Intel Fireface 800 - Manual (Page 67)

User's Guide Fireface 800 © RME
67
29.15 Level Meter
The Fireface 800 calculates all the display values Peak, Over and RMS in hardware, in order to
be capable of using them independent of the software in use, and to significantly reduce the
CPU load.
Tip: This feature, the Hardware Level Meter, is used by DIGICheck (see chapter 15/22) to
display Peak/RMS level meters of all channels, nearly without any CPU load.
The level meters integrated in TotalMix - considering their size - cannot be compared with
DIGICheck. Nevertheless they already include many useful functions.
Peak and RMS is displayed for every channel. 'Level Meter Setup' (menu Options or F2) and
direct keyboard entry (hotkeys) make various options available:
• Display range 40 or 60 dB (hotkey 4 or 6)
• Release time of the Peak display (Fast/Medium/Slow)
• Numerical display selectable either Peak or RMS (Hotkey E or R)
• Number of consecutive samples for Overload display (1 to 15)
• RMS display absolute or relative to 0 dBFS (Hotkey 3 or 0)
The latter is a point often overlooked, but
nonetheless important. A RMS measurement
shows 3 dB less for sine signals. While this is
mathematically correct, it is not very reasonable
for a level meter. Therefore the RMS readout is
usually corrected by 3 dB, so that a full scale
sine signal shows 0 dBFS on both Peak and
RMS meters.
This setting also yields directly readable signal-
to-noise values. Otherwise the value shown with
noise is 3 dB better than it actually is (because
the reference is not 0 dB, but -3 dB).
The value displayed in the text field is
independent of the setting 40/60 dB, it
represents the full 24 bit range of the RMS
measurement. An example: An RME ADI-8 QS
connected to the Fireface's ADAT port will show
around -114 dBFS on all eight channel's input
level meters.
This level display of TotalMix also provides means for a constant monitoring of the signal qual-
ity. Thus it can be a valuable tool for sound optimization and error removal in the studio.
Measuring SNR (Signal to Noise) is best done with RME’s free software DIGICheck. The
function Bit Statistic includes three different RMS meters for exactly this purpose (RMS
unweighted, A-weighted and DC).