User`s guide

User's Guide Fireface 400 © RME
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27.3 Instrument / Line Front
The instrument inputs 3/4 of the Fireface 400 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 0 dBFS @ Setting 3/4
Lo Gain +19 dBu Pad
+4 dBu +13 dBu No Pad
-10 dBV +2 dBV Inst
- +8 dBu Inst + Pad
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 to –10 dBV. Using active instruments this
setting can already cause overloads. Therefore the option Pad is still available, reducing the
sensitivity by 6 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 to use sources with low level output signals, but for exam-
ple also to adjust the balance between channel 3 and 4 precisely, already before the recording
takes place.
Overall the inputs 3/4 can work with levels from –16 dBu up to +19 dBu. Two LEDs display a
present signal (from –65 dBFS on) and warn against overload (-2 dBFS).