| Data on CDs is 16 bits, full stop.
18 and 20 bit players just use an 18 or 20 bit DAC with the two or four
(respectively) least significant bits unused. The rationale behind this
that it is difficult (and expensive) to make 16 bit DACs with the
required low level resolution/linearity.
However, by using 18 and 20 bit DACs
their low level resolution bits are wired out by the player
manufacturer, therefore the lowest cost DACS can be used. This was done
because the early 16 bit players sounded so dreadful. Beyond this, the
"no. of bits" quoted for a player has no effect on sound quality at
all.
"Single-bit" players are so-called because they convert the 16 bits
into a single pulse whose width varies with the number represented by
the bits. This pulse is fed to a "1-bit DAC" whose output level is
equivalent to the pulse width. There are two or three different ways of
doing this conversion, but they all follow the same basic "pulse width
modulation" principle. Why do it? For the same reason 18 and 20 bit
players were developed, and 1-bit is actually more succesful in terms
of low level linearity and distortion.
In the early days 1-bit was less well understood than multibit and had
lots of problems of its own, but it seems the 1-bit machines are leading
the market in terms of price performance now.
Dave
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| I believe Gramaphone magazine did a good introduction as to how CD
works back in about 1986. The book had a brown and silver cover if I
remember correctly.
It was informative and explained some of the technicalities about it
too.
Perhaps if you wrote to a major supplier, they might be able to give
you some info....or look in the library?
Cheers,
Tim
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