User Manual
User's Guide Fireface UCX © RME
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10. Operation under ASIO 
10.1 General 
Start the ASIO software and select ASIO Fireface USB as the audio I/O device or the audio 
driver. 
The Fireface UCX supports ASIO Direct Monitoring (ADM). 
The Fireface UCX MIDI I/O can be used with both MME MIDI and DirectMusic MIDI. 
10.2 Channel Count under ASIO 
At a sample rate of 88.2 or 96 kHz, the ADAT optical input and outputs operate in S/MUX mode, 
so the number of available channels is reduced from 8 to 4. 
At a sample rate of 176.4 and 192 kHz, the ADAT optical input and output operates in S/MUX4 
mode, so the number of available channels is limited to 2. 
Note
: When changing the sample rate range between Single, Double and Quad Speed the 
number of channels presented from the ASIO driver will change too. This may require a reset of 
the I/O list in the audio software. 
Single Speed  Double Speed  Quad Speed 
Analog 1 to 8  Analog 1 to 8  Analog 1 to 8 
SPDIF coax L / R  SPDIF L / R  SPDIF L / R 
SPDIF opt LR / ADAT 1/2  SPDIF opt LR / ADAT 1/2  SPDIF opt LR / ADAT 1/2 
ADAT 3 to 8  ADAT 3 to 4  - 










