Crown MPX-6 User Manual

Page 13

IQ Mixer / Multiplexer  Hardware Installation

Rev. 0

Crown Bus can have the same address. Suppose,
for example, an 

IQ System has two Crown Bus

loops as shown in Figure 3.1 and an 

SMX-6 is

installed in loop 1 and given IQ address 77. No
other 

SMX-6 can be given the same address in

Crown Bus loop 1. However, an 

SMX-6 can have the

same address if it is installed in loop 2. Different IQ
components can have the same address and be in
the same Crown Bus loop. In the previous example,
an 

AMB-5 could be installed in loop 1 and use IQ

address 77 because it is not an 

SMX-6.

A valid IQ address is any number from 1 to 250. 

Do

not use a number higher than 250

 since they are

reserved for special use. An address of ÷0š (zero)
should not be used. The IQ address is determined
by adding the values of each segment of the DIP
switch which is turned on (pushed down). Figure 3.5
shows the value of each DIP switch segment. For
example, if the desired unit address is 1, only
switch 1 should be down. If the desired unit address
is 217, switches 8, 7, 5, 4, and 1 should be down
(128+64+16+8+1=217). See Appendix A for list of
all valid DIP switch settings.

If the IQ interface used is an IQ-INT, the system can
have up to eight separate Crown Bus loops. This will
enable the audio system to be divided into different
zones, each with its own Crown Bus loop. Dividing
the 

IQ System into multiple Crown Bus loops has

advantages and disadvantages which are listed be-
low:

Multiloop Advantages

• A break in communication in one loop does not

affect other loops.

• Over 250 IQ components of the same model

can be use in a system.

• The same IQ address can be used more than

once (once per loop per model).

Single Loop Advantages

• The 

IQ System can send and retrieve data

faster in a single loop.

• ÷Real timeš level display of a greater number

of units is possible.

The Crown Bus is implemented in IQ mixer/multi-
plexers as a 20 milliamp current loop operating at
38.4 K baud so that it can function with inexpensive
twisted-pair wiring. If fiber optic wiring is required
contact Crown Tech. Support or Amcron Tech. Ser-

vices (see page 22) for information on adding the
appropriate transceivers.

Here are some guidelines for twisted-pair wiring:

•

 at least 26

AWG in size. The wire should be of good qual-
ity and should NOT have high capacitance (30
picofarads/foot or less is good). Shielded wire
is recommended for situations where interfer-
ence is a problem. (West Penn 452 or an
equivalent wire works well.) The shield serves
two purposes: First, it helps prevent the IQ
data signal from transmitting to nearby audio
wiring. Second, it helps prevent outside RF
from interfering with the data signal. However,
in most cases interference is not a problem
and, since unshielded wire has lower capaci-
tance, it is a better choice.

• If shielded wire is used, 

connect the shield

only to the input connector

.

•

 for very long

loops…greater than 1,000 feet (305 m)…or
when required by high-capacitance wire. Al-
though we recommend adding a repeater for
loops longer than 1,000 feet, it is often pos-
sible to go 2,000 feet (610 m) or more. The
most significant characteristic of the wire is its
capacitance. The lower the capacitance, the
longer the loop can be. Unshielded wire typi-
cally has less capacitance.

•

     It may sometimes be convenient to run

Crown Bus data signals to and from stage
monitor amplifiers along unused wire pairs in a
mic snake. If this is done, do not use the
ground wire which is normally connected to pin
1 on an XLR connector or data noise will be

Fig. 3.6  Crown Bus Wiring for Removable Barrier Blocks

Cable connectors are numbered as they appear from the front.