Comparison Onkyo TX-8020 vs Sherwood RX-5502

The range of audio frequencies that the audio receiver can handle. The wider this range, the more complete the overall picture of the sound, the less likely it is that too high or low frequencies will be “cut off” by the output amplifier. However, note that the range of sound audible to a person is on average from 16 Hz to 20 kHz; There are some deviations from this norm, but they are small. At the same time, modern Hi-Fi and Hi-End technology can have a much wider range — most often it is a kind of "side effect" of high-end circuits. Some manufacturers may use this property for promotional purposes, but it does not carry practical value in itself.

Note that even within the audible range it does not always make sense to chase the maximum coverage. It is worth, for example, to take into account that the actually audible sound cannot be better than the speakers are capable of giving out; therefore, for a speaker system with a lower threshold of, say, 70 Hz, there is no need to specifically look for a receiver with this figure of 16 Hz. Also, do not forget that a wide frequency range in itself does not absolutely guarantee high sound quality — it is associated with a huge number of other factors.

The nominal sound power output by the audio receiver per channel when operating with a load having a dynamic resistance (impedance) of 8 ohms. In our catalog, this parameter is indicated for the mode when both channels of the receiver work under load; when working on one channel, the rated power may be slightly higher, but this mode cannot be called standard.

Rated power can be simply described as the highest average output signal power at which the amplifier is able to operate stably for a long time (at least an hour) without negative consequences. These are average figures, because in fact, an audio signal is, by definition, unstable, and individual jumps in its level can significantly exceed the average value. However, the key parameter is still the nominal (average) power — it is on it that the overall sound volume directly depends.

This indicator also determines which speakers can be connected to the device: their rated power should not be lower than that of the receiver.

According to the laws of electrodynamics, with different dynamic load resistance, the output power of the amplifier will also be different. In modern speakers, values of 8, 6, 4 and 2 ohms are standard; the latter option, however, is rare, therefore, in audio receivers, the power for it, usually, is not indicated at all. As for the specific values for 8 ohms, the indicator up to 50 W is considered relatively low, 50 – 100 W is average, and with more than 100 W we can talk about high power.

The nominal sound power output by the audio receiver per channel when a load with a dynamic resistance (impedance) of 6 ohms is connected to it. It is customary to specify this parameter when the receiver is operating in two-channel mode (stereo); when using only one channel, the power may be slightly higher, but this mode cannot be called standard.

Rated power is the highest average (rms) output signal power at which the receiver is able to work for a long time without failures or malfunctions. The average power is taken because the audio signal is, by definition, unstable, and individual jumps in its level can significantly exceed the average value. However, the key parameter is still the rated (average) power. It determines two points — the overall volume of the sound and compatibility with one or another passive acoustics. The higher the power of the receiver, the louder the sound it can provide; at the same time, this power should not exceed the rated power of the speakers — otherwise, overloads and even damage to the equipment are possible.

As for the resistance, according to the laws of electrodynamics, with a different load impedance, the output power of the amplifier will also be different. In modern speakers, values of 8, 6, 4 and 2 ohms are standard; the latter option, however, is rare, therefore, in audio receivers, the power for it, usually, is not indicated at all.

The lowest speaker impedance that the audio receiver can handle 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.

Signal-to-noise ratio when operating the audio receiver through the RCA line input (see below).

Any signal-to-noise ratio describes the ratio of the level of pure sound produced by the device to the level of extraneous noise that occurs during its operation. This parameter is the main indicator of the overall sound quality — and very clear, because. its measurement takes into account almost all the noise that affects the sound in normal operating conditions. A level of up to 90 dB in modern receivers can be considered acceptable, 90 – 100 dB is not bad, and for advanced audiophile-class devices, a signal-to-noise ratio of 100 dB or more is considered mandatory.

The signal-to-noise ratio when the audio receiver is connected to the Phono input. This input is for connecting turntables; see "Inputs" for more details. The value of this parameter is described in detail in the "Signal-to-noise ratio (RCA)" section.

— Lossless formats. The receiver's support for audio formats that use lossless compression. Unlike lossy compression (in the same MP3), with this compression, the sound is not cut, all its details are preserved as much as possible. Nowadays, there are several lossless formats, including FLAC and APE; the specific set of standards that the player is compatible with should be clarified separately. However, anyway, this function will be useful to those who appreciate the most complete and reliable sound.

— Formats without compression (uncompressed). Receiver support for non-compressed audio formats. Most of these standards are professional, they provide very high quality and reliability of sound, but they also take up a lot of space. Examples of uncompressed formats include DSD and DXD.

— RS-232. Also known as a COM port. Service connector to control the audio receiver, used to connect the device to a computer or specialized equipment. Such control can provide more options than using the original control panel or remote control.

— I2S support. The presence in the receiver of an input and/or output for a digital audio signal in the I2S format. This format is mainly intended for signal transmission within audio devices, but sometimes it is also used for communication between devices; the latter is implied in this case. The I2S interface does not have a standard connector; it can use ports of various types — in particular, BNC, RJ-45 (LAN) and ev...en HDMI. Anyway, the purpose of this connector is similar to the coaxial S / P-DIF (see "Inputs", "Outputs"); while the I2S standard, on the one hand, provides higher quality and noise immunity, on the other hand, it is less common and significantly affects the cost of devices.

— Multizone. Possibility of simultaneous transmission of signals from different sources to acoustic systems located in different places (zones). For example, in a large house, you can simultaneously broadcast music from the player into one room, and a radio programme into another. Another use case for Multi-Zone is entertainment centers with several rooms of different types (for example, a table tennis room, a roller skating rink and a cafe).

— Direct connection (By-pass/Direct). The ability to feed the audio signal coming to the input of the audio receiver directly to the amplification stages, bypassing all additional controls (timbre, balance, etc.). Direct connection not only minimizes distortion in the processed signal, but also ensures that the sound is as close to the original as possible, which allows demanding listeners to appreciate the skill of sound engineers. For such a connection, either a separate set of Main connectors (see "Inputs") or a conventional line interface switched to By-Pass/Direct mode by a special regulator can be used.

— Smartphone control. The ability to control the receiver from a smartphone, tablet or other gadget with a special application. In this case, the connection is usually carried out via Wi-Fi or Bluetooth, and the specific capabilities and features of such control may be different, depending on the model. However, the app is often more convenient and visual than using a control panel or even a traditional remote control; and some functions of the receiver can only be accessed via a smartphone.

— Voice assistant. The ability to control the receiver using one or another voice assistant. It is worth noting that own voice assistants in this technique are not provided, and we are talking about compatibility with external devices that have this function (for example, with a smartphone or tablet). The most popular voice assistants nowadays are Google Assistant, Apple Siri and Amazon Alexa.

— Connecting an iPod/iPhone. Extended capabilities for working with portable devices from Apple — primarily the iPhone and iPod touch, often also the iPad. The specific set of such features may be different, it should be specified separately in each case. So, in some models, an “apple” gadget can be connected using a dock or a special cable and used as a signal source, controlling playback from the remote control or receiver panel and at the same time recharging the gadget. In other devices, the connection is made via Wi-Fi or Bluetooth, while the iPhone / iPod can work not only as a signal source, but also as a remote control (see "Control from a smartphone"). Other additional features may be provided, such as synchronizing the multimedia libraries of the receiver and the Apple device.

— mini-Jack (3.5 mm). A standard connector widely used in modern audio equipment and other electronics, mostly portable. Technically, the mini-Jack input can be used for different types of signal, but in fact in audio receivers it most often plays the role of a line interface and is mainly used to connect the mentioned portable equipment — for example, audio players.

— Amplifier input (Main). An input designed to connect an external source directly to the power amplifier (in fact, in By-pass / Direct mode, see "Communications"). In different models, the Main inputs may differ in the type of interface, most often either RCA (“tulip”) or XLR is used. The first option is extremely widespread in modern high-end audio equipment due to its low cost, simplicity and good connection quality, however, in terms of signal purity and resistance to interference (especially when working with long wires), it still loses to XLR. It is also worth noting that “tulip” connectors can also be used for the main line input — see “RCA” for details; do not confuse this input with Main (especially since they may differ in technical parameters — for example, input impedance).

— Phono. Special input for connecting turntables; often has a suffix indicating the type of cartridge that is compatible, such as "Phono MM" or "Phono MM/MC". A feature of "...vinyl" is that the sound coming from the pickup must be passed through a phono stage. Actually, the presence of the Phono input just means that the receiver is equipped with a built-in phono stage and you can connect a “turntable” directly to it, without additional equipment.

— XLR (balanced). Audio line input using balanced connection via XLR — characteristic round 3-pin plug; one input consists of a pair of these connectors, for the left and right stereo channels. A feature of a balanced connection is that the XLR cable itself dampens external interference coming to it; and the connector provides tight contact and is often supplemented with a retainer for reliability. All this allows you to achieve high quality connections and maximum purity of sound, even when using long wires. However, such inputs are rare — this is due not so much to their shortcomings, but to the fact that audio receivers are rarely used as linear balanced audio receivers.

— Coaxial S/P-DIF. A kind of S/PDIF digital audio interface that uses an electrical coaxial cable with RCA connectors (“tulip”) for connection. Such a cable, unlike optical (see below), is subject to electromagnetic interference to a certain extent, but is more reliable and does not require special care in handling. And the connection bandwidth is enough to transmit multi-channel audio up to 7.1. Note that despite the identical connectors, the coaxial digital interface is not compatible with analogue RCA (see below); and even cables for S / P-DIF are recommended to use specialized ones.

— Optical. A variation of the S/PDIF digital audio interface that uses a TOSLINK fiber optic cable connection. In terms of bandwidth, it is completely similar to the coaxial interface (see above), but it compares favorably with its complete insensitivity to electromagnetic interference. On the other hand, due to their design, optical cables are sensitive to sharp bends and mechanical stress — for example, accidentally stepping on such a cable can damage it.

— Balanced digital (AES/EBU). An interface used primarily in professional audio equipment. It can use different types of connectors, but is most often implemented via XLR. For more information about this connector and the principle of balanced connection, see "XLR (balanced)", but do not confuse these two interfaces: AES / EBU works with a digital signal transmitted over a single cable, regardless of the number of channels.

— Composite (video). An input for connecting a composite video signal. Uses the same RCA connector as many audio inputs, but is most often highlighted in yellow. The signal is transmitted in analogue format, via a single cable, which simplifies the connection, but limits the bandwidth; because of this, this standard is not suitable for working with HD. Nevertheless, it is very popular in modern video technology, in addition, it is found even in outdated devices (like VHS VCRs). Note that composite audio inputs are not provided in modern audio receivers — their role is played by standard RCA line inputs (see below).

— BNC. Bayonet type connector used to connect coaxial cable. Theoretically, it can be used for various purposes, but in fact it is most often used similarly to coaxial S / P-DIF, for digital analogue audio. BNC connectors are more reliable in connection due to the bayonet lock; there is also a version with a threaded fixation.

— Trigger. Service input that allows the receiver to turn on and off at the same time as other components of the audio system. Such an input is connected to the trigger output of a control device (for example, an amplifier), and when this device is turned on and off, a control signal is sent to the receiver. This eliminates the need for the user to separately manage the power on of each device.

— Control input (IR). Connector for connecting an external infrared remote control receiver. Such a receiver can be useful in cases where the signal from the remote control does not reach the built-in IR sensor of the receiver. Note that other components of the system that are compatible with the remote control and have IR control outputs, for example, players or tuners, can play the role of an external sensor.

The number of line inputs in the design of the audio receiver using the RCA interface are characteristic “tulip” connectors. This interface allows for an analogue connection to transmit only one channel of sound per connector, and audio receivers traditionally work with stereo sound. Therefore, it is customary to consider a pair of two RCA connectors (one for the left and right channels) as one output, and the calculation of the total number is carried out precisely by pairs, and not by individual sockets.

When connected to a line input, the signal goes through all the stages of processing provided in the device — for example, adjusting the balance or frequencies (see "Adjustments"). In this respect, this input differs from Main (see "Inputs"). The number of connectors determines how many signal sources can be simultaneously connected to the audio receiver. Accordingly, it is worth choosing a model according to the number of inputs, taking into account the expected number of such sources: after all, it is easier to connect them all and select through the remote control or control panel than to fiddle with reconnecting every time. As for the specific number of RCA inputs, most often it does not exceed three, however, there are exceptions.