User Manual

Rear Panel 17Apollo x16 Hardware Manual

Digital I/O

(17) 75 Ohm Word Clock Termination Switch

This switch provides internal 75-ohm word clock input signal termination when required.

Word clock termination is active when the switch is engaged (depressed).

Apollo x16’s termination switch should only be engaged when Apollo x16 is set to sync

to external word clock and it is the last device at the receiving end of a word clock cable.

For example, if Apollo x16 is the last “slave” unit at the end of a clock chain (when

Apollo x16’s word clock OUT port is not used), termination should be active.

(18) Word Clock I/O

Word Clock In

Apollo x16’s internal clock can be synchronized (slaved) to an external master word

clock. This is accomplished by setting Apollo x16’s clock source to Word Clock within the

Console application, connecting the external word clock’s BNC connector to Apollo x16’s

word clock input, and setting the external device to transmit word clock. If Apollo x16 is

the last device in the clock chain, the Termination switch (#17) should be engaged.

Important: Apollo x16’s sample rate must be manually set to match the incoming

clock’s sample rate.

Note: Apollo x16 can be synchronized to an external “1x” clock signal only.

Superclock, overclocking, and subclocking are not supported.

Word Clock Out

This BNC connector transmits a standard (1x) word clock when Apollo x16 is set to use

its internal clock. The clock rate sent by this port matches the current system sample

rate, as speciﬁed within the Console application.

When Apollo x16 is set to use external word clock as its clock, Apollo x16 is a word clock

slave. If the incoming external word clock is within ±4% of a supported sample rate

(44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, 192 kHz), Word Clock Out will mirror

Word Clock In with a slight phase delay (about 40ns).

Because Apollo x16’s word clock output is not a true mirror of the word clock input,

word clock out should not be used to daisy chain the word clock if Apollo x16 is in the

middle of the word clock chain. The correct method to connect Apollo x16 in the middle

of a word clock chain is to use a T-connector at Apollo x16’s word clock input and leave

Apollo x16’s word clock output unconnected. In this conﬁguration, the Termination

switch should not be engaged.