sound processing in some home theatre set ups, which is responsible for a lack of 'lip sync'. It's called 'A/V SYNC' on our SONY examples, but other manufacturers may use different names.

Auto set up and calibration

Usually involves attaching a supplied microphone and placing it in the normal listening position, then running an automated set up process. This uses a variety of sounds to determine the location of each speaker and the characteristics of the room to give a balanced sound at the listening position. SONY calls its system Digital Cinema Auto Calibration (DCAC). Other common names for this sort of system are Audyssey and MCACC.

DAB, or digital audio broadcast

More commonly known as digital radio. Some AV receivers have a built-in tuner. Digital radio broadcasts are currently available in capitol cities only, but this will change over time.

DAC

Digital to analogue converter which takes the digital information from a CD or DVD and converts it into electronic pulses that can be amplified to produce sound. (Burr Brown is a brand name often associated with DACs.)

Dolby

A brand name for technologies that are used to manage sound production. Some of Dolby's products are:

  • Digital / Plus is an upgrade of the Dolby codec (a method of making data smaller for storage or transmission, and then unpacking it again for playback) to allow for more channels and greater efficiency.
  • Digital Surround EX includes encoding for an extra centre surround channel which can be mixed into the rear speakers in a 6.1 or 7.1 system.
  • Pro Logic II / IIx takes stereo or 5.1-channel audio and makes it possible to play back via a 6.1 or 7.1 channel system.
  • TrueHD is designed with Blu-ray discs in mind. It's a lossless (no data is lost in the process) coding technology and can support more than eight audio channels, even though Blu-ray supports only eight at present.

DTS

Also a brand name for sound encoding technologies. Some common products are:

  • Digital Surround is an encoding often found on standard DVDs. It supports both two and 5.1 channels.
  • DTS-ES is similar to Digital Surround, but supports 6.1 channels.
  • DTS-HD Master Audio is a lossless encoding designed for use on Blu-ray (and formerly HD-DVD) discs. Like Dolby TrueHD, it can support up to eight channels.
  • DTS Neo:6 enables stereo audio to be played back via a 6.1 channel system.

HDMI

High-Definition Multimedia Interface is a protocol (set of instructions). It's also a digital connection which can carry video, sound and device control information.

Faroudja

A brand name for a video processing chip often associated with 'up-scaling'.

PCM

Pulse code modulation, is a method of encoding sound waves into a digital form. Higher bit rates generally mean better quality.

RMS

Root mean square and applies to the power figures for amplifiers. It's considered a better means of comparison than 'peak' or 'dynamic' power because it is a better measure of the power an amp can deliver over a reasonable length of time rather than in very short bursts.

THX

A trade name for a set of quality standards for hi-fi equipment and cinemas.

Toroidal Power Transformers

Smaller, more efficient and may have less interference problems than some other types of transformer.

Up scaling

Where a video signal from a DVD, which has 576 lines of data for each frame on the screen, has extra lines added to appear on a high-definition screen with typically 720 or 1080 lines.

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