USL CM-8E - Manual (Page 17)

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5.4.2 Crossover and Spare Inputs
This connector receives the high band audio for the screen channels (left, center, right) when
there is a crossover before the CM-8E (either in the processor or between the processor and
the CM-8E). These inputs drive the “channel B” pins on the DE-15 connectors for the left,
center, and right channels. This connector also has an additional spare input that can drive an
additional amplifier or additional LFE outputs and be monitored. The inputs are active balanced
(differential) inputs. They may be driven by balanced or unbalanced sources. When driven by
an unbalanced source, the negative input should be connected to the low side of the source at
the source equipment to minimize ground loop noise. The cable should be twisted pair with
individual shields, even when driven by an unbalanced source. The DB25F connector uses the
THX® pin out as specified in the table in Appendix A.
5.4.3 DE-15F Amplifier Connectors
The CM-8E converts the DB-25 audio connector common on sound processors to the DE-15F
connector (also called HD-15 or VGA) connector common on amplifiers. As described
previously, the surround channels are “stereo” with two channels per connector. The screen
channels have one channel per connector. If the screen channel is biamped before the CM-8E,
channel A carries the low frequencies, and channel B carries the high frequencies. If the screen
channel is not biamped before the CM-8E, channel A carries the full range audio, and channel B
is silent.
The DE-15F connectors also provide an amplifier output return (Vmon or Voltage Monitor) to
the CM-8E. Surround channels return the left on channel A and the right on channel B. The
screen channels return the low band on channel A and the high band on channel B if the
crossover is located before the CM-8E (in the processor or between the processor and the CM-
8E) or if crossovers in the amplifier are enabled.
The CM-8E, by itself, always sends one screen channel through a two channel amplifier on the
assumption there is a crossover in the processor or amplifier. This is not always the case. USL
offers the "PXC" series of adapters for those auditoriums that have crossovers in the speakers
and need to carry two screen channels through one two-channel amplifier.
Figure 5.4.3a Figure 5.4.3b
The PXC-3 combines left and right to drive
one amplifier. A second PXC-3 combines
center and LFE1 to drive a second amplifier.
The PXC-4 combines left and center to drive
one amplifier. A second PXC-4 combines the
right and LFE1 to drive a second amplifier.