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VPA600MB VELLEMAN
9
9. Operating Modes
Stereo Operation:
This is the normal operation mode of an amplifier, in which every channel gets its own signal. The most commonly
used mode of amplifiers is stereo operation at 4 ohms. Make sure that the operation mode switch is correctly set
(see “7.b.10”).
Remark: The input impedance of the speaker system should at least be the same or even higher than the output
impedance of the amplifier.
Bridged Operation:
Possibility to run the amplifier in mono via one input channel. In bridged operation mode, the voltage is doubled.
Consequently, the output impedance is doubled.
For stereo operation, 2 amplifiers are needed. Connect the input signal to the input CH-1 on the rear panel. Make
sure that the amplifier is disconnected from the mains before you set the operation mode switch on the rear panel
to bridge. Connect your speakers to the red mono bridged speaker socket.
CAUTION! Before switching on your amplifier, please refer to the explanations under “10. Operation”. Adjust the
level with the gain control CH-1 on the front panel.
10. Operation
After connecting your amplifier to the mains, turn both gain controls in an anticlockwise direction to the minimum
position. The last device to be switched on is the amplifier. The ON and PROTECT LED light up now. If not, check if
the amplifier is properly connected to the mains.
After the activation delay the speakers are activated (PROTECT LED is off).
After setting the volume controls of the pre-amplifier in the minimum position, turn the gain controls of your amplifier
to the midway position. If there is any humming, check the connection cables between the pre-amplifier and your
amplifier (switch off components first). Now adjust the volume with gain controls CH-1 and CH-2.
CAUTION! Never set the level of the individual channels so high that the LIMIT LED remains lit continuously. Make
sure the output signal isn’t distorted to avoid damage to your speakers.
All important operating modes of the amplifier can be monitored on the front panel.
SIGNAL output level
LIMIT short circuit or impedance too low or signal distorted
PROTECT activated momentarily when switching on or when one of the protective circuits is activated.
When operating the amplifier system, make sure the sound quality of the loudspeakers is OK. Distortion indicates
that either the amplifier or the loudspeaker is overloaded. Overloads can quickly lead to amplifier or speaker damage.
Reduce the volume immediately to avoid damage. The warranty becomes void when the speaker systems are
damaged by overload.
Always check the sound pressure level with a meter in order not to surpass threshold values.
If you want to switch off the system, switch off the amplifier first and then the pre-amplifiers in order to avoid
transients on the speaker.