General AVR FAQIntroduction
This is an attempt to cover some basics of the modern AVR (Audio/Video receiver). This type of receiver is also known as a home theater receiver. The modern AVR should include at minimum –
* Video switching
* Analog and digital audio switching
* Five channels of amplification
* A Dolby Pro Logic II surround sound processor
* A Dolby Digital decoder
* A DTS decoderWhat's an AVR?
An audio/video receiver.
They provide switching for multiple audio-video devices, amplification for a surround sound setup, an AM/FM tuner and video switching capabilities.
An AVR paired up with decent speakers should give you much better sound than your TV speakers, and is highly reccomended.How important is amplifier power?
Much has been written on receiver power ratings. The bottom line is that they are practically worthless. Firstly, power ratings use an artifical test which does not duplicate real world use. Secondly, there are many ways to state power ratings and they are not compatible. Differences in power ratings are not what they seem either. The difference between 100 watts / channel and 110 watts / channel is not huge. You have to DOUBLE your power to get a 3Db gain in SPL. 10 watts just gives you a little more breathing room. And you can pay quite a bit just to step up to the next model with perhaps 10 watts more per channel. Due to these reasons, don't put much emphasis on power. As you step up models in a manufacturers line you will get more power, but not usually a dramatic amount. Consider something in the 100 watt / channel range measured from 20hz-20khz with a THD (total harmonic distortion) of less than 1%.
If you really want/need a lot of power, consider a separate power amp. Some people have been pleased with running a stack of three cheap pro stereo amps at $200 a pop. There is much to read on this topic in the AVS forums.
If you have or are thinking of getting 4ohm speakers you need to be more careful about your AVR purchase. Many AVRs can handle 4ohms whether they are rated for 4ohms or not, but you takes your chances. A few AVRs are rated into 4ohms if you want to go that route. AVRs should have adequate protection circuits. But if I were you, I would not buy a room full of 4ohm speakers and then try to drive an 8ohm rated AVR to movie house/concert hall volumes.How about sound quality?
A common question is whether one AVR sounds better than another. The answer is ... maybe. AVRs have a complex signal chain involving preamps, digital to analog and analog to digital conversion, digital decoders and amplifiers. Ideally an AVR amplifies an input signal without adding any distortion, but obviously all AVRs add some distortion. And with the complex signal path of the modern AVR, there’s arguably more room for them to add distortion than a simple stereo amplifier.
For various reasons, there’s no consensus of opinion on a method to measure sound quality of an amp. Some argue that specifications alone don’t determine sound quality. Some argue that even the best blind listening tests don’t tell the whole story. Some argue that you can’t reliably tell the difference between two AVRs under normal operating conditions. When it comes to reviews, reviewers rarely perform any blind comparisons. People don’t respond to sound the same way either; and people have psychological biases.
Listening to AVRs in a demo room is unreliable because of the number of variables involved. For one thing, modern AVRs often have auto setup. That alone can make a substantial difference in how the AVRs sound. Level matching is almost impossible, and many people claim even a small difference in volume will bias you towards the louder amp.
Richard Clark created a $10,000 challenge for anyone who could tell the difference between any two amps, and no one has. For more details on the challenge, see this link (http://www.tom-morrow-land.com/tests/ampchall/index.htm
) Whether you think his conditions are fair or not, all indications are that differences between amps are subtle.
Audio lovers often overlook the room their system is installed into. Rooms color sound more than you may realize. Bass response is one issue because rooms will reinforce some frequencies and attenuate others. Some surfaces reflect sound other absorb sound which can give sound a “live” or “dead” quality. Ideally you would experiment with room acoustics and speaker placement, but many people don’t have those options.
Speakers make a bigger difference in sound than AVRs do. If you ever compared two different speakers at a store you have probably noticed how different they can sound. The cheaper the speaker the more compromises were likely made. You may also note that manufacturers don’t list any measurement of speaker distortion (which according to various sources can be as high as 10%.)
Your AVR is not likely to fix problems with room acoustics, or your speakers. My suggestion is to choose AVRs based on features, and purchase speakers for sound quality. There are also some options for treating rooms to improve their acoustics. Obviously, not all people agree, do your own homework, and you be the final judge.What is 5.1/6.1/7.1 ?
A 5.1 AVR has five amplifiers.
A 6.1 AVR has six amplifiers, the additional amplifier is for an optional rear surround speaker, see the sections on Dolby EX and Dolby Pro Logic IIx for more explanation.
A 7.1 AVR has seven amplifiers the additional amplifiers are for two optional rear surround speakers, see the sections on Dolby EX and Dolby Pro Logic IIx for more explanation.
The .1 indicates that the AVR handles the Low Frequency Effects channel present on movie soundtracks. AVRs don’t have amplifiers for the LFE channel (no AVR I know of anyway.) They have an output connector for hooking up a powered subwoofer.
AVRs offer various bass management modes. Owners can set the AVR to output low frequencies (all low frequencies, not just the LFE) to the main speakers if they don’t have a powered subwoofer. Or if they have a subwoofer, they can send all low frequencies to it. A powered subwoofer reduces the load on the AVRs amplifier section. There’s usually a setting for which frequencies are handled by the powered subwoofer. This is called the crossover setting. A typical value is 80hz which indicates that frequencies below 80hz will be sent to the sub.What are Dolby Digital and DTS?
Back in the mid 70s, Dolby developed a method of adding surround sound to 35mm films, with it first being used on Logan's Run. Since then many different surround sound technologies have been created.
Perhaps the most successful format of all time is Dolby Digital which is present on almost every DVD soundtrack. To take advantage of Dolby Digital you need to hookup your player to your receiver with a digital cable, or a set of multi-channel analog cables. And you need at least four speakers (one each for the left, right, left-surround and right-surround channel.) A common setup is six speakers (left/center/right/left-surround/right-surround/powered subwoofer.) AVRs can send the center channel to the left/right channels if desired and can send the LFE channel to the left/right channels as well if you prefer fewer speakers in your setup.
Besides Dolby Digital, DTS is also relatively common. DTS has a higher bandwidth signal, but that does not mean it's gauranteed to sound better. They both compress the original signal using methods which try to remove parts of the audio signal a human cannot hear. Dolby Digital is considered to use a more efficient method of compression which partially explains there difference in bandwidth. The bottom line is both are impressive achievements and were a large step up from soundtracks available to the consumer on VHS tapes. The difference between the original soundtrack and the soundtrack is likely audible to few.
These technologies are referred to as codecs.What are Dolby Digital EX and DTS ES?
Some DVD soundtracks have 6.1 rather than 5.1 soundtracks. 6.1 soundtracks contain a rear surround channel. AVRs with 6.1 capability 7.1 capability have Dolby and DTS decoders for these soundtracks along with additional amp(s). In most cases, the AVR can automatically detect the proper decoder to use. To take advantage of these, one or two speakers are needed to play back the rear surround channel.
Using a 6.1 or 7.1 speaker setup is optional; you can play 6.1 DVD soundtracks back in 5.1. And 6.1 DVD soundtracks are still uncommon.What is Dolby Pro Logic/Dolby Pro Logic IIx?
Dolby Pro Logic was a surround format commonly used on VHS tapes. The next technology from Dolby available in AVRs was Dolby Pro Logic II. This decoder could generate surround sound from two channel sources which were not specifically encoded in Dolby Pro Logic.
The latest Dolby Surround mode is Dolby Pro Logic IIx which can produce a 6.1 or 7.1 soundtrack from a stereo or 5.1 channel soundtrack.
Each version includes all the capabilities of the previous version.
Because Dolby Pro Logic IIx can be used with a 5.1 soundtrack, you can use it to get more use out of a 6.1/7.1 speaker setup due to the fact that 6.1 DVD soundtracks are uncommon.What about action, game, cinema, 7-channel stereo modes (etc.) ?
AVRs usually contain some sort of artifical surround sound generation modes. To get a little less technical, these usually suck. Some people may like them though. You simply have to try them out. These often work in conjunction with the existing surround sound decoders which can be confusing.
Five and seven stereo mode while hated by some, are at very least, great for parties. The overall volume needed to cover a room can be lower - or you can just crank it up if you didn’t really want to talk to the people you invited.
Cinema usually modes work on top of existing decoders. For example, Yamaha has a number of various cinema modes. (This writer never found one worth using.)
Some AVRs include enchanced modes that are supposed to improve the playback of MP3 sources. They supposedly help restore what got lost from the lossy encoding process.
Only you can decide if you like these. In terms of buying decisions, artificial surround modes features probably should not be high up on the list of features to look for.What about Dolby Digital+, DTS-HD Master Audio and TrueHD ?
These are the latest digital formats available with HD DVD and Blu-ray players. Except for Dolby Digital+ they are lossless codecs. The audio is compressed but no audio data is thrown away; think of TrueHD and DTS-HD Master audio as a ZIP file for audio. Dolby Digital+ is a lossy compression method similar to Dolbty Digital but of higher quality.
TrueHD is a common format used on HD DVD discs. It’s also used on Blu-ray discs, but it’s less common than on HD DVD. It’s mandatory for all HD DVD players to decode TrueHD, but it’s possible players with no decoders may show up on store shelves one day.
DTS-HD Master Audio is a common format on Blu-ray discs, but no players have the decoder (as of the time this was written, some players with the decoder have been announced). Even though they lack the full DTS-HD MA decoder, they should be able to play back the soundtrack, because DTS-HD MA includes a core DTS soundtrack. If the player can output DTS-HD as bitstream (see comments below,) and you have an HDMI 1.3 AVR with a DTS-HD MA decoder, you can enjoy DTS-HD MA.
Some HD DVD soundtracks use Dolby Digital+ which is a mandatory decoder for HD DVD players. For Blu-ray, DD+ is optional, but a core Dolby Digital soundtrack should be available.
To take advantage of these “new” codecs, you need the following:
* A high definition (Blu-ray or HD DVD) player
* An HDMI connection between the player or receiver or a set of multi-channel analog cables (An S/PDIF connection will not support these formats)
* A player with the proper decoder; or that can send bitstream, and an AVR with the proper decoder
* A receiver that can handle at least 5.1 channel PCM over HDMI (most recent AVRs should)
TrueHD decoding is mandatory for HD DVD players and optional for Blu-ray players.
DTS-HD Master Audio decoding is optional for both Blu-ray and HD DVD.
Dolby Digital decoding is mandatory for HD DVD players.
AVRs which support Multi Channel PCM over HDMI allow for playback of these codecs when the high definition player decodes them. This is true for any version of HDMI. Not all AVRs support MPCM over HDMI. AVRs which do support HDMI/MPCM vary in their exact capabilities. Some only support 5.1 MPCM while others support 7.1 MPCM. Many won’t allow any processing modes to be applied to MPCM.
A new generation of HDMI 1.3 AVRs include some or all of these decoders. To utilize your AVR as a decoder, you need a player that can output the appropriate soundtrack as bitstream (similar to how Dolby Digital over S/SPIF works.) For example, if your player can output bitstream for TrueHD soundtracks you can send TrueHD to an AVR with a TrueHD decoder.
There are a few advantages to using bit stream. Some users claim bitstream will avoid bass management issues. Another advantage is the receivers are more likely to be able to apply processing such Dolby Pro Logic IIx to bit stream than MCPM.
HD DVD and Blu-ray support interactive audio in menus. To hear this audio, you must currently allow you player to do the decoding regardless of whether you have an AVR with the proper decoders. This is a disadvantage to using bit stream to send the audio to the AVR.
An HDMI 1.3 AVR with Dolby Digital+, DTS-HD Master Audio and TrueHD decoders will give you the most options when dealing with high definition players with varying capabilities. If you are buying one of these receivers, you should get a high definition player which can output bit stream if possible.
A popular Blu-ray player, the Sony PS3 can’t output bit stream and can’t decode DTS-HD Master Audio. So owners of this console using it as a Blu-ray player are stuck with the core DTS soundtrack for discs with a DTS-HD Master Audio soundtrack.Why are there so many connections on the back of my AVR?
Technology changes have produced an obscene number of connections. The most common are:
* RCA terminated stereo connection
- This is a pair of RCA jacks usually color coded red (for the right channel) and white for the white channel.
* RCA terminated multi-channel audio connection
- This is a set of RCA plugs for a multi-channel audio connection as from a DVD player. One use for this would be from a player with an SACD or DVD Audio decoder.
* Optical or COAX terminated S/PDIF connection
- This common digital connector comes in two flavors - optical or coax (RCA terminated.) While the merits of these connections have been debated, pratically speaking they perform the same job. This cable can be used for CD players, DVD players or high definition players to send stereo, Dolby Digital or DTS. It does not support the newer high defintion audio formats sush as TrueHD.
* RCA terminated composite video connection
- Usually color coded yellow this is used for analog composite video. It's commonly used to connect VHS players, DVD players, cam corders and game systems. It's the worst possible quality video connection as composite video suffers from some signal degredation due to combining the color and chrominance (color) and luminance (brightness) signals.
* RCA terminated component video
- Often color coded red, green and blue, component video carries two separate color difference signals and a luminence signal. Color coding may not be consistent. Make sure that the same physical cable connects Y to Y, Pb to Pb and Pr
. This is the best analog video connection found on AVRs.
HDMI (Digital audio and video)
- See "What is HDMI?"What is HDMI?
HDMI is a single cable connection for digital audio and video. It provides for the best possible audio and video from a high definition player. It's suffered from some issues such as compatibility with set top (cable) boxes. HMDI has perhaps more restrictive length limitations than component video cables which could be a factor with a projector or custom installations.
HDMI has three different common versions; 1.1, 1.2 and 1.3. 1.2 mainly added support for SACD. 1.3 adds the ability to send bitstream high defintion audio, such as TrueHD, so decoding can be done in the AVR rather than in the player ( similar to how Dolby Digital is usually handled.) All versions of HDMI support high defintion audio when sent as MPCM. All version of HDMI support 1080p video, but many AVRs were not implementing it. That situation is changing and most current generation AVRs handling 1080p video.
Many HDMI features are optional. Not every HDMI AVR is made alike. Some AVRs may not handle 1080p as mentioned above. Some may only switch HDMI video, and not handle audio. Some may not be able to apply the desired processing to MPCM (such as the ability to produce 6.1 or 7.1 from a 5.1 signal.) Some may suffer from an incorrect adjustment to the LFE signal. Many of these complaints have been seen in this forum. You are encouraged to use these forums to educate yourself on any potential limitations of HDMI for a given AVR.What about YPAO and Audyssey (or what about auto setup features) ?
Auto setup is a great idea. YPAO and Audyssey use a microphone and software to set critical setting involving levels, crossovers and even bass EQ. For many people auto setup is perfect as they don't have the time, patience or desire for manually making adjustments.
Some people use the auto setup, but go back and tweak setting they think are wrong, so don't think you are stuck with the choices your auto setup has made.
This writer thinks auto setup is a desirable feature for most consumers as it can really improve their sound with almost no work on their part. For serious audio lovers, it's a tool to be used as desired.What is upconverting?
The answer depends on whether you are talking about DVD players, or AVRs. Upconverting DVD players can output video signals such as 720p, 1080i or even 1080p. That's the way manufacturers use the term for DVD players, and sometimes high defintion players.
Upconverting AVRs can convert the video signal to a different type such as composite to component. The reason to consider an upconverting AVR is to be able to make a single connection from your AVR to your TV even though your video sources output different signals.
Some scenarios -
In one scenario, your AVR can upconvert to component video. You have a game cube connected with composite (RCA) jacks. Your DVD player is connected with component video. No problem, just run a component video cable to your TV. Saves you a connection, and you can keep your TV set to it's component input whether you watch DVDs or play games.
In another scenario, your AVR upconverts to HDMI. You have a VHS player connected (for your old Duke's of Hazzard recordings,) you have a DVD player connected with component video, and your PS3 connected with HDMI. Run a single HDMI cable, and do all the switching at the AVR.
Make sure you understand exactly what the upconversion feature offers, there are a a number of variations.What is upscaling?
There are two key terms to understand when upscaling is discussed, deinterlacing and scaling.
When the television specification was created, the engineers chose to send only half the scan lines at a time (almost certainly due to broadcast bandwidth limitations.) We are stuck with that legacy, DVDs and cable use the same system. You may have seen the number 480i, which refers to standard definition interlaced video. For various reasons, we have moved to progressive scan displaying of interlaced signals. This requires assembling the even and odd fields of the interlaced signal into a single video frame. This sounds simple, but there are some issues involved. Because the two fields were scanned at slightly different times, moving images would be at slightly different positions on the even and odd scan lines. Another issue involves movies stored on DVDs at 24 frames per second being displayed at a higher frame rate (google 3:2 pulldown for the gory details.) Thus deinterlacing is non trivial.
Why all this talk of deinterlacing? AVRs usually have to include a deinterlacer as part of their video processing solution, and it's probaby a good idea to realize there's more to the process than simply adding more pixels.
Scaling is pretty simple to understand, the AVR simply adds pixels to a lower resolution signal to convert it to a higher resolution signal. For example from 640x480 (standard defintion TV) to 1280x780 (780p high defintion.) Note that this cannot add detail to the orignal image! It simply adds pixels, using information from existing pixels to create new ones (known as interpolation if you are mathematically inclined.) This looks just fine. To prove my point about not adding detail, goto into your photo editing program and keep zooming in until the image looks blurry. The photo program can't add detail missing from the photo and neither can your scaler. Which is why the term near HD quality when applied to scaling DVDs to higher resolutions may be a little misleading.
Understand this - all fixed pixel TVs and projectors have to deinterlace and scale signals which don't match their native resolution. Fixed pixel TVs include LCD, plasma and DLP based TVs whether they are projector based or flat screen models. Only CRT based TVs and projectors don't fall into that category. If you have a fixed pixel TV or projector, you don't need a deinterlacer/scaler in your DVD player or AVR to see the image in high defintion! All signals will be scaled to match the display's native resolution.
So why do you care whether your AVR has upscaling capabilities? Likely you don't. If your DVD player is good at upscaling, by all means use it's upscaler. Some people claim TVs usually have pretty good deinterlacing/scaling simply because that's what you are going to be seeing when looking at them in a store. In a store environment HDTVs are often fed with poor standard definition video signals. Manufacturers likely know this, and aren't going to totally skimp on an inferior solution.
Don't expect the AVR scaler to make a bad looking cable signal suddenly look like a DVD! And be at least somewhat suspicious of marketing buzz words like near high definition. They seem to be implying they can magically add missing detail - they can't!
If you have multiple options available, try them all out to see which works best.