The simplest case is whether the data is 44.1 KHz sampling as is the case for CD music or 48 KHz as it is for most movie content. This means that the source determines the rate at which the downstream device, in this case the DAC inside your equipment, needs to output the digital audio samples. There is an unwritten rule about the design of consumer electronics equipment that says the source is the master. The interconnect can be HDMI, S/PDIF (coax), Toslink (optical), network connection (wired or wireless) or a computer connection such as USB. In these situations the digital data exists in the source and is transmitted over some sort of cable to the device that contains the DAC. The source of the digital stream is often separate device in the form of a Blu-ray player, cable, satellite or Internet set-top box or a computer acting as music or movie server. The DAC is either part of a dedicated device by the same name, an Audio Video Receiver (AVR), or a Home Theater processor. As we expect, there are digital samples on its input in the form of “PCM” formatted values. Let’s review how it works.įigure 1 shows the basic block diagram of a Digital to Analog Converter (DAC). At the risk of stating the obvious, the output is an analog signal – something entirely different than how our computers operate for us. The reference “digital” relates to the input of the system, not its output. Just because it has the word “digital” in it doesn’t mean it works like it does inside our computers. By the same token we think that digital audio also means perfect reproduction. For example, copying a file from a hard disk to a flash thumb drive produces an identical file. We equate how things work there for how they work in the digital audio domain. The misconceptions are caused by our familiarity with another digital technology: computers. Unfortunately those answers are often not correct. But if I ask how digital audio works I will immediately get answers. If I asked you how a TV works you likely will give me a blank stare. Sometimes I feel that digital audio is the most misunderstood technology around. It was published in January 2014 I think. Note: this is a slightly revised version of an article I wrote for the Widescreen Review Magazine.
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