Tascam X-48 - Manual (Page 22)

Configuration
Digital Audio Clock
When digitally connected, two or more pieces of audio equipment must be running at
exactly the same digital audio clock rate and have their sample exactly lined up. If this is
not done, audio artifacts like clicking and popping or completely muted audio will result.
The X-48 provides the ability to operate in many digital audio clock scenarios. Each
available setting is shown below along with an example of why it may be used. These
settings are made on the Sync tab of the Settings window.
Internal – When selected, the X-48’s digital audio clock is running on its own at the
selected sample rate. Choose this when the X-48 is connected to an analog mixer or when
the X-48 is the clock master for other pieces of digital audio equipment.
Varispeed – The term “varispeed” refers to a recorder’s ability to run faster or slower than a
base rate. This may be used to record off speed for later playback at normal speed for a
special effect. It can also be used to slightly alter the pitch of a recording for tuning
purposes. Varispeed is only available when the X-48 is set to Internal clock. When clocked
externally, the X-48 must follow the rate of that external clock.
Word Clock – When selected, the X-48’s digital audio clock will be locked to any word
clock signal present at its BNC Word Clock input. If this is selected, but no word clock
signal is present, the sample rate indication in the GUI and the Sample Lock LED on the
front panel will flash indicating no clock lock.
Word clock is commonly used when many pieces of digital audio gear are connected
together in a system and clock is correctly distributed from a central clock generator or one
of the connected devices.
Invert Word Out Polarity – Some manufacturers of digital audio equipment lock to the
rising edge of a clock signal while others use the falling edge. This setting allows the X-48
to operate as a clock master with either type of equipment. This may not be documented by
all manufacturers, so if your clock configuration appears correct but you are still hearing
artifacts such as clicks, try changing the value of this setting.
Clock Rate Multipliers – Some older word clock generators only support base clock rates
(44.1k, 48k). For scenarios where such a clock generator is used in a system running at
higher clock rates, the X-48 provides the ability to lock to, and output, word clock rates that
are exact multiples of its operating rate. For example, a system may be running at 96k, but
the clock generator’s maximum output rate is 48k.
ADAT Card/AES Card(1, 2) – When selected, the X-48’s digital audio clock will be
locked to the digital audio signal present at the first group of eight inputs of a digital I/O
card installed in the specified slot. This would typically be used when the X-48 is digitally
connected via one of its slots to one other piece of equipment such a mixer or another
recorder.
S/PDIF – When selected, the X-48’s digital audio clock will be locked to the digital audio
signal present at the rear panel S/PDIF input. This would typically be used when the X-48 is
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