AIYIMA @aiyimaofficial - Tumblr Blog

Posts

According to different types of power amplifier tubes, power amplifiers can be divided into tube amplifiers and transistor amplifiers. As early as the 1960s, tube amplifiers have become popular all over the world, but from the 1960s to the 1980s, transistor amplifiers began to gradually rise. By the 1980s, the number o

What is a tube amplifier? The role of tube amplifier

What is a Class A amplifier? What are its advantages and disadvantages？by liu yeqiang on Apr 03, 2020

Class A power amplifiers are Class A power amplifiers. Two or two sets of output tubes in the output stage of this amplifier are always in a conductive state, and they maintain a conducting current state with or without signal input. This power amplifier has the best linearity, and each output tube amplifies the full wave of the signal, and there is basically no distortion.

Two currents in a Class A amplifier are equal to the peak value of the alternating current, and the alternating current flows into the load under the condition of the maximum signal. When there is no signal, the output tubes each pass the same current, and there is no unbalanced voltage or current on the output center, so there is no current input to the speaker. When the positive current in the signal area starts to flow unbalanced into the loudspeaker to promote sound.

Class A power amplifier principle and circuit diagram:

Class A static current is large, the current of a tube is changing in the positive and negative half cycles, there is no crossover distortion, the efficiency is low, and the sound quality is good. The operating point of the output transistor (or tube) of the Class A amplifier is at the midpoint of its linear portion. No matter how the signal level changes, the current it takes from the power supply is always constant. Because the signal amplitude constantly changes, its actual efficiency cannot exceed 25%, and it can be operated by a single tube or push-pull.

Class A power amplifier advantages:

The advantages of Class A amplifiers are no crossover distortion and switching distortion, and the harmonic components are mainly even harmonics. The circuit is simple, frequency loan, small instant distortion.

In the sense of hearing, the bass is thick, the midrange is soft and warm, the treble is clear and sharp, and the layering is good. In actual applications, the sound quality may not be as good as everyone thinks.

In any Class A power amplifier circuit under any design, the current negative feedback can be perfectly compatible with nonlinear distortion and instantaneous intermodulation distortion, and has ideal amplification effect.

Disadvantages of Class A amplifiers:

Because it has always consumed a lot of power, low efficiency, easy heating and high heat dissipation requirements, it has not been widely used in high-power amplifiers. Because the device works under high current and high temperature for a long time, it is easy to cause problems in reliability and life.

And the cost of the whole machine is high, so the manufacturers that make famous Class A power amplifiers have now stopped producing transistor Class A power amplifiers.

What does the post amplifier mean? What are its characteristics?

What does the post amplifier mean? Back-stage power amplifier, commonly known as pure back-stage, is simply a device that amplifies the "front-stage" audio signal to provide sufficient power to drive the speaker sound (always connected in front of the speaker). So what is the "preamp" mentioned here? It is a device that provides appropriate audio level signals and adjusts the sound quality (commonly known as preamplifier, connected between the audio source and power amplifier).

How to connect the post amplifier

The pre-amplifier is generally connected to a pure post-stage power amplifier. The front-stage output is connected to the input of the post stage, and the post stage is connected to the speaker. The preamp is to amplify the voltage, and the pure post-stage power amplifier is to amplify the current. The preamp is the linking device between various audio source equipment and power amplifier. The output signal level of the audio source equipment is relatively low, which cannot promote the normal operation of the power amplifier. The preamplifier plays the role of signal amplification.

Features of the post amplifier

The input signal of the post stage is very simple, that is, it accepts the output of the previous stage. But the load of the post stage is the speaker, which is what makes many audio fans and even magazine review writers confused. The post stage is the front stage load, which is a high impedance load; the horn is the post stage load, which is a low impedance load. It looks almost the same, only one word apart, but the high or low impedance makes it easy to push or not move. The current stage is connected to a high-impedance post stage, which mainly provides a suitable output voltage because the post stage amplifier.

Summary:

Amplifiers are generally divided into front-stage amplifiers, post-stage amplifiers, and merged-stage amplifiers. The merger machine combines the front-stage and post-stage machines into one. The front stage is used to preliminarily amplify the signal and adjust the volume; the latter stage is to amplify the signal from the pre-stage to a large extent to promote the speaker. Usually we use the pre-stage and post-stage together, so which is better than the merge stage? If the price is similar, personally recommend the combination of the front level + the back level, instead of choosing the merge level.

Tube amplifiers originated in the 1960s. With their warm and durable sound, good music and other characteristics, they have always been sought after by enthusiasts of amplifiers. So what exactly is a tube amplifier? What are the characteristics, principles, advantages and disadvantages? What is a tube amplifier? A tube

What is a tube amplifier? Detailed analysis of its characteristics, principles, advantages and disadvantages

What are the technical principles of power amplifiers? And buying guide?

In general, an amplifier is any device that can use less energy to control more energy. Nowadays, in everyday use, the term often refers to amplifier circuits, often used in audio applications. The input-output relationship of an amplifier is often expressed as a function related to the input frequency. This relationship is called the amplifier's transfer function, and the coefficient of this transfer function is defined as the gain.

In general, an amplifier is any device that can use less energy to control more energy. Nowadays, in everyday use, the term often refers to amplifier circuits, often used in audio applications.

The input-output relationship of an amplifier is often expressed as a function related to the input frequency. This relationship is called the amplifier's transfer function, and the coefficient of this transfer function is defined as the gain.

Buy

When selecting a power amplifier, you must first pay attention to some of its technical indicators: 1. Input impedance: usually indicates the size of the power amplifier's anti-interference ability, generally in the range of 5000-15000Ω, the larger the value, the stronger the anti-interference ability; 2. Distortion: refers to the degree of distortion of the output signal compared to the input signal. The smaller the value, the better the quality, generally below 0.05%; 3. Signal-to-noise ratio: the ratio between the music signal and the noise signal in the output signal. The larger the sound, the cleaner the sound.

In addition, when purchasing a power amplifier, you must also make your purchase intention clear. If you want to install a subwoofer, it is best to buy a 5-channel amplifier. Usually, 2-channel and 4-channel speakers can only drive the front and rear speakers, and the subwoofer can only be equipped with another power amplifier. The 5-channel power amplifier can solve this problem. The output power of the power amplifier must be greater than the rated power of the speaker.

Principle

The high-frequency power amplifier is used for the final stage of the transmitting stage. Its role is to amplify the high-frequency modulated signal to meet the transmission power requirement, and then radiate it to space through the antenna to ensure that the receiving stage in a certain area can Receive a satisfactory signal level without interfering with communication on adjacent channels.

A high-frequency power amplifier is an important component of a transmitting device in a communication system. According to the width of its operating frequency band, it is divided into two types: narrow-band high-frequency power amplifier and wide-band high-frequency power amplifier. Resonant power amplifier; the output circuit of a broadband high-frequency power amplifier is a transmission line transformer or other broadband matching circuit, so it is also called a non-tuned power amplifier. A high-frequency power amplifier is an energy conversion device that converts DC energy supplied by a power source into a high-frequency AC output. It is known in the course of "low-frequency electronic circuits" that amplifiers can be classified into three types of working states according to the current conduction angle. Class A amplifier current flow angle is 360 degrees, suitable for small signal low power amplification. Class B amplifier current flow angle is approximately 180 degrees; Class C amplifier current flow angle is less than 180 degrees. Both B and C are suitable for high power work. The output power and efficiency of Class C working state are the highest of the three working states. Most high-frequency power amplifiers work in Class C. However, the current waveform distortion of the Class C amplifier is too large, so it cannot be used for low-frequency power amplification, and can only be used for resonance power amplification using a tuning loop as a load. Due to the filtering capability of the tuning loop, the loop current and voltage are still very close to the sinusoidal waveform, and the distortion is very small. In addition to the above types of working states classified by the angle of current flow, there are D-type amplifiers and E-type amplifiers that make electronic devices work in the switching state. The efficiency of Class D amplifiers is higher than that of Class C amplifiers, theoretically up to 100%, but its maximum operating frequency is limited by the device power consumption (collector dissipated power or anode dissipated power) generated by the switching transition .

If the circuit is improved to minimize the power consumption of the electronic device at the moment of on-off transition, the operating frequency can be increased. This is a class E amplifier. We already know that in order to obtain sufficient low-frequency output power in a low-frequency amplifier circuit, a low-frequency power amplifier must be used, and the low-frequency power amplifier is also an energy converter that converts the energy provided by a DC power supply to an AC output. The common characteristics of high-frequency power amplifier and low-frequency power amplifier are high output power and high efficiency, but the working frequency and relative frequency bandwidth of the two are very different, which determines that there is an essential difference between them. Low-frequency power amplifiers operate at low frequencies but have a relatively wide frequency band. For example, from 20 to 20000 Hz, the ratio of high and low frequencies is 1000 times. Therefore, they all use non-tuned loads, such as resistors and transformers. High-frequency power amplifiers have high operating frequencies (from hundreds of kHz to hundreds, thousands, or even tens of thousands of MHz), but the relative frequency band is very narrow. For example, the AM radio station (535-1605 kHz frequency range) has a frequency bandwidth of 10 kHz. If the center frequency is set to 1000 kHz, the relative bandwidth is only one hundredth of the center frequency. The higher the center frequency, the smaller the relative bandwidth. Therefore, high frequency power amplifiers generally use a frequency selection network as the load circuit. Due to this latter characteristic, the working states selected for these two amplifiers are different: low-frequency power amplifiers can work in Class A, Class B, or Class B (limited to push-pull circuits); high-frequency power amplifiers generally work in C Class (some special cases can work in class B).

In recent years, a new type of broadband high-frequency power amplifier is widely used in each intermediate stage of a wideband transmitter. It does not use a frequency selection network as a load circuit, but uses a transmission line with a wide frequency response as a load. In this way, it can change the operating frequency over a wide range without having to retune. In summary, it can be seen that the common point of high-frequency power amplifiers and low-frequency power amplifiers is that they require high output power and high efficiency; the difference between them is that their operating frequencies and relative bandwidths are different. So the load network and working status are also different.

The main technical indicators of high-frequency power amplifiers are: output power, efficiency, power gain, bandwidth, and degree of harmonic suppression (or signal distortion). These several index requirements are contradictory. When designing the amplifier, some indicators should be highlighted, and other indicators should be taken into consideration. For example, in some circuits, preventing interference is the main contradiction, requiring higher levels of harmonic suppression, and reducing the bandwidth requirements appropriately. The efficiency of a power amplifier is a prominent issue, and its efficiency is directly related to the working state of the amplifier. The working status of the amplifier can be divided into Class A, B and C. In order to improve the working efficiency of the amplifier, it usually works in class B and C, that is, the transistor operation extends to the non-linear region. However, there are serious non-linear distortions between the output current and output voltage of the amplifiers in these operating states. Low-frequency power amplifiers, because of their large frequency coverage factor, cannot use a resonant circuit as a load, so they generally work in Class A status; they can work in Class B when a push-pull circuit is used. The high frequency power amplifier has a small frequency coverage factor of the signal, and can use a resonant circuit as a load, so it usually works in class C. With the frequency selection function of the resonant circuit, the harmonic components in the collector current of the amplifier can be filtered and selected. The fundamental component thus substantially eliminates non-linear distortion.

Therefore, high-frequency power amplifiers have higher efficiency than low-frequency power amplifiers. Because high-frequency power amplifiers work in the non-linear state of large signals, linear equivalent circuit analysis cannot be used. In engineering, the analytical approximation analysis method—polyline method is generally used to analyze its working principle and working state. The physical concept of this analysis method is clear, and the analysis work status is convenient, but the calculation accuracy is low. Among the various types of high-frequency power amplifiers discussed above, narrow-band high-frequency power amplifiers are used to provide sufficiently strong narrow-band signal power centered at the carrier frequency, or to amplify narrow-band modulated signals or achieve frequency doubling functions, usually working at Class, C status. Broadband high-frequency power amplifier: It is used to amplify short-wave frequencies of certain carrier signals, and mid-level amplifier stages of ultra-short-wave radio stations to avoid tedious tuning of different fc. Usually works in a Class A state.

Performance

No matter the AV amplifier and Hi-Fi amplifier have strict requirements on the power amplifier, they have clear requirements in terms of output power, frequency response, distortion, signal-to-noise ratio, output impedance and damping coefficient.

Output Power

Output power refers to the power delivered to the load by the amplifier circuit. At present, the measurement methods and evaluation methods of output power are not uniform, so pay attention when using them.

1.Rated power (RMS):

It refers to the high power (strictly speaking a sine wave signal) that can be output by the power amplifier in a certain harmonic range for a long time. The average power when the harmonic distortion is 1% is often referred to as the rated output power or the maximum useful power, continuous power, and undistorted power. Obviously, when the prerequisites for the specified distortion are different, the rated power values will be different.

2.Maximum output power

When the distortion is not considered, the output power of the power amplifier circuit can be much higher than the rated power, and it can also output a larger amount of power. The high power it can output is called the high power output. The aforementioned rated power and high output power Is the output power of two different prerequisites

3.Music output power (MPO)

Music output power MPO is the abbreviation of English Music Power Outpur. It refers to the output power of the power amplifier circuit when it works on music signals, that is, the instantaneous output power of the power amplifier to the music signal under the condition that the output distortion does not exceed the specified value.

Music output power can be used to evaluate the dynamic listening effect of the amplifier. For example, after a smooth music process, a strong percussion instrument sound suddenly appears. Some amplifier circuits can provide a large output power to the sense of strength. Unstoppable; some power amplifiers seem to be inadequate. In order to reflect the ability of sudden output power at this moment, it can be measured by the output power of music.

4.Peak music output power (PMPO)

It is the maximum music output power, and it is another dynamic indicator of the power amplifier circuit. If you do not consider the distortion, the maximum music power that the power amplifier circuit can output is the peak music output power.

Usually the peak music output power is greater than the music output power, the music output power is greater than the maximum output power, and the maximum output power is greater than the rated output power. According to practical statistics, the peak music output power is 5-8 times the rated output power.

Frequency response

The frequency response reflects the power amplifier's ability to amplify each frequency component of the audio signal. The frequency response range of the power amplifier should not be lower than the hearing frequency range of the human ear. Therefore, in the ideal case, the operating frequency range of the main channel audio power amplifier is 20 -20kHz. The international regulation of the general audio power amplifier frequency range is 40-16 kHz ± 1.5dB.

Distortion

Distortion is a phenomenon in which the waveform of a reproduced audio signal changes. There are many causes and types of waveform distortion, including harmonic distortion, intermodulation distortion, and transient distortion.

Dynamic Range

The ratio of the amplifier's undistorted amplified small signal to the large signal level is the dynamic range of the amplifier. In practice, the ratio uses dB to indicate the level difference between the two signals. The dynamic range of the high-fidelity amplifier should be greater than 90dB.

Various noises in nature form the surrounding background noise, and the surrounding background noise and the sound intensity of the performance are very different. In normal cases, this intensity difference is called dynamic range. A good sound system should not input a strong signal. Overload distortion occurs, and when a weak signal is input, it should not be overwhelmed by the noise generated by itself. For this reason, a good sound system should have a large dynamic range. The noise can only be reduced as much as possible, but it is impossible to not generate noise.

Signal to noise ratio

The signal-to-noise ratio refers to the proportional relationship between the size of the sound signal and the size of the noise signal. The decibel number of the ratio of the sound signal level output to the various noise levels output by the attack-amplifier circuit is called the size of the signal-to-noise ratio.

Output impedance and damping coefficient

1.Output impedance

The equivalent internal impedance shown by the output end of the power amplifier and the load (speaker) is called the output impedance of the power amplifier.

2.Damping coefficient

The damping coefficient refers to the ability of the power amplifier circuit to resistively load the load.

AIYIMA

Focus on Audio

Aiyima T6 Tube Pre-Amplifier Review!!----- JBL Bass Tester

УСЬ AIYIMA ПРОКАЧАЛ КОЛОНКИ ОТ МУЗ. ЦЕНТРА УСЬ AIYIMA 2.0： https://www.aiyima.com/pro…/amplifier-board-aiyima-tpa3116-2 УСЬ AIYIMA 2.1： https://www.aiyima.com/…/p…/amplifier-board-aiyima-tpa3116-1 PartyBox 300 https://youtu.be/up4QQvukims ПО вопросам рекламы и сотрудничества: [email protected]

#aiyima amplifier board #diy speaker

Aiyima TUBE-A3 PRO 6J1 preamplifier (Unboxing & Sound Test)---- ALS-TechReview

Just got that preamplifier from Aiyima brand to make a review, and guess what? This thing is just awesome! It amplifies your music signal to your power amplifier and you can even adjust your bass and treble to get the best sound out of it.. in my case that is amazing! I finally get the eq for playing Youtube music via Bluetooth!

Aiyima Premplifier links：https://www.aiyima.com/collections/tube-preamplifier

Aiyima TUBE-A3 PRO 6J1：https://www.aiyima.com/products/tube-amplifier-preamp-aiyima-a3-pro

#aiyima #tube preamp #preamp

Advantages and Disadvantages of Class D Amplifier

Advantages of Class D Amplifier

1. The battery usage rate of Class D power amplifier can reach more than 90%, which meets the requirements of environmental protection. 1, class d power amplifier has a very high energy conversion rate, and its volume is very small, and has strong reliability. 2. The usage range of class d power amplifier is very wide, and the minimum value of the connected load can reach very low. In addition, the battery conversion rate can basically be said to be the same regardless of the change of the load capacitance value. 3. Class d amplifier has no high frequency, intermediate frequency, the relative changes allowed, its sound is very clear, and the sound image has a very accurate positioning. 4. Class d amplifier is very suitable for mass production of products. As long as you ensure that the components are installed properly, you can make the product have good consistency, and no debugging is required during the production process, which is safe and reliable. 5. Class d amplifier can directly achieve group control, remote control, monitoring and other functions without adding any devices.

Disadvantages of Class D amplifiers

Although class D power amplifiers have many advantages, they also have many disadvantages, and these shortcomings have seriously affected the development of class D power amplifiers. Let me specifically talk about the disadvantages of class D power amplifiers. 1. There is no special switch for Class D power amplifier. If the installed power transistor and other devices are not matched well, the quality of the entire product will not pass. 2. In the power transistor of the Class D power amplifier, the potential close to the ground will fluctuate during the initial connection and the final shutdown process, thereby increasing noise. 3. The output circuit of the Class D power amplifier may have a dead zone. 4. Class D power amplifier speakers may appear distorted for some reason.

AIYIMA Focus on Audio

#AIYIMA #amplifier #tubeamp

How Class D Amplifiers Work

Class D amplifiers refer to Class D audio power amplifiers (sometimes called digital amplifiers). By controlling the ON / OFF of the switch unit, the amplifier driving the speaker is called a Class D amplifier. Class D amplifiers were first proposed in 1958, and have become increasingly popular in recent years. It has been available for many years. Compared with the general linear AB power amplifier circuit, the D power amplifier has the characteristics of high efficiency and small size.

The design considerations of Class D amplifiers are completely different from those of AB amplifiers. At this time, the linearity of the power amplifier tube is no longer significant, the more important switching response and saturation voltage drop. Because the pulse frequency processed by the power amplifier tube is dozens of times of the audio signal, and it is required to maintain good pulse front and back edges, the switching response of the tube is better. In addition, the efficiency of the whole machine lies in the pipe consumption caused by the saturation pressure drop of the pipe. Therefore, not only the saturation tube pressure drop is high, the heat dissipation structure of the power amplifier tube can also be simplified. A few years ago, the high-frequency and high-power tube was expensive, which limited the development of Class D amplifiers to a certain extent. Now MOSFETs with low current control and high current have been widely used in the industrial field, especially UHC MOSFETs have been applied to Hi-Fi power amplifiers in recent years, and the obstacles of the device have been eliminated.

Modulation circuit is also a special link of class D power amplifier. To modulate audio below 20KHz into a PWM signal, the frequency of the triangle wave must reach at least 200KHz. If the frequency is too low to meet the same THD standard, the requirements for the components of the passive LC low-pass filter are high and the structure is complicated. The frequency is high, the jaggedness of the output waveform is small, it is closer to the original waveform, and the THD is small. In addition, the filter can be made of inductors and capacitors with low values, small size, and relatively poor accuracy requirements, and the cost is reduced accordingly. However, at this time, the switching loss of the transistor will increase as the frequency rises. The high-frequency loss in the passive device and the skin effect of the radio frequency will reduce the overall efficiency. Higher modulation frequencies will also cause radio frequency interference, so the modulation frequency cannot be higher than 1MHz.

At the same time, the shape of the triangular waveform, the accuracy of the frequency, and the jitter of the clock signal will affect the distortion of the recovered signal that is different from the original signal. So to achieve high fidelity, many of the same considerations as digital audio fidelity have arisen.

Another factor that has a lot to do with sound quality is the passive filter located between the drive output and the load. The low-pass filter works under high current, and the load is the speaker. Strictly speaking, the impedance change of the speaker should be taken into consideration when designing, but it is not feasible to specify the speaker as an amplifier product, so the combination of Class D amplifier and speaker is more enthusiastic. It is actually proved that when the distortion requirement is below 0.5%, the second-order Butterworth flattened response low-pass filter can meet the requirements. If higher requirements are required, a fourth-order filter is required. At this time, issues such as cost and matching must be considered.

In recent years, general-purpose Class D power amplifiers already have integrated circuit chips, and users only need to design low-pass filters as required.

AIYIMA

Focus on Audio

#aiyima #amplifier #class d amplfieir

Trending Blogs

Recently Viewed Blogs

AIYIMA