User’s Guide Hammerfall DSP MADI
© 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 21.2). 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 an ADI-648 and then to the MADI
card will therefore show around -113 dBFS 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’.