User Manual

User's Guide Fireface 800 © RME

18.9 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.

The level meters integrated in TotalMix - considering their size - cannot be compared with

DIGICheck (chapter 21). 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 measure-

ment devices for. An ADI-8 DS connected to the Fire-

face will therefore show around -113 dB on all 8 chan-

nels.

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’.