Iso-Float Electronic Balancing; Digital Inputs And Links - Lab.gruppen PLM Series Operation Manual

10 BACK PANEL INTERFACE
HOT
SCRN
Unbalanced Output
(Typically phono)
Figure 10.2.1.1b: Unbalanced wiring and pin out

10.2.1.2 Iso-Float electronic balancing

The PLM's electronic input balancing circuits use
Dolby Laboratories patented 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 DLC
PLM Edition software.

10.2.2 Digital inputs and links

INPUT 1-2
Figure 10.2.2: Rear panel AES digital connectors
The AES/EBU digital audio input is on an XLR3F
connector, which is directly paralleled to the adjacent
XLR3M AES/EBU Link connector.
Please read the warnings regarding the
connection of digital audio signals in section
6.2.1 before attempting to use the AES/EBU
input.
48 PLM Series Operation Manual
2
HOT
SCRN
3
Balanced Input
(XLR)
LINK 1-2
AES/EBU
The AES/EBU digital audio format uses a balanced
electrical configuration similar to balanced analog
1
audio. The pinout is shown in table 10-2.
Pin 1
Pin 2
Pin 3
Table 10.2.2: AES connector wiring and pin out
Note that this is the only possible method of wiring –
there is no equivalent of an "unbalanced" connection
in the digital domain.
The AES/EBU signal format carries 2 channels of
audio (plus other control data) on a single cable/
connector. Selection of Ch 1 or Ch 2 is performed
within the digital processing section of the PLM and
is controlled from the menu system. See section
9.12.3.1 for full details.
The AES/EBU Link connector may be used to "daisy-
chain" the inputs of multiple PLMs together. Unlike
daisy-chaining of analog inputs, attention must be
paid to line termination. When daisy-chaining PLMs
together, only the "last" PLM in the chain should be
set to Terminated. All other PLMs should be set to
Unterminated. See section 9.12.3.3 for full details
of setting input termination.
As with balanced analog audio, there is a finite
limit to how many PLMs may have their AES/EBU
inputs "daisy-chained" together. The practical limit
will be determined by cable type and length as well
as the output circuit of the driving source. It may
be necessary to employ an AES/EBU line driver or
distribution amplifier to achieve reliable results in
some situations.
Factory tests indicate that it may be possible
to connect up to 20 PLMs in this way, but
the number achievable in any given situation
may be less than this. See section 12.5 for
further information on interconnecting digital audio
equipment.
AEs/EbU Wiring Table
Ground/Shield
Hot (+)
Cold (-)