Hi-Fi in the digital age. Part 2
Previous part: “Hi-Fi in the digital age. Part 1 , ”was devoted to digital audio sources and conversion (D / A, Digital-Analog Conversion) of a digital stream into an analog audio signal.
Further, this signal must be strengthened before you bring to the speakers. This article focuses on stereo amplifiers.
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Stereoamplifiers, devices in which there is an amplification of an analog audio signal from a source to the value required for the speaker systems. Basically, most amplifiers are analog devices and do not contain a DAC.
There are three types of amplifiers: integral, pre-amps and power amplifiers.
An amplifier is generally a series of amplification stages.
Conventionally, its block diagram of the amplifier is divided into three parts:
All these three parts perform one task - to increase the output signal power to such a level that it is possible to unload the load with a low impedance — the speaker system or headphones. How do they do it? It is very simple - a DC power supply is taken and converted to AC, but so that the output waveform follows the input waveform.
All this is physically "wrapped" in:
Various ways to build end stages, which are also called classes (or modes of operation) of amplifiers. They probably heard - Class A amplifier, Class AB amplifier, Class D amplifier - this is what they are.
Class “A” is linear, amplification occurs on the linear portion of the current-voltage characteristic (current-voltage characteristic), without transient distortion, but low efficiency (10–20%), i.e. This class is uneconomical in terms of energy consumption and heating. Class A mode is characterized by the best gain linearity, however, it is the worst in terms of energy efficiency. What good is class A? First of all, excellent linearity and the absence of distortion - the waveform at the output remains the same as it was at the input. For this you have to pay a deadly power consumption and extremely low efficiency of the amplifier. They look at the same time simply frightening and warm like a stove.
Class “AB” is a compromise between signal quality and power parameters: due to the initial bias, transient distortions of the signal are reduced (“docking” closer to the ideal), but the economy is lost and there is a danger of through current, because the transistor (lamp) of the opposite shoulder is completely not closing But class AB is a compromise solution and suits everyone in terms of price / quality ratio.
Class “D” is a special class based on PWM (pulse width modulators). Their main feature is the use instead of amplification of pulse width modulation (PWM, it is also PWM - pulse width modulation). Unlike analog amplifiers, where the output signal is an “enlarged” copy of the input, the output signal of the class D amplifiers is rectangular pulses. Their amplitude is constant, and the duration (“width”) varies depending on the amplitude of the analog signal at the input of the amplifier. After the formation of pulses amplified terminal transistors operating in the key mode. The conversion of a pulse signal to an analog occurs in a low-pass filter at the output of the amplifier or directly in the load (in acoustic systems).
Advantages - very high efficiency, disadvantages - HF impulse noise, which must be suppressed. Depending on the load resistance, the efficiency of amplifiers of this type can reach 90% -95%. Of course, with such efficiency, the heating of the output transistors is practically absent, which allows you to create a hell of a small and economical amplifiers. But (IMHO) unfortunately they are not particularly friendly with music and musicality.
Although the preamplifier and power amplifier are combined in an integrated stereo amplifier, they are usually located on separate boards and sometimes in separate compartments of the case inside the case.
Pre-amplifier - contains all the controls and switching sources: inputs for connecting the CD, tuner, and others; input selector, allowing you to select the source from which the signal will go; volume control; timbre.
Power Amplifier - contains amplification stages on either discrete elements or microchips. In contrast to the preamplifier - fully consistent with its name - it enhances power.
Great importance is paid to the "purity" of the current from the power supply, with a powerful toroidal transformer and filter capacitors of giant tanks.
Quite rarely, the integrated stereo amplifier has a built-in DAC for “receiving” digital streams from the SPDIF input (coaxial RCA or optical Toslink).
I think not, because in 99.99% of the cases these are class D amplifiers (I can hardly imagine the dimensions of the receiver in which 5 + 1 or 9 + 2 amplifiers of class A or even AB will be built in, that's because the “stove” will be the size of a cabinet). As well as most of them are cheap and low cost DACs.
Here is an example: The Cambridge Audio Azur 650R AV receiver, priced at 50-60 tr, contains the Cirrus Logic CS49700 single-chip multichannel (shipped serially at a wholesale price of $ 7.50 per piece), we read the datasheet and find out that this crystal has a built-in budget Cirrus Logic stereo DAC - CS4344, which according to the manufacturer's classification is lower class than the CS4392 which is used in the cheapest external Creative Professional E-MU 0202 DAC USB DAC. Not to mention the fact that there are compact compromise amplifiers of class D.
IMHO AV-receivers are for movies and not demanding listeners.
At this point in time (the end of 2010), the Marantz CD6003 CD player and the Marantz PM6003 integrated stereo amplifier are considered the best in the budget class (“King of the budget sector”).
Review of “What Hi-Fi?” 5 out of 5 points - link
“Coherence across the entire frequency range, full-blooded and smooth midrange and multi-layered sound stage”
“It is impossible to resist: the sound is amazingly detailed, incredibly large-scale and convincing, and dynamic control is accompanied by complete control”
“Turn on“ source direct ”- timbreblock, loudness and balance bypassing mode - and you get a device of rare reasoning, which you can use in the teeth: from fresh, not overloaded with the processing of the same Wilco album to crazy Eminem Relapse.”
As well as the title of “The Best Stereo Amplifier of 2009” from the British award “What Hi-Fi Sound and Vision” AWARDS 2009 of the “Hi-Fi World” magazine.
The cost of PM6003 in Russia is 21 tr. - link
That's probably all, articles 3 and 4 will be about acoustics, listening room and using a PC as a hi-fi source.
Further, this signal must be strengthened before you bring to the speakers. This article focuses on stereo amplifiers.
')
0. Why is this necessary?
Stereoamplifiers, devices in which there is an amplification of an analog audio signal from a source to the value required for the speaker systems. Basically, most amplifiers are analog devices and do not contain a DAC.
1. Types of stereo amplifiers:
There are three types of amplifiers: integral, pre-amps and power amplifiers.
1.1 Integral stereo amplifier
- the device in one case of which there are a pre-amplifier and a power amplifier.1.2 Preamplifier
- a device in which the switching of inputs, volume control, balance, and in some cases, pre-amplification of the signal. A preamplifier cannot function independently, only in conjunction with a power amplifier.1.3 Power Amplifier
- A device to amplify the audio signal to the level required by the acoustic systems. It has only one input and does not have a volume control and therefore can only work together with a pre-amplifier.2. How is the signal gain?
An amplifier is generally a series of amplification stages.
Conventionally, its block diagram of the amplifier is divided into three parts:
- Input cascade
- Intermediate cascade
- Output stage
All these three parts perform one task - to increase the output signal power to such a level that it is possible to unload the load with a low impedance — the speaker system or headphones. How do they do it? It is very simple - a DC power supply is taken and converted to AC, but so that the output waveform follows the input waveform.
All this is physically "wrapped" in:
- discrete amplifying element for one channel
- to a large chip (a complete amplifier for both stereo channels) which contains, among other things, a preamp block, timbre, balance controls, etc. stuffing
3. What are amplifier classes?
Various ways to build end stages, which are also called classes (or modes of operation) of amplifiers. They probably heard - Class A amplifier, Class AB amplifier, Class D amplifier - this is what they are.
3.1 Class A Mode
Class “A” is linear, amplification occurs on the linear portion of the current-voltage characteristic (current-voltage characteristic), without transient distortion, but low efficiency (10–20%), i.e. This class is uneconomical in terms of energy consumption and heating. Class A mode is characterized by the best gain linearity, however, it is the worst in terms of energy efficiency. What good is class A? First of all, excellent linearity and the absence of distortion - the waveform at the output remains the same as it was at the input. For this you have to pay a deadly power consumption and extremely low efficiency of the amplifier. They look at the same time simply frightening and warm like a stove.
3.2 Class AB Mode
Class “AB” is a compromise between signal quality and power parameters: due to the initial bias, transient distortions of the signal are reduced (“docking” closer to the ideal), but the economy is lost and there is a danger of through current, because the transistor (lamp) of the opposite shoulder is completely not closing But class AB is a compromise solution and suits everyone in terms of price / quality ratio.
3.3 Class D Mode
Class “D” is a special class based on PWM (pulse width modulators). Their main feature is the use instead of amplification of pulse width modulation (PWM, it is also PWM - pulse width modulation). Unlike analog amplifiers, where the output signal is an “enlarged” copy of the input, the output signal of the class D amplifiers is rectangular pulses. Their amplitude is constant, and the duration (“width”) varies depending on the amplitude of the analog signal at the input of the amplifier. After the formation of pulses amplified terminal transistors operating in the key mode. The conversion of a pulse signal to an analog occurs in a low-pass filter at the output of the amplifier or directly in the load (in acoustic systems).
Advantages - very high efficiency, disadvantages - HF impulse noise, which must be suppressed. Depending on the load resistance, the efficiency of amplifiers of this type can reach 90% -95%. Of course, with such efficiency, the heating of the output transistors is practically absent, which allows you to create a hell of a small and economical amplifiers. But (IMHO) unfortunately they are not particularly friendly with music and musicality.
4. What are the integrated stereo amplifiers?
Although the preamplifier and power amplifier are combined in an integrated stereo amplifier, they are usually located on separate boards and sometimes in separate compartments of the case inside the case.
Pre-amplifier - contains all the controls and switching sources: inputs for connecting the CD, tuner, and others; input selector, allowing you to select the source from which the signal will go; volume control; timbre.
Power Amplifier - contains amplification stages on either discrete elements or microchips. In contrast to the preamplifier - fully consistent with its name - it enhances power.
Great importance is paid to the "purity" of the current from the power supply, with a powerful toroidal transformer and filter capacitors of giant tanks.
Quite rarely, the integrated stereo amplifier has a built-in DAC for “receiving” digital streams from the SPDIF input (coaxial RCA or optical Toslink).
5. Are AV receivers suitable for listening to stereo music?
I think not, because in 99.99% of the cases these are class D amplifiers (I can hardly imagine the dimensions of the receiver in which 5 + 1 or 9 + 2 amplifiers of class A or even AB will be built in, that's because the “stove” will be the size of a cabinet). As well as most of them are cheap and low cost DACs.
Here is an example: The Cambridge Audio Azur 650R AV receiver, priced at 50-60 tr, contains the Cirrus Logic CS49700 single-chip multichannel (shipped serially at a wholesale price of $ 7.50 per piece), we read the datasheet and find out that this crystal has a built-in budget Cirrus Logic stereo DAC - CS4344, which according to the manufacturer's classification is lower class than the CS4392 which is used in the cheapest external Creative Professional E-MU 0202 DAC USB DAC. Not to mention the fact that there are compact compromise amplifiers of class D.
IMHO AV-receivers are for movies and not demanding listeners.
6. What to choose from "integral" in the budget class Hi-Fi?
At this point in time (the end of 2010), the Marantz CD6003 CD player and the Marantz PM6003 integrated stereo amplifier are considered the best in the budget class (“King of the budget sector”).
Review of “What Hi-Fi?” 5 out of 5 points - link
“Coherence across the entire frequency range, full-blooded and smooth midrange and multi-layered sound stage”
“It is impossible to resist: the sound is amazingly detailed, incredibly large-scale and convincing, and dynamic control is accompanied by complete control”
“Turn on“ source direct ”- timbreblock, loudness and balance bypassing mode - and you get a device of rare reasoning, which you can use in the teeth: from fresh, not overloaded with the processing of the same Wilco album to crazy Eminem Relapse.”
As well as the title of “The Best Stereo Amplifier of 2009” from the British award “What Hi-Fi Sound and Vision” AWARDS 2009 of the “Hi-Fi World” magazine.
The cost of PM6003 in Russia is 21 tr. - link
That's probably all, articles 3 and 4 will be about acoustics, listening room and using a PC as a hi-fi source.
Source: https://habr.com/ru/post/109969/
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