Feature	Feature Description
D/A Converter	DAC (Digital-to-Analog Converter) Electronic device that decodes digital data (ones and zeroes) into an analog waveform electrical signal that can be amplified and played by loudspeakers (or that can be used by a video display to form an image in the case of video DACs). When an analog signal is recorded onto a digital medium, it is split up into thousands of very thin slices. Each of these slices is given a height and an order, and then the information is digitally stored. When digital signals are played back, the thousands of slices are lined up in the proper order. The digital to analog converter forms a solid, flowing line from the tops of the slices to create a continuous, analog waveform. This process can be seen in the pyramids. Each pyramid is made of thousands of blocks forming a stair-step pattern up the side of the structure. However, from a distance, the individual blocks blend together to form what appears to be a straight, continuous line. If you drew a line up the ends of the blocks, you would get that same straight line. Digital encoding works the same way. It would save a triangle like a pyramid as a series of slices or blocks of varying height. When decoded, a line would be drawn from block top to block top recreating the pyramid. The important thing is having enough individual slices to accurately portray the analog data. The digital medium must have a high resolution - just like with a video display you can see the individual picture elements at low resolutions but at high resolutions they merge to form a complete, high-quality image. The number of samples (individual slices) varies by the sampling rate, which is given in kilohertz (44.1 kHz is the sampling rate for common CDs). The higher the sampling rate, the more individual slices of the signal are created. The digital-to-analog converter uses the individual pieces to recreate the original analog signal and thus allows digital music to be played over analog loudspeakers (all speakers and amplifiers operate on an analog level). The other important aspect when decoding an analog signal from a digital format is the quantisation. The quantisation is measured in bits. The number of bits used is often referred to as the word length. For each sample or slice of the analog signal, the height of the sample must be given. Quantisation works by taking the maximum signal level and dividing it up into pieces. These pieces are used to measure the height of the sample similar in effect to using a ruler with inch markings. The greater the word length (more bits used), the finer the measurement markings. Using a small number of bits is like measuring using only inches while using a high number of bits is like measuring uses millimeters - using more, smaller units allows more precision and equates to a more accurate signal. Most digital playback devices (CD, DVD, laserdisc, etc.) include a digital-to-analog converter. There are also separate DACs available that use higher quality components than those typically found in digital playback devices allowing an improvement in sound quality. Any CD player, DVD player, laserdisc player or other digital playback component with the proper digital output can be linked to an external DAC to improve its sound quality.
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