User`s guide

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User's Guide Fireface UC © RME
22. Analog Inputs
22.1 Line Rear
The Fireface has balanced line inputs as 1/4" TRS jacks on the back of the unit. 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.
One of the main issues when working with an AD-converter is to maintain the full dynamic
range within the best operating level. Therefore the Fireface UC internally uses hi-quality elec-
tronic switches, which allow for a perfect adaptation of all rear inputs to the three most often
used studio levels.
The 'standardized' studio levels do not result in a (often desired) full scale level, but take some
additional digital headroom into consideration. The amount of headroom is different in different
standards, and again differently implemented by different manufacturers. Because of this we
decided to define the levels of the Fireface in the most compatible way.
Reference 0 dBFS @ Headroom
Lo Gain +19 dBu 15 dB
+4 dBu +13 dBu 9 dB
-10 dBV +2 dBV 12 dB
With +4 dBu selected, the according headroom meets the latest EBU recommendations for
Broadcast usage. At -10 dBV a headroom of 12 dB is common practice, each mixing desk op-
erating at -10 dBV is able to send and receive much higher levels. Lo Gain is best suited for
professional users who prefer to work balanced and at highest levels. Lo Gain provides 15 dB
headroom at +4 dBu nominal level.
The above levels are also found in our ADI-8 series of AD/DA converters, the Multiface, and
even in our Mic-Preamps QuadMic and OctaMic. Therefore all RME devices are fully compati-
ble to each other.
22.2 Microphone / Line Front
The balanced microphone inputs of the Fireface UC offer an adjustable gain of 10 dB up to 65
dB. The soft switching, hi-current Phantom power (48 Volt) provides a professional handling of
condensor mics. The usage of a hi-end integrated circuit (PGA 2500) guarantees outstanding
sound quality, stunning low THD, and maximum Signal to Noise ratio in any gain setting.
The two combo jacks also allow for the usage of mono and stereo TRS jacks. The TRS jacks
have a fixed level attenuation of 11 dB. Based on the adjustable amplification from +0 dB up to
+65 dB, the sensitivity is +21 dBu down to –44 dBu, referenced to full scale of the AD-converter.
Therefore the TRS inputs are true full level Line inputs, and the unit can also be used as Line
amplifier.
The TRS jacks are free of phantom power.
Two LEDs display a present signal (from –65 dBFS on) and warn against overload (-2 dBFS).