Instrument / Line Front - RME Audio Fireface UC User Manual

22.3 Instrument / Line Front

The instrument inputs 3/4 of the Fireface UC are exceptionally flexible. Several gain and im-
pedance options make them the ideal receivers for both line and instrument signals.
Line
Inputs 3/4 have balanced line inputs as 1/4" TRS jacks. The electronic input stage is built in a
servo balanced design which handles unbalanced (mono jacks) and balanced (stereo jacks)
correctly, automatically adjusting the level reference.
When using unbalanced cables with TRS jacks: be sure to connect the 'ring' contact of the
TRS jack to ground. Otherwise noise may occur, caused by the unconnected negative input
of the balanced input.
Inputs 3/4 operate in perfect harmony with the rear inputs 5 to 8, as they use the same level
references:
Reference 5-8
Lo Gain
+4 dBu
-10 dBV
-
Instrument
The main difference between a line- and instrument input is the input's impedance. Via the op-
tion Inst 3 and Inst 4 in the Settings dialog, the input impedance changes from 10 kOhm to 470
kOhm. At the same time the input sensitivity rises by 10 dB. Using active instruments this set-
ting can already cause overload. Therefore the option Pad is still available, reducing the sensi-
tivity by 12 dB.
The instrument input operates servo-balanced, thus handles balanced signals correctly as well.
Input Gain
Via Input Gain in the Settings dialog, or using the rotary encoder on the front, an additional gain
can be applied to the input signals of channels 3/4. The gain range is 0 dB up to 18 dB, in steps
of 0.5 dB. This option not only allows for the use of sources with low level output signals, but for
example also to adjust the balance between channel 3 and 4 precisely, already before the re-
cording takes place.
Overall the inputs 3/4 can work with levels from –16 dBu up to +25 dBu. Two LEDs display a
present signal (from –65 dBFS on) and warn against overload (-2 dBFS).
0 dBFS @
+19 dBu
+13 dBu
+2 dBV
+15 dBu
User's Guide Fireface UC © RME
Setting 3/4
Pad
No Pad
Inst
Inst + Pad
Input Gain 3/4
+6 dB
0 dB
0 dB
0 dB
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