Comparison Harman Kardon HK 3770 vs Harman Kardon HK 3700

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.

— Airplay. A technology for transmitting multimedia data over a wireless connection ( Wi-Fi). Developed by Apple, it is intended mainly for broadcasting content from various Apple technology (primarily portable gadgets) to compatible external devices. Allows you to transfer audio files (in the audio streaming mode, see "Tuner and Playback" for details), as well as images, text data and even video. The presence of AirPlay in the audio receiver will allow you to connect Apple devices with support for this technology to it — for direct playback.

— Airplay 2. The second version of the AirPlay technology described above, released in 2018. One of the main innovations introduced in this update is multi-room support, the ability to simultaneously stream multiple separate audio signals to different compatible devices installed in different locations. Thus, for example, you can turn on the acoustics in the living room for training music from the iPhone, in the kitchen — a relaxing melody from the iPod, etc. In addition, AirPlay 2 received a number of other improvements — better buffering, the ability to stream to stereo speakers, as well as support for voice control via Siri.

— Chromecast. The original name is Google Cast. A technology for broadcasting content to external devices developed by Google. Allows you to transmit an au...dio signal from a PC or mobile device to the receiver, broadcasting is standardly carried out via Wi-Fi, while the receiver and signal source must be in the same Wi-Fi network (Chromecast media players are an exception). Chromecast technology supports two modes — the actual broadcast through special applications (available for Windows, macOS, Android and iOS) and "mirroring" content opened in the Google Chrome browser. However, the second option for audio receivers is not relevant, given the specifics of their application.

— Wi-Fi. A wireless interface originally used to build computer networks, but more recently, it also supports a direct connection between devices. It can be used in audio receivers in different formats: for network functions (streaming audio, Internet radio, DLNA, etc.), for broadcasting content via AirPlay or Chromecast (see above), and for connecting a smartphone as a remote control. An alternative option for connecting to networks is a wired LAN interface (see below), but Wi-Fi is more convenient due to the lack of wires and the ability to work through obstacles, including walls. In addition, the mentioned AirPlay and Chromecast work as standard through a wireless channel.

— LAN. Connector for wired connection to computer networks — "LAN" and/or the Internet. By itself, such a connection is less convenient than Wi-Fi (see above) due to the need to pull wires, but LAN support is somewhat cheaper, and the connection is faster and more reliable (especially when Wi-Fi channels are heavily loaded).

— Bluetooth. The technology of direct wireless communication between different devices at a distance of several metres. It can be used for a variety of purposes, but the main use of Bluetooth in audio receivers is to transmit an audio signal. At the same time, depending on the model, the sound can be transmitted both to the receiver (from a smartphone, tablet, etc.), and from the receiver to wireless speakers or Bluetooth headphones. It is believed that wireless transmission degrades sound quality, but this point is corrected in many devices using various advanced technologies such as aptX. Other uses for Bluetooth include remote control from an external gadget and file sharing between that gadget and the audio receiver's built-in memory.

— NFC chip. NFC technology is used for wireless communication over short distances (up to 10 cm). Potentially, it has many applications, but in audio receivers it is most often used as an auxiliary, to simplify the connection via Wi-Fi or Bluetooth. If there is NFC in a smartphone or other gadget, it is enough to bring it to the NFC chip of the receiver — and the devices will automatically “recognize” each other; then, depending on the settings, they will connect either automatically or after confirmation from the user. In addition, additional "chips" may be provided — for example, if music was playing on the smartphone at that moment, it will start broadcasting it to the receiver.

— DLNA. A technology used to connect various electronic devices into a single digital network with the ability to directly exchange content. Devices for which support for this standard is claimed are able to effectively interact regardless of the manufacturer. An audio receiver with DLNA is capable, for example, of playing music directly from a computer hard drive in the next room or from a smartphone in the user's hands. Connection to the Network can be carried out both wired (LAN) and wireless (Wi-Fi) way.

— USB A. The classic USB connector, familiar to most users from computers and laptops. In audio receivers, it is mainly used as an input for direct playback of music from flash drives and other drives, sometimes also for updating firmware and exchanging files between an external drive and built-in memory. Other application formats are also possible: for example, some models have a Type A output for transmitting a digital signal to an external DAC.

— USB B. This type of USB connector has an almost square shape, noticeably different from the popular USB A. The most common way to use it is to connect it to a computer as a peripheral device to control the audio receiver from a PC. However, there are other options — in particular, the use of this connector as an input for a digital audio signal.

— Card reader. A device for reading memory cards — most often various types of SD, although it's ok to clarify the specific types of compatible cards separately, as well as the possibilities for working with them. In general, this function is similar to USB Type A (see "Inputs"). Most often it is used for direct playback from memory cards, but other uses are possible — for example, copying music from a laptop to the receiver's built-in storage via a memory card.

— Internet radio. The ability to "receive" Internet radio stations using the receiver. Such transmissions are similar to conventional radio broadcasting, but are carried out not on the air, but through the World Wide Web; such broadcasting is carried out by many large radio stations, and there are also many specialized network channels. One of the key advantages of Internet radio is the lack of range restrictions, which allows you to listen to broadcasts from almost anywhere in the world and provides a wide range of choices. And for additional convenience, tools for searching and sorting Internet stations (by genres, languages, popularity, etc.) can be provided.

— 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 power consumed by the audio receiver during normal operation. Note that this parameter can be indicated in different ways: for example, some manufacturers measure it when the amplifier is operating at full power, while others measure it at 80% or 50% power. In addition, the power consumption of modern receivers is usually not so high as to put a serious strain on the power supply systems. Therefore, power consumption information usually plays a supporting role.