13
switch again.
NOTE:
The digital ADAT input is derived from any one of the four channel pairs of an eight channel
ADAT interface. The input pair is selected in CAL mode. To choose ADAT input pair do the following:
Press the CAL switch. The switch LED will begin to flash, letting you know that CAL mode is now active.
Press the optical input switch. The LCD display will indicate weather you are in TOSLINK or ADAT mode. If you
are in TOSLINK input mode, press the optical input switch once again to reach ADAT mode. The menu is stepped
as follows: TOSLINK INPUT OFFSET > ADAT INPUT OFFSET > ADAT SOURCE PAIR SELECT >
Once in ADAT INPUT OFFSET MODE, pressing the OPTICAL input switch one more time will bring up the ADAT
SOURCE PAIR SELECT menu. Simply use the main/edit rotary encoder to choose the desired input source pair.
Press the CAL switch to exit CAL mode and return to normal operation.
Once the input selector switch has been pressed, the selected input will become active and the switch will illu-
minate green. The name of the current input will be displayed on the first line of the SYSTEM LCD (screenshot 2).
screenshot 2
digital input selected, DAC status
The first line will also indicate s-Lock status once PLL lock has been achieved. Line two will display the selected
clock source for the currently selected digital input in addition to the current sample rate.
chanGinG diGiTal inpUT clocK soURce
The m904 DAC (Digital to Analog Converter) can be clocked by the embedded clock of a connected digital
source such as AES3, ADAT, S/PDIF or TOSLINK. An external Word Clock, ProTools Loop Sync clock or Super Clock
signal can also be used to clock the DAC. The clock type you choose to use is entirely up to you. You may like a
particular external Word Clock generating device that you reference your entire digital audio system to or you
might feel completely comfortable with an embedded clock from a digital audio stream. From our point of view,
it matters little as our s-Lock
tm
PLL (Phase Lock Loop) will automatically be applied once it detects the incoming
clock source. (
more about s-Lock below
)
The SEL switch, located left of the SYSTEM LCD window, is used to select the clock source you’d like to use as a
reference for the m904 system. The LCD will show the currently selected source. If you’d like to change the cur-
rent selection, repeatedly pressing the SEL switch will cycle you through the available choices, which are: AES or
ADAT (depending on input), WORDCLOCK (WORD), PROTOOLS LOOP-SYNC (LOOP), and SUPERCLOCK (SUPC). If
WORD is selected, the LCD text will flash if there is not a valid wordclock available. The clock source preference
for each digital input is saved in non volatile memory.
aboUT s-locK™
s-Lock
tm
is our new PLL circuitry that has been specifically developed for both the m904 and its big brother
multi-channel controller, the m906. The truly wonderful thing about s-Lock is that regardless of the condition of
the external clock used as a reference for the m904, s-Lock will take this clock source and provide an extremely
stable and ultra-low jitter clock to run the DACs. The goal, of course, is pristine audio. Here’s a bit more detail on
how this works.
s-Lock is a crystal-based PLL used for regenerating the incoming digital clock. The crystals used have extremely
low intrinsic jitter and are capable of locking to sample rates of up to 192kHz. When the digital input selected
for the DAC is active, the s-Lock circuitry automatically captures the incoming recovered clock from AES3, S/PDIF,
TOSLINK, or ADAT or from an external Word Clock or Super Clock. Once phase-lock with the incoming signal has
been achieved, the DACs, which have been running off the original clock, are switched to run off the ultra-low
jitter s-Lock system clock. If at any time s-Lock is lost or not achieved, the DACs are run off the original clock. The
s-Lock system can effectively lock to input sample rates of 44.1kHz or 48kHz +/- 10Hz, 88.2kHz or 96kHz +/- 20Hz
and 176.4kHz or /- 40Hz.
