Preamplifiers and Power Amplifiers
What is class B operation?
In class B operation, different transistors or vacuum tubes amplify the audio signal's positive and negative polarity components. As a result each transistor or vacuum tube works only half the time. Class B amplifiers however generate a lot of distortion and are not used for Hi-Fi.
Why class A/B amplifiers are popular?
Practically most class A/B amplifiers initially work in class A operation and switch to class B when there is an increase in power demand. Class A/B amplifiers often come close to class A performance and sound quality with out the cost of manufacture and operation of the later. This is the reason why most amplifiers are class A/B amplifiers.
Why vacuum tube amplifiers are favored by audiophiles?
Solid-state power amplifiers and vacuum tube amplifiers are quite similar. The major difference is the use of vacuum tubes instead of transistors in the amplification circuits. Vacuum tube amplifiers are famous for their musicality. These are the first and oldest types of amplifiers. Because of the warm and musical sound they reproduce, vacuum tube amplifiers are highly regarded by audiophiles. So even though they are generally very expensive and made in small quantities, they are still available for sale by high-end audio stores.
What are the main advantages and disadvantages of each type of tubes used in amplifiers?
Vacuum tube amplifiers are characterized as triode or pentode amplifiers, depending on the type of vacuum tubes used in their amplification stages. Triode tubes have superior audio performance but are limited to 60 Watt RMS power output. Pentode tubes produce more power with a very small compromise in audio quality. However even this small compromise is very important to some audiophiles.
What are the two types of digital power amplifiers?
The audio sources of home entertainment systems become ever increasingly digital based. This results in an increase in popularity of digital power amplifiers. There are two methods to making a digital amplifier. True digital power amplifiers and power amplifiers which incorporate digital technology. The later type accepts a digital signal at its input which is then converted to an analog signal by its integrated Digital to Analog (D/A) converters, and is amplified in the traditional analog way.
What form is the digital input signal converted to by a true digital power amplifier?
The true digital power amplifier converts incoming digital signals from the Pulse Code Modulation (PCM) form to a Pulse Width Modulation (PWM) form. In simple terms, the PCM data represents the audio signal in binary form (ones and zeros) of fixed length pulses with varying magnitude, while the PWM data with of varying length pulses of fixed magnitude. The length of the PWM pulse determines the audio signal amplitude.
How is the PWM data converted to analog audio signal?
The conversion of PWM data to audio is performed at the power amplification stage. The PWM data switches conventional transistors on and off depending on the length of the data pulse. The signal amplitude depends on how long the transistors are on or off. The on / off output of the transistors, represents the audio wave.
Why is the multichannel A/V integrated amplifier, a common choice for setting up a Home Theater system?
The use of a multichannel A/V integrated amplifier is very popular for setting up a home cinema system. The multichannel A/V amplifier has numerous analog and digital audio inputs and outputs and analog video inputs and outputs and can therefore be the control center of a home theater system. In addition the multichannel A/V amplifier has built-in the necessary amplification stages to drive all the speakers of a typical home cinema system.
Why are some typical audio adjustments that can be performed by an A/V amplifier?
The A/V amplifier permits various adjustments to the sound to improve the home cinema experience. First of all we can declare each speaker as large or small and in effect route the bass either to the speaker or to a separate subwoofer. We can also adjust the level and the delay of each speaker to match it with our listening room requirements.
Why is a typical A/V amplifier capable of being the control center of a Home Theater system?
Most A/V amplifiers have various sound format decoders and Digital Signal Processors that allows them to reproduce, in our room, an impressive three-dimensional sound stage from the soundtrack of a movie or the content of any stereo program. In essence an A/V amplifier is a fully equipped audiovisual laboratory, that can be the control center of a home entertainment system. It allows the process of all audio and video sources and the improvement of the final audio output.
What are the technical characteristics of an amplifier capable of driving low impedance speakers?
How many speakers can my amplifier drive?
How much power do I need?
My amplifier does not have a subwoofer output. How can I connect my subwoofer?
My amplifier delivers 100 W per channel. Do I need to buy speakers with the same power rating?
What is amplifier bridging?
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