zapco PX User manual

Model PX
Paragraphic Equalizer With
Electronic Crossover
Owner’s Manual
A.R.P.A. OF AMERICA CORP.
MADE IN MODESTO, CA U.S.A.

Contents
Introduction 2
Installation Instructions 3
PX Equalization Modules 5
Input Gain Adjustment 6
Technical Assistance 7
Manufacturing 8
1

Introduction
The ZAPCO model PX is a programmable four-band equalizer and
12dB per octave electronic crossover housed in an attractive
anodized aluminum chassis designed to be mounted either in-
dash or under-dash. The PX is comprised of two pieces: the PX
Main containing all of the audio circuitry and PSi, an isolated
power supply that provides the audio circuitry with + or - 15V
supply rails.
A master volume control and four filter control knobs are readily
accessible on the PX front panel. The filter controls have a
maximum boost or cut of 18dB at either extreme of rotation.
Independent left and right channel INPUT GAIN adjustments are
made via access holes in the lower left hand corner of the front
panel. A main power ON indicator and three OVERLOAD
indicators are provided to aid in system troubleshooting and
calibration.
Signal inputs and outputs are made to the rear of the unit by way
of gold plated RCA connectors. The back panel also contains the
controls for the electronic crossover. The crossover frequency is
continuously variable in a range of 70Hz to 1.6 kHz by using the
CROSSOVER FREQUENCY control pot. Separate LOW / HIGH
PASS OUTPUT LEVEL controls are provided for system
balancing. An auxiliary FULL RANGE output is provided for
possible use with full range satellites or 600 ohm earphone. The
modular “phone” DC POWER INPUT connector at the upper right
hand corner of the back plate is used to connect the PX Main to
the external power supply, the PSi.
The power supply, model PSi, is a highly efficient and compact
switching power supply that provides the PX Main with all
necessary operating voltages. An extra modular output connector
is provided for use with an additional PX. A fifteen foot
interconnecting cable is supplied to allow for remote mounting of
the supply. The PSi is used to trigger on/off operation of the PX
Main. A plug-in barrier strip is used to terminate the necessary
+12V, GND and TURN ON connections to the unit.
2

Installation Instructions
Careful thought and planning is a must in installing a mobile audio
system. Extra consideration is always recommended when
routing the signal cables to guard against injecting noise into the
system. NEVER mount any piece of ZAPCO equipment in the
engine compartment. Avoid routing signal and power cables
together in one bundle; isolate these lines on opposite sides of the
vehicle if at all possible.
Keep the above thoughts firmly in mind when determing a suitable
mounting location for the PX Main. It may be mounted under-
dash using the supplied bracket or in-dash using the four
countersunk mounting holes in the front panel. If mounting in-
dash, allow sufficient slack in the cabling to and from the unit as
access to the back panel controls may be necessary in fine tuning
the crossover point or output levels.
The PSi can be mounted virtually anywhere within the vehicle that
is free from moisture. Its compact design, plug-in barrier strip and
power connections enable the installer to mount the unit in
potentially hard to reach locations. While the stock, fifteen foot
cable length should be taken into consideration when determing
the mounting location, custom length cables can be ordered from
A.R.P.A. of America Corp.
The plug-in barrier strip is used to terminate all necessary power
and turn-on connections. The connector is polarized and will only
plug into the unit one way. Care must be taken to insure that each
connection terminates to the proper position on the plug! Note
that when looking at the screw side of the plug-in module all
connections are reverse of the label on the top of the unit.
BEFORE INSTALLING ANY PIECES OF EQUIPMENT: LIFT
THE NEGATIVE (GROUND) BATTERY LEAD.
3

The “+12 INPUT” must be connected to the PSi through an AGC
2A in-line fuse. Although the PSi is internally fused, an additional
fuse should be placed as close to the 12V source as possible to
protect system wiring in the event of “short” to chassis ground
from a pinched power input lead. The PSi “GND” connection
should be securely attached to the car chassis ground using a
suitable lug to terminate the connection to bare metal. Bare wires
do not make adequate, permanent connections. The PSi “TURN
ON” can be connected to any switched 12V sources such as a
tape deck, “power antenna," or CD “switched to 12V output”.
ONLY wire sizes between AGW 12 and 22 gauge should be used
when making these connections. Strip 1/4 inch of insulation from
the end wire, insert into the proper position in the barrier strip and
tighten screw securely. It is always recommended that wiring be
securely terminated BEFORE APPLYING VOLTAGE. This will
eliminate the possibility of damage to the vehicle wiring by
shorting +12V to chassis ground.
PX TURN ON
PX “power up” is initiated by application of +12V to the “TURN
ON” terminal located on the plug-in barrier strip of the PSi. Note
that the PSi will not turn on unless the power cable is securely
connected to the DC INPUT connector on the rear of the PX Main.
The POWER indicators on the PSi and the PX should both
illuminate upon “power up”.
4

PX Equalization Modules
The equalizer section of the PX Main features plug-in modules
that enable the user to select both the center frequency and
bandwidth of the four front panel FILTER controls. The “stock” PX
comes equipped with the following modules:
Filter # Frequency Q-(Bandwidth)
135Hz 2.1
2129Hz 2.2
31.1Khz 0.6
418Khz 1.3
These stock filters are found to be effective in most applications
and are a good starting point in the process of equalizing the
typical system. If it is determined that there are acoustic problems
that the stock filters do not effectively cover, there are 120
additional filters from which to select. Contact Technical
Assistance at the factory for ordering information. Please specify
center frequency and ‘Q’ when ordering additional filter modules.
NOTE: ‘Q’ is a numeric expression of the effective width of a
filter. In general the larger the ‘Q’ the narrower the effective
bandwidth. For example, a filter with a ‘Q’ of 4.5 would be a spike
filter effecting a very narrow band of frequencies while a filter such
as the stock #3 centered at 1.1Khz with a ‘Q’ of 0.6 effects
virtually the entire midrange.
5

Input Gain Adjustment
The pre-amp circuit built into the PX is capable of 26dB of gain.
Separate left and right channel INPUT GAIN adjustments are
made via two access holes in the lower left hand corner of the
front panel. Adjustments to the INPUT GAIN may be necessary
to match the source (TAPE DECK, TUNER, OR CD) output level
to the input sensitivity of the system amplifiers. If this adjustment
is set too low, the source may distort before the system is able to
achieve full power. If the INPUT GAIN is adjusted too high, the
internal circuitry of the PX and/or system amplifiers may distort.
Three OVERLOAD indicators located on the front panel of the PX
are supplied to aid in the gain adjustment procedure. Each of
these are WARNING indicators and should NOT illuminate with
any degree of regularity once the system gains have been
properly adjusted. The red indicator labeled PRE is calibrated to
illuminate when the internal circuitry of the PX is within 1dB of
clipping. The yellow indicators labeled LO & HI are calibrated to
ZAPCO power amplifiers with an input sensitivity of 2.5V RMS and
indicate the onset of amplifier clipping.
Insert tape or compact disc recorded at high level into the source
unit. If the source unit has a balance control, ensure that it is set
to center. Set the PX filter controls flat (white strip on control
knobs completely vertical). Using a small plastic screw driver
included with the PX adjust the INPUT GAIN trim pots fully
counterclockwise. These trim pots are 20 turn pots and will
ratchet at the end of their throw. Turning each pot more than 20
turns counterclockwise (or until ratcheting can be heard) will
ensure that left & right channels are matched before the gain
adjustment procedure begins. If the source has a volume control,
set it from approximately 1/2 to 3/4 full output. With the PX
volume control rotated completely counterclockwise, begin by
turning only one INPUT GAIN pot clockwise (count the number of
turns) until PRE indicator flashes, rotate 1 to 2 turns
counterclockwise or until flashing ceases. Rotate the other INPUT
GAIN trim pot the same number of turns as the first. Turn up the
6

PX volume control and adjust LOW & HIGH OUTPUT levels to
achieve an overall system balance. Minor INPUT GAIN
adjustments may be necessary to achieve left/right balance or for
louder tapes or compact discs. Setting filter controls at a high
boost position may also cause the PRE indicator to flash,
necessitating reduction in INPUT GAIN. If LO or HI indicators
flash, adjust LOW or HIGH OUTPUT level controls accordingly.
Technical Assistance
Should you experience a problem with your PX, please contact the
dealer that sold you this product. If your dealer is unable to solve
your problem, you may contact the factory customer service
department directly.
Phone: [phone] Monday-Friday 8am-5pm Pacific time
Fax: [phone]
If you need to return this product for repair, please call the factory
for a return authorization number. We will ask you for information
which will include your name, return shipping address, daytime
phone number, model and serial number, and a detailed
description of your problem. A photocopy of your original
purchase receipt is necessary to determine warranty status and
should also be included. Once we issue you a return authorization
number, please write it in a highly visible area on the package.
Zapco will not accept any packages that do not have a valid return
authorization number clearly marked on the outside of the
package.
Send all repairs to:
A.R.P.A. of America Corp.
Attn: Service Department
413 S. Riverside Drive, Suite D
Modesto, CA 95354
7

Manufacturing
This product is designed and manufactured in the USA. The
following operations are ENTIRELY performed in our Modesto,
California plant.
1. PC Board insertion
The components are inserted into American made printed
circuit boards.
2. PC Soldering
The printed circuit board assembly is wave soldered.
3. Testing
The PC board is 100% tested to design specs.
4. Extrusion Machining
American made aluminum extrusion is cut and machined
to precise tolerances.
5. Assembly
The product is assembled.
6. Final Test
Every product is tested with the highest quality audio test
equipment to meet or exceed their published
specifications.
7. Inspection and final packaging.
*Many companies claim that their products are built in the USA,
but only a few of the above steps are actually performed in
America. Many of these companies only do the final assembly,
with steps 1 - 4 being done outside the USA.
8

A.R.P.A. of America Corp.
413 S. Riverside Drive, Suite D
Modesto, CA 95354
[phone]
Fax [phone]
PX
Rev. G
12/96