Comparison Knowledge Zenith AM02 vs Ugreen AV161

The nominal impedance (impedance) of the headphones for which the amplifier was originally designed.

Modern headphones can have different impedance. In particular, among the most popular options are 16 ohms and 32 ohms, and advanced models have values from 300 ohms and even from 600 ohms. High-resistance is considered to be "ears" with a resistance of 100 ohms. These characteristics improve the purity of the sound, but require increased signal strength — and built-in amplifiers in handheld devices, computer audio cards, etc. usually have difficulty with this. Therefore, external amplifiers are often used for this very purpose — to effectively "shake" high-end headphones with high impedance. For the same reason, some of these amplifiers are not compatible with low-impedance “ears”: there are many devices that require headphones with an impedance of at least 32 ohms, or even higher, and in some models the lower limit of the operating range can reach 100 ohms. As for the maximum resistance, the range of its values is very impressive — from 32 ohms in relatively simple portable "amps" to thousands and even tens of thousands of ohms in high-end stationary models.

Anyway, you should not violate the manufacturer's recommendations for headphone impedance. If the resistance of the “ears” is too low, at best, the sound will be s...ubject to noticeable distortion, at worst, equipment failure and even fire may occur. Too high resistance, in turn, not only reduces the volume, but also worsens the frequency response.

Rated power delivered by the amplifier when connected to headphones (or other load) with an impedance of 32 ohms.

By itself, the rated power is the highest average power that the device is capable of delivering for a long time without overloading; individual "jumps" of the signal may have a higher level, but in general, the capabilities of the amplifier are determined primarily by this indicator. At the same time, the physical features of the audio equipment are such that the actual power delivered to the load will depend on the resistance of this load. Therefore, in the characteristics of headphone amplifiers, data is often given for different impedance values. A resistance of 32 ohms allows you to achieve quite good sound quality by the standards of low-impedance headphones, while it is not so high as to create problems for the built-in amplifiers of smartphones and other compact equipment. Therefore, most wired general-purpose (non-professional) headphones are made precisely in this resistance, and if the amplifier characteristics generally indicate power for a certain impedance, then most often it is for 32 ohms.

In the most modest modern amplifiers, the output power at this impedance is between 10 and 250 mW ; values of 250 – 500 mW can be called average, 500 – 100 mW are above average, and the most powerful models are capable of delivering more than 1000 watts.... The choice for specific power indicators depends on the sensitivity of the headphones used, as well as on the sound pressure level (in other words, loudness), which is planned to be achieved by the amplifier. There are special formulas and tables that allow you to calculate the minimum required power for a certain volume at a given sensitivity of the "ears". However, in the case of 32-ohm headphones, it does not always make sense to "get into the calculations." For example, the mentioned 10 mW is more than enough to drive headphones with a modest sensitivity of 96 dB to a volume of more than 105 dB — this is already enough to listen to music at quite a decent volume. And in order to achieve the same "ears" level of 120 dB, which provides a full perception of the loudest sounds (like explosions, thunder, etc.), you need to give out a power slightly higher than 251 mW. So in fact, you have to pay attention to this characteristic and resort to calculations / tables mainly in those cases when you have to use 32 Ohm headphones with a relatively low sensitivity — 95 dB or less.

The ratio between the overall level of the desired signal produced by the amplifier and the level of background noise resulting from the operation of electronic components.

It is impossible to completely avoid background noise, but it is possible to reduce it to the lowest possible level. The higher the signal-to-noise ratio, the clearer the sound produced by the device, the less noticeable its own interference from the amplifier. In the most modest amplifiers from this point of view, this indicator ranges from 70 to 95 dB — not an outstanding, but quite acceptable value even for Hi-Fi equipment. You can often find higher numbers — 95 – 100 dB, 100 – 110 dB and even more than 110 dB. This characteristic is of particular importance when the amplifier operates as a component of a multi-component audio system (for example, "vinyl player — phono stage — preamplifier — headphone amplifier." The fact is that in such systems the final noise of all components at the output is summed up, and for sound purity it is extremely it is desirable that these noises be minimal

Separately, it is worth emphasizing that a high signal-to-noise ratio in itself does not guarantee high sound quality in general.

The dynamic range provided by the amplifier.

The most simplified dynamic range can be described as follows: this is the range between the highest and lowest signal level at the output, within which normal audibility and the signal-to-noise ratio claimed in the characteristics (see above) are maintained. This parameter is calculated from the logarithmic ratio between the maximum and minimum signal level and is indicated in decibels; the larger the number, the wider the dynamic range.

Note that the overall range of any amplifier is wider than the dynamic range; however, if the output level is too low, the audible sound will be "clogged" by the device's own noise, and if the output level is too high, the level of distortion will increase markedly. Thus, the overall sound quality is usually determined precisely by the dynamic range; in particular, this indicator determines how effectively the amplifier is able to cope with sound that has significant differences in volume (for example, orchestral parts). As for specific numbers, the most modest values in modern headphone amplifiers are about 90 dB, in the most advanced models this figure can reach 130 dB or more.

The type of power used by the amplifier.

In modern models, you can find mains power, battery and USB port. At the same time, some devices may provide two options at once (or even all three at once) — this allows you to choose the most convenient way of feeding, depending on the situation. In addition, there are amplifiers with support for Power Bank mode — this feature is also indicated in this paragraph, although it is not a type of power supply, but an additional function of models with a built-in battery.

Here is a more detailed description of each option:

— From the network. Powered from a conventional 230 V socket. Such power is very convenient from a practical point of view: the operating time of the amplifier is unlimited (as long as there is voltage in the network), and the output power can be almost any. The main disadvantage of this option is the actual dependence on sockets; however, for stationary models (see "Type") this point is not critical, so most of these devices use mains power (and most often — as the only option). There are also portable amplifiers with the ability to connect to the network — in such cases it is provided as an additional option that allows you to save battery power if there are outlets nearby (and most often also charge the battery during such use).

— From t...he battery. Powered by its own built-in battery. Such a power supply complicates the design of the amplifier, increases its weight and cost, and the operating time on a charge is inevitably limited. On the other hand, the battery allows you to work regardless of the presence of outlets nearby. Therefore, this option is extremely popular among portable amplifiers (see "Type") — especially since it is easier to achieve high output power with a battery than with USB power (which is also suitable for such equipment). But stationary solutions with their own batteries are extremely rare — and in them, usually, the battery is a “fallback option” in addition to another type of power supply (and in some stationary amplifiers, the presence of a battery also depends on the modification).

— From the USB port. Powered by a USB connector — usually the same one that is used as a source of digital audio signal. The features of such a power supply no longer depend so much on the specific amplifier, but on the device with which it is used. So, when used with a PC, such a connection is in many ways similar to connecting to a network: the operating time is unlimited, and the power of the amplifier can be quite high (although not as high as when using an outlet), but there is no talk of freedom of movement. Smartphones and other mobile gadgets, on the contrary, are autonomous, but their power outputs are not very powerful. On the other hand, it is most often not required for them, and the unequivocal disadvantage can only be called the moment that the amplifier additionally consumes the battery of the gadget. Connecting to a laptop combines the features of both options described above: the power supply is comparable to the USB ports of stationary PCs, while the laptop can work without an outlet.

— Power bank function. The ability to operate the amplifier in power bank mode — that is, an external battery for charging various gadgets, such as smartphones or pocket players. This function by definition means that the amplifier has a built-in battery (see above); the device itself is most often portable (see "Type"), however, there are also stationary solutions with Power Bank mode. Note that the specific battery capacity in amplifiers with this function is different; often it is very low, and the device allows you to “prolong the life” of the gadget rather than fully charge it. However, even this possibility can be very useful — for example, if you need to wait for an important call, but you forgot to charge your smartphone, and there is no charger or outlet for it at hand.

The presence of a metal case in the design of the amplifier.

This feature has both aesthetic and quite practical significance. In other words, it not only gives the case a stylish and solid appearance, but also has a positive effect on its strength and reliability. And since aluminium alloy is most often used as a metal, the weight of the structure is also small. The main disadvantage of this material is the higher cost than another popular option — plastic; however, against the background of the overall price of the device, the difference in the price of materials is often insignificant. So in most modern headphone amplifiers, the cases are made of metal.