5 adjust the levels & scale factors, 6 a closer look at crown bus wiring – Crown Audio IQ P.I.P.-DSP User Manual

Page 12

Page 12

IQ–P.I.P.–DSP Programmable Input Processor with DSP for IQ Systems

Reference Manual

Fig. 3.6 Amplifier Scale Factor Values

and Output Signal Pad Settings

Channel 1

Channel 2

Scale Values (Decimal)

Com-Tech 200 (8 ohm)

Com-Tech 400 (8 ohm)

Com-Tech 800 (8 ohm)

Com-Tech 1600 (8 ohm)

All Com-Tech (70-volt)

Macro-Tech 600

Macro-Tech 1200

Macro-Tech 2400

Macro-Tech 24x6

Macro-Tech 3600VZ

Macro-Tech 36x12

Macro-Tech 5000VZ

Macro-Tech 10000

Reference I

Reference II

PIP2-Compatible (Auto)

Amplifier

Model

Output Signal Pads

(JP4, JP5)

OUT

Section 3.8 for more information.

3.5 Adjust the Levels & Scale Factors

13.

Turn the level controls of the amplifier to their
full or maximum setting.

This is required by the

IQ–P.I.P.–DSP. If needed, use the software-con-
trolled input attenuators on the

IQ–P.I.P.–DSP to re-

duce the audio levels.

14.

Configure the amplifier scale factors.

(Standard

P.I.P.-compatible amplifiers only—the scale factors for
PIP2-compatible amplifiers are set automatically.) It is
necessary to configure software scale factors in the
microprocessor of the

IQ–P.I.P.–DSP in order for it to

properly interpret the output signal level of the ampli-
fier model in which it is installed. This is easily done by
connecting a host computer to the

IQ–P.I.P.–DSP via

an IQ interface and the Crown Bus and running the
appropriate software (see the IQ software

User’s

Manual for details). In the appropriate input area of the
software, specify the amplifier model. The software
will then send the appropriate scale factors to the P.I.P.
Note that for some amplifiers, the scale factors will
also need to be specified by the user. When
prompted by the software, input the appropriate scale
factor. The scale factor values are listed in Figure 3.6

along with the settings of jumpers JP4 and JP5.

Note: Since it is possible to configure one chan-
nel of a Com-Tech amplifier in the 8-Ohm output
mode and the other channel in the 70-Volt output
mode, it may be necessary to configure the
scale factors differently for each channel.

3.6 A Closer Look at Crown Bus Wiring

The

IQ–P.I.P.–DSP must be connected to a Crown Bus

loop having an

IQ2-compatible IQ interface in order for

the

IQ System to control or monitor it. The Crown Bus is

a serial communication loop designed to transmit IQ
commands and data. As implemented in the

IQ–P.I.P.–

DSP, it is a 20 milliamp current loop operating at a
BAUD rate of 38.4 K. The loop must be unbroken to
function properly.

If the system includes an

IQ–INT II interface, it can ac-

cept eight different Crown Bus loops or zones. Dividing
the sound system into different zones, each with its own
Crown Bus loop, can have several advantages. The fol-
lowing list contrasts those advantages with those of a
single loop.

Multiloop Advantages

• A break in communication in one loop does not

affect other loops.

• Over 250 IQ components of the same type can

be used in a system.

• The same IQ address can be used more than

once (once per loop per model).

Single Loop Advantages (with IQ-INT II interfaces)

• The

IQ System can send and retrieve data faster

in a single loop.

• “Real time” level display of a greater number of

units is possible.

The

IQ–P.I.P.–DSP can be connected to the Crown Bus

with inexpensive twisted-pair wiring (shielded or
unshielded). If fiber optic wiring is required contact the
Crown Technical Support Group (see page 4).

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
capacitance—30 picofarads/foot or less is good.
(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
capacitance, it is a better choice.

•

Minimize the total capacitance of each Crown
Bus loop.

The total capacitance should be less

than 30 nanofarads. Allow for approximately 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

for very long loops—greater