Comparison Parasound Halo A23 vs Parasound 2125

— Preamplifier. Preamplifiers are designed to initially process a weak signal and bring it to a level sufficient for transmission via a linear interface to a power amplifier (see below). Such models are able to work directly with sound pickups, microphones and other similar devices, may have additional sound correction functions, play the role of switches for connected signal sources, etc., but are not suitable for outputting sound to passive speakers or headphones.

— Power amplifier. Such models are designed to take the signal processed by the preamplifier and output it to the power sufficient to operate the connected speaker system. They can already work with passive type speakers, but they cannot do without a preamplifier for the input signal. However, it is worth noting here that most modern players are equipped with built-in preamps and can be used directly with power amplifiers.

— Integrated amplifier. Amplifiers that combine the capabilities of both of the above types in one package. The main advantage of such models is obvious: instead of two specialized devices, you can buy one universal one. This saves money, time and installation space, and reduces the chance of interference as there are no external connecting cables between the preamplifier and main amplifier and the components are usually optimally matched to each other. On the other hand, th...e integrated model provides fewer options for choosing the option for your own preferences: you have to purchase the device "as is", without the ability to separately select a preamplifier and power amplifier.

— Amplifier-processor. Professional models, typically for live use, are rack mounted and often use Euroblock jacks as Main inputs (see below). In terms of general application, processors are similar to power amplifiers, however, in addition to these features, they are also characterized by an abundance of settings that facilitate the work of sound engineers.

— Subwoofer amplifier. Specialized power amplifiers designed for low-frequency speakers — subwoofers. The design of such models usually provides for crossovers with an upper limit of the transmitted range at the level of 150 – 200 Hz; this allows only “native” frequencies to be fed to the subwoofer and has a positive effect on sound quality. In addition, many amplifiers of this type have specific settings such as phase control.

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.

The range of audio frequencies that the amplifier is capable of handling. 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 look for an amplifier 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 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.

The nominal sound power output by the amplifier per channel when a load with a dynamic resistance (impedance) of 2 ohms is connected to it. See Power per Channel (8Ω) for more information on power rating and its relationship to impedance.

Signal-to-noise ratio when the amplifier is operating through the Main input. For more details on the value of the signal-to-noise ratio, see the relevant paragraph above, about the Main input — p. "Input to the amplifier (Main)".

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.

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.

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.