Manual CC2 © Grimm Audio
12
timing chatters, the further away from the main
frequency you’ll find energy.
The red curve in the bottom graph shows only random
jitter. Sometimes jitter is periodical and then you
wouldn’t see a smooth slope but sharp peaks. An
important note is that frequency accuracy has
absolutely nothing to do with jitter at all. The red graph
shows a jittery clock with an exactly correct frequency,
say 44100.0000000Hz, the blue one shows a clock that’s
somewhat off but otherwise brilliantly stable. A
frequency error can be annoying from a practical
perspective, but as far as signal quality is concerned
you’re better off with a stable clock at an inexact
frequency.
Jitter is not a problem in fully digital processes. As long
as it isn’t so large that a processor can’t distinguish the
previous bit from the next, all-digital processes are
completely indifferent about jitter. The problem occurs
when you go from the analogue domain into the digital
domain or back. Digital audio presumes uniform
sampling. That way, given a string of numbers and
knowledge of the sampling interval, you can perfectly
reconstruct a sampled signal. With jitter that theory falls
apart.
frequency
frequency
A
m
p
li
tu
d
e
A
m
p
li
tu
d
e
Jittery clock
Jitter-free clock,
slightly off the
ideal frequency
Spectra of clock signals
6.
Jit
te
r
E
xp
la
in
ed
