Cramming useless information

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Nothing upset me more about school than being asked to cram useless unrelated information in my head. Later in today’s post I will ask you to do just that. If you fail, I will come after you with a ruler across the knuckles.

We’re in the middle of a set of posts helping us understand what DoP is. DoP is DSD over PCM which, if you don’t understand what those Three Letter Acronyms stand for, makes no sense whatsoever. To help wade through this mess I’ve replaced the acronym for the CD standard, PCM, with another term: Multi-bit Audio. I’ve then replaced the SACD standard, DSD, with a second term, Single-bit Audio.

Using these easier terms, DoP is a means to send Single-bit Audio to a computer using the language of Multi-bit Audio. And here’s the thing to take away from this understanding: when using DoP, Single-bit Audio is NOT converted to Multi-bit Audio. That’s a popular misconception that we’re working on getting straightened out. There is no conversion of Single-bit to Multi-bit when we use DoP. Single-bit stays as Single-bit.

Before we get into the nuts and bolts of it I would ask you to put one fact inside your head (my ruler is itching to rap someone’s knuckles). Put it in there, let it rattle around, even if it doesn’t make sense, and hopefully it’ll stick somewhere in the deep caverns for later use. Yes, there’s a test later. I know, it’s the same terrible request your teachers made of you in school. “Just stuff this fact in your head, despite the fact it makes no sense.” Terrible way to teach someone. The worst. But it did give them the excuse to whack a few students around.

Inside a computer, bits are bits. The bits of Single-bit Audio are the same as the bits in Multi-bit Audio. Bits is bits. Got it? I promise, it’s all I will ask you to store. Onward.

What does DSD look like? How does it work? It’s actually simple. It is a system that uses bits to generate energy. The greater the energy generated the higher the signal level; the lower the energy, the lower the signal level. Have you ever seen a wind turbine that generates electricity, or a solar cell doing the same? The stronger the wind, the brighter the light, the more energy generated. In the case of DSD, more ON bits means more energy. Fewer ON bits, less energy. Take a look at the following picture.

dsd_encoding_comparison

The blue rectangles represent ON bits and the white rectangles represent OFF bits (click the picture to expand it). The red line is the resulting music in the form of a sine wave. See how the red sine wave is going up whenever there’s a bunch of blue rectangles, and down when there’s lots of blank ones? That’s it. That’s all you need to know to understand Single-bit Audio (DSD).

Remember there are only two kinds of bits: ON and OFF. An ON bit simply means there’s voltage present – just like you had connected a battery between the plus and minus terminals of your loudspeaker. An OFF bit has no voltage present, it’s just an empty space, as if you removed the battery from your your loudspeaker. Connect a battery across your loudspeaker and the driver will jump forward and move the air. Remove the battery and the loudspeaker driver returns to its resting position.

If you were able to connect and disconnect your battery from the loudspeaker 2.8 million times a second, you’d probably get a free Guinness beer and a place in the record book of the same name. But if you could ….. then you could duplicate what’s in the picture and sound would come out. Music would be there if you followed the right pattern to match the music.

And that’s Single-bit Audio. Now, don’t forget what I asked you to cram into your addled brain. You’re going to need that important piece of useless information tomorrow. Now, where’s that ruler of mine ……