Comparison Onkyo TX-NR646 vs Onkyo TX-NR545

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.

The lowest impedance of the loudspeakers of the speaker system, with which the amplifier is able to work normally. The nominal impedance of the speakers, also referred to as the term "impedance", is one of the key parameters in the selection of audio system components: for normal operation, it is necessary that the speaker impedance match the characteristics of the amplifier. If the speaker impedance is greater, the sound volume will decrease significantly, if it is less, distortion will appear in it, and in the worst case, even overloads and breakdowns are possible. Therefore, in the characteristics of receivers, it is usually the minimum resistance that is indicated — after all, connecting a load of too low impedance is fraught with more serious consequences than too high.

Audio and video file formats that the receiver is capable of playing on its own. Models with player features generally support most popular media file types (particularly AVI, MPEG and MKV for video, MP3, WAV and WMA for audio), but the file set may have its own peculiarities. This item allows you to find out.

A decoder can be broadly described as a standard in which digital audio (often multi-channel) is recorded. For normal playback of such sound, it is necessary that the corresponding decoder is supported by the device. The first signs of multi-channel decoding were Dolby Digital and DTS, gradually improving and introducing new features. The final stage for 2020 is Dolby Atmos and DTS X decoders. And the intermediate ones were Dolby TrueHD, Dolby Pro Logic II, DTS-HD, DTS ES, DTS Neural: X, DTS Neo (6, X).

Dolby Atmos. A decoder that does not use a rigid distribution of sound across channels, but the processing of audio objects, due to which it can be used with almost any number of channels on a reproducing system — the sound will be divided between channels so that each audio object is heard as close as possible to its proper place. When using Dolby Atmos, in-ceiling speakers (or speakers facing the ceiling) are highly desirable. However, in extreme cases, you can do without them.

— DTS X . An analogue of the Dolby Atmos described above, when the sound is distributed not through individual channels, but through audio objects. The...digital signal contains information about where (according to the director's intention) the object audible to the user should be and how it should move, and the processor of the reproducing device processes this information and determines exactly how the sound should be distributed over the available channels in order to achieve the required localization. Thanks to this, DTS X is not tied to a specific number of audio channels — there can be as many as you like, the system will automatically divide the sound into them, achieving the desired sound. Also note that this decoder allows you to separately adjust the volume of dialogues.

— IMAX Enhanced. The IMAX Enhanced Mark of Conformity is awarded to equipment that meets the audio certification requirements of IMAX Corporation. Combined with DTS audio technology to deliver signature IMAX theater-like sound in the home. The most accurate reproduction of such audio is possible in systems with a large number of channels (5.1 or more). Note that for a fully immersive experience, IMAX Enhanced certification must also apply to video equipment for playing content (TV, projector, etc.).

The number of analogue stereo RCA inputs provided in the design of the AV receiver. The more such inputs there are, the more transmitting devices can be simultaneously connected to the receiver. Thanks to this, when choosing between them, you do not have to reconnect cables — just set the signal source in the receiver settings.

By itself, the RCA connector (colloquially — "tulip") can be used in different interfaces. However, in this particular case, we are talking about a linear audio input responsible for an analogue audio signal. RCA is the most popular connector used in modern audio equipment for such inputs; it allows you to connect the receiver to an external audio source such as a CD player.

Note that connectors of this type are usually counted in pairs; in other words, one input consists of two RCA connectors. This is due to the fact that in this case only one channel of analogue audio can be transmitted over one wire; accordingly, two RCA jacks are required for stereo transmission.

The number of HDMI inputs provided in the design of the receiver.

This interface is one of the most advanced digital standards used in modern electronics. It was originally developed for HD television and already in the first version it allowed to transmit a video signal with Full HD (1920x1080) resolution, accompanied by eight-channel (7.1, see "Number of channels") sound; in the future, the maximum resolution increased even more. Almost all modern TVs, monitors and plasma panels have at least one HDMI interface, the same applies to playback devices (players, media centers, etc.).

As for the quantity, the presence of several inputs allows you to connect several signal sources to the receiver at once with the corresponding outputs and switch between them through software settings without fiddling with switching cables. In the case of HDMI, the abundance of connectors is especially important, given the prevalence of this standard in modern video equipment; in some receivers, the number of such inputs can be up to 10.

The number of composite inputs provided in the design of the receiver.

Note that in this case, we do not mean a full-size composite interface that uses three sockets (video and two stereo sound channels), but only one connector — video. This is due to the fact that the sound can be output through standard RCA audio connectors. The video output also uses an RCA type connector, usually a characteristic yellow colour.

Due to the fact that all image data is transmitted over a single cable, the composite interface is somewhat inferior to the component (see above) in terms of video quality, and the bandwidth allows you to work only with a standard definition signal (not HD); and there is no talk of volumetric sound. On the other hand, this connection method has long been used in video technology and can be useful for connecting outdated devices (such as VHS VCRs).

As for the quantity, the presence of several inputs allows you to connect several signal sources to the receiver at once with the corresponding outputs and switch between them through software settings without fiddling with switching cables.

The presence of the Phono input in the design of the AV receiver.

This type of input is used to connect turntables. Despite the widespread popularity of digital media, classic vinyl records do not leave the scene. And it's not just a matter of nostalgia: many audiophiles believe that it is the record that provides the most authentic and complete sound, which is why turntables for vinyl are quite often found in high-end audio systems. However, the sound from such a player must be passed through a phono stage, otherwise there can be no question of any quality. For these purposes, in high-end equipment, including AV receivers, the Phono input is provided: the signal received at this input is fed to the built-in phono stage. This allows you to connect turntables directly, without additional external equipment.

Note that phono stages can be designed for different types of pickups — MM or MC; therefore, before connecting, check to see if the Phono input is compatible with your turntable's cartridge. However, many receivers with this function are equipped with a universal MM/MC phono stage.

The number of HDMI outputs provided in the design of the receiver. The presence of several outputs allows you to connect several signal receivers at the same time (in the case of HDMI, these can be, for example, TVs or monitors) and select a playback device without reconnecting cables — by changing the settings of the receiver. And in models that support Multi Zone (see above), you can simultaneously broadcast different signals to different receivers.

HDMI is one of the most advanced digital interfaces used in modern electronics. It was originally developed for HD television and already in the first version it allowed to transmit a video signal with Full HD (1920x1080) resolution, accompanied by eight-channel (7.1, see "Number of channels") sound; in the future, the maximum resolution increased even more. Almost all modern TVs, monitors and plasma panels have at least one HDMI interface, the same applies to playback devices (players, media centers, etc.).