Steadyclock - RME Audio Hammerfall DSP System MADI User Manual

30.6 SteadyClock

The SteadyClock technology of the HDSP MADI guarantees an excellent performance in all
clock modes. Its highly efficient jitter suppression refreshes and cleans up any clock signal, and
provides it as reference clock at the word clock output.
Usually a clock section consists of an analog PLL for external synchronization and several
quartz oscillators for internal synchronisation. SteadyClock requires only one quartz, using a
frequency not equalling digital audio. Latest circuit designs like hi-speed digital synthesizer,
digital PLL, 100 MHz sample rate and analog filtering allow RME to realize a completely newly
developed clock technology, right within the FPGA at lowest costs. The clock's performance
exceeds even professional expectations. Despite its remarkable features, SteadyClock reacts
quite fast compared to other techniques. It locks in fractions of a second to the input signal,
follows even extreme varipitch changes with phase accuracy, and locks directly within a range
of 25 kHz up to 200 kHz.
SteadyClock has originally been de-
veloped to gain a stable and clean
clock from the heavily jittery MADI data
signal. The embedded MADI clock
suffers from about 80 ns jitter, caused
by the time resolution of 125 MHz
within the format. Common jitter values
for other devices are 5 ns, while a very
good clock will have less than 2 ns.
The picture to the right shows the
MADI input signal with 80 ns of jitter
(top graph, yellow). Thanks to Steady-
Clock this signal turns into a clock with
less than 2 ns jitter (lower graph, blue).
Even word clock can gain a lot from
SteadyClock. The screenshot to the
right shows an extremely jittery word
clock signal of about 50 ns jitter (top
graph, yellow). Again SteadyClock
provides an extreme clean-up. The
filtered clock shows less than 2 ns
jitter (lower graph, blue).
The cleaned and jitter-freed signal can
be used as reference clock for any
application, without any problem.
User's Guide HDSP MADI © RME
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