Quantec Zombies 12xx Series, Operation Manual

Page: 65 / 145

2. Menu Structure - 2.6 Config SRC(ZOMBIEs with SRCs only)
ZOMBIEs 12xx
65
Hands On
Adjustment time constant 200ms
FAST
or 800ms
SLOW
?
If constant irregularities in the sample rate are to be expected, as when working with varispeed, the
constant should be set to
FAST.
In contrast, if an input signal with strong jitter is to be processed, in which the medium value for the
sample rate remains constant,
SLOW
should be selected. In this manner, even signals with quite
extreme jitter can be calmed sufficiently before the interpolation to the new sample rate for the
conversion errors to remain below -90dB.
The correct understanding of the »jitter bandwidth« is fundamental to this process. The jitter
suppression on the basis of a digital loop is NOT a PLL with 12dB/oktave. The value given here
should be understood such that the incoming jitter is weakened in proportion to the frequency -
therefore with 6dB/Oktave - above the given cut-off frequency.
Standard setting :
FAST
Input to output delay 0.7ms
SHORT
or 3ms
LONG
?
When
SHORT
is selected, the minimum delay necessary for the SRC algorithm to function - the
group delay time of the FIR interpolation filter – is selected. In all situations in which the
propagation delay is a critical factor and should be minimized, this is the correct setting.
When
LONG
is selected, an extra FIFO is inserted before the FIR-Filter. With this extra buffering,
very large jumps in the sample rate are possible, e.g. a ratio of 2:1 can be absorbed. How the PLLs
involved and their lock detectors would react in such situations is of course another question
entirely…
(the latter option LONG is not featured on all SRC ZOMBIEs)
Standard Setting:
SHORT