Comparison Atoll PR400 vs Atoll PR300

The total capacitance of the capacitors installed in the power supply of the amplifier. Usually, for ordinary lovers of high-quality sound, this indicator is not practically significant: the capacitance is selected in such a way as to optimally (or at least minimally) match the characteristics of the amplifier. However, for demanding audiophiles who pay attention to the smallest details of audio system components, capacitors are also often of interest.

The fact is that they are an important part of the rectifier circuit — they smooth out current fluctuations that arise both due to the imperfection of the rectifiers themselves and due to various external factors. Knowing the total capacitance of the capacitors, one can also evaluate the efficiency of their work: the higher this indicator, the more stable the power supply will work and the lower the likelihood of sound distortion due to its fault. There are special formulas that allow you to derive the optimal capacitance of capacitors depending on the type, power and other parameters of the amplifier; they can be found in specialized sources.

— 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 stereo inputs in the design of the amplifier with XLR connectors having three pins and capable of providing the so-called balanced connection. Note that we are talking about an analogue line input, the signal from which passes through all additional processing circuits (for example, bass / treble settings, see "Adjustments"); do not confuse it with Main and balanced digital AES / EBU — these are different interfaces, despite the identity of the connectors.

The main advantage of this connection is that the functions of noise reduction and shielding from interference are performed by the cable itself. This moment is especially useful when it is necessary to connect system components located at a large distance from each other (from 2 m): a balanced cable maintains signal purity even at a rather large length. The quality of such a connection is at least indicated by the fact that balanced XLR is a standard interface for professional recording studios. And its presence in the amplifier, usually, indicates a high level of the device.

There are usually two XLR inputs in amplifiers — this is the minimum number needed to work with stereo sound, and more is most often not required in fact.

The number of outputs in the design of the amplifier with XLR connectors and the possibility of balanced connection. For details on this audio transmission format, see "XLR (balanced)" above.

— 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.

The material from which the base of the amplifier is made is the internal frame on which boards, a transformer and other circuit components are mounted. Theoretically, this moment can affect the sound quality, because. different materials have different magnetic properties, differ in the degree of shielding of the hardware from interference, etc. However, in modern factory-assembled amplifiers, the sound characteristics depend on a huge number of other factors, much more significant, and against their background the influence of chassis materials is completely lost. Therefore, in fact, only the weight and cost of the device depend on this parameter, and even then only slightly.

The following variants can be used in modern devices:

— Aluminium. This material combines good strength and low weight, durable, but quite expensive.

— Steel. Steel is very reliable, while being easy to process and inexpensive. Its main disadvantage can be called a lot of weight.

— Copper. Due to a number of physical properties, copper is considered a well-suited material for high-end electronics. On the other hand, it is quite heavy and expensive to manufacture.

— Dural. An alloy based on aluminium and copper, which is a cross between these two materials: it weighs significantly less and costs less than copper, while at the same time, the characteristics of duralumin are considered more advanced than those of pure aluminium.