User’s Guide HDSP System RPM
© RME
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15.10 Level Meter
Having set a new standard with the level meters of DIGICheck, Hammerfall DSP goes even
further: The calculation of the Peak, RMS and Over is realized in hardware, in order to be
capable of using them independent of the software in use, and to significantly reduce the CPU
load.
The level meters integrated in TotalMix - considering their size - cannot be compared with the
HDSP Meter Bridge
(chapter 20.2). Nevertheless they already include many useful functions.
Peak and RMS is displayed for every channel. 'Level Meter Setup' (Menu Options or F2) or
direct keyboard entry (
hotkeys
) makes 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. RMS shows 3 dB less for sine signals. This is
mathematically correct, but not very reasonable for a level
meter. Therefore, we had corrected DIGICheck's RMS
display by 3 dB, a full scale sine signal shows both 0 dBFS
Peak and RMS. This setting also yields directly readable
signal-to-noise values, while other applications (like
WaveLab) will show a value 3 dB better than actual
(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, thus making possible a SNR
measurement 'RMS unweighted', which you would
otherwise need extremely expensive measurement
devices for. An ADI-8 DS connected to the RPM will
therefore show around -113 dB on all 8 channels.
This level display will constantly bring the reduced
dynamic range of your equipment, maybe of the whole
studio, in front of your eyes. Nice to have everything 24 bit
- but still noise and hum everywhere in the range around -
90 dB or worse... sorry, but this is hard reality. The up-side about it is that TotalMix allows for
constantly monitoring the signal quality without effort. Thus it can be a valuable tool for sound
optimization and error removal in the studio.
Measuring SNR (Signal to Noise) requires to press R (for RMS) and 0 (for referring to 0
dBFS, a full scale signal). The text display will then show the same value as an expensive
measurement system, when measuring ‘RMS unweighted’.
Note: There is no RMS calculation for the third row, the physical outputs. Therefore these green
bars show the peak value.
