Comparison NAD C658 vs Onkyo TX-8250

The range of audio frequencies that the audio receiver can handle. 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 specifically look for a receiver 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 audio receiver 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 both channels of the receiver work under load; when working on one channel, the rated power may be slightly higher, but this mode cannot be called standard.

Rated power can be simply described as the highest average output signal power at which the amplifier is able to operate stably for a long time (at least an hour) without negative consequences. These are average figures, because in fact, an audio signal is, by definition, unstable, and individual jumps in its level can significantly exceed the average value. However, the key parameter is still the nominal (average) power — it is on it that the overall sound volume directly depends.

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

According to the laws of electrodynamics, with different dynamic load resistance, the output power of the amplifier will also be different. In modern speakers, values of 8, 6, 4 and 2 ohms are standard; the latter option, however, is rare, therefore, in audio receivers, the power for it, usually, is not indicated at all. As for the specific values for 8 ohms, the indicator up to 50 W is considered relatively low, 50 – 100 W is average, and with more than 100 W we can talk about high power.

The nominal sound power output by the audio receiver per channel when a load with a dynamic resistance (impedance) of 6 ohms is connected to it. It is customary to specify this parameter when the receiver is operating in two-channel mode (stereo); when using only one channel, the power may be slightly higher, but this mode cannot be called standard.

Rated power is the highest average (rms) output signal power at which the receiver is able to work for a long time without failures or malfunctions. The average power is taken because the audio signal is, by definition, unstable, and individual jumps in its level can significantly exceed the average value. However, the key parameter is still the rated (average) power. It determines two points — the overall volume of the sound and compatibility with one or another passive acoustics. The higher the power of the receiver, the louder the sound it can provide; at the same time, this power should not exceed the rated power of the speakers — otherwise, overloads and even damage to the equipment are possible.

As for the resistance, according to the laws of electrodynamics, with a different load impedance, the output power of the amplifier will also be different. In modern speakers, values of 8, 6, 4 and 2 ohms are standard; the latter option, however, is rare, therefore, in audio receivers, the power for it, usually, is not indicated at all.

The nominal sound power output by the audio receiver per channel when a load with a dynamic resistance (impedance) of 4 ohms is connected to it. It is customary to specify this parameter when the receiver is operating in two-channel mode (stereo); when using only one channel, the power may be slightly higher, but this mode cannot be called standard.

Rated power is the highest average (rms) output signal power at which the receiver is able to work for a long time without failures or malfunctions. The average power is taken because the audio signal is, by definition, unstable, and individual jumps in its level can significantly exceed the average value. However, the key parameter is still the rated (average) power. It determines two points — the overall volume of the sound and compatibility with one or another passive acoustics. The higher the power of the receiver, the louder the sound it can provide; at the same time, this power should not exceed the rated power of the speakers — otherwise, overloads and even damage to the equipment are possible.

According to the laws of electrodynamics, with a different load impedance, the output power of the amplifier will also be different. In modern speakers, values of 8, 6, 4 and 2 ohms are standard; the latter option, however, is rare, therefore, in audio receivers, the power for it, usually, is not indicated at all. As for specific power indicators at a 4-ohm load, values up to 100 W...are considered relatively small for modern receivers, more than 100 W — respectively, high.

The lowest speaker impedance that the audio receiver can handle normally.

The nominal impedance of the speakers, also referred to as the term "impedance", is one of the key parameters in the selection of audio system components: for normal operation, it is necessary that the speaker impedance match the characteristics of the amplifier. If the speaker impedance is greater, the sound volume will decrease significantly, if it is less, distortion will appear in it, and in the worst case, even overloads and breakdowns are possible. Therefore, in the characteristics of receivers, it is usually the minimum resistance that is indicated — after all, connecting a load of too low impedance is fraught with more serious consequences than too high.

The signal-to-noise ratio when the audio receiver is connected to the Phono input. This input is for connecting turntables; see "Inputs" for more details. The value of this parameter is described in detail in the "Signal-to-noise ratio (RCA)" section.

The sampling rate of the digital-to-analogue audio signal converter provided in the design of the audio receiver.

A digital-to-analogue converter (DAC) is an indispensable element of any system designed to reproduce digital sound. The DAC is an electronic module that translates sound information into pulses that are sent to the speakers. The technical features of such a conversion are such that the higher the sampling rate, the better the signal at the output of the DAC, the less it is distorted during conversion. The most popular option in receivers today is 192 kHz — it corresponds to a very high sound quality (DVD-Audio) and at the same time avoids unnecessary increase in the cost of devices.

Audio file formats that the receiver is capable of working with. Among those, there may be lossy compressed (MP3, WMA, etc.), lossless compressed Lossless(FLAC, APE, etc.) and Uncompressed uncompressed formats (DSD, DXD, etc.).

In general, compression is used to reduce the volume of audio files. Lossy compression (the most common option) cuts off some of the audio frequencies (mainly those that are poorly perceived by the ear), making such files take up the least amount of space. Lossless compression preserves all original frequencies; this format is preferred by many lovers of high-quality sound, however, such files take up a lot of space, and the difference between normal compression and lossless compression becomes clearly noticeable only on high-quality equipment. Uncompressed formats, in turn, are intended primarily for professional audio work; their full reproduction requires Hi-End audio equipment, and the volumes of such materials are very large. However, these standards are quite popular among sophisticated audiophiles.

Separately, it is worth touching on the uncompressed DSD format. This standard and its direct derivatives DSF and DFF use coding using the so-called pulse density modulation. It is considered more advanced than traditional pulse-frequency modulation, and allows you to achieve more accurate sound, a higher signal-to-noise ratio...and less interference with a relatively simple element base.

A set of streaming services supported by the receiver.

Streaming (streaming) services are designed to broadcast content (in this case, mainly music) over the Internet. With such a broadcast, audio files are not saved on the receiver, but are played directly from the corresponding resource on the Internet; Nowadays, there are many such resources, varying in the range of music and access conditions. In any case, the main advantages of online streaming include a wide selection of content and almost instant access to the desired composition; Some services can also work like a radio, automatically selecting music according to the producer's preferences. Key resources include Spotify, TIDAL, Qobuz, Amazon Music.