AUDIOropa PROLOOP DCCplus Mode D'emploi page 23

3.7 Adjusting the amplifiers
In order to adjust a LOS system, you will require a field strength gauge, e.g. the FSMplus (A-4292-0).
1. Before you switch on the amplifiers, turn the input regulators IN1, IN2 and the loop current control CURRENT
as far to the left as possible.
2. Plug in the power cords supplied with the amplifiers and switch the master amplifier on. The power supply
indicator (3) blinks for 10 seconds and should light up than.
3. Before you adjust the line level, don't forget to apply a test signal to the INPUT2. We recommend using our
test CD, which comes with the FSMplus (A-4292-0).
Use a 1kHz sine signal (track 3 on the CD) and set the volume control (master fader) on the mixing desk or
the audio amplifier as it is normally used at your events.
4. Adjust the input sensitivity regulator (5) of the INPUT2 so that two green LEDs of the level indicator for com-
pression light up on the front panel of the device.
5. Turn the master current regulator (10) to the central setting. The control indicator (2) on the front panel should
now light up.
6. Set the FSMplus to "Norm" and "0dB scale" and hold it vertically to the induction loop level. The ideal height
depends on what the induction loop system is being used for; typically, this might be 1.20m (for seated au-
diences) or 1.70m (for standing audiences).
7. Check the average field strength by running diagonally over the induction loop area and determine the aver-
age of the values indicated. The average value has to measure 0dB (±3dB).
If you do not obtain this value, adjust the corresponding control until this value is reached. Please note that
every time you cross a cable, the field strength will drop briefly. This is normal as long as only one loop is in
operation.
8. Once the master amplifier is adjusted, switch off the master amplifier and disconnect the induction loop.
9. Now switch on the master and slave amplifier. Important: Do not alter any of the controls of the master
amplifier.
10. Turn the slave current regulator (10) to the central setting. The control indicator (2) on the front panel should
now light up.
11. If you have set up the slave amplifier, switch the master and slave amplifier off.
12. Re-connect the induction loop of the master amplifier.
13. Switch on the master and slave amplifer, again.
14. For the final check, use a normal audio signal, such as music or voice via the microphone and check the
field strength with the FSMplus. The value should read 0dB (±3dB) in the signal peaks.
If you do not read these values, repeat the measurement process starting from Step 3 and set the controls
higher than for the first test.
15. If the values lie within the stipulated range, the amplifiers are set to the ideal levels. Use the headphone jack
of the FSMplus to evaluate the sound of the signal with a pair of headphones.
English 23