Owner`s manual

The digital scale (‘dBFS’ or ‘decibel full-scale’) differs significantly from the conventional analog scale. The dif-
ference is that these ‘zeros’ are not the same kind of thing. The maximum level on a digital meter is 0dBFS, (a
digital “word” of all ones), which is a real, absolute limit, whereas analog signals can go well over ‘0 dB’ on a
VU meter without a problem. The Rosetta is set at the factory so that an analog input of ‘+4dBu’ (0 VU on a
professional console meter) translates into a digital level of ‘–16dBFS’ (so, to attain 0dBFS, the converter must
be fed +20 dBu). It can be adjusted so a +4dBu analog signal translates into a digital level in the range from
–12dBFS (louder) to –20dBFS (softer). See L/R LEVEL TRIM below.
The ‘over’ LED indicates a digital level of 0 dBFS (full scale). The number of consecutive samples at 0 dBFS
required to indicate an ‘over’ on the meters is selectable via DIP switches 3 and 4 on the back panel. See ‘DIP
Switches 1-8’ below.
METER CLEAR
Clears the ‘OVER’ indication (red LEDs) on the L/R level meters.
When the ‘Meter Clear’ button is
pressed and held for two seconds it will take on its secondary function which
is an internal calibration of the 24-Bit Analog to Digital converter. Although the A/D converter is automatically
calibrated as part of the power up sequence, you can re-calibrate whenever you want to – just be sure to wait
five minutes after power has been applied. After five minutes the converter has reached thermal equilibrium,
so re-calibration at this time will yield ultimate performance. The converter is also re-calibrated each time the
sample rate is changed. You can visually tell that calibration is being performed: the L/R meter displays momen-
tarily, illuminating the middle LEDs of each segment. As the Rosetta recalibrates itself fairly frequently, you will
seldom need to do it manually. Note that this calibration is only an internal calibration of the A/D converter chip
and has nothing to do with the manual level settings using the L/R level trim below.
L/R LEVEL TRIM
Adjusts the level sensitivity of the A/D section.
As discussed in the METERS description, digital and analog scales are different. The level trim pots allow you
to set the Rosetta to an operating level that is convenient for your particular application.
See page 18 for prop-
er level adjustment of your Rosetta.
Tracking
Because of the unpredictable dynamic range of live performance, it’s often desirable to have plenty of head-
room to capture a performance without risking overs. In this case, you may want to set the Rosetta to –20 or
–18dBFS. The SOFT LIMIT function will also prove to be a useful feature in live recording.
Mixing
Levels are usually more controlled during a mix. In this case, the Rosetta can be adjusted to –16 to –12 dBFS to
lay down the final mix.
Mastering
In the mastering stage, it’s often desirable to get the hottest signal on to tape. Hot transients are usually bet-
ter-controlled at this stage. The converter does not need as much headroom, so it can be set to –12dBFS.
The chart on the next page shows the relationship between dBu and dBFS for the purposes of setting the lev-
els on the Rosetta.
Rosetta AD User’s Guide
Page 14