RME Fireface UCX II 40-Channel USB-B Audio/MIDI Interface - Manual (Page 26)

26 User's Guide Fireface UCX II © RME
9.3 Known Problems
If a computer does not provide sufficient CPU-power, and/or sufficient USB or PCI bus transfer
rates, and/or sufficient PCIe-bus transfer rates, then drop outs, crackling and noise will appear.
Raising the buffer size in the Settings dialog of the Fireface UCX II helps in most cases. It is also
recommended to deactivate all PlugIns to verify that these are not the reason for such effects.
Further information is found in chapter 40.3.
Another common source of trouble is incorrect synchronization. ASIO does not support asyn-
chronous operation, which means that the input and output signals not only have to use the
same sample frequency, but also have to be in sync. All devices connected to the Fireface UCX
II must be properly configured for full duplex operation. As long as SyncCheck (in the Settings
dialog) only displays
Lock instead of Sync , the devices have not been set up properly.
The same applies when using more than one Fireface UCX II - they all have to be in sync. Else
a periodically repeated noise will be heard.
RME devices support
ASIO Direct Monitoring (ADM). Please note that not all programs support
ADM completely or error-free. The most often reported problem is the wrong behaviour of pano-
rama in a stereo channel. Also try to avoid setting the TotalMix FX hardware outputs (third row)
to mono mode. This will most likely break ADM compatibility.
In case of a drift between audio and MIDI, or in case of a fixed deviation (MIDI notes placed
close before or behind the correct position), the settings in Cubase/Nuendo have to be changed.
At the time of print the option 'Use System Timestamp' should be activated. The Fireface UCX II
supports both MME MIDI and DirectMusic MIDI. It depends on the used application which one
will work better.
10. Using more than one Fireface UCX II
The driver supports up to three Fireface UCX II or a combination of up to three supported inter-
faces. All units have to be in sync, i.e. have to receive valid sync information (either via word
clock or by using AutoSync and feeding synchronized signals).

If one of the Firefaces is set to clock mode Master, all others have to be set to clock mode
AutoSync, and have to be synced from the master, for example by feeding word clock. The
clock modes of all units have to be set up correctly in the Fireface Settings dialog.

If all units are fed with a synchronous clock, i.e. all units show Sync in their Settings dialog,
all channels can be used at once. This is especially easy to handle under ASIO, as the ASIO
driver presents all units as one.
Please be aware that operating more than one Fireface UCX II may cause resource problems
on the computer side.
Note: TotalMix is part of the hardware of each Fireface. Up to three mixers are available, but
these are separated and can't interchange data. Therefore a global mixer for all units is not pos-
sible.