When we start in the world of home cinema, we have many doubts about the numerous types of devices, components, equipment, speakers, players and other technological paraphernalia that are available for us in specialized stores. But without a doubt, one of the most doubts is the so-called A/V receiver or audio and the video receiver.
They are those voluminous, hot and heavy devices to which speakers are generally connected and which form the heart of our home cinema. Do not you know what they are, what they are for, or what the differences are that they present with respect to other types of devices such as preamplifiers, power stages, signal processors, etc.? In this series of articles, we are going to try to clarify it.
We will start at the beginning. In a home theater system that claims to be one, having a good sound is as important as the quality of the image we get through projectors or televisions. Due to the physical and technical characteristics of the latter, it is almost impossible to incorporate speakers of quality or at least with the appropriate dimensions to reproduce the entire range of audible frequencies at appropriate power levels.
Therefore, it is necessary to use external speakers that, in turn, will need an electronic system that provides them with the electrical power necessary to move the electromagnets and produce the sound. This is the task of general audio amplifiers, commonly used in all types of devices such as music chains, MP3 players, televisions, sound bars, etc.
On the other hand, today’s films usually have digital multi-channel audio, which means that to enjoy them at their best, we will have to have a number of speakers that corresponds to the number of channels of the recording (usually 5 normal channels and one of bass) and some devices that decode this digital audio and transforms it into analog signals understandable by the electronics of the speakers.
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A/V Receivers: Audio receiver and decoder:
This is where the A/V receivers come into play, since one of their main functions is to be the decoders of this audio digitally inserted in DVDs and Blu-Rays (in Doby Digital, DTS, etc. formats ), transforming the zeros and ones into sinusoidal analog signals that once amplified will feed the different speakers that we have installed.
That is to say, its first and most important function is to “pick up” the audio signals coming from the outside, whether they are in digital or analog format, from the multiple and different sources that we have connected (DVD, Blu-Ray, CD, TV, game console, PC, etc.) and adapt them to the language that the speakers understand: volts and watts .
To do this, the A/V receivers usually have many connections on the back, both analog and digital, which will allow us to connect the different sources of content playback that we have at home and select at any time the one we want to listen to.
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A/V receivers: preamplifier, DSP and power stage:
The second and most important function of the A/V receivers is to also serve as preamplifier and power stage. The preamplifier is the device that adapts the electrical levels of the input signals to suitable levels for further processing by a DSP (digital signal processor) or amplifier.
The power stage, as the name suggests, is responsible for raising the millivolts provided by the preamplifier or DSP to volts, to generate the watts needed to move the cones of the speakers, that is, it is the part that generates us the final power that will go to our speakers.
The third fundamental function of an A/V receiver is to act as a digital processor of audio signals, applying different effects, equalizations, delays, etc. adapting them to the frequency characteristics of our speakers and to the acoustic characteristics of the room (we will see in depth these functions in a later article).
In addition, depending on the models, they can also incorporate advanced functions to handle the digital or analog video signals that we connect to them, making or not processing them to adapt them to different resolutions and final representation systems (TV or projectors), for example by passing a signal in low definition to one in 1080p by rescaling.
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A/V Receivers: Summary of functions:
To sum up, the A/V receivers are the devices in charge of receiving the audio signals (and also video) from the different sources that we have at home, decoding the digital ones (Dolby Digital, DTS , etc.), adapting them at a suitable signal level to be processed , process them to modify their amplitude, phase and frequency response (equalization), adapt them to the characteristics of our speakers and room, and finally amplify them up to the power levels necessary so that we can listen to them by speakers.
That is, the A/V receivers integrate the preamplification stage, the digital decoder and multichannel audio processor, the digital signal processor (both audio and video) and the power stages (one for each speaker) into a single device), reducing costs and simplifying the management of all these devices.
In later articles, we will review these functions more thoroughly and discuss the advanced functionalities that have converted A/V receivers into the neurological centers of our home theater systems.
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Stereo or multichannel? (Which is Better):
The main function of a stereo receiver is to listen to music and point. Occasionally, we can use it for movies, but it is not its reason for being. On the contrary, it happens with the A/V receiver, whose objective is to be the center of interconnection of the equipment of the living room (console, multimedia player, TV, Blu-ray, etc.) to improve its sound by offering multichannel decoding, advanced functions and, of course, also listen to music in stereo.
If we have good speakers that do not need support from an external subwoofer, HiFi stereo receivers are the best option for listening to music. For the same budget, we will generally have more real power (we must pay attention to the specifications), support for more complex speakers to amplify, better DAC with audiophile features, better construction and overall better sound quality in stereo which is what has been designed.
However, with a stereo receiver, we will miss the multi-channel audio and additional functions (although not always all) as the acoustic correction (there are stereo models that also incorporate it), possibility of connecting more channels and speakers. Sometimes we cannot install a subwoofer to improve the bass, we cannot decode the formats present in movies such as Dolby Digital, Atmos, DTS, DTS: X, etc.
So, what is better? Well, in my opinion, if we mainly listen to music only, the best choice is a stereo receiver, since it will give us more sound quality and as we have said before, more power. The multi-channel low budget A/V receivers have many features and will probably do a good job with the movies but offer less benefits when dealing with music alone.
This does not happen if we go to higher ranges, where multichannel receivers can compete without messing with HiFi stereo equipment by incorporating powerful stages of amplification, quality DACs and other audiophile features. In these cases, it is worthwhile to get an A/V receiver instead of a stereo receiver because, in the future, we can give more uses than just listening to music.