MTX Road Thunder RT202 User manual

AMPLIFIER
OWNER’S
MANUAL
RT202 RT404

AMPLIFIER OWNER’S MANUAL
2
CONGRATULATIONS...
on your purchase of a new MTX Audio
Road Thunder Amplifier! MTX has long
been the industry leader in mobile audio,
and we have reached new heights with
the development of the new MTX Road
Thunder amplifiers. You couldn’t have
chosen a more reliable, powerful, or
better performing amplifier.
We manufacture every amplifier using
the latest Intelligent Surface Mount
Technology. Some of the advantages of
the new design are significant improve-
ments to the amplifier’s electrical and
mechanical properties. ISMT devices feature
substantially shorter internal and external
lead lengths. This reduces stray capacitance
and inductance, which results in cleaner and
more accurate musical reproduction with sig-
nificantly less noise interference. The ISMT
mounter produces amplifier boards with
smaller and lighter components, which are
more resistant to vibrations inherent in the
automotive environment.
We want to ensure you get continuous high
performance from your MTX Road Thunder
amplifier, so we recommend that you have it
professionally installed by your authorized
MTX dealer.
HOW TO USE THIS MANUAL
If you are installing this amplifier yourself, we
recommend that you read the manual cover-
to-cover before you install it. Familiarize
yourself with the features and details on the
input and output panels. Make sure you have
all the equipment you need. Then follow the
step-by-step installation instructions included.
Sample installation diagrams may be found
on our website:
mtx.com
If you have any questions, write or call us:
MTX Audio
4545 E. Baseline Rd. Phoenix, AZ 85042
602-438-4545 • 800-CALL MTX
[email protected]
mtx.com
Please take a moment to register your
purchase online at mtx.com.
Please, also record the serial number of
your amplifier in the space provided below,
and keep this manual for future reference,
as well as your sales receipt as proof of
ownership. (The serial number of your
amplifier is marked on the bottom of its
metal chassis.)
Serial Number:
Date of Purchase:
Introduction
ENGLISH

3
• Unique rubber Insulated Iso-Feet™
• Nickel-plated, heavy duty terminal block type connectors
• Speaker and low level inputs
• Input select 2CH/4CH switch on RT404 functions as a built-in Y connector
• Color-coded wire harness for speaker level input installation
• Smart-Engage™ auto-turn on for easy integration with factory head units
• Built-in, defeatable18dB/octave HP/LP crossover at 85 Hz
• RT404 front channel crossover is a defeatable18dB/octave, high pass, at 85Hz
• Adjustable input sensitivity
• Bridgeable, multi-channel circuit design
• Regulated PWM Mosfet Switching Power Supply
• New, more reliable high powered transformers
• Buffered, isolated output for daisy chaining multiple amplifiers
• Pure N-Channel Design
• Intelligent Surface Mount Technology
• Class A 100% discrete driver circuit topology
• Real-time computerized protection circuit
• Anti-shock PCB mounting design
• Acoustically Seamless Turn-on/Turn-off
Features
Specifications
RT202
RMS Power measured at 14.4 Volts DC:
37.5 Watts x 2 into a 4 Ohm load with < 1% THD
75 Watts x 2 into a 2 Ohm load with < 1% THD
150 Watts bridged into a 4 Ohm load with < 1% THD
Dynamic Power measured at 14.4 Volts DC:
50 Watts x 2 into a 4 Ohm load
100 Watts x 2 into a 2 Ohm load
200 Watts bridged into a 4 Ohm load
Signal to Noise Ratio: 100dB A-Weighted
(Referenced to Rated PWR at 1VRMS Input Sensitivity)
Frequency Response: 20-20,000 Hz ±.25dB
Crossover: Defeatable, 18dB/octave at 85 Hz,
selectable for high pass, low pass
Dimensions: Including Iso-Feet™
7.98" x 9.75" x 2.1" (20.3cm x 24.8cm x 5.3cm)
RT404
RMS Power measured at 14.4 Volts DC:
37.5 Watts x 4 into a 4 Ohm load with < 1% THD
75 Watts x 4 into a 2 Ohm load with < 1% THD
150 Watts x 2 bridged into a 4 Ohm load with < 1% THD
Dynamic Power measured at 14.4 Volts DC:
50 Watts x 4 into a 4 Ohm load
100 Watts x 4 into a 2 Ohm load
200 Watts x 2 bridged into a 4 Ohm load
Signal to Noise Ratio: 100dB A-Weighted
(Referenced to Rated PWR at 1VRMS Input Sensitivity)
Frequency Response: 20-20,000 Hz ±.25dB
Crossover: Defeatable, 18dB/octave at 85 Hz,
selectable for high pass, low pass, or full range on
rear channels and high pass or full range for front
channels
Dimensions: Including Iso-Feet™
11.5" x 9.75" x 2.1" (29.2cm x 24.8cm x 5.3cm)

AMPLIFIER OWNER’S MANUAL
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1. RCA Input Jacks – These RCA input jacks are for use with source units that have RCA or Line Level
Outputs. An independent set of jacks are provided on the RT404 for front and rear stereo inputs. A source
unit with a minimum level of 200mV is required for proper operation. The use of high quality twisted pair
cables is recommended to decrease the possibility of radiated noise entering the system.
2. Input Select 2CH/4CH – This switch, found on the RT404, is used to match the amplifier’s input to the
source unit’s output so all four channels of the amplifier are driven. If your source unit has 2 outputs (left
and right) connect them to the amplifier’s front channel inputs, and place the input select switch in the 2CH
position. If your source unit has 4 outputs, (left front, left rear, right front, right rear) connect them to the
amplifier inputs and place the input select switch in the 4CH position. In the 4CH position, the fader on
your source unit will operate.
3. Speaker Level Inputs – This input will allow the amplifier to operate from source units with speaker level
outputs. Output speaker leads from the source unit should be tied directly to the wire harness provided
with the amplifier.
Wire harness color codes:
Grey/Black = Source unit right negative (-) White/Black = Source unit left negative (-)
Solid Grey = Source unit right positive (+) Solid White = Source unit left positive (+)
With the Smart-Engage™ auto-turn-on circuit, a remote turn-on wire is not necessary when connecting
the speaker-level input wire harness to a high powered source unit. The amplifier will automatically turn
on when music is received.
4. RCA Output – These RCA outputs allow for a signal to be sent to other amplifiers in a daisy-chain
configuration. The RCA outputs on all Road Thunder series amplifiers will send a full-range signal to
additional amplifiers.
5. Gain Controls – These controls are used to match the input sensitivity of the amplifier to the particular
source unit that you are using. The controls are factory set to 1Vrms. Note that the RT404 has a separate
gain control for front and rear channels.
6. Crossover Select – This switch controls the type of crossover configuration that you desire. Road
Thunder series 2-channel amplifiers include a defeatable 18dB/octave, 85Hz crossover that is high
pass/low pass or full range selectable. The RT404 four channel amplifier includes a defeatable
18dB/octave, 85Hz crossover that is high pass or full range for the front channels, and a high pass, low
pass or full range for the rear channels.

5
FRONT
GAIN
AMP
X–OVER
2CH 4CH
FR HP
R– L–
FRONT IN SUM OUT REAR IN
AMP
X–OVER
REAR
GAIN
LP FR HP
R+ L+
R– L–
R+ L+
L
R
L
R
SPEAKER
LEVEL
INPUT
FRONT
RCA
INPUT
SPEAKER
LEVEL
INPUT
REAR
❷❶
❸
❹
❺❻❶
❸❻❺
Input Panel Layout
❶❸
❹
❺❻

AMPLIFIER OWNER’S MANUAL
6
1. Fuses - For convenience, all amplifiers utilize ATC type fuses. For continued protection in the event that
a fuse blows, replace the fuse only with the same value.
Caution: The power fuses on the amp are for protecting the amp against overdrive. To protect the vehicle’s
electrical system, an additional fuse is required within 18" of the battery on the 12V+ cable.
RT202 – 20 Amp
RT404 – 25 Amp x 2
2. Power Terminal – This is the main power input for the amplifier and must be connected directly to the
positive terminal of the car battery for the amplifier to operate properly. See the chart below for recom-
mended cable sizes for each amplifier. Use caution when running this cable through the car. Try to avoid
the input RCA cables, antenna cabling, or other sensitive equipment as the large amount of current flow-
ing through this cable can induce noise into your system. It is also very important to have a tight connec-
tion to ensure maximum performance.
RT202 – 10 Gauge
RT404 – 8 Gauge
3. Ground Terminal – A good quality ground is required for your Road Thunder Amplifier to operate at peak
performance. A short length of cable the same gauge as your power cable should be used to attach the
ground terminal directly to the chassis of the car. Always scrape or sand any painted surfaces to expose
bare metal where the ground wire will attach.
4. Remote Terminal – All Road Thunder Amplifiers can be turned on by applying 12 volts to this terminal.
Typically this voltage is supplied by a wire from the source unit marked “remote” or “electric antenna”.
5. Speaker Terminals – As shown in the wiring diagrams, be sure to observe speaker polarity through the
system. Failing to wire the speakers in proper phase could result in a loss of bass response and/or poor
overall sound quality. Caution: Road Thunder amplifiers are not recommended for loads below 2 ohms
stereo or 4 ohms bridged.
6. Power LED - A lighted LED indicates that power has been applied to the amplifier. +12V from the battery
to the +BATT terminal and +12V from a switched ignition or remote lead from a head unit. An unlighted
LED indicates power has been removed or the amplifier has overheated. In the case of the overheat con-
dition, the amplifier will turn back on after it cools down.

7
Output Panel Layout
❶
❺
❶
❷❹❸
❷❹❸❺
❻
❻

AMPLIFIER OWNER’S MANUAL
8
The following list of terms with their definitions is offered as
help in understanding the set-up and operation of your
amplifier.
1. Crossover (xover) - an electrical filter with high-pass or
low-pass characteristics that divides the frequency range
into playable bands for certain speakers. Subwoofers, mid-
bass, midrange and tweeters are all designed to play differ-
ent frequencies and should do so to avoid damage. The
xover point is where the playable frequencies cross from
one speaker to the next at -3dB below reference level.
2. Full-range - refers to signals which cover the entire audio
frequency span from 20Hz to 20kHz.
3. High-pass - simply put, this blocks lower frequencies
which damage smaller speakers, and passes the higher
frequencies for smaller speakers like the midrange and
tweeter.
4. Low-pass - you got it, this is the inverse of a high-pass. It
blocks higher frequencies and passes the playable lower
frequencies to the larger speakers, like subwoofers.
5. Impedance - the resistance to the flow of current in an
alternating current circuit (such as with music). Line level
circuits are typically a high impedance of several thousand
ohms, while speaker level circuits are usually a low imped-
ance of a few ohms.
6. Line level - the type of signal produced at the outputs of
tape decks, CD tuners, preamplifiers, etc., with a typical
value of a volt or less in a high impedance circuit.
7. Speaker level - the type of output that is meant to drive
speakers. These signals are sometimes called high level
and are usually connected by two conductor speaker wires.
8. Signal - the signal of an audio system is what is heard
from the speakers. These signals may be high pass, low
pass or full-range.
We don’t have enough space for Electronics 101, so if you
have a good, bad or amusing question, please call us TOLL
FREE at 800-CALL MTX! (800-225-5689)
Adjusting the Gain
1. Turn the gain control on the amplifier all the way down.
2. Turn up the volume control on the source unit to
approximately
3
⁄ 4 of maximum.
3. Adjust the gain control on the amplifier until audible distor-
tion occurs.
4.
Adjust the gain control down until audible distortion
disappears.
5. Follow steps 3-4 for other gain control settings.
(RT404)
6. The amplifier is now calibrated to the output of the
source unit.
Typical Speaker
Wiring
Configurations
Definitions of Common Terms
Stereo Amplifier
Bridge Mode Application
Impedance Requirement
4 ohm bridge minimum
2 ohm stereo minimum
AMP
+ - - +
L L R R
Two 8 ohm Speakers
OK
8 ohm
8 ohm
AMP
+ - - +
L L R R
Two 4 ohm Speakers
not
ok
4 ohm
4 ohm

9
Read this if you wanna be a do-it-yourselfer or give us a call at 800-CALLMTX.
Problem Cause Solution
No LED indication No +12V at remote connection Supply +12V to terminal
No +12V at Power connection Supply +12V to terminal
Insufficient ground connection Verify ground connection
Blown power fuse Replace fuse
LED on, no output Volume on head unit off Increase volume on head unit
Speaker connections not made Make speaker connections
Gain control on amplifier off Turn up gain
Signal processing units off Apply power to signal processor
All speakers blown Replace speakers
Output distorted Head unit volume set too high Lower head unit volume
Amplifier gain set too high Lower amplifier gain
Balance reversed Speakers wired L + R reversed Wire speakers with correct orientation
RCA inputs reversed Reverse RCA inputs
Some balance reversed Some Speakers wired L + R Wire speakers with correct orientation
reversed
Some RCA inputs reversed Reverse appropriate RCA inputs
Bass is weak Speakers wired out Wire with correct phase
of phase
Not using MTX woofers Buy MTX woofers
Blowing fuses Excessive output levels Lower volume
Amplifier defective Return for service
Troubleshooting Guide

AMPLIFIER OWNER’S MANUAL
34
NOTES

35
All MTX Audio Road Thunder Amplifiers purchased in the United States from an
authorized MTX dealer are guaranteed against defects in material and workmanship
for a period of one year from the date purchased. This warranty is limited to the orig-
inal retail purchaser of the product.
Product found to be defective during that period will be repaired or replaced by MTX
at no charge. This warranty is void if it is determined that unauthorized parties have
attempted repairs or alterations of any nature. Warranty does not extend to cosmet-
ics or finish. Before presuming a defect is present in the product, be certain that all
related equipment and wiring is functioning properly. MTX disclaims any liability for
other incurred damages resulting from product defects. Any expenses incurred in
the removal and reinstallation of products are not covered by this warranty. MTX's
total liability will not exceed the purchase price of the product. If a defect is present,
your authorized MTX dealer may be able to effect repairs.
Proof of purchase is required when requesting service, so please retain your sales
receipt, and take a moment to register your warranty on line @ www.mtx.com.
For Warranty Inquiries, please call:
800-CALL MTX
602-438-4545
MTX Audio
4545 E. Baseline Rd.
Phoenix, Arizona 85042
Register Warranty Online:
mtx.com
Warranty

© 2002 MTX. All rights reserved. MTX and Road Thunder are trademarks of MTX. MTX001285 RevA 6/02 NDM0200
Due to continual product development, all specifications are subject to change without notice.
The Pointe at South Mountain
4545 East Baseline Road
Phoenix, AZ 85042
602-438-4545
800-CALL MTX
mtx.com