Defining The Rate: Set, Auto & Learn - Brainstorm DCD-8 Operation Manual

DCD-8 User Manual
11. Defining the rate: Set, Auto & Learn
Part of the DCD-8's great flexibility comes from the fact that the rate generated does not have
to match the rate of the reference. Different frequencies can be cross-locked if necessary.
This is done through the use of the SET, AUTO and LEARN functions.
11.1. RATE MENU
In the Rate menu, the DCD-8 offers a choice between SET and AUTO:
- SET lets the user select a specific rate;
- AUTO mirrors the Reference menu (i.e. with a 48k reference, the output is 48K).
Keep in mind that, when locked to an external reference, the DCD-8 always tracks small
variations (see examples in 11.5 below).
NOTE: Auto is not available if the reference selected is Internal or Video.
11.2. REFERENCE MENU
In the Reference menu, the DCD-8 offers a choice between LEARN and SET:
- with LEARN, the DCD-8 measures the input reference and determines it's rate;
- with SET, the user defines the expected rate.
Most of the time LEARN will work fine. However, at times, the user may choose SET to be
sure the DCD-8 does not misinterpret an input frequency which is slightly incorrect. The
SET mode may also be chosen for more fail-safe operation, in that there is no chance that
the DCD-8 will re-define a frequency which drifts over time.
To illustrate this, let's look at a reference frequency of 95,950Hz. This frequency is slightly
below the standard 96k rate but slightly above the pulled down 96k (95,904Hz).
- If the DCD-8 interprets this as 96k, it will run slow by 0.052%;
- if it interprets it as a pulled down 96k, it will run fast by 0.047%
In SET mode, the user can make that choice; in LEARN mode, the DCD-8 automatically
selectes the closest frequency, i.e. the pulled down 96K in this case.
11.3 ABOUT USING THE SET MODE FOR THE REFERENCE
When SETTING the rate of the reference, there is the possibility that the selected rate will
not match the measured rate (actual rate). If that is the case, the DCD-8 will still lock to the
reference but the output frequency will be adjusted proportionately.
WARNING: When using this function, the user can potentially mislead the DCD-8 and
affect the output frequency, even if that is also SET. This could be done intentionally, but
caution should be used here.
For example, if the input reference is SET for PAL, and NTSC video reference is connected,
the output frequency SET at 44100Hz will actually be 52867Hz (44100 x 29.97/25).
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