Comparison Rotel RA-1572 vs Rotel RA-1570

Most modern amplifiers have toroidal transformers - with a toroid-shaped core, in other words, a donut. This type is considered optimal for amplifiers of any level up to Hi-End: it creates a minimum of "extra" electromagnetic radiation and, accordingly, interference. Some time ago, E-core transformers were also widely used, but they are considered obsolete and are becoming less common today.

The damping factor describes the quality of interaction between the amplifier and the speaker system connected to it.

Due to the design features, any speaker is prone to the occurrence of so-called parasitic oscillations — oscillations that continue after the main impulse from the amplifier has ceased (similar to how a string continues to vibrate after a pluck). This phenomenon has a negative effect on sound quality, and manufacturers use various means to reduce it to an absolute minimum; suppression of parasitic oscillations is called damping.

The most effective type of damping is electrical, by reducing the output impedance of the amplifier. The lower this resistance, the better the amplifier keeps the speakers from unnecessary vibrations. To evaluate this effect, they introduced the concept of “damping factor” (damping factor) — the ratio of the load resistance (impedance) to the output resistance of the amplifier. The minimum value of such a coefficient for Hi-Fi class equipment is 20; indicators at the level of 100 – 120 can be called good, and among the Hi-End segment there are numbers of the order of several thousand.

At the same time, it is worth noting that when increasing to three-digit numbers, the original meaning of this parameter is, in fact, lost, and other points appear. The most important of them from a practical point of view is that models with a high damping factor are very demanding on the quality of the connection to t...he speakers — the high resistance of cables and connectors can negate the damping properties of the amplifier itself. There are other nuances associated with this indicator (in particular, recommendations for choosing an amplifier and speakers for each other); they are described in detail in specialized sources.

The sensitivity and dynamic impedance of the amplifier when a signal is applied to the balanced XLR input.

Under the sensitivity of any input (except optical) is meant the lowest signal voltage at this input, at which the amplifier is able to provide normal nominal power values (see "Power per channel (8Ω)"). This parameter determines, first of all, the requirements for the signal source. On the one hand, the voltage provided by this source must not be lower than the input sensitivity of the amplifier, otherwise the latter simply will not give the claimed characteristics. However, a significant excess in voltage should not be allowed, otherwise the sound will begin to be distorted. More detailed recommendations on choosing an amplifier by sensitivity are described in special sources.

For any input other than optical, it is believed that the higher this indicator, the less distortion the amplifier introduces into the signal. The minimum level of input impedance in modern models is considered to be 10 kOhm, and in high-end devices it can reach several hundred kOhm.

The sensitivity and dynamic impedance of the amplifier when a signal is applied to the RCA line input.

Under the sensitivity of any input (except optical) is meant the lowest signal voltage at this input, at which the amplifier is able to provide normal nominal power values (see "Power per channel (8Ω)"). This parameter determines, first of all, the requirements for the signal source. On the one hand, the voltage provided by this source must not be lower than the input sensitivity of the amplifier, otherwise the latter simply will not give the claimed characteristics. However, a significant excess in voltage should not be allowed, otherwise the sound will begin to be distorted. More detailed recommendations on choosing an amplifier by sensitivity are described in special sources.

For any input other than optical, it is believed that the higher this indicator, the less distortion the amplifier introduces into the signal. The minimum level of input impedance in modern models is considered to be 10 kOhm, and in high-end devices it can reach several hundred kOhm.

The sensitivity and dynamic impedance of the amplifier when a signal is applied to the Phono MM/MC input.

Under the sensitivity of any input (except optical) is meant the lowest signal voltage at this input, at which the amplifier is able to provide normal nominal power values (see "Power per channel (8Ω)"). This parameter determines, first of all, the requirements for the signal source. On the one hand, the voltage provided by this source must not be lower than the input sensitivity of the amplifier, otherwise the latter simply will not give the claimed characteristics. However, a significant excess in voltage should not be allowed, otherwise the sound will begin to be distorted. More detailed recommendations on choosing an amplifier by sensitivity are described in special sources.

For any input other than optical, it is believed that the higher this indicator, the less distortion the amplifier introduces into the signal. The minimum level of input impedance in modern models is considered to be 10 kOhm, and in high-end devices it can reach several hundred kOhm.

— Euroblock. Analogue audio input (usually line level) using a Euroblock connector. This connector, used mainly in professional audio equipment, is remarkable in that it is attached to the wire using terminals. This is extremely convenient when working with stripped wires (which is often required in professional applications): screwing such a wire to the plug once and connecting / disconnecting the plug to the Euroblock connector is much easier than constantly unscrewing / screwing the terminals. In addition, such a connection is often made balanced (see "XLR (balanced)" below). Inputs of this type are found mainly in information and information-concert amplifiers (see above).

— Phono. Dedicated input for connecting to the amplifier turntables; often has a suffix indicating the type of cartridge that is compatible, such as "Phono MM" or "Phono MM/MC" (see "Advanced — Phono Stage" for details). Despite the proliferation of digital formats, these players are still highly regarded by audiophiles for their high quality and fidelity, and are often used in premium audio systems. However, connecting a "turntable" has its own characteristics — in particular, it requires a phono stage (for more details, see ibid.) — and standard inputs are unsuitable for this purpose. Therefore, a Phono jack is a must if you want to connect your turntable directly, without an external phono stage.

— USB B. The USB interface is widely used in com...puter technology for various peripherals. The presence of a type B input means that the amplifier can be connected to a computer as an external controlled device (slave). Most often, with this connection, it is used as an external sound card or audio interface — this provides higher sound quality and more extensive options for its settings than most built-in sound cards, even expensive ones. However, the matter is not limited to this: in some models, via USB type B, you can update the firmware or change the special parameters of the amplifier.

— Coaxial S / P-DIF. Digital audio input, a variation of the S/P-DIF interface based on a conventional electrical signal (the second variation, optical, is described below). Usually uses a common RCA connector, known as a "tulip", but has rather strict cable requirements. The bandwidth of any version of S / P-DIF is quite sufficient even for high-quality multi-channel sound, and the coaxial version itself is simpler, cheaper and more reliable than the optical one, but more susceptible to interference.

— Optical. Input for transmitting digital sound using light signals, via TOSLINK fiber optic cable; one of the versions of the S/P-DIF standard. The main advantage of optical fiber over traditional electrical cables is complete insensitivity to electrical interference; at the same time, it is more expensive and requires rather careful handling (in particular, it does not tolerate sharp bends).

— Balanced digital ( AES/EBU). The AES/EBU interface is used in the professional field to transmit audio in digital format. It can use several connection types; in this case, it means transmission over the so-called balanced line using an XLR connector. Both the principle of balanced connection and the connector itself are described in detail in the “XLR (balanced)” section below — however, in the case of AES / EBU, we are talking about a digital signal, not an analogue signal.

— COM port ( RS-232). A connector used to control the amplifier from a computer. Through it, you can change the settings, incl. and quite thin, and in some models even update the firmware. Usually, for such purposes, special software is required, which can be supplied with the amplifier.

— Control input (IR). Connector for connecting an external infrared remote control receiver. When properly placed, such a receiver will allow you to use the remote control even in places where the signal from the remote control cannot reach the main (built-in) sensor — for example, in another room. For such purposes, not only sensors can be used as a separate device, but also system components that are compatible with the remote control — for example, players or tuners.

The number of line inputs in the amplifier design using the RCA interface. Unlike the Main input (see above), which can work with the same connectors, when connected to a linear RCA, the signal goes through all the stages of processing provided for in the amplifier — for example, adjusting the balance or frequencies (see "Adjustments"), etc. .P.

See “Amplifier Input (Main)” for details on the connector itself. Here we note that when using RCA as a linear interface, a pair of such connectors is considered one input. This is due to the fact that only one channel can be transmitted over one coaxial cable, so a pair is needed to work with stereo sound.

The number of signal inputs (of any type) determines how many signal sources can be simultaneously connected to the amplifier. 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 them through the amplifier’s remote control or control panel than to fiddle with reconnecting every time.

— Preamplifier (Pre-Amp). The presence in the design of the device of a separate output for the signal from the preamplifier. In the type of amplifiers of the same name (see "Type"), such an output is available by definition and is the main, and sometimes the only one. On integrated models (see ibid.) , the Pre-Amp output allows you to connect an external power amplifier and use it instead of the internal one. This feature can be useful, for example, to connect a more powerful speaker instead of the original one, or to work in Bi-amping mode. It is worth noting that the Pre-Amp output can also be installed in power amplifiers, playing the role of a "splitter".

— Subwoofer. The presence in the amplifier design of a separate subwoofer output. Usually, such an output uses an RCA connector (see "Input to the amplifier (Main)"), and the function itself is implemented through a crossover, which selects the low-frequency range in the signal and redirects it to a subwoofer. The "own" output makes it much easier to connect a subwoofer : it does not require any additional equipment, the amplifier itself is enough. This usually provides for the possibility of working with any type of subwoofer — both passive and active; however, in the first case, you will need an additional external amplifier.

— Coaxial S/P-DIF. The presence in the design of the amplifier of the S / P-DIF output of an electric typ...e, with signal transmission via a coaxial cable. For more information about this interface, see the relevant paragraph in the "Inputs" section.

— Optical. The presence in the design of the amplifier output for transmitting a digital audio signal over a fiber optic cable TOSLINK. For more information about this interface, see the relevant paragraph in the "Inputs" section.

— Jack (6.35 mm). Presence of TRS type outputs in the design of the amplifier. These outputs are jacks for 6.35 mm Jack plugs and may look like the corresponding headphone jack (see below). However, this similarity is misleading: TRS produce sound on the principle of "one channel per plug" (an exception may be information amplifiers). This type of Jack connector is found mainly in high-end professional amplifiers.

— Speakon. An interface used in professional audio equipment to connect acoustics to a power amplifier. It has become widespread in high power equipment, including concert amplifiers (see "Intended Use"), due to its increased reliability and suitability even for working with very powerful audio signals. But in household appliances it is rarely used.

— Control output (IR). The control output allows the amplifier's built-in IR receiver to be used to control other components in the audio system, such as a DVD player in another room, out of range of the remote control, from the remote control. With this scheme of operation, the amplifier actually plays the role of a remote sensor, receiving commands and transmitting them through the control output to another device. Note that the very presence of such inputs and outputs does not guarantee the compatibility of various devices, especially if they are produced by different manufacturers; Sharing details should be clarified in the official documentation.

— Bass adjustment. The presence in the amplifier of a separate low-frequency level control, in other words, bass volume. The ratio of low and high frequencies largely determines the overall picture of the sound; the optimal options for this ratio for different cases will be different, and they depend on a number of factors — from the type of audio being played to the personal tastes of the listener. Anyway, the bass control provides an additional opportunity to fine-tune the sound of the entire system. It is often combined with a treble control (see below); in fact, this combination is the simplest version of the equalizer.

— Treble adjustment. The presence in the amplifier of a separate volume control for high frequencies. The meaning of this function is completely similar to the bass control described above, only it works with a different frequency band.

— Balance adjustment. The presence in the amplifier of adjusting the balance between the channels. This setting is used in stereo sound: by changing the position of the knob, you can increase the volume for one channel and decrease it for another. Due to this, the conditional centre of the perceived sound shifts towards the speaker that sounds louder. This feature can be very useful for correcting the sound stage — for example, if the speakers have different sensitivity, badly placed, or the signal itse...lf is not properly balanced. At the same time, the balance controller introduces additional elements into the design, which increases the likelihood of interference. And therefore, in top-class amplifiers, it may not be provided at all.

— Adjustment of input sensitivity. Ability to change the input sensitivity of the amplifier; For details on this parameter, see "Input Sensitivity (Line Input)". Also note here that the adjustment itself can be useful when working with several sound sources: it allows you to easily reconfigure the amplifier for each of these sources in order to provide the desired output power level and at the same time avoid distortion.

— Level adjustment. The presence in the amplifier of its own level control, in other words, a system that allows you to change the volume of the sound (by changing the actual output power). In modern home amplifiers (see above), this adjustment is common to all channels, and it is responsible for the actual volume; sometimes using the control on the amplifier is more convenient than on another component of the audio system. But in concert models, each channel, usually, is equipped with its own regulator, thanks to which there are many opportunities for fine-tuning the sound to a specific situation.

— Loudness. This function allows you to adjust the tone of the sound at a low volume. Its necessity is connected with the fact that the human ear perceives a quiet sound differently than a loud one; because of this, even high-quality sound at low volume will seem “blurry”, not clear enough. Loudness corrects this by boosting certain frequencies. Usually this mode is enabled by the user at will.