Lab.gruppen LAB 1600 - Manual (Page 6)

SLEEVE SHIELD/GROUND
Figure 4. TRS phone plug
The input impedance is high enough (20 kohms
balanced) to allow ”daisy-chaining”, or multiple
parallel input connections. To daisy chain, use the
TRS jacks provided on each channel. The input
circuits also have a high enough headroom, to accept
the maximum output level from virtually any low
level signal source.
Figure 5. Rear panel connectors
Do not use XLR and TRS jacks on the same
channel simultaneously for mixing or other
purposes.
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. To minimize
hum in the audio, use balanced inputs whenever
possible.
Fi gure 8. Balanced line with unbalanced equipment
7. Connecting speakers
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
2 R losses.
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