DAC frequency
A digital-to-analogue converter (DAC) is an indispensable element of any system designed to reproduce digital sound. The DAC is an electronic module that translates sound information into pulses that are sent to the speakers. The technical features of such a conversion are such that the higher the sampling frequency, the better the signal at the output of the DAC, the less it is distorted during conversion. The most popular option in receivers today is 192 kHz — it corresponds to a very high sound quality (DVD-Audio) and at the same time avoids unnecessary increase in the cost of devices.
Audio DAC
Another indicator that determines the overall quality of the digital-to-analogue audio converter. For details on the converter, see "Audio DAC Sampling Rate"; here we note that the bit depth is standardly expressed in bits, and the higher it is, the more accurately the signal at the output of the DAC corresponds to the original signal and the less distortion is introduced into it. Today, it is believed that a 16-bit indicator provides quite acceptable signal quality, and 24-bit DACs are suitable even for premium-level equipment.
Auto sound calibration
In this case, the function of automatic adjustment of each individual sound channel in terms of level and delay is implied so that all of them together provide surround sound that best matches the intention of the creators of the film or musical composition. The need for such a setting is due to the fact that practically no room (neither residential, nor even specialized) is acoustically perfect: the sound propagation is affected by the wall material, floor covering, furniture (sofas, wardrobes, etc.) and other factors. Therefore, the technically correct arrangement of the speakers alone does not guarantee a full-fledged surround sound.
Typically, automatic tuning uses a microphone placed at the intended listening position. During the calibration process, the device outputs test sound signals through the acoustics and “listens” to the features of the sound through the microphone, if necessary, independently changing the audio parameters.
Such a function can greatly simplify the preparation for work — after all, the device will carry out the main part of the setup on its own. However, keep in mind that even in the most advanced receiver models, automatic calibration algorithms are not perfect. As a result, it is highly likely that the automatically set parameters will not meet the tastes of demanding audiophiles. In addition, the reliability of the calibration is also highly dependent on the characteristics of the microphone used — and options with high...sound quality can be quite expensive.
eARC
The audio receiver
supports eARC, an enhanced version of the Audio Return Channel (ARC) used with an HDMI connection (see below).
By itself, the audio return channel allows you to "swap" the HDMI output of the AV receiver and the HDMI input of the TV or other external device — thus, this device turns into an audio signal source, and the receiver starts to work as a receiver. Such functionality is designed mainly for those cases when the TV receives a signal not from the receiver, but from another source (built-in tuner, media player, flash drive, etc.), however, the soundtrack must be output to external speakers through the receiver. Without ARC, you would have to use an additional connection (for example, via an optical interface), while the audio return channel eliminates the need for extra wires: the same HDMI cable is used both for transmitting video / audio from the receiver to the TV and for transmitting audio from TV to receiver. Also, the advantages of ARC over traditional audio interfaces are higher bandwidth, as well as the ability to use the CEC function (control of connected devices from one remote control).
Specifically, eARC was introduced simultaneously with the HDMI 2.1 standard and received a number of improvements compared to conventional ARC. Here are the main ones:
— Up to 40x more bandwidth, allowing uncompressed 5.1 and 7.1 surround sound, HD audio and Dolby Atmos and DTS:X "object-orie
...nted" multi-channel codecs (see Decoders).
— Technology Lip Sync Correct, eliminating desynchronization between video and sound.
— Proprietary protocol to automatically detect audio formats supported by both connected devices and select the best option.
Of course, in order to use eARC, both the receiver and the TV it is connected to must support it.HDR
Receiver support for
HDR technology; this clause may also specify the specific supported HDR format.
HDR stands for High Dynamic Range. This technology allows you to expand the range of brightness reproduced simultaneously on the screen; to put it simply, the viewer will see brighter whites and darker blacks. In practice, this means a significant improvement in color quality: colors are more vibrant and at the same time more faithful than without HDR. However, to use this function, in addition to the receiver, a TV/projector that supports the appropriate HDR format and content recorded in this format is required.
In terms of specific formats, the most popular options these days are basic HDR10, advanced HDR10+, and high-end
Dolby Vision. Here are their features:
- HDR10. Historically the first of the consumer HDR formats, less advanced than the options described below but extremely widespread. In particular, HDR10 is supported by almost all streaming services that provide HDR content at all, and it is also common for Blu-ray discs. Allows you to work with a color depth of 10 bits (hence the name). At the same time, devices of this format are also compatible with content in HDR10 +, although its quality will be limited by the capabilities of the original HDR10.
- HDR10+. Improved version of HDR10. With the same color depth (10 bits), it uses the so-called dynamic metadata,
...which allows transmitting information about the color depth not only for groups of several frames, but also for individual frames. This results in an additional improvement in color reproduction.
Dolby Vision. An advanced standard used particularly in professional cinematography. Allows you to achieve a color depth of 12 bits, uses the dynamic metadata described above, and also makes it possible to transmit two image options at once in one video stream - HDR and normal (SDR). At the same time, Dolby Vision is based on the same technology as HDR10, so in modern video technology this format is usually combined with HDR10 or HDR10+.Power per channel
the
maximum sound power that can be delivered by the power amplifier (if the receiver has one, see "Type") per speaker channel. It is worth noting here that in this case it is customary to indicate the so-called RMS (Rated Maximum Sinusoidal), or rated power. Rated is considered the highest power that the amplifier is guaranteed to be able to produce without interruption for an hour without any failures or breakdowns. Short-term jumps in the signal level can significantly exceed this value, but the main indicator is still the rated power.
The power of the amplifier largely determines the sound volume of the speaker system connected to the device. In fact, the loudness also depends on the characteristics of the speakers — sensitivity, impedance, etc.; however, other things being equal, the same acoustics on a more powerful amplifier will sound louder. In addition, this parameter also affects the compatibility of the speakers and the amplifier — it is believed that the difference in the nominal powers of these components should not exceed 10-15% (and ideally, the powers should generally match). And since different rooms require speakers of different power, this also affects the choice of amplifier for a particular environment; specific recommendations on the ratio of room characteristics and acoustic power can be found in special sources.
Also note that if the amplifier can operate with a load of different resistance (see
..."Permissible acoustic impedance"), then for different options the power per channel will be different — the lower the resistance, the higher the power. In the characteristics, in this case, the maximum value of this parameter is usually indicated — that is, the power at the minimum allowable resistance.Signal to noise ratio
This indicator determines the amount of extraneous noise that accompanies the sound output by the receiver's amplifier. It is convenient because it takes into account almost all possible significant noise — both created by the device itself and due to external causes. The higher the signal-to-noise ratio, the lower the noise volume compared to the main signal, the cleaner the amplifier will sound. A reading of 70-80 dB is considered normal for most consumer electronics, but in AV receivers, which are usually premium devices, this can only be called satisfactory. In the most advanced models, this figure can significantly exceed 100 dB.
Tuner and playback
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AM/FM radio. The presence of a built-in tuner that allows you to receive AM and FM radio broadcasts without additional devices (except perhaps an antenna is required, and then not always). In FM, it is possible to realize the transmission of high-quality stereo sound, however, the waves propagate only within the line of sight (10-20 km); therefore, most of the stations in this range are classified as "urban music". In AM, the transmission range is already measured in hundreds of kilometers, but the sound quality is noticeably lower; therefore, such stations usually specialize in talk programs (particularly news).
—
USB stick. The ability to connect a USB drive to the receiver — for example, a "flash drive" or an external hard drive — and play content from it directly. This requires a USB connector. Most often, in models with this function, it is located on the front panel (see below) — this provides ease of connection; at the same time, there are exceptions. Also note that the very presence of USB does not necessarily imply the possibility of playing from external media — this interface can be used for service purposes, for example, to update the firmware or play from a PC (see "Advanced (inputs) — USB Type B").
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Network audio streaming. The ability to play streaming audio over a local network or the Internet (including from services like Grooveshark o
...r Last.Fm). The name "streaming" is due to the fact that each song is played directly from the network, without being written to the receiver's own permanent storage. This function, by definition, requires connection to computer networks; most often, a Wi-Fi module is used for this purpose (see "Interfaces") or a LAN connector.
— Internet radio. The ability to use the receiver to receive and play Internet radio broadcasts. This feature is similar in many ways to the network audio described above — in particular, it requires a network connection to work, and the data is streamed; however, in the case of network audio, the user himself chooses what and when to listen, here the broadcast is similar to conventional radio transmissions and is controlled from the radio station. Actually, many major stations broadcast their programs not only on the traditional air, but also via the Internet; There are also specialized projects broadcasting only on the Web. In general, the choice of programs is much more extensive than for conventional radio broadcasting — after all, Internet radio has no range restrictions. And the receivers themselves may provide additional tools for managing such broadcasting — for example, catalogs, search by genres, languages, etc.Streaming services
A set of streaming services supported by the AV receiver.
Such services are designed for streaming audio content over the Internet. In this case, the files are not saved to the device, but are played directly from the corresponding resource on the global network. Streaming services allow you to access vast libraries of music without having to take up your device's internal storage. The key advantages of online streaming include a huge selection of content and almost instant access to the desired audio tracks. Popular ones include
Amazon Music,
Deezer,
SoundCloud,
Spotify,
TIDAL,
YouTube Music.