Crown Audio IQ-MCA-IQ-MC8 - Manual (Page 18)

Page 18 Reference Manual
IQ-MC Modules
The IQ-MC module can be con-
nected to the IQ Bus with inexpen-
sive twisted-pair wiring (shielded or
unshielded). If fiber optic wiring is
required contact Crown Technical
Support (see page 28).
Here are some guidelines for twisted-
pair wiring:
• Use shielded twisted-pair wire
at least 26 AWG in size when
interference is a problem. The
wire should be of good quality
and should have low capaci-
tance—30 picofarads/foot or
less is good. The shield serves
two purposes: First, it helps pre-
vent the IQ data signal from
transmitting to nearby audio wir-
ing. Second, it helps prevent out-
side RF from interfering with the
data signal. However, in most
cases interference is not a prob-
lem and, since unshielded wire
has lower capacitance, it is a
better choice.
• Minimize the total capacitance
of each IQ Bus loop. The total
capacitance should be less than
30 nanofarads. Allow for ap-
proximately 60 picofarads for
each IQ component in a loop.
This accounts for a slight delay
which occurs as data signals
pass through a component.
• Add an IQ Repeater (RPT3) for
very long loops—greater than
1,000 feet (305 m)—or when re-
quired by high-capacitance
wire. Although we recommend a
repeater for loops longer than
1,000 feet, it is often possible to
go 2,000 feet (610 m) or more.
The most significant characteris-
tic of the wire is its capacitance.
Lower capacitance allows
longer loops. Unshielded wire
usually has less capacitance.
• Never use the ground wire in a
mic snake line. It may some-
times be convenient to run IQ
Bus data signals to and from
stage monitor amplifiers along
unused wire pairs in a mic snake.
Do not use the ground wire which
is normally connected to pin 1 on
an XLR connector or data noise
will be added to the audio lines.
Use only the signal lines which
normally connect to pins 2 and 3
of the XLRs.*
Outside RF interference is seldom a
problem for a IQ Bus loop—espe-
cially if shielded twisted-pair wire is
used. However, there are extreme
situations when fiber optic wiring is
recommended. For example, locat-
ing a IQ Bus loop next to an AM radio
transmission line may require fiber
optic cabling. An extremely long IQ
Bus loop distance may also require
fiber optic cabling.
5.2 Using the AUX
Connector
The IQ System offers tremendous
flexibility and the auxiliary feature
connector provides a means of tap-
ping into it. It can be used to turn
peripherals on/off, send a signal to
another system component, receive
a signal from another component,
and send a line level audio signal of
amplifier’s output.
The AUX connector is an RJ-11 type.
Pins 2 and 5 are used to receive a
signal and pins 3 and 4 are used to
send a signal.
* Because typical mic cables have high ca-
pacitance, the maximum possible Crown
Bus loop distance will be less.