Hi WillieWonka,
Below is an excerpt about the SPdif routing for the MX 400.. IHTH..
S/PDIF Digital In/Out
Digital input accepts 44.1kHz / 48kHz signals. When the S/PDIF digital input is selected
and active, the S/PDIF LED on the front panel lights.
Important: It is recommended that you do not connect any digital device to the
MX400’s S/PDIF inputs that transmits at sample rates other than 44.1 kHz or 48 kHz
(such as 96kHz). Doing so can cause unpredictable performance. Make sure the device
you are connecting to the MX400’s S/PDIF In is set as the Clock Master (if that option
is available) and transmitting at a sample rate of 44.1kHz or 48kHz only. As with any
other connection, if you need to unplug the S/PDIF cable, it is recommended that you
switch to the analog inputs (see Input Source in the System menus) or bypass both
processors before disconnecting the cable.
The MX400 and Digital I/O
The MX400 is equipped with two digital inputs and outputs (S/PDIF A and B). Each
S/PDIF pair is the digital equivalent of analog input/output pairs A and B. The digital
outputs on the MX400 are always active and will always mirror their analog output
counterparts. This allows you to plug in an analog input source and have it be output
as a digital stream.
The MX400 has three options for input sources which are configurable in the System
Menu: Analog Mono Left, Analog Stereo and Digital. (Press the System
button to access the System Menu; turn the Page/Select knob to scroll up and down
the menu.) Each input pair (A and B) can have different audio sources selected depending on your
needs. While in the System Menu, use Knobs A, B, and C to change values. As with
all equipment that receives digital audio streams, when setting either Input Source A or
B to Digital, the MX400 can no longer use its own internal clock source for the audio
stream, and it is necessary to change the clock source from the MX400’s internal clock
to Digital. Furthermore, the MX400 only receives external clock sync on the S/PDIF A input.
This means when using both Digital inputs (A and B), the devices that are connected
must be synced to a common clock source to work properly with the MX400.
If the Clock Source isn’t changed to Digital when digital input sources are selected,
there will be synchronization problems between the incoming digital audio stream
and the MX400’s processing, and the System Input Source menu will display DIG NO
LOCK. When the MX400 is properly synchronized with the incoming digital audio,
the System’s Input Source menu will display DIGITAL.
The MX400 only runs at 44.1 kHz or 48 kHz sample rate (using internal or external
clock sources). Do not connect external digital outputs to the MX400 that run at higher
sample rates (88.2 - 192 kHz) as the MX400 cannot accept them.