Comparison Arcam FMJ A29 vs Arcam FMJ A39

The nominal sound power output by the amplifier 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 all channels of the amplifier work under load (see "Number of channels"); in the presence of unused channels, the rated power may be slightly higher, but this mode cannot be called standard.

Rated power can be simply described as the highest output signal power at which the amplifier is able to work stably for a long time (at least an hour) without negative consequences. These are average figures, because in fact, the audio signal is by definition unstable, and individual level jumps can significantly exceed the rated power. However, it is she who is the main basis for assessing the overall loudness of the sound.

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

According to the laws of electrodynamics, with different dynamic load resistance, the output power of the amplifier will also be different. In modern speakers, the standard values \u200b\u200bare 8, 6, 4 and 2 Ohms, and power levels are indicated for them.

The nominal sound power output by the amplifier per channel when a load with a dynamic resistance (impedance) of 4 ohms is connected to it. See Power per Channel (8Ω) for more information on power rating and its relationship to impedance.

This indicator describes the amount of non-linear distortion introduced by the amplifier into the processed signal. Such distortions are not necessarily perceived as extraneous noise, but they degrade the quality of the sound anyway — for example, they can make it more deaf. It is almost impossible to avoid them, but it can be reduced to levels inaudible to the human ear.

As a result, the harmonic distortion factor (harmonics) is one of the main parameters describing the overall sound quality in Hi-Fi and Hi-End amplifiers. The lower it is, the clearer the sound. Hundredths of a percent are considered a good indicator for modern amplifiers, thousandths and below are excellent. The exceptions are tube and hybrid models, for which rather high harmonic coefficients are allowed; see "Element base" for more details.

Signal level and dynamic impedance provided by the device at the preamplifier output (see "Outputs" for details).

The signal level must not be lower than the sensitivity of the power amplifier (see "Type") to which the signal is received — otherwise the power amplifier will not be able to provide a normal signal level already at its outputs.

Dynamic resistance (impedance) of the preamplifier output. This value is exactly the same as the input impedance of the REC output — see the relevant paragraph above. For more information about the exit itself, see "Exits".

The number of outputs in the design of the amplifier, designed for direct connection of speakers. One such output is usually a pair of screw terminals designed to connect one speaker. Accordingly, the standard set for sound in stereo mode is two outputs (two pairs). However, in multi-channel devices (see “Number of channels”), as well as in models with the ability to connect additional speakers and/or Bi-Wiring (see “Additionally”), more speaker outputs are installed — in accordance with the capabilities of the amplifier.

— Direct connection ( By-pass/Direct). The ability to turn on the amplifier in By-pass / Direct mode. Its name is due to the fact that the signal is sent directly to the amplification stages, bypassing all additional controls (timbre, balance, etc.). Power amplifiers (see "Type"), by definition, use just such a scheme of operation. In integrated models, direct connection not only minimizes distortion in the processed signal, but also provides the sound closest to the original, which allows demanding listeners to appreciate the skill of sound engineers.

— Automatic power off. This function ensures that the amplifier automatically turns off if no signal is received from its input for a certain period of time. In this way, downtime is avoided — for example, if the owner left on business, forgetting to turn off the audio system. And considering that many modern amplifiers require a lot of energy even “at idle”, the savings can be quite significant. It is worth clarifying that in this case we are usually not talking about a complete shutdown, but about switching to standby mode; but the power consumption (see below) in this mode is usually so small that in fact the difference is practically not noticeable.

— MM phono stage. The presence of a phono stage in the amplifier for working with turntables equipped with MM type pickups (with a moving magnet). The phono stage itself is a mandatory attr...ibute of models with a Phono input (see "Inputs"); its necessity is due to the fact that the signal from the pickups for vinyl has specific characteristics and needs additional processing. At the same time, two types of pickups can be used in modern record players — the already mentioned MM plus MC (with a moving coil), each with its own signal characteristics. Therefore, for the normal operation of the turntable, you will anyway need a phono stage of the appropriate type. Such equipment is also available as separate devices, but it is usually easier and cheaper to buy an amplifier with a built-in phono stage.

— MS phono stage. The presence of a phono stage in the amplifier to work with turntables equipped with MC type pickups (moving coil). For more information about this function, see the subsection “MM Phono Stage” above.

— Limiter. The presence of a limiter in the amplifier — a device that limits the dynamic range of the processed signal. This device is also called an "audio signal compressor" (due to the fact that it "compresses" the dynamic range). In simpler terms, a limiter essentially reduces the difference between the quietest and loudest sound output from an amplifier. This feature can be useful in any situation where you have to deal with uneven sound volume. For example, a limiter can make it more comfortable to listen to a symphony that has large volume differences — so that the listener can access the slightest nuances of sound and at the same time, loud fragments, as they say, do not beat on the ears. And for professional concert activity, the presence of a compressor is almost mandatory — in particular, to compensate for changes in volume that occur when the distance from the microphone to the acoustic instrument or the vocalist's mouth changes. Of course, the limiter can also be made as a separate device; however, its presence in the amplifier itself is sometimes more convenient. At the same time, this function is complex and expensive, and therefore is found mainly in professional equipment and top-class consumer models.

— Connecting an additional speaker. The ability to connect an additional set of speakers (one or more) to the amplifier. Note that we are not talking about individual speakers, but about sets designed to work with full-length sound. In other words, if such an amplifier produces sound in stereo format at the main outputs (see "Number of channels"), then an additional set of acoustics will be able to work in this format. Models with this function are designed primarily for situations where you need to output sound to several rooms, and the signal can go either to all sets at once, or only to one at the user's choice. Also, an additional set of connectors can be used for Bi-Wiring (see below).

— Biwiring. Amplifiers with this feature use two separate channels of amplification for bass and treble, and are able to output each frequency band through a separate set of connectors. Due to this, it is possible to apply low-frequency and high-frequency signals via separate wires, and directly to the corresponding specialized speakers of the speaker system — instead of outputting a common signal to it and dividing it into frequencies using the built-in speaker crossover. In fact, this means that the Bi-Wiring connection reduces the likelihood of interference and improves the sound quality. However, keep in mind that this will require not only an amplifier, but also speakers that support this function. Note that Bi-Wiring is usually combined with the ability to connect an additional speaker described above.

— Management of external devices. The ability to use the amplifier as a control device for other components of the audio system — for example, preamplifier, turntable, etc. Control is usually carried out from the universal remote control supplied with the amplifier, and the control signal is transmitted through special connectors — this is much more convenient than adjusting each component separately. On the other hand, the construction of such systems is possible only from devices of the same manufacturer — different companies use different control standards, in most cases they are not compatible with each other.

— Bluetooth. A wireless communication technology with a range of about 10 m (more "long-range" versions are not used in amplifiers), originally created for direct connection between various devices. The functionality of such a connection may be different, but in this case, most often it is possible to broadcast to the sound amplifier from an external device — for example, a smartphone or laptop. However, other functions may be provided, for example, remote control from a mobile gadget through a special application.

— Emergency notification. The ability of the amplifier to work in an emergency warning system, more precisely, the availability of special functions and tools for working in such systems. Such tools may include, for example, connecting to fire detectors and automatically triggering warnings or evacuation messages to areas where the detectors have been triggered; selection of message type depending on the triggered sensor; connecting the notification microphone to the “priority input” and muting all other channels when sound is received from the microphone, etc. A specific set of features should be specified separately. Specialized security units may also be responsible for these functions, but sometimes it is more convenient to use an amplifier with built-in support for emergency notification.

The power consumed by the amplifier during normal operation. Some manufacturers may indicate average power values, some — indicators at maximum load. However, anyway, this parameter allows you to quite adequately assess the power consumption of the device and the requirements for connected power.

In addition, it can be useful if you have doubts about the accuracy of the claimed data on the output power (see "Power per channel (8Ω)"). The basic rule is that the total power rating of all channels cannot exceed the total power consumption of the amplifier. In addition, there are special formulas that allow you to derive the maximum possible rated power depending on the power supply and type of amplifier; they can be found in special sources.