Operation Modes - Lab.gruppen LAB 300 User Manual

Figure 6. Balanced line
To connect an unbalanced source, tie pin 3 (ring on
TRS jack) down to the shield of the connector. If you
leave one pin disconnected, you will lose 6 dB in
gain.
Figure 7. Unbalanced line connection
A more optimal method for handling unbalanced
sources is shown in Figure 8. This is similar to the
connection for balanced lines, but pin 3 is tied down
to shield, at the source side instead. The hum and
noise rejection for the cable is equivalent to that for a
balanced line.
Figure 8. Balanced line with unbalanced equipment
To minimize hum in the audio, use balanced inputs
whenever possible.
7. Connecting speakers

Operation modes

1. Stereo operation
For stereo (dual channel ) operation, leave the Link
and Phase reverse switches in the undepressed
position. In this mode, both channels operate
independently of each other, with their level
attenuators controlling their respective levels.
Never connect either output terminal to ground
or in parallel. The recommended minimum
nominal impedance, for stereo or tandem operation,
is 2 ohms per channel.
2.
Tandem mono
For tandem ( dual channel-single input) operation ,
depress the Link switch. Both channels can now be
driven by a signal, at either input connector. The
output connection is the same as in stereo mode.
Speaker connections are made via the two Neutrik
NL4FC Speakon connectors (1).
They are the only connectors currently available to
meet the EC safety requirements. They are wired in
the following manner:
Pin -1 Speaker ground.
Pin +1 Speaker positive.
Pin -2 No connection.
Pin +2 No connection.
Figure 9. Speakon connector
Please note that this is the standard wiring
convention for Speakon connectors adopted world-
wide.
Never connect either output terminal to ground
or to some other output or input terminal (see
warning on page 2).
For normal two-channel operation, connect each
speaker load across the outputs positive and ground
terminals. Pay attention to speaker polarity;
loudspeakers connected out of polarity degrade
sound quality and may be damaged as a
consequence.
Keep the speaker cable wires as short as possible,
and use a good quality stranded speaker cable. Do
not use shielded wire, such as microphone or guitar
cable. Remember that the speaker cable robs the
power of the amplifiers in two ways:
Increases the load impedance and introduces
resistive power losses, so called I
You can use either TRS connectors for linking out
etc.
Do not use the remaining XLR and TRS
connectors for mixing or other purposes. Both
level attenuators are active, allowing you to set
different levels for each channel.
Never connect either output terminal to ground
or in parallel.
3.
Bridged mono
To bridge the amplifier, depress the Link switch (7)
and Phase reverse switch (6). Both channels are then
driven by a single signal at either input. You can
use any remaining input connectors for linking etc.
Do not use the remaining XLR and TRS as input
jacks simultaneously for mixing or other purposes.
To obtain an output, connect the speaker leads to pin
+1 on channel A Speakon to speaker positive
terminal and pin +1 on channel B Speakon to
speaker negative terminal . Do not connect either
2
R losses.
6