Legend Audio ISA 828 - Manual (Page 12)

176.4/192kHz sample rates:
Connector 1 = channels 1 and 2
Connector 2 = channels 3 and 4
ADAT™ lightpipe cables are available from your local dealer, or in the UK from Studiospares (tel +44 (0)20 74821692):
stock number 585-510.
Word Clock In and Out
The internal ADC can be synchronised to an external word clock. By pressing the front panel Ext switch, the
synchronisation mode can be switched between standard external word clock and 256x external word clock.
Both types of external word clock should be connected to the ISA 828 ADC card at the Word Clock In BNC connector.
The Word Clock Out BNC connector either regenerates the external word clock connected at the Word Clock In BNC
connector, or transmits the internal sample frequency of the ADC card. Where the ISA 828 is being used as a slave device
within a larger digital system, the Word Clock Out BNC connector can be used to pass on the external word clock signal
to the next device. When the unit is not slaved to another device and is in internal clock mode, the Word Clock Out BNC
connector outputs the sample frequency selected on the ISA 828 front panel.
Digital Output Front Panel Controls
Clock Select
Pressing this switch allows the user to select between sample frequencies of 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz
and 192kHz.
Ext Select
Pressing EXT allows the ISA 828 to be slaved to an external word clock source, connected to the word clock input on
the rear panel. Selecting 256x allows the ISA 828 to be slaved to an external clock running at 256 times faster than the
sample frequency and enables connection to systems such as the Digidesign ‘Superclock’ or other 256x slave clock
devices. Both options have LEDs to indicate selection; with neither LED illuminated, the 828 will synchronise to its
own internal clock.
Lock LED
When lit, LOCK indicates that the unit is successfully synchronised to an external clock. Note: When using 256x external
clock, no lock indication is given, if audio can be heard in this mode then 256x clock is locked.
Applications
Mic Pre-amp Input Impedance
A major element of the sound of a mic pre is related to the interaction between the specific microphone being used and
the type of mic pre-amp interface technology it is connected to. The main area in which this interaction has an effect is
the level and frequency response of the microphone, as follows:
Selects sample rate
Selects the ADC to lock to an external source
connected to the word clock input on the rear
panel (either standard word clock or 256x)
Lock LED indicates when a successful
synchronisation is achieved
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