External Clock De-jittering settings – NEW FEATURE!
The DLD uses sophisticated technology so that the unit can follow an external
Ping
clock accurately. In most
situations, the default method of the DLD will work fine without issues, and you do not need to adjust this parameter
unless you are experiencing sync issues with an external clock. The first thing to try is to use the DLD as a master
clock. This is the easiest solution, but it is not always possible.
When syncing an external clock that contains some jitter or drift to the DLD, the optimum algorithm for tracking
depends upon the application. A very accurate time-lock requires that the input responds slowly to changes, and this
can be a detriment when tracking of tempo changes is desired. Likewise, a very accurate lock may product audible
phasing when used with analog VCOs (which inherently drift in phase). Tracking behavior also depends very much on
the characteristics of the incoming clock. Many clock signals in modular systems have a measurable amount of jitter
or drift, and must be processed to allow sync for the DLD audio.
The DLD has five different approaches to clock de-jitter algorithms, and any of these can be chosen in the
System
Settings
mode. Certain settings will work better with certain external clocks, in certain types of patches. It's easy to
try all five clock modes, and experimenting is typically the quickest way to find the optimal setting for your situation.
To experiment with these settings, enter the
System Settings
mode, set toggle switches both to center position. Then,
hold down the
Reverse B
button while adjusting
Time B
(see the diagram above for how to set Time B).
Note: These settings only change how the DLD processes external clocks patched into the Ping jack. They do not
change how the Ping button works, or how the DLD works as a master clock (using the Clock Out or Loop Out jacks)
Ignore 0.2ms deviation,
and
Ignore 1% deviation:
These two settings lock onto a clock and ignore any small changes
in the tempo. The former ignores timing changes greater than a flat number of microseconds, and the latter ignores
timing changes greater than a percentage of the current tempo. These methods are suited for syncing to clocks that
have a small amount of jitter and no drift, where tiny differences in clock speed don't matter but you want the DLD to
respond quickly to large changes in tempo. Locking to a drum loop that changes tempo (from 120BPM to 90BPM, for
example) is an example where you may want to use these settings.
ECD Disabled (one-to-one):
This method simply makes the DLD's ping time equal to the time between the last two
clock pulses. Thus the DLD will always be lagging by one clock period, but will respond instantly to every clock pulse.
This is suited if you want to track small changes in an external clock or if you don't want the DLD to try to process the
external clock. Example uses might be clocking the DLD with a stable VCO to get resonant delay sounds.
Moving Average of 2
: This algorithm looks at the last two clock periods and uses the average value to determine the
current ping value. Thus, this method responds to any change in the external tempo, but takes longer to “catch-up”
than if ECD was disabled. Its advantage is that small amounts of jitter will cancel themselves out, so this makes for a
decent compromise between tracking and ignoring jittery clocks.
Linear Average of 4:
This method looks at the previous 4 clocks and updates the ping time to their average. However,
it's not a “moving average” so it only updates the ping every 4 clocks. Thus, of all the algorithms, this method
responds the slowest to changes in tempo. However it also has the highest stability if you are using a fixed external
tempo. Example usages would be clocking the DLD with a drum sequencer at a fixed BPM. Changing the tempo will
take 4 – 8 clock pulses for the DLD to catch up, but after the catch-up period, the DLD will stay locked even if the
external clock drifts in tempo. This is the recommended setting for syncing to external analog drum machines (analog
clocks are prone to drift), or in any situation where the tempo is fixed.
Note: The Linear Average of 4 technique is essentially the same as running the external clock into a clock divider and
patching the /4 output jack into the DLD's Ping input jack (and then using the Time settings to compensate for the
slowed down clock). Using clock divider such as the RCD is a good de-jitter technique, and bigger divider outputs (/8, /
24, etc) can be used to create an average of a larger group of pings.
