Meyer Sound Compact VariO UPJ-1P, Operating Instructions Manual

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CHAPTER 2
The UPJ-1P uses sophisticated amplification and protec-
tion circuitry to produce consistent and predictable results
in any system design. This chapter will help you under-
stand and harness the power of the UPJ-1P amplifier and
audio systems.
The rear panel of the UPJ-1P (Figure 2.1) provides two
slots for processor modules. The top slot contains the
audio input/control module. The optional RMS™ commu-
nications module sits in the bottom slot if installed; a blank
plate covers the bottom slot if RMS is not installed.
Figure 2.1. The rear panel of the UPJ-1P with looping audio input
module and optional RMS
NOTE: See Chapter 3, “RMS Remote Moni-
toring System (Optional)” for more informa-
tion on using RMS with the UPJ-1P.
AUDIO INPUT
The UPJ-1P uses a balanced, female XLR connector for
the audio input module in the UPJ-1P, and a male XLR
loop connector to interconnect multiple UPJ-1Ps. The
loop connector, wired in parallel to the audio input, trans-
mits the input signal if the UPJ-1P is turned off for any
reason.
The UPJ-1P audio input presents a 10 kOhm balanced
input impedance to a three-pin XLR connector with the
following connectors:

Pin 1 — 220 kOhm to chassis and earth ground (ESD
clamped)

Pin 2 — Signal ( + )

Pin 3 — Signal ( - )

Case — Earth (AC) ground and chassis
There are two interchangeable audio input modules with
and without controls for different applications.
!
CAUTION:
Shorting an input connector pin
to the case can form a ground loop and
cause hum.
Looping Audio Input Module
If the UPJ-1P is equipped with the looping audio input
module (Figure 2.2), Pins 2 and 3 carry the input as a dif-
ferential signal; pin 2 is hot relative to pin 3, resulting in a
positive pressure wave when a positive signal is applied to
pin 2.
Figure 2.2. The looping audio input module
Pin 1 is connected to earth through 220-kOhm, 1000 pF,
15 V clamp network. This ingenious circuit provides virtual
ground lift at audio frequencies, while allowing unwanted
signals to bleed to ground. Use standard audio cables
with XLR connectors for balanced signal sources with all 3
pins connected on both ends. Telescopic grounding is not
recommended.
Looping, Polarity, and Attenuating Audio Input Module
This looping, polarity, and attenuating audio input mod-
ule (Figure 2.3) has a balanced, female XLR audio input
connector, a male XLR loop connector, an input polarity
switch, and a level attenuator. The input polarity switch
offers a convenient method of reversing the polarity of the
loudspeaker system.
+
-
Figure 2.3. The looping, polarity, and attenuating audio input module
When the input polarity switch is in the up ( + ) position,
pin 2 is hot. When the switch is down ( - ), pin 3 is hot rela-
tive to pin 2, resulting in a positive pressure wave when
a positive signal is applied to pin 3. The level attenuator
operates between 0 dB (no level attenuation) when turned
all the way to the right, to –18 dB when turned all the way
to the left.
CHAPTER 2: AMPLIFICATION AND AUDIO