Digital Inputs - Any receiver or system that has true digital surround processing (like Dolby Digital or DTS) will have digital inputs. A single optical or coaxial cable can transfer a multi-channel signal from a digital source, like a DVD player, to a receiver, where it will be processed and turned into multi-channel surround sound. The more inputs you have, the more components you'll be able to hook up in the future.

S-Video Inputs - This small, round, multi-pin jack can carry a signal with separate black-and-white and color video signals. S-jacks provide a better picture than standard RCA (composite jacks) in that they eliminate cross-color and dot crawl effects. Because this is now the connection of choice for high-resolution sources like DVD and DIRECTV, look for receivers and systems that have an adequate number of S-Video inputs. Receivers and systems with these inputs will be able to route video signals from more than one source to a TV with S-Video inputs.

A/V Inputs (composite) - These are the standard jacks used to hook up audio and video components to each other. Input jacks allow the signals to be received from other components; having more inputs than you need right now is helpful for future system expansion needs.

AM/FM - The two commercial radio systems in use in the US. Amplitude Modulation stations can be heard at great distances -- especially at night, but are subject to interference and low fidelity. Frequency Modulated signals can only travel in a line of sight manner (generally 30-40 miles) but offer higher fidelity.

AM/FM Presets - Allow you to store your favorite stations in memory for recall at the touch of a button.

Amplifier Power - Measured in watts, amplifier power is used to drive speakers. More power generally provides a clearer sound as well as an increase in loudness. However, other features can influence clarity in addition to just power.

Bandwidth @ Rated Power - This specification tells you the range of frequencies the amplifier was reproducing when it achieved the claimed power or "wattage." Some manufacturers rate their amplifiers down to only 40Hz or while using a 1kHz test tone. Amplifiers that use a full 20Hz to 20kHz (20,000Hz) bandwidth are designed to put out their rated power under real-world conditions while playing music and movies.

Basic Remote - Just controls the functions of the product you've bought.

Bass Driver(s) - These are the larger speaker components within a cabinet and are used to produce low frequencies.

Center Channel Speaker - This type of speaker is used in a home theater system to deliver movie dialog clearly and "anchor" all action to the screen. It is typically placed above or below the TV screen and should be magnetically shielded if placed on a tube TV.

Digital Inputs - Dolby Digital receivers and decoders can accept the Dolby Digital output from a DVD player (or the stereo digital output from compatible digital sources like CD and MiniDisc) using their optical or coaxial digital inputs. A special cable is needed for optical digital connections.

Dolby® Digital - This type of surround sound can have as many as 6 separate channels (front right, center left, right and left surround, plus subwoofer) of high quality digital surround. These discrete channels can create realistic sound effects that move around the room and bring movies to life. Dolby Digital soundtracks are found on digital sources like DVD and some high definition television broadcasts.

Dolby® Pro Logic - Still one of the most common surround sound technologies, this system uses just three audio channels to create surround sound from 5 speakers (front right, center, left and two rear). The information you'll need for Pro Logic surround sound is found on virtually every VHS movie you'll find at your video store. To hear Dolby® Pro Logic, you'll need a receiver with a Pro Logic decoder, 5 speakers, and a HiFi source like a VCR or DVD player.

Dolby® Pro Logic II - This surround system is designed to create a surround sound experience from virtually any stereo source. Using advanced matrix processing, Dolby Pro Logic II employs all five speakers (right, center, left, right surround, left surround) in a home theater system to turn your favorite CDs or old movies into multi-channel theater.

Dolby® Surround Sound - This is the predecessor to Dolby® ProLogic and it only has right left and rear channels (3 total). The sound is less focused and dialog is less clear, but it still provides a nice overall surround effect.

DSP Modes - Digital Signal Processing uses digital circuitry to manipulate music and soundtracks to create a sense of space; or different spaces. For example the same singer may be placed inside a concert hall or in a jazz club or in a stadium using DSP-all off the same disc! Some manufacturers actually recreate the acoustics of specific places so you can listen as if you were sitting inside of Carnegie Hall or the Hollywood Bowl.

DTS Decoding - Like Dolby® Digital, DTS is a 6-channel digital surround format that provides a separate channel of sound to five speakers (right, center, left, right surround, left surround) and a subwoofer. There are fewer DTS than Dolby Digital recordings today, but popularity seems to be on the rise. These days, most receivers and systems with Dolby Digital also have built-in DTS decoders. See also: Dolby® Digital.

DVD - Stands for Digital Video Disc or Digital Versatile Disc, depending on who you ask. DVDs look just like CDs, but contain high quality video and multi-channel audio. Some home theater systems come with DVD players and some don't, but using digital sources like DVD are the only way to take advantage of digital surround sound modes like Dolby® Digital and DTS.

EQ or advanced tone modes - Allows equalization or emphasis of particular parts of the audible sound range. Use to add just a little bass, bring the singers voice out more, eliminate bass boominess or bring out the high notes.

Frequency Response - This is the range of sound that a component reproduces accurately. Human beings (who haven't attended too many rock concerts) can hear from about 20Hz (low bass) to 20,000Hz (very high treble).

Midrange Driver(s) - This is the speaker component within a speaker cabinet that produces vocals and many instruments. About 70% of music comes from the midrange, so this driver can be critical in providing a natural sound.

Multi-Brand/Multi-Component Remote Control - This kind of remote has the capability of controlling multiple components from different manufacturers. Most such remotes have the necessary "codes" built in; others are taught using your existing remotes.

On-Screen Menus - Many home theater receivers have an video output to a TV set, which lets you see the status of the audio system on your TV screen, rather than the smaller display on the receiver.

Powered Subwoofer - This is a speaker designed to produce the very deepest bass notes with impact. The built-in amplifier provides the power so it may be used with any system. Particularly useful in home theater situations where special sonic effects are an important part of the movie experience.

Receiver Inputs - This refers to the number of components that can be hooked up to the receiver. These inputs might be audio-only or have jacks for both audio and video signals.

Receiver Power - Measured in watts, this is the amount of power the amplifier in a receiver produces to drive speakers. More power generally provides a clearer sound as well as an increase in loudness.

Remote Control Type - Virtually every home theater component and system will come with a remote control. Virtually all of these remote controls will fall under one of three categories.
1. A Basic remote simply controls the component it came with.
2. A Branded remote adds controls for other items made by the same manufacturer. (Example: Sony TVs AND VCRs).
3. A multi-brand remote can control components from different manufacturers because it either has the necessary information built in OR because it can be "taught." (Example: An RCA TV remote controls your cable box, a JVC VCR, and a Pioneer receiver).

S-Video Inputs - This small, round pin jack allows a signal with separate black and white and color signals to be used as an input for a high resolution video source. S-Video jacks are better than standard RCA (composite jacks) in that they eliminate cross-color & dot crawl effects while providing the same high resolution as RCA jacks. If you have more than one digital video source (such as both DIRECTV and a DVD player), look for a system with more than one S-Video Input.

Sensitivity (SPL @ 1 watt/1 meter) - A measurement of how loud a speaker will play with a given amount of amplifier power. Higher dB (decibel) ratings mean speakers will play louder given the available amplifier power. While greater sensitivity is a good thing, it has NOTHING to do with sound quality.

Shielded for Video Use - Speaker magnets can grossly deform a TV picture when placed to close to a tube TV set, often necessitating a service call. Shielded speakers eliminate this problem. Shielding is an especially important feature for center channel speakers because they're often placed directly on the TV.

Subwoofer - A large bass driver built into its own cabinet. Since the human brain cannot detect the point of origin of deep bass frequencies, a single sub-woofer can be placed almost anywhere to reproduce the lower end of sound. Subwoofers come in two types -- passive and powered. Powered subs have their own amplifiers, while passive subs use a system's main amplifier.

Subwoofer Driver(s) - This is the speaker component (a large cone) found in the subwoofer cabinet.

Subwoofer Output - This jack sends a low-level signal to a subwoofer for amplification, providing a clean bass signal, which is the start of good sound.

Surround Sound - Refers to the simulation of the theater or concert experience by surrounding the listener with sound coming from different points around the room. See also Dolby Surround Sound, DTS, DSP, Surround modes.

Surround Sound Modes - There are several surround sound formats, but you'll find that almost all videotapes are designed to work with Dolby® ProLogic surround, and that DVDs are designed to work with Dolby® Digital and DTS surround sound.

Surround Speakers - The pair of speakers that is placed to the side or rear of the listening position in a home theater to provide surround sound effects. Although these speakers don't have to be able to produce the deepest bass notes, we recommend speakers that are competent over a wide frequency range.

THD% @ rated power & bandwidth - THD stands for Total Harmonic Distortion. This specification tells you how much distortion the amplifier adds to the incoming signal at the rated power output. There was a time when this was "The" spec to look at, but you'd be hard-pressed today to find an amplifier that introduces audible amounts (over 1%) of harmonic distortion.

Tweeter Driver(s) - Tweeters are the smallest speaker components and deliver only the high notes. Because they deal with notes requiring that they vibrate up to 20,000 times per second, tweeters need to be small and lightweight to react quickly.

Video Inputs - These inputs allow for the delivery of picture (and sometimes sound) information into a device. Your TV or receiver should have enough inputs for all the video sources you plan to connect (DBS, VCR, DVD, camcorder, TV game, etc.).

Watts (per channel stereo into 8 ohms, 20-20,000Hz w/< .1% THD) - By government standard, all home receivers and amplifiers must state:
· The power they produce in watts per channel
· Tell you what kind of speaker ohms they are using
· What frequency range the are capable of reproducing at this wattage
· How much total harmonic distortion (look for under .1%)

Watts Front/# of Channels - In a surround sound receiver their are three front channels (right, center and left). Each channel should have equal wattage.

Watts Rear/# of Channels - In a surround sound receiver, the rear or surround section may have one mono channel as in Dolby® ProLogic or two channels (rear right & left) as in Dolby® Digital.

Watts, Center Channel - The center channel contains most of the dialog and action in movies. Power (in wattage) to the center channel should be similar to the left and right front power to ensure that proper balance is maintained.

A/V Receiver Glossary

5.1-channel, 6.1-channel, and 7.1-channel inputs
A receiver's 5.1-channel input features preamp-level jacks for 6 channels: left main, right main, center channel, left surround, right surround, and subwoofer (sometimes called "LFE" or "Low-Frequency Effects"). Because the LFE channel carries a limited range of very low frequencies, it's the ".1" in 5.1.

A 5.1-channel input allows you to hook up a separate multichannel surround sound (Dolby® Digital, DTS®) decoder, such as those built into some DVD players. You can also use these inputs with up-and-coming multichannel music sources like DVD-Audio and SACD players.

Some receivers feature a 6.1 or 7.1-channel input. These let you hook up any of the 5.1 sources described above, but also pave the way for future upgradability. One potential use for these inputs is hooking up decoders for surround formats that offer 6.1 channels, such as Dolby™ Digital EX, DTS-ES™ and THX Surround EX™.

Audio inputs and outputs
An audio input consists of two RCA jacks — one for the left stereo channel and one for the right. It can be used with most audio components with analog output. The major exception to this rule is turntables, which require either specialized audio input, called a phono input, or a phono preamplifier.

A/V inputs and outputs
An A/V input consists of three RCA jacks — two for the stereo audio signal, and one for the video signal. Receivers with A/V inputs offer convenient remote switching for your A/V sources.

Component video inputs and outputs
A single component video input includes three RCA jacks — one for the brightness (luminance) portion of the video signal, and two for the color (chrominance) portion. Because component video connections split chrominance between two jacks/cables, they offer even higher-quality video transfer than S-video connections, with improved color accuracy and less bleeding.

Receivers with component video switching allow you to select between multiple component video sources. However, just because a receiver offers component video switching doesn't mean it can pass on all video signals flawlessly. Component video bandwidth is the key figure to look for here. You'll need bandwidth over 10 MHz to pass on progressive-scan video without noticeable softening of the picture. And for HDTV signals, you'll need bandwidth in the upper 20s or higher to avoid noticeable softening of the picture (with most TVs).

Digital inputs and outputs
A home theater receiver's optical or coaxial digital inputs accept Dolby Digital and DTS signals from digital home theater sources (such as DVD and DBS). They also accept PCM stereo audio from components with compatible output (such as CD and MD players). Digital inputs on stereo receivers are designed for the latter use only.

A digital output lets a receiver send PCM stereo digital audio directly to digital recorders (such as CD-R, MiniDisc, or DAT). Optical digital outputs are the type most commonly found on receivers, but many models offer coaxial outputs, too.

Optical digital connections require a special type of fiber optic cable, usually with Toslink connectors. And although coaxial digital connections use standard RCA-style jacks, you'll definitely want to use a coaxial digital audio cable designed specifically for the wider frequency bandwidth of digital signals.

Digital Signal Processing (DSP)
Home theater receivers use Digital Signal Processing for creating soundfields (simulated acoustic environments) and for precise steering of multichannel soundtrack information. When an audio signal is processed and routed in the digital domain, it is less susceptible to signal loss and added distortion.

Discrete output transistors
Found in higher-quality receivers and amplifiers. An amplifier output section comprised of discrete transistors offers some big advantages over the more common, low-cost IC chip amplifier: higher current capacity, ability to handle more heat, quicker response to sonic transients, lower distortion, more dynamic and lifelike sound.

Dolby® Digital
The digital audio format used on the large majority of DVDs, all HDTV programs, and selected satellite TV broadcasts, Dolby Digital can include from one to six channels of sound. "5.1-channel" Dolby Digital has 6 discrete digital audio channels: 5 full-bandwidth channels (for front left/right, center, and surround left/right) and 1 "low frequency effects" subwoofer channel.

Dolby® Digital EX
Dolby Digital EX encoding is based on standard Dolby Digital technology (see above), but employs a sixth channel of audio information to deliver 6.1-channel sound through a back surround speaker or speakers. This sixth channel is encoded as a matrixed signal within the standard left and right surround channels.

You'll need a receiver with either Dolby Digital EX decoding or THX Surround EX decoding to enjoy these 6.1-channel soundtracks. The receiver must also have 6-channel power in order to drive the back surround speaker. Alternately, you can use a 5.1-channel receiver with an auxiliary amplifier or a powered speaker.

A Dolby Digital EX receiver can also use special processing to create 6.1-channel sound from standard 5.1-channel Dolby Digital sources.

Dolby Pro Logic®
Pro Logic processing can be found on almost all home theater receivers. It delivers 4-channel playback of Dolby Surround-encoded stereo sources (primarily VHS tapes and stereo TV broadcasts). Pro Logic includes a center channel for on-screen sound; front left and right channels for sound that moves with the action; and a limited-bandwidth mono surround channel sent to the left and right surround speakers to provide ambience and sound effects.

Dolby Pro Logic® II
A relatively recent invention that significantly improves on the original Dolby Pro Logic processing. Its primary purpose is to give Dolby Surround-encoded sources a three-dimensionality that approaches the realism of Dolby Digital soundtracks. Pro Logic II transforms any Surround or stereo source — including music — into full 5.1-channel sound. This includes full-bandwidth stereo surround channels and a subwoofer channel.

DTS®
DTS is a multichannel audio encoding system used both in movie theaters and home theater systems. DTS provides 5.1-channel sound, but uses less compression than Dolby Digital. As a result, some say that the sound produced by DTS is slightly more accurate than the sound produced by Dolby Digital. A relatively small number of DTS-encoded DVDs and CDs are currently available, but almost all new DVD players and home theater receivers are now DTS-compatible.

DTS-ES®
DTS-ES is a newer format that gives you 6.1 discrete channels of sound — the 5.1 channels of standard DTS, plus a discrete, full-bandwidth "back surround" channel. That additional channel may be played through one or two speakers, using either a receiver with six-channel amplification, a five-channel receiver supplemented with an additional amplifier, or a powered back surround speaker.

The sixth channel of full-bandwidth sound on a DTS-ES soundtrack is discrete, so some consider DTS-ES an improvement on THX Surround EX, which uses a matrixed sixth channel. Currently, only a few DVDs are encoded with 6.1-channel DTS-ES sound. But for DVDs with 5.1-channel DTS soundtracks, DTS-ES processing can generate a sixth matrixed channel for 6.1-channel sound.

DTS Neo:6
Many receivers with DTS-ES decoding (see above) also offer DTS Neo:6 modes, which can translate any home theater or stereo source into 6.1-channel sound. Some Neo:6 modes are designed to enhance movies, while others are specialized for music applications.

Dual room/dual source receivers
These receivers let you and a housemate enjoy different sources in different areas of the house simultaneously. For example, many of these receivers allow you to experience the 5.1-channel surround of a DVD soundtrack in your main listening room while a housemate listens to stereo music from a CD in a second room.

Most dual-room/dual-source receivers require you to have a separate stereo receiver and set of speakers, or a set of powered speakers, for the second room.

FM sensitivity
Indicates a receiver's ability to pick up FM signals (a lower number is better).

Full-bandwidth-rated power ratings
When shopping for a receiver, notice the range of frequencies, or bandwidth, listed next to the amplifier power rating. For audio components, "full bandwidth" is generally considered to be the entire frequency range of human hearing — 20-20,000 Hz. Full-bandwidth power ratings are a more conservative measure of power than ratings derived using a narrower range of frequencies.

High-current power
The flow of current through your speakers' voice coils creates the electromagnetic force that moves the cones and domes, creating sound. The dynamic qualities of music and movie soundtracks create short-term high-current demands. If current flow is limited, the sound will be, too. A high-current amplifier (or a receiver that uses one) may sound punchier and more powerful than other models with the same wattage rating.

On-screen display
Some A/V receivers let you view system information and menus on your TV screen. Some use a GUI (Graphical User Interface) for easy remote point-and-click control via on-screen menus and icons. An alternative approach is to display menus and icons on a remote's built-in LCD screen.

Phono Input
Lets you connect a turntable directly to your receiver. Phono signals are a much lower voltage than other audio signals — a phono input lets you make the connection without the need for a separate phono preamp.

Power amplifier
A power amplifier takes the low-voltage signal supplied by a preamplifier, and increases it to a sufficient level to drive speakers. Receivers contain both preamplfier and power amplifier sections, eliminating the need for a separate amp and preamp.

Preamplifier
Also called a control amplifier or control center. A preamplifier (or preamplifier section of a receiver) handles the switching and selecting of signals, tonal adjustment, digital signal processing, and surround decoding. The preamp also boosts signals to the voltage level required for the input of a power amplifier.

Preamp inputs and outputs
Some receivers and almost all preamplifiers include RCA-style preamp input and output jacks. Used together, these jacks allow you to add an external sound processor or graphic equalizer to your system. The preamp output jacks can also be used to provide unamplified, low-voltage, line-level signals for components like a powered subwoofer or a separate power amplifier.

Receiver
An audio component that combines a preamplifier, amplifier, and an AM/FM tuner in a single chassis. A stereo receiver offers two channels of amplification and is primarily intended for listening to stereo music sources.

A home theater receiver is designed to deliver both music and the surround soundtracks of movies found on DVDs, VHS tapes, and some TV programs. Home theater receivers offer between five and seven channels of amplification, and usually include several types of surround decoding (such as Dolby Digital and DTS).

Remote control
The capabilities of receiver remotes can vary a lot from brand to brand, and even from model to model:
Audio/video remotes can operate several audio/video components from the same manufacturer.
Multibrand remotes (also called "universal" remotes) have pre-programmed codes for popular brands of gear.
Learning remotes (also called "programmable" remotes) can be programmed to carry out specific commands from your other remotes.
Some remotes have RF capability that lets you control your receiver from other rooms in your house — these are especially useful for use with dual-room/dual-source receivers.

Another useful feature of some remotes is an LCD screen that aids in the navigation of system controls. A few of the most sophisticated remotes incorporate an LCD touchscreen that puts even greater system control at your fingertips via customizable control screens. For an overview of advanced remote features, see our article on remote controls.

S-video inputs
Using a 4-pin connector, an S-video jack transmits the chrominance (color) and luminance (brightness) portions of a video signal separately, for improved color accuracy and reduced distortion. Receivers with S-video inputs and outputs offer convenient remote switching for your high-quality video sources.

Tape monitor loop
An especially versatile type of tape input/output loop found on some receivers and preamplifiers. It allows you to record and play back like a standard tape loop, but can also be used for connecting an equalizer, surround sound decoder, or other external signal processing device.

THD (total harmonic distortion)
A measurement of the accuracy of an amplifier (or the amplifier section of a receiver). THD refers to the amount of internally generated noise. The lower the number, the better.

THX® Select and THX® Ultra
Unlike THX Surround EX (see below), THX Select and THX Ultra are not surround sound formats. Rather, they are sets of performance standards developed by the engineers at Lucasfilm to ensure excellent audio/video reproduction in cinemas and home theater settings. To garner THX certification, a home theater receiver must meet Lucasfilm's rigorous standards for audio performance, user interface, construction, and compatibility with other THX-certified products.

A THX Select-certified receiver is designed to deliver superbly cinematic performance in rooms up to 2,000 cubic feet. The standards necessary for THX Ultra certification are even more stringent, since THX Ultra receivers are required to provide a premium home theater experience in rooms up to 3,000 cubic feet.

THX Surround EX™
THX Surround EX provides direct decoding of Dolby Digital EX and Dolby Digital soundtracks. It can also be used in tandem with DTS-ES, DTS, Dolby Pro Logic, or Pro Logic II decoding. In either case, THX Surround EX applies unique processing enhancements such as Cinema ReEqualization™, Decorrelation™ and Timbre Matching™ to increase the realism and impact of the home theater experience.

THX Surround EX decoding is capable of producing 6.1-channel sound from any home theater source. With Dolby Digital EX and DTS-ES DVDs, the 6.1 channels are implicit in the soundtracks themselves (in the case of Dolby Digital EX DVDs, the back surround channel is matrixed in the left and right surround channels). With 4-channel (Dolby Surround) and 5.1-channel (Dolby Digital and DTS) sources, the extra channel(s) are derived using special THX processing.

You'll need a receiver with 6-channel power (or a 5.1-channel receiver with an auxiliary amplifier or a powered speaker) to enjoy THX Surround EX's back surround channel.

Ultra-wide bandwidth
Until recently, no common audio technologies existed that could reproduce frequencies much above the audible range of 20-20,000 Hz. New high-resolution formats like DVD-Audio and SACD, however, are capable of frequency response up to 50,000 Hz and higher.

Some higher-end receivers — those designated as having ultra-wide bandwidth — are capable of reproducing these extremely high frequencies. Keep in mind, though, that standard speakers usually have a frequency ceiling between 20,000 and 25,000 Hz. Even with an ultra-wide bandwidth receiver, you'll still need extended definition speakers to reproduce ultra-high frequencies.

USB input
A few newer receivers have USB inputs that let you easily make a direct digital connection between your PC and your receiver. Such a connection allows you to play PC audio — such as MP3, WMA, and WAV files — through your main A/V system. Your PC's sound card is bypassed entirely and the digital-to-analog conversion is handled by your receiver, so you'll enjoy PC audio with the best possible sound quality.

Video upconversion
Some home theater receivers offer video upconversion, which lets you send video signals from at least two video connection types through a single connection to your TV. For example, some receivers let you send composite and S-video signals through an S-video connection. The most versatile form of upconversion lets you send composite and S-video signals through a component video connection.