Precision Power PCX 250 User manual

PrecisionPower 9235 South McKemy Street, Tempe, Arizona 85284 www.precisionpower.com
8900-4005
PCX250
PCX280

Power Bandwidth 10 Hz - 50 kHz
Total Harmonic Distortion < 0.02 %
S/N Ratio > 110dB
Input Topology Instrumentation
Input Sensitivity 150mv - 12 Volts RMS
Input Impedance 10k Ohms
Load Impedance (stereo) 2 - 8 Ohms
Load Impedance (bridged) 4 - 8 Ohms
Supply Voltage 11 - 15 Volts
Damping Factor >500
Slew Rate >50 V/µS
QBASS™ Up to +12dB Boost @ 40Hz
QBASS PLUS™ Up to +18dB Boost
@ 30, 36, 44, or 60Hz
Crossovers 12dB/Octave
Crossover Frequency 30-4kHz
Idle Current: PCX 250 1.5 Amps
PCX 280 2 Amps
NEW! Advanced Instrumentation Input Stage.
NEW! 12dB/Octave; HP/LP/FULL; 30-4kHz Crossover.
NEW! Independent Line Output Crossover 30-4kHz.
Adaptive PWM Power Supply.
Triple Darlington Output Stage.
AP-IV Protection Circuitry.
Forced Air Thermal Management. (PCX 280)
QBASS ™ Bass Boost (PCX 250)
QBASS Plus™ Bass Boost. (PCX 280)
High Voltage Input Capability with -12dB Attenuation Switch.
Gold Plated RCAInput and Output Connectors.
PowerLock™ Speaker and Power Wire Connectors.
Mixed Mono/Stereo Operation.
3-Yr Warranty when installed by an Authorized PrecisionPower Dealer.
MODEL 4ohm STEREO 2ohm STEREO 4ohm MONO
PCX 250 2 X 50 2 X 100 1 X 200
PCX 280 2 X 80 2 X 160 1 X 320
* ALL POWER RATINGS SHOWN ARE TESTED @ 12V; 20-20kHz
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You will need to install an in-line fuse or circuit breaker in the power wire
within 18" of the battery. This fuse or circuit breaker is to protect your vehicle
from fire in case the power wire shorts to the vehicle body. If you are only
using one amplifier, use the fuse rating indicated in this chart. If you are using
more than one amplifier, add up the fuse ratings for all the amplifiers. This sum is
the rating for your main fuse or circuit breaker.You may also want to add a power
distribution block near your amplifiers to distribute large gauge power cable to
multiple amplifiers.
NOTE: TOOLS ARE NOT SUPPLIED
Small flat blade screwdriver
Phillips screwdriver (#2 or medium sized)
Wire cutters
Wire strippers
4 - #6 round head screws, and 1 - #8 sheet metal screw (or nut, bolt, flat washer
star washer) [see detail]
2 - Ring connectors (large enough to accommodate your method of grounding)
In-line fuse or circuit breaker - see fuse chart below
Power and ground wire - see Power Wire Calculator on page 4
Speaker wire - 12 to 16 gauge
Grommets (sized to work with the power wire you plan to use in your installation)
Tube of silicone sealant
Amplifier
PCX 250
PCX 280
Maximum Fuse Rating
30 Amp
35 Amp
318

Before beginning, disconnect the negative (-) terminal of the battery prior to
working on the positive (+) terminal to prevent a short to ground. This is important,
unless you want to spend the rest of your life with a nickname like "Sparky," or
"Smokey." Reconnect the negative terminal only after all connections have been
made.
5
Warning! A Main Fuse must be installed within 18" of battery!
16

Once you have run both the power and ground wires, it's time to connect the
cables to the amplifier. Cut off excess wire and, using wire strippers, strip the ends
of the power and ground cables approximately 1/4 inch. Locate the PowerLock
power and ground connector (supplied). With a small flat bladed screw driver,
loosen the screws before attempting to insert the cables. Insert the wires into the
appropriate hole, and tighten the screws. Check for stray strands of wire which
may short out. Once the wires are secure, the PowerLock™ may be plugged into
the amplifier. The Power/Ground PowerLock™ will accommodate 6 gauge wire
for the PCX 250 and PCX 280.
Power/Ground PowerLock™
7
Short Circuit Protection engaged: The amplifier will turn off and try to come
back on immediately. The amplifier will cycle like this indefinitely, with "blips" of
sound each time. If this is the case, check your speakers and wiring for low
impedance and short circuits.
Thermal Protection engaged: The amplifier will turn off and several minutes
later will come back on. In this case, ensure that there is nothing blocking the
normal convective airflow of the amplifier. No obstruction should be within 2" of
the amplifier on all sides.
NOTE: Low battery voltage will cause the amplifier to run warmer and
possibly damage the amplifier.
NO SOUND Is the LED lit?
YES NO
Check Power and Remote turn-on
wire for voltage. Make sure Ground
wire is secure.
STILL NO SOUND
See your Authorized PrecisionPower Dealer or call 1-800-62POWER.
SOUND IN ONE CHANNEL ONLY
Reverse left and right speakers by unplugging the speaker connector, turning it
over and plugging it back in.
SOUND IS NOW IN
OPPOSITE CHANNEL SAME CHANNEL
Reverse RCA inputs Problem is in the speaker or
speaker wire of the silent channel
SOUND IS NOW IN
OPPOSITE CHANNEL SAME CHANNEL
Reverse RCAs at head unit Problem is in the Amplifier. See your
local Authorized PrecisionPower Dealer
or call 1-800-62POWER.
SOUND IS NOW IN
OPPOSITE CHANNEL SAME CHANNEL
Problem is in the head unit Problem is in the RCAcables
or before the amplifier
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1. Adjust all amplifier input gain controls to just above minimum sensitivity (fully
counterclockwise).
2. Using the cleanest music source (CD) playing, turn up the head unit source
volume until you can hear distortion. Now turn it down a bit until you cannot hear
the distortion (usually just below full volume).
3. Increase the Amplifier gain (clockwise) until the onset of audible distortion.
Then decrease the gain to the point just before the distortion starts. This setting
minimizes background noise and prevents overload.
4. Repeat step 3 for any remaining amplifiers in the system.
Your New! PCX™ amplifier has a TC-X Crossover (Total Control X-over©) 30-
4kHz (See page 19 for crossover Detent Chart). 12dB per octave phase correlat-
ed crossover built in to provide superior system flexibility without the added
expense and installation of an outboard crossover. The speaker outputs of
your amplifier are high-pass, low-pass, or all-pass depending to the HP/LP/Full
switch on the front endplate. You would choose low pass (switch middle) to use
this amp for subwoofers, choose high pass (switch left), or full (switch right) to use
this amp for full range speakers.
The RCAoutputs are controlled by a separate HP/LP/Full switch, and are always
independent of the speaker output crossover. As well as being able to independently
select HP/LP/Full, your new PCX™ amplifier allows independent selection of
frequencies from 30-4kHz (See page 19).
NOTE: The System Diagrams beginning on page 15 show several ways to use
the virtually unlimited PCX™ amplifiers internal crossovers in your system.
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1. Cooling Plenums: Maintain a minimum 2” clearance around cooling plenums
for proper amplifier cooling.
2. Crossover HP/LP/FULL Select Switch: Adjust this switch to select the
HPF/LPF/FULLfunction for the speaker outputs.
3. Crossover Frequency Selector Control: Use this control to adjust the
crossover frequency for the speaker output. (See Crossover frequency chart pg.19)
4. RCA Inputs: Connect the RCA cables from source unit, or line driver to these
RCAconnectors.
5. Gain Control: Use this control to match the output level of the source-unit to
the input of the amplifier.
6. -12dB Input Attenuation: Push this switch ‘IN’ for high voltage input (4V-12V)
capability. This button pushed ‘IN’ must be used for speaker level input on common
ground head-units or for high voltage line drivers.
7. QBASS™ Frequency Control: Buttons 1 and 2 offer the capability of selecting
30, 36, 44, or 60Hz to boost by the QBASS™ Control. (See page #2)
8. Output Crossover HP/LP/FULL Select Switch: Adjust this switch to select
the HP/LP/FULL function for the RCAoutputs.
9. Output Crossover Frequency Knob: Use this control to adjust the crossover
frequency for the RCAoutput. (See Crossover frequency chart pg.19)
10. RCA Outputs: Left and right RCA outputs provide HP/LP/Full; 30-4KHz to
another amplifier.
11. Speaker Output Connections: Plug the speaker PowerLock™ connector in
here.
PCX 250, 280 Control Panel

All two-channel PCX™amplifiers are capable of being bridged into a 4 ohm mono
output without switches or bridging modules. This feature permits the creation of
a mono channel for a subwoofer or center channel. Deriving the mono channel
is accomplished by using the Left Channel Positive wire (L+) as the positive speaker
wire and the Right Channel Negative wire (R-) as the negative speaker wire.
NOTE: It is important that a minimum 4 ohm impedance is observed. If the
impedance drops below 4 ohms while the amplifier is wired in the bridged
configuration, the amplifier's protection circuitry (AM-IV) may engage.
Run the speaker wires from the amplifier location through the vehicle to the
speakers. Observe the same precautions for routing these wires that you followed
for running the power and remote turn-on wires. Cut off excess and, using wire
strippers, strip 1/4 inch of insulation. Locate the speaker/remote turn-on
PowerLock connector. Loosen the outer screws on the underside of the connector.
Insert the speaker leads into the end. Check to be sure you've maintained proper
polarity before securing each wire, and plug the PowerLock into the amplifier.
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The Advanced Instrumentation Input has trickled down from the $15,000
PrecisionPower2500F1.This circuit completely isolates the chassis ground from
the audio circuit of the amplifier and reduces noise radiated into your signal cables
by up to 40dB. This is equivalent to a noise reduction of approximately one hundred
times what the noise level would be without this circuitry. It provides all the benefits
of a true 'balanced' line without the need of any special cables (see diagram
below). This type of input works with any conventional RCAcable.
There are two sets of RCA jacks on the front end of your amplifier. The RCA
cables from your source unit go in the set labeled INPUTS. If your source unit doesn't
have RCA outputs don't worry. Simply add a set of RCA plugs (available at your
dealer) to your front or rear set of speaker leads (see drawing below), plug them
into the input jacks, and push to the IN the -12dB input attenuation switch.
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1. Cooling Plenums: Maintain a minimum 2” clearance around cooling plenums
for proper amplifier cooling.
2. QBASS™ Control: Add more bass to the system by turning this control clock-
wise to boost the selected QBASS™ frequency up to 18dB.
3. QBASS™ Remote Port: Port to plug in the optional QBASS Plus™ Remote
knob.
4. Power & Ground Connections: After connecting the power and ground
cables to the PowerLock™ wire connector, plug it in here.
5. Power Indicator: Agreen light indicates that the amplifier power is ON.
8
To manage the additional heat associated with higher output capability, a thermally
controlled fan has been designed into the PCX 280. When the heatsink temperature
reaches a pre-determined value, the fan is activated and cool air is drawn in
through the lower intake vents on the endplate. This cool air flows below the circuit
board, through the fan and across the internal fins, cooling the heatsink. The
warm air is then forced out through the upper endplate exhaust vents.
The New! PCX™ amplifiers mass has been increased by 2 lbs. per linear foot
over last year’s POWERCLASS™ amplifiers, resulting in far superior heat
dissipation. The unique heatsink on your PCX™amplifier has been designed with
fins on the inside of the aluminum extrusion. This allows for the transfer of heat
from the circuitry to the heatsink fins and out through the vents in the endplates.
Be sure you have ample space around the amplifier for cooling; at least 2" on all
sides.
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PCX 280 Power Panel
PCX 250 Power Panel
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2345

If your grand total current draw is over 100 amps (or total output power is over
600 watts), you are probably exceeding the capability of your charging system.
Dimming lights and fluctuating voltage are solid indicators that you need to
upgrade your alternator, battery, or both. Keep in mind that your amplifiers simply
convert electrical energy to acoustical energy, and any electrical deficiency will
compromise the performance of your sound system. For more information about
charging system upgrades, see your local authorized PrecisionPower Dealer or
call PrecisionPower Technical Support at 1-800-62POWER x 229.
Locate an area near the amplifier(s) that is metal and clean an area about the size
of a quarter to bare metal. Inspect the area around and underneath to be sure you
won't drill into wires, brake or fuel lines, etc. Drill a pilot hole in the middle of this
area. Terminate the ground wire with a ring connector and attach it to the bare
metal using a #8 sheet metal screw and washer or preferably, a bolt, nut and a
star washer (not supplied). We suggest crimping and soldering this connection.
After the connection is complete, coat the area (on both sides) with silicone or
some similar material to prevent rust from developing on the bare metal. If your
grand total current draw is over 50 amps(or total output power is over 300 watts),
you should run a separate ground wire beside your power wire from the battery
to the amplifier(s). Keep the ground and power wires as close together as possi-
ble, and use the same gauge wire for both. This will ensure that you have a good
ground path, and may eliminate such potential problems as engine noise and
overheated amplifiers.
6
The ability to run stereo speakers while simultaneously running a mono output
from the same amplifier is accomplished by running the stereo speakers normally
and tapping into the appropriate wires for the "mixed mono" channel (left channel
positive for the positive speaker wire and right channel negative for the negative
speaker wire). Speaker impedance should be no lower than 2 Ohms on the stereo
channels and 4 ohms on the mono channel.
NOTE: Passive crossovers must be used for "mixed mono" operation. Choose a
low pass crossover around 100Hz for your subwoofer, then choose a high pass
crossover for your stereo channels. The high pass crossover must be at the same
or slightly higher frequency than the low pass crossover to maintain the correct
impedance. See your PrecisionPower dealer or call 1-800-62POWER for more
information about passive crossovers.
15

The following is a basic formula to be used as a guide to determine current draw.
A50% amplifier efficiency rating is used as an average. Your new PCX™amplifier
is more efficient than most other amplifiers. This formula is to be used as a guideline.
Using wire of a larger gauge can only improve the current transfer of your system.
Do not use smaller gauge wire.
Total Amplifier RMS output x 2 = Total Input Wattage from car
Total Input Wattage = Current Draw (in Amps)
Supply Voltage
Example: APOWERCLASS™ PCX 280 amplifier has two channels at 80w per
channel RMS rating into 4 Ohms (80 x 2 = 160).
You would use the formula in the following way:
160W x 2 = 320W
320W = 26.6 Amps Total current draw.
12V
If the same amplifier is driven into a 2 Ohm stereo or 4 Ohm mono load, double
it's 4 Ohm RMS rating. All POWERCLASS™ amplifiers will effectively double their
power at this load.
160W x 2 x 2 = 640W
640W = 53.3 Amps Total current draw.
12V
If you are using more than one amplifier, add up the total current draw for all of
them and choose the appropriate gauge based on the grand total.
NOTE: The ground wire must be the same gauge or larger as the power wire.
Recommended Minimum Gauge
(in amps) Up to 4ft. 4 to 7ft. 7 to 10ft. 10 to 13ft. 13 to 16ft. 16 to 19ft. 19 to 22ft. 22 to 28ft.
25-50 10 10 8 8 6 6 4 4
50-65 8 8 6 4 4 4 4 2
65-85 6 6 4 4 2 2 2 0
85-105 6 6 4 2 2 2 2 0
105-125 4 4 4 2 2 0 0 0
125-150 2 2 2 2 0 0 0 00
150-200 0 0 0 0 00 00 00 000
200-250 00 00 00 000 000 000 000 0000
Total Current Draw Length Of Wire To Be Run
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