Owner`s manual

Internal Adjustments
The following information is provided for authorized technicians only and is not intended for use
by the user. Adjustment of internal settings by non-authorized personnel will void the warranty.
Technicians are expected to follow appropriate ESD practices.
The Voltage selector
This is located inside the Rosetta, adjacent to the AC connector. The two settings are as follows: “115VAC”
accepts 95 to 145 V ac (USA and Japan). “230VAC” accepts 200 to 250 V ac (most of Europe). 50 or 60 Hertz
supplies may be used in either case. The correct setting should already be selected for your area so, unless oth-
erwise indicated, this should not be changed.
Fuses
The AC fuses are also inside the Rosetta, next to the voltage selector. If the Rosetta does not power up for
some reason, check that all AC lines are connected, check that there is power coming from the wall (by con-
necting another device), and then check the internal fuses.
CAUTION For protection against risk of fire, replace only with same type and rating of fuse:
115V~ operation: 250V, 250mA, T (Slow Blow); 230V~ operation: 250V, 125mA, T (Slow Blow)
DO NOT LIFT THE GROUND PIN. When tracing down hums and buzzes, the AC ground pin is often lifted to
break ‘ground loops’. Apogee does not recommend that you lift the ground pin on the Rosetta as AC spikes
(that have no path to ground) can severely damage the unit.
Soft Limit Adjustment
1. Make sure that your converter is properly aligned as discussed below.
2. Generate a 1 kHz tone using a function generator or oscillator from your console or test equipment.
3. Increase the output level of the oscillator until the ‘OVER’ LEDs illuminate.
4. Slowly reduce the output level of the oscillator while repeatedly tapping the ‘METER CLEAR’ button until
the ‘OVER’ LEDs
JUST go off. Note the output level of the oscillator.
5. Select the amount of headroom you wish to achieve using the Soft Limit circuit. The Soft Limit comes cali-
brated from Apogee at +4dB headroom, so we will use this number as an example.
6. Increase the output level of the oscillator by 4 dB. The ‘OVER’ LEDs should illuminate again.
7. Turn Soft Limit on.
8. Adjust the Soft Limit trimpots (VR12 for left, VR15 for right) on the AD Module inside the unit while repeat-
edly tapping the ‘Meter Clear’ button until the ‘OVER’ LEDs JUST go off.
9. You have just adjusted Soft Limit for +4 dB of additional headroom. You can change the amount of head-
room by changing the output level of the oscillator in step 6.
Rosetta Level Adjustment
Here is a quick guide to adjusting the level sensitivity of the Rosetta.
1. Press and hold the ‘Soft Limit’ button for two seconds. The Rosetta will enter “Calibration Mode” indicat-
ed by the Soft Limit LED flashing slowly.
2. Now the 12-segment bar graphs will have a range of –21dBFS (leftmost LED) to –10dBFS (rightmost LED)
– ie, one dB per LED, rather than the value indicated by the labeling. In CAL mode, the “OVER” LED will
illuminate when the signal level is within ±0.1 dB of the level indicated by the appropriate meter segment.
3. Generate a 1kHz, +4dBu / 0VU tone using a function generator or oscillator from your console or test equip-
ment and insert it into the analog input jacks.
4. Increase/decrease the analog input level with the ‘Level Trim’ pots using a ‘tweaker’ or small screwdriver.
5. As you increase/decrease gain you will notice the ‘OVER’ LEDs going on and off indicating you were at, and
then passed, one of the standard calibration points within ±0.1 dB.
Rosetta AD User’s Guide
Page 18