An amplifier is one of the main components in a car audio system. With its help you can make your speakers work much more productively. For everyone who is partial to high-quality sound, the selection of amplifiers should be taken very seriously. An equally important system that forms high quality sound- car amplifier for subwoofer. There are different types of these devices. You can also assemble the amplifier yourself. Let's find out how to choose a device so that it really pleases your ears.
Why do you need an amplifier when you have a radio?
In the majority car radios already has a built-in And for many drivers this system is completely suitable. Some people don’t change the standard sound in their car for years at all. But there are also those who like the music in the car to sound high-quality and loud. In this case, there is no way to do without an amplifier. A car subwoofer without an amplifier will not give the desired effect. Such equipment can improve the performance of acoustics regardless of the quality of the head unit.
A distinctive feature of an external amplifier is the absence of strict restrictions on settings. Your favorite music tracks will always sound good - at minimum volume levels and even at the maximum.
A car subwoofer amplifier included provides several serious benefits. With it you can increase not only the sound power, but also its quality.
Very often, car speakers are purchased after installation. If the selected speakers, as well as the subwoofer, are of high quality, then they will need more energy at peak performance. A standard radio cannot provide this. That's why they buy a separate car amplifier for the subwoofer. This solution gives good results.
Types of Acoustic Amplifiers
There are several types of this equipment. Thus, mono amplifiers, or monoblocks, are intended only for low-frequency sounds. Dual-channel solutions can also be distinguished. They are used in the absence of rear speakers, when only front speakers are available. Three-channel amplifiers allow you to connect a subwoofer. Well, the most expensive solutions are four-channel. These models allow you to amplify the sound of the entire acoustic system.
The subwoofer is the most difficult speaker to artificially amplify. Therefore, professionals recommend as car amplifier For a subwoofer, choose a monoblock. These types of devices can work with a wide variety of resistances. The design has a tone block for special settings and filters. The latter help loud bass sound at full power.
Multichannel devices are also capable of playing low frequencies, but they have difficulty handling low impedance. Amplifiers quickly overheat when the subwoofer is running at full power.
Differences between monoblocks and amplifiers
A monoblock is technically the same device as multi-channel devices. However, single-channel models have certain characteristics that their analogues do not have. What does it mean? The monoblock has only one channel and is designed to enhance low-frequency bass. The load for which these devices are designed most often has a resistance of 1 ohm. If this condition is met, high power can be obtained at the output. At the same time, the load on on-board network will be minimal. For resistances of 2 Ohms and 4 Ohms there is no point in purchasing a monoblock.
According to the classification of electric amplifiers, modern monoblocks have class “D”. They differ high power, but the sound quality is very low. Quality for a subwoofer is a secondary characteristic. There are also amplifiers of another class - “AB”. These are average level indicators. There are other classes as well.
How to choose an amplifier for a subwoofer in terms of power?
If, to enhance sound, everyone pays attention to sound quality, then in the case of subwoofers, the main characteristic is power. She can be two various types. This is the maximum possible (or PMPO) and nominal. The inscription "PMPO mono" can be seen on the body. This parameter indicates the total power for all channels inclusive. You should not rely on PMPO - the numbers only serve to ensure that devices are purchased better. In practice, this figure does not matter. Another type of power is nominal. It is recorded in the technical passport. Reviews say that this characteristic should be used as a guide when choosing. This parameter should be indicated at a THD of less than 0.1 percent and a voltage of 14.4 volts.
Some people believe that you need to choose a device so that the amplifier power is less. This is a misconception - weak devices will lead to coil failure. You need to select an amplifier whose power matches the subwoofer. But there is a small catch here - the rated power is calculated at a voltage of 14.4 volts. This voltage will never be maintained at the amplifier output. This may cause the coil to overheat. Reviews say that the right amplifier is the one whose power is higher than that of the subwoofer. This is the best option. The only risk is mechanical damage to the coil.
Other characteristics
Reviews say that, in addition to power, it is worth paying attention to frequency range. The parsing shouldn't be too big. Serious manufacturers make values from 15 to 350 hertz. The amplifier class can be “AB” or “D”. The first are analog amplifiers with good sound, but low efficiency and low power. The second ones are powerful, with high performance. But judging by the reviews, such devices have low quality sound.
Another criterion is the number of channels. Monoblocks are very expensive and rare. They can only be seen in professional audio systems. The class of such monoblocks is “D”. Two-channel models are suitable for a subwoofer designed for a resistance of 4-8 ohms. The connection diagram for a car amplifier and subwoofer in this case is of the “Bridge” type.
Three-channel models are not available. They have been completely replaced by four-channel analogues.
Making a car amplifier with your own hands
To build the system, you will need an output power amplifier, as well as a voltage converter. You can make them yourself, but it takes a very long time. You can simply purchase ready-made items in the store. Then you can proceed directly to making an amplifier for a car subwoofer with your own hands.
The device requires two channels, and the amplifier is single-channel. How is this fixed? This is corrected by connecting two radio channels using an adder. Then sound signal will be filtered - frequencies that fall outside the range from 16 to 300 hertz will disappear from it. The signal then goes to the filter. The latter removes frequencies from 35 to 150 Hz.
When the engine is idling, according to the car amplifier circuit for the subwoofer, it is supposed to consume 1.5 amperes. To prevent the battery from being discharged, install a relay with a separate REM terminal and a voltage of 12 volts, as well as a current above 20 amperes. This REM connects to the +12 volt output of the radio. The subwoofer will turn on along with the head unit.
Connecting an amplifier at home
It often turns out that there is a subwoofer with an amplifier, but it is impossible to operate them in a car. There is a way out - to put the equipment at home. How to connect a car subwoofer to an amplifier at home? The amplifier has input jacks and output jacks for connecting a speaker system and subwoofer. They are connected by “tulips”. They are shown in the photo below.
The amplifier is powered from computer unit nutrition. It is better to connect a subwoofer using the “Bridge” principle (the same as a car one).
Finally
So, we figured out how to connect a car subwoofer to an amplifier. The type of connection depends on the number of channels of the amplifier. Often installation is carried out using a bridge circuit, which is shown in the photo in the article. In the case of the subwoofer is connected to both channels. Installation of a capacitor is optional.
A power amplifier is an electronic device designed to convert a low-power electrical signal into a more powerful one. Its action must extend within the audio range audible to humans.
The main requirement for the device is ideal compatibility with various electroacoustic transducers (headphones, loudspeakers), no influence on the input signal in terms of its possible distortion.
By design, it can be an independent device or be part of more complex ones: televisions, radio transmitters, radio receivers, radio broadcasting networks, music centers etc.
A little history
Until the 19th century, the only device that amplified sound was the pipe organ. It was located, as a rule, in churches and was a musical instrument consisting of tubular resonator elements, bellows for creating air flow and control keys.
Alternating pressing of the latter led to the passage of air flows in pipes of different sections and sizes. Each of them caused a certain vibration in the air, which gave rise to its own sound, different from the others. At the same time, it became stronger.
The year 1875 was marked by another invention of the famous American Edison, who proposed the first pneumatic amplifier (or aerophone). In it, a person’s voice, arriving at a membrane (fixed in a valve), controlled the flow of compressed air in the tube.
At first, the idea caused great optimism, but it did not justify itself and was gradually forgotten. On its basis, the Pathé brothers created a phonograph at the beginning of the 20th century, patented under the name “oxetophone”. In them, they directly connected the membrane to the needle.
Intensive development of various amplifier designs became possible after the advent of electronic devices.
The first event was the improvement by American inventor Lee de Forest of D. A. Fleming's vacuum diode. It was expressed in the use of a control electrode in the form of a thin wire mesh to regulate the flow of electrons.
This led to the appearance of the first triode, which is, in fact, an electrical analogue of a mechanical valve.
Having a whole range positive qualities, it had a number of significant disadvantages: low power, low reliability, severe overheating. All this made its service life limited.
In the 50s of the last century, the first transistor was created - semiconductor element, in which the movement of electrons occurs not in a vacuum, but in a solid substance. According to some audiophiles, the different properties of this material affect the sound characteristics of transistor power amplifiers.
Amplifier selection
Choosing an amplifier, especially one with above-average performance, is not as simple as it might seem to a user uninitiated in electronics.
First of all, the buyer must decide what the device will be used for and the amount of money he plans to spend on its purchase. Information about the acoustic properties of the room where the acoustic systems are supposed to be installed, and what will be heard with their help, will not be superfluous.
The decisive factors when choosing are always sound quality, design and specifications amplifier Everything else is secondary and has minimal impact on the decision.
The ideal option would be to be able to borrow all the amplifiers that meet the requirements, connect them one by one to the existing speaker systems and select the appropriate one.
But, given that this is practically unlikely, most buyers have to re-read (more than once) all possible information about the devices and their manufacturers, test results of amplifiers and reviews of people who have already bought them. At the same time, rethink everything critically, go around numerous stores and specialized markets, salons. Listen to their managers, choose and refuse, and listen and choose again.
- Firstly, the first data that a buyer should be interested in is the frequency response of the device, the signal-to-noise ratio and the output power. The latter has a significant impact on the quality of the amplification and therefore should be of the greatest interest. You should find out what technique was used to measure it, what resistance was used and what power is implied (short-term dynamic, musical or sinusoidal). It is also necessary to find out the amount of distortion that was observed during measurements. As practice shows, to ensure high sound quality, the power for each individual channel must be at least 100 W. Although, in reality, it all depends on the sensitivity of the speaker system, for which the recommended power of the device is given.
- Secondly, the level of noise emanating from an amplifier connected to the speaker system is affected by the signal-to-noise characteristic. According to the existing rule, you need to choose a device that has more. However, not everything is so simple, because its value strongly depends on the measurement with a short-circuited input, on the position of the volume control (in the minimum or other position), on the state of the amplifier output (loaded or not) and other conditions.
- Third, frequency response amplifier Today little attention is paid to it, since the development of electronics easily ensures its balance in the region of 20...20000 Hz. It is important that this be observed over the entire power range possible for the device.
- Fourthly, you should pay attention to dynamic qualities amplifier, which are expressed by the rate at which the output signal rises. This property affects the quality of music reproduction, especially with frequently and sharply changing musical intonations.
- Fifthly, it would not be amiss to find out the magnitude of nonlinear, intermodulation and transient distortions. The value of the former is usually in modern devices very low and can be neglected.
Please note right away that I do not say “sound.” I say: “they may sound.” Absolutely all amplifiers audio frequency are made exclusively for the same purpose, as well as have exclusively one purpose. And that is why they are all created using more or less the same technology, and in any case, using the same theoretical and theoretical scientific base.
Ideally, all amplifiers under the same conditions should sound completely indistinguishable - not a single sane manufacturer even thinks about intentionally “distorting” the sound of their amplifier in some way they like. Such a distortion (if it occurs - as, for example, in the amplifier of the “genius” Aleshin, who sued Sony for 0 Hz until his gray pubis) is always and everywhere considered a defect and incompetence of the creator.
But since we live in a real and not an ideal world, some deviations from ideality still occur. These deviations are, as a rule, small, often vanishingly small, but sometimes they are noticeable. Keyword- Sometimes. We will talk about the reasons for this below. There will be no revelations - we’ll just remember well-known but long-forgotten things.
The main reason for the appearance of possible nuances (and these are just nuances, because nothing radical ever occurs in the absence of defects or malfunctions in the sound) in the sound of the same amplifier with different speaker systems is, oddly enough, not in the amplifier. It is found in AC and is called “impedance”.
Power amplifiers (PA) are calculated based on the ideality of the load, i.e. based on the adoption as a load element of a resistor with a resistance constant over the entire audio frequency range (for example, 8 or 4 Ohms), which, as it were, replaces a real speaker. If you load the PA on such a resistor and measure the voltage at its terminals, you will get the frequency response of the PA, which ideally should look almost straight horizontal line with inhomogeneity of the order of fractions of a decibel (for example +/-0.2 dB) throughout the entire audible frequency band, i.e. from 20 to 20,000Hz.
The same PA, but loaded onto a real speaker, will no longer give such a straight line of frequency response at the terminals - the unevenness of the voltage at the terminals will be significantly higher - in fact, it will, to one degree or another, repeat the impedance of the speaker. And this degree will be determined by the value of the output impedance of the PA - the smaller it is, the less heterogeneity. And, accordingly, the higher the output impedance of the PA, the stronger the voltage fluctuations at the speaker terminals will be.
Actually, this situation can rightfully be considered as a forced, non-switchable timbral correction.
I will illustrate the above with real examples.
It is easy to see that with an increase in both the “sweep” of the speaker impedance and with an increase in the output impedance of the PA, the situation changes in a very dramatic way. Once again, I draw your attention to the fact that we are dealing with forced, non-switchable timbral correction that occurs against the user’s desire.
It is this reason - various forced distortions of the timbral balance - that is the main reason that determines the different perception by a person of the sound of a PA with different speakers.
In this regard, I will allow myself a small lyrical digression entitled “The Myth of Transistor Rigidity” or “Do not chase zero distortion!”
Recently, when organizing auditions speaker systems For clients who were thinking about purchasing certain speakers, I was lucky enough to become a participant in a number of interesting experiments. Many clients, when choosing speakers, brought with them their own amplifiers, to which they asked to connect the speakers they were interested in - by this act they sought to assure themselves that they would not have any problems with “compatibility” at home. My plans do not include transfer specific models- I’ll just say that the amplifiers they brought were purely modern, transistor ones, from brands such as Cambridge Audio, NAD, Rotel, Roksan and something else (I didn’t write it down). A comparison of the sound of each such modern amplifier was made, depending on the wishes of the client, or with three amplifiers that are included in one of my own systems - an integrated Technics, an integrated Aurex, a two-unit Pioneer, respectively 69th, 84th and 80th years of production - or with three amplifiers, which at that time constituted my second system - two-block Technics, three-block Diatone and two-block Diatone - respectively, 77, 78 and 76 years of production. The comparison was, of course, carried out on several pairs of speakers from which clients chose.
The results of the experiments are as follows: there was a difference between the various amplifiers. Not such that I personally would undertake to identify amplifiers in blind testing, but, nevertheless, it took place to be noticed. Especially by clients who listened to every nuance, every little detail.
All modern amplifiers(of course, we are talking only about those listed above) were inferior in sound to each of the amplifiers used in my systems.
Most common comparative characteristics when switching from my amplifiers to modern ones there were these:
"the sound collapsed"
“the sound became muddy”
"permission lost"
“It’s like a veil has been thrown over the sound”
“The sound became like through cotton wool.”
More often than not, the top rated sound was the 1969 Technics amplifier. It is this, in the opinion of those who listened, that is distinguished by the greatest musicality, clarity, precision, air, transparency... in a word, extremely high comfort.
And, finally, absolutely no increase in sound harshness was observed as we moved from the most modern amplifiers to more and more ancient ones (up to 1969). Moreover, such a concept as “rigidity” was not used at all by the listeners. “Mudiness”, “vatness” - yes, but not “hardness”.
Thus, it becomes clear that the widespread myth about some incredible harshness of the sound of the first transistor amplifiers is bursting like a soap bubble. Nothing like this is observed in practice. On the contrary, the first transistor amplifiers turn out to be the most musical, clean and comfortable sounding. And vice versa - a head-on “collision” in one system of the most modern amplifiers, manufactured according to the most seemingly modern technologies, with first and second generation amplifiers, literally brings tears to many listeners' eyes. Grief for lost money is the most genuine.
End of digression
It has been noticed that the less nonlinear distortion an amplifier has, the more muddy and dull it sounds. This explains the fact that despite a completely smooth, tonally undistorted sound, modern amplifiers with a large number of zeros after the decimal point in the “Distortion” column sound extremely boring and uninteresting.
The situation is to some extent the same as with speakers - the deader the body of the speaker, the fewer after-sounds the speaker has, the “cleaner” and “smoother” all its characteristics are, the deader its sound. It's the same story with amplifiers: complete absence of distortion is a guarantee of death.
For reference
The power amplifier on which I performed the measurements shown above is equipped with a variable damping factor, i.e. in other words, variable (switchable) output impedance. In the passport for my PA it is written (in 1977) that this was done in order to ensure “flexibility of working with various speakers” - understand it however you want. I see this as another opportunity to distort the sound (perhaps even in a pleasant way).
The DF of an amplifier is traditionally defined as the ratio of the rated load (usually 8 ohms) to the output impedance of the PA (i.e., the impedance value at a frequency of 1 kHz). If the output impedance of the PA is 100 mOhm, then DF = 8/0.1 = 80.
It is believed that good solid-state amplifiers have a DF > 200. The best ones have a DF > 500. Many manufacturers do not indicate the DF at all. High output impedance values (several ohms) are typical for tube amplifiers. Transistor amplifiers are characterized by impedance values of the order of 50-200 mOhm.
The stated meaning of a high DF is to dampen the dynamic head, i.e. reduce (or eliminate) the effects of mechanical resonance. Electrical damping is clearly visible in the example of a head without a housing. Tap your finger on the diaphragm of the woofer and you will hear a long dull sound. Then short-circuit the head leads and tap again. Now the sound is clearly shorter and more like a “tong”. Now short-circuit the speaker with a resistor (8/20 =) 0.4 Ohm. Get something in between. When a woofer is placed in an acoustic design, it is as if it is already partially damped. Maybe in this case DF = 20 is more than enough, but maybe not.
It is believed that the higher the DF of the amplifier, the better it is (ideally, the speaker responds only to the useful signal and never to its natural resonance). Nobody knows whether DF = 20 is sufficient, but for some reason everyone is convinced that if DF = 500, then this is definitely better than 20.
In this regard, it is worth saying a few words about the incorrect interpretation of the concept of DF given by some people. Definition of DF as “AC resistance according to DC"divided by the amplifier's output impedance" is incorrect. Because it does not take into account the resistance of speaker cables and filter elements of speaker systems, but all this is located directly in the signal path. Or does someone connect the speakers wirelessly?
When it comes to DF, it is necessary to compare not abstract DF (those that are sometimes indicated in UM passports), but effective ones, i.e. taking into account the resistance of at least the cables. DF(eff.) can be defined as /.
Let me give two numerical examples:
Load Z = 8 ohms
Z out UM = 0.08 Ohm (read: “passport” DF = 8/0.08 = 100)
Z cables = 0.033 (2 x x [1m cable resistance]).
Then DF(eff.) = 71.
Obviously, if to connect speakers you use three-meter cables with a core cross-section of 3 squares (diameter ~ 2 mm, R ~ 0.033 Ohm), then the maximum effective DF will be equal to 242, even if the “passport” DF of the amplifier is equal to infinity (i.e. the output resistance is 0).
Let's now recalculate the same for Z out. UM = 0.016 Ohm (DF “passport” = 500) - now DF (eff.) = 160.
If you are very concerned about the “DF problem,” then even taking into account cable resistance, having an amplifier with a large DF is generally more profitable. Moreover, more advantageous does not mean “absolutely necessary.” Of course, if for some reason you need to stretch speaker cables 30 meters long, the effective DF will be very, very low - about 24(!) - regardless of the smallness of the output impedance of the amplifier (i.e. the hugeness of its nameplate DF).
Thus, if when using an amplifier with DF = 100, your acoustics clearly and unequivocally benefit in sound, then you need to think about purchasing such an amplifier. If your speakers are already well damped, and DF = 20 is already more than sufficient, then there will be no difference between amplifiers with DF = 100 and DF = 20.
More examples. Let's take the same, for simplicity ohmic, load of 8 ohms, and load two PAs onto it, which differ only in the DF (say, 50 and 150). We will make the connection using the same cable - say, some 3-meter AWG10 (i.e., about 2.6 mm in diameter).
The first DF(eff.) will be 45 (not much different from 50, right?), and the second DF(eff.) will be only 110 (almost one and a half times lower than the passport value).
When using even thinner speaker cables of the same length, say, AWG15 (i.e. about 1.5 mm in diameter), the situation is even more leveled. DF(eff.) of the first will be 36, and DF(eff.) of the second will be 69.
A conversation about large DFs can only be “relevant” in cases where cables as thick as an arm are used. DF=150, of course, is abstractly “better” than DF=50, but to the same degree of significance as THD=0.0005% “better” THD=0.005%.
Moreover, practice shows that for most speakers connected with a reasonable cable, DF(passport) = 50 is more than enough.
Instead of a resume
“Forced tone correction” at the speaker terminals absolutely always occurs. With a purely ohmic load (let it be an 8 Ohm power resistor), the unevenness of the typical frequency response transistor amplifier power is +/-0.2dB in the audible frequency band. When real acoustics are loaded, it will always be noticeably greater. For example, no longer +/-0.2dB, but +/-0.5dB or even +/-1dB. Of course, not every unevenness is noticeable by ear, but if this unevenness exceeds +/-1dB, then the chances of its noticeability (in the form of sensations of “pleasantness” or, conversely, “unpleasantness”) increase.
When comparing different amplifiers (on the same acoustics), it is extremely important to ensure strictly the same listening volume. This task is somewhat more difficult than it seems, since this is not done by ear. And the second “ambush” is that two different amplifiers can have completely different impedance versus frequency dependences, which again can give a more or less noticeable difference even on the same speakers.
Yes, distortions exist everywhere and always. The question is: how audible and noticeable are these very distortions? I, for example, believe that the notorious “tube distortions” (even harmonics), which supposedly give the sound of tube PAs some “pleasant softness” or “fullness”, is complete nonsense. It is also complete nonsense that odd harmonics (usually meaning high-order harmonics), characteristic of transistor PAs, supposedly give the sound some kind of “hardness” and “roughness”. In reality there is none of this.
Please note right away that I do not say “sound.” I say: “they may sound.” Absolutely all audio amplifiers are made exclusively for the same purpose, as well as have exclusively one purpose. And that is why they are all created using more or less the same technology, and in any case, using the same theoretical and theoretical scientific base.
Ideally, all amplifiers should sound completely indistinguishable under the same conditions.- not a single sane manufacturer even thinks about intentionally “distorting” the sound of his amplifier in some way he likes. Such curvature is always and everywhere considered marriage And incompetence creator.
But since we live in a real and not an ideal world, some deviations from ideality still occur. These deviations are, as a rule, small, often vanishingly small, but sometimes they are noticeable. The key word is sometimes. We will talk about the reasons for this below. There will be no revelations - we’ll just remember well-known but long-forgotten things.
The main reason for the appearance of possible nuances (and this is precisely the nuances, because nothing radical ever occurs in the absence of defects or malfunctions in the sound) in the sound of the same amplifier with different acoustic systems there is, oddly enough, Not in the amplifier. It is found in AC and is called “impedance”.
Power amplifiers (PA) are calculated based on the ideality of the load, i.e. based on the adoption as a load element of a resistor with a resistance constant over the entire audio frequency range (for example, 8 or 4 Ohms), which, as it were, replaces a real speaker. If you load a PA onto such a resistor and measure the voltage at its terminals, you will get the frequency response of the PA, which ideally should look like an almost straight horizontal line with inhomogeneity on the order of fractions of a decibel (for example ±0.2 dB) over the entire audible frequency band, i.e. . from 20 to 20000 Hz.
But here's the problem - real speakers are not even close to being permanent resistors. AC impedance different frequencies very different and is, as already mentioned, called impedance. You can read more about impedance in paragraph 19.
The same PA, but loaded onto a real speaker, will no longer give such a straight line of frequency response at the terminals - the unevenness of the voltage at the terminals will be significantly higher - in fact, it will, to one degree or another, repeat the impedance of the speaker. And this degree will be determined by the value of the output impedance of the PA - the smaller it is, the less heterogeneity. And, accordingly, the higher the output impedance of the PA, the stronger the voltage fluctuations at the speaker terminals will be.
In fact, this situation can rightfully be considered as a forced, non-switchable timbral correction.
With an increase in both the “sweep” of the speaker impedance and an increase in the output impedance of the PA, the situation changes in a very dramatic way. Once again I draw your attention to the fact that we are dealing with forced, non-switchable timbre correction that occurs against the user’s desire.
It is this reason - various forced distortions of the timbral balance - that is the main reason that determines the different perception by a person of the sound of a PA with different speakers.
It is also worth mentioning here the notorious “mudiness” and “vatness” of sound, often attributed to amplifiers.
In this regard, I will allow myself a small lyrical digression entitled “The Myth of Transistor Rigidity” or “Do not chase zero distortion!”
Recently, while organizing listening to acoustic systems for clients who were thinking about purchasing certain speakers, I was lucky enough to become a participant in a number of interesting experiments. Many clients, when choosing speakers, brought with them their own amplifiers, to which they asked to connect the speakers they were interested in - by this act they sought to assure themselves that they would not have any problems with “compatibility” at home. My plans do not include listing specific models - I will only say that the amplifiers were purely modern, transistor ones, from brands such as Cambridge Audio, NAD, Rotel, Roksan and something else (I did not write down). A comparison of the sound of each such modern amplifier was made, depending on the wishes of the client, or with three amplifiers that are included in one of my own systems - an integrated Technics, an integrated Aurex, a two-unit Pioneer, respectively 69th, 84th and 80th years of production - or with three amplifiers, which at that time constituted my second system - two-block Technics, three-block Diatone and two-block Diatone - respectively, 77, 78 and 76 years of production. The comparison was, of course, carried out on several pairs of speakers from which clients chose.
The results of the experiments are as follows: there was a difference between the various amplifiers. Not such that I personally would undertake to identify amplifiers in blind testing, but, nevertheless, it took place to be noticed. Especially by clients who listened to every nuance, every little detail.
All modern amplifiers (of course, we are talking only about those listed above) are inferior in sound to each of the amplifiers used in my systems.
The most common comparisons when switching from my amps to modern ones were:
"the sound collapsed"
“the sound became muddy”
"permission lost"
“It’s like a veil has been thrown over the sound”
“The sound became like through cotton wool.”
More often than not, the top rated sound was the 1969 Technics amplifier. It is this, in the opinion of those who listened, that is distinguished by the greatest musicality, clarity, clarity, air, transparency... in a word, extremely high comfort.
And, finally, absolutely no increase in sound harshness was observed as we moved from the most modern amplifiers to more and more ancient ones (up to 1969). Moreover, such a concept as “rigidity” was not used at all by the listeners. “Mudiness”, “vatness” - yes, but not “hardness”.
Thus, it becomes clear that the widespread myth about some incredible harshness of the sound of the first transistor amplifiers is bursting like a soap bubble. Nothing like this is observed in practice. On the contrary, the first transistor amplifiers turn out to be the most musical, clean and comfortable sounding. And vice versa - a head-on “collision” in one system of the most modern amplifiers, manufactured using the most seemingly modern technologies, with amplifiers of the first and second generations, literally brings tears to the eyes of many listeners. Grief for lost money is the most genuine.
End of lyrical digression.
It has been noticed that the less nonlinear distortion an amplifier has, the more muddy and dull it sounds. This explains the fact that despite a completely smooth, tonally undistorted sound, modern amplifiers with a large number of zeros after the decimal point in the “Distortion” column sound extremely boring and uninteresting.
The situation is to some extent the same as with speakers - the deader the body of the speaker, the fewer after-sounds the speaker has, the “cleaner” and “smoother” all its characteristics are, the deader its sound. It's the same story with amplifiers: complete absence of distortion is a guarantee of death.
For reference:
The power amplifier on which I performed the measurements shown above is equipped with a variable damping factor, i.e. in other words, variable (switchable) output impedance. In the passport for my PA it is written (in 1977) that this was done in order to ensure “flexibility of working with various speakers” - understand it however you want. I see this as another opportunity to distort the sound (perhaps even in a pleasant way).
The DF of an amplifier is traditionally defined as the ratio of the rated load (usually 8 ohms) to the output impedance of the PA (i.e., the impedance value at a frequency of 1 kHz). If the output impedance of the PA is 100 mOhm, then DF = 8/0.1 = 80.
It is believed that good solid-state amplifiers have a DF > 200. The best ones have a DF > 500. Many manufacturers do not indicate the DF at all. High output impedance values (several units Ohms) are typical for tube amplifiers. Transistor amplifiers are characterized by impedance values of the order of 50-200 mOhm.
The stated meaning of a high DF is to dampen the dynamic head, i.e. reduce (or eliminate) the effects of mechanical resonance. Electrical damping is clearly visible in the example of a head without a housing. Tap your finger on the diaphragm of the woofer and you will hear a long dull sound. Then short-circuit the head leads and tap again. Now the sound is clearly shorter and more like a “tong”. Now short-circuit the speaker with a resistor (8/20 =) 0.4 Ohm. Get something in between. When a woofer is placed in an acoustic design, it is as if it is already partially damped. Maybe in this case DF = 20 is more than enough, but maybe not.
It is believed that the higher the DF of the amplifier, the better it is (ideally, the speaker responds only to the useful signal and never to its natural resonance). Nobody knows whether DF = 20 is sufficient, but for some reason everyone is convinced that if DF = 500, then this is definitely better than 20.
In this regard, it is worth saying a few words about the incorrect interpretation of the concept of DF given by some people. The definition of DF as “the DC resistance of the speaker divided by the output impedance of the amplifier” is incorrect. Because it does not take into account the resistance of speaker cables and filter elements of speaker systems, but all this is located directly in the signal path. Or does someone connect the speakers wirelessly?
When it comes to DFs, it is necessary to compare not abstract DFs (those that are sometimes indicated in passports for minds), but effective, i.e. taking into account the resistance of at least the cables.
DF(eff.) can be defined as /.
Let me give two numerical examples:
Load Z = 8 ohms
Z out UM = 0.08 Ohm (read: “passport” DF = 8/0.08 = 100)
Z cables = 0.033 (2 x x [1m cable resistance]).
Then DF(eff.) = 71.
Obviously, if to connect the speakers you use three-meter cables with a core cross-section of 3 squares (diameter ~ 2 mm, R ~ 0.033 Ohm), then the maximum effective DF will be equal to 242, even if the “passport” DF of the amplifier is equal to infinity(i.e. output resistance is 0).
Let's now recalculate the same for Z out. UM = 0.016 Ohm (DF “passport” = 500) - now DF (eff.) = 160.
If you are very concerned about the “DF problem,” then even taking into account cable resistance, having an amplifier with a large DF is generally more profitable. Moreover, more advantageous does not mean “absolutely necessary.” Of course if for some reason you need to stretch speaker cables 30 meters long, the effective DF will be very, very low - about 24 (!) - regardless of the low output impedance of the amplifier(i.e. the enormity of his passport DF).
Thus, if when using an amplifier with DF = 100, your acoustics clearly and unequivocally benefit in sound, then you need to think about purchasing such an amplifier. If your speakers are already well damped, and DF = 20 is already more than sufficient, then there will be no difference between amplifiers with DF = 100 and DF = 20.
More examples. Let's take the same, for simplicity ohmic, load of 8 ohms, and load two PAs onto it, which differ only in the DF (say, 50 and 150). We will make the connection using the same cable - say, some 3-meter AWG10 (i.e., about 2.6 mm in diameter).
The first DF(eff.) will be 45 (not much different from 50, right?), and the second DF(eff.) will be only 110 (almost one and a half times lower than the passport value).
When using even thinner speaker cables of the same length, say AWG15 (i.e. about 1.5 mm in diameter), the situation is evened out even more. DF(eff.) of the first will be 36, and DF(eff.) of the second will be 69.
A conversation about large DFs can only be “relevant” in cases where cables as thick as an arm are used. DF=150, of course abstract“better” than DF=50, but to the same degree of significance as THD=0.0005% “better” THD=0.005%.
Moreover, practice shows that for most speakers connected with a reasonable cable, DF(passport) = 50 is more than enough.
Even if you get confused in calculations and wires, remember one simple thing: in practice, all advertising statements about sky-high DFs are broken by the filter elements in the speakers (crossover), or more precisely, by the inductor in the low-frequency section with an active resistance of 0.4 to 1 Ohm!
Instead of a resume:
“Forced tone correction” at the speaker terminals absolutely always occurs. With a purely ohmic load (let it be an 8 Ohm power resistor), the frequency response is uneven standard transistor power amplifier is ±0.2 dB in the audible frequency band. When real acoustics are loaded, it will always be noticeably greater. For example, no longer ±0.2 dB, but ±0.5 dB or even ±1 dB. Undoubtedly, not every unevenness is noticeable by ear, but if this unevenness exceeds ±1 dB, then the chances of its noticeability (in the form of sensations of “pleasantness” or, conversely, “unpleasantness”) increase.
When comparing different amplifiers with each other (on the same acoustics) it is extremely important to ensure strictly the same listening volume. This task is somewhat more difficult than it seems, because by ear it is Not is being done. And the second “ambush” is that two different amplifiers can have completely different impedance versus frequency dependences, which again can give a more or less noticeable difference even on the same speakers.
Yes, distortions exist everywhere and always. The question is: how audible and noticeable are these very distortions? I, for example, believe that the notorious “tube distortions” (even harmonics), which supposedly give the sound of tube amplifiers some “pleasant softness” or “fullness”, is complete nonsense. It is also complete nonsense that odd harmonics (usually meaning high-order harmonics), characteristic of transistor PAs, supposedly give the sound some kind of “hardness” and “roughness”. In reality there is none of this.
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