There is a lot of buzz about DSD these days, and how it
sounds more like Analog than PCM does.
Well that’s just opinion of course, but a lot of people seem to be
lining up behind that idea. So here’s a
tidbit just to get you thinking...
What exactly is Analog anyway? Lets look at an analog electrical
waveform. When we transmit an electrical
signal from one place to another (such as from an amplifier to a loudspeaker,
or from one place on a circuit board to another), that transmission takes place
in the form of electrical current flow.
The variations in the magnitude of the current flow represent the
information that is being transmitted.
When we play music through an electronic device, the variations in
current flow, backwards and forwards, represent exactly the variations in air
pressure, up and down, that we perceive as sound. In a loudspeaker these variations in current
are converted into corresponding variations in air pressure, and thus we get to
hear the music.
Electrical current flow is carried by fundamental particles
called electrons. These, together with
protons and neutrons, are the building blocks that together comprise
atoms. Electrons carry an “electronic
charge”. Just like balloons do when you
rub them against a nylon sweater. But
unlike the balloon, an electron’s electric charge is built right into it. Electrons cannot acquire or lose their
electric charge, they always have the same amount of charge and they keep it
permanently. So when electrons flow
along a metal wire, for example, their electric charge is also flowing along
the wire. It is this flow of electric
charge that we define as an Electric Current.
The more charge that flows along the wire, the bigger the current.
Now, it is a very interesting property of electrons that the
amount of electric charge that each one carries is a fixed and very precise
amount. There is absolutely no variation
whatsoever – not even the smallest imaginable amount – in the magnitude of the
charge on an electron. Every single one
is absolutely identical. Electrical
charge can only exists in amounts which are whole-number multiples of this
fundamental quantity. This has an
interesting consequence on current flow.
An electrical current measured in Amperes is, to all intent and purpose,
a measure of the number of electrons flowing through the wire in question. And that number is a whole number – there is
no such thing a “part of” an
electron. Either the whole electron has
flowed through the wire or none of it has.
Current flow therefore has a fundamental “granularity” to it.
Can we detect this granularity? Yes we can, but in ordinary electronic
circuits the answer is no. The number of
electrons that flow down a wire per second when it is carrying a current of one
Ampere is so big that, if you wrote it down, it would have eighteen
digits. Try writing down an 18-digit
number and see if you can make sense of it!
(During the Iraqi war, Condoleeza
Rice enters the Oval Office and informs George Bush that two Brazilian soldiers
were killed in Baghdad that morning.
President Bush instantly turns an ashen shade of grey and slumps into
his office chair, holding his head between his hands. Finally he looks up through red eyes and asks,
“Just how many, exactly, is a bazillion?...”).
But the concept does have some relevance to the line of
thought that caused me to write this post.
Because any electrical current flow comprises a discrete flow of
electrons, I can represent that current flow by recording when each and every
electron arrives at the detection point.
Since an electron has either arrived or it hasn’t, I can indicate this
by writing “1” every time an electron arrives, and “0” every time an electron
doesn’t arrive! If the current flow is
large, I will be writing more 1’s than 0’s and vice-versa if the current flow
is small.
Strange thing, but isn’t that exactly how DSD works?...
