Owner manual

Page 15
Reference Manual
P.I.P.-RPA
3.8 Using the Audio Bus
The audio bus inputs and outputs are
provided so additional signals can
be added to the mixed bus (input) of
each channel or the mixed (output)
signals can be fed to other compo-
nents or amplifiers (see Section A.4
in the Appendix). As such they are
very similar to the “Aux Return” and
“Aux Send” connections on a typical
mixer.
One common use for the audio bus
inputs is to “stack” multiple P.I.P-RPAs.
For example, by interconnecting the
audio bus inputs and outputs of two
P.I.P.-RPAs (as shown in Figure 3.17)
you can create an 8x2 mixer.
Fig. 3.18 Audio Bus Wiring
The audio bus inputs are actually
“current” inputs so a 10 K ohm
source resistor (
1
/
4
watt) is required
for connection. This allows an al-
most unlimited number of sources to
be connected. The best place to
locate the 10-K resistor is at the input
connector since this results in the
lowest noise. This is shown in Figure
3.18. No resistor is required for con-
nection to the audio bus outputs.
Since the audio bus inputs and out-
puts are unbalanced, two things
should be considered: First, the input
grounds are always “lifted” from the
chassis ground. Second, in-line isola-
tion transformers should be added for
long input or output wire runs.
Note: Only the mixed audio signal
from Inputs A, B, C, and D appear at
the audio bus outputs. Any signal fed
into the audio bus inputs will
not
appear at the audio bus outputs (to
avoid a feedback loop).
Important: The polarity of the au-
dio bus outputs is inverted. The
mating audio bus inputs perform the
necessary polarity inversion so that
all inputs to the amplifier are the
same polarity. When using the audio
bus output to drive another compo-
nent the signal should be connected
to the (–) in put and ground.
4 Specifications
General
Note: All specifications referenced
to a 0.775-V input signal.
Signal to Noise: Line: Nominally 80
dB from 20 Hz to 20 kHz. Mic: Nomi-
nally –115 dB equivalent input noise,
20 Hz to 20 kHz (Rs=300Ω).
Fig. 3.17 Stacking Two P.I.P.-RPAs