Lab.gruppen PLM 10000Q, Operation Manual

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PLM Series Operation Manual rev 1.1.3
10. Back Panel Interface
71
10.2.1.1 Unbalanced operation
Balanced interconnections are recommended whenever possible. However, if it is necessary to drive the
PLM from equipment with an unbalanced output, wire the inputs as shown in the diagram below:
1 2
3
COLD
HOT
SCRN
COLD
HOT
SCRN
Unbalanced Output
(Typically phono)
Balanced Input
(XLR)
Figure 10.2.1.1a: Balanced-to-unbalanced analog
wiring and pin out
This method still uses twin-and-screen (‘balanced’) cable and standard XLR pin connections at the PLM end,
but the ‘cold’ wire and the cable screen are connected together to the signal ground of the equipment at the
source end.
This usually provides better noise and hum rejection than the more common method of joining pins 1 and 3
together in the XLR. However, if only a single-core (“unbalanced”) cable is available, the following method
may be employed. See figure 2.2.1b.
1 2
3
HOT
SCRN HOT
SCRN
Unbalanced Output
(Typically phono)
Balanced Input
(XLR)
Figure 10.2.1.1b: Unbalanced-analog wiring and pin
out
10.2.1.2 Iso-Float electronic balancing
The PLM’s electronic input balancing circuits use the Lake Iso-Float system.
The Iso-Float technology combines the benefits of transformer-coupled isolation with the advantages of
clean, direct-coupled inputs and outputs. The audio converters are galvanically isolated, and not connected
to the main ground. High-quality transformers and opto-isolators create a barrier between the PLM and
possible grounding aberrations from the outside electrical environment.
Iso-Float on the PLM is accessed via the menu system; see section 9.12.3.2 for details. Additionally it is
possible to control Iso-Float directly from the Lake Controller software.
When paralleling analog inputs of several PLMs,
either by using the Link connectors or an external
paralleling system, bear in mind that the drive
capability of the source’s output stage (typically a
mixing console) may be limited. As a general rule, it is inadvis-
able to attempt to parallel more than four PLM inputs together
in this way. (Two inputs on the same PLM do count as two!) If it
is necessary to drive a greater number, the use of a good
quality balanced audio line driver or distribution amplifier is
recommended.