MTX Audio RT251D User Manual [en, de, es, fr]

AMPLIFIER

OWNER’S
MANUAL

RT251D

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AMPLIFIER OWNER’S MANUAL

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• Intelligent Surface Mount Technology

• Patented PWM MOSFET switching power supply (#5,598,325)

• Adaptive Class D technology

• High powered transformer

• High powered stacked inductor

• Pure N-channel design

• Doubles power into 2 ohms

• Real time computerized protection circuit

• Color-coded wire harness for speaker-level input installation

• Smart-Engage™ auto turn on for easy integration with factory head units

• Acoustically Seamless Turn-on/Turn-off (i.e. no noise)

• Low-pass crossover, 85Hz, 24dB/octave low pass

• Switchable Bass Boost @ 0, 6 or 12dB centered at 40Hz

• Low level inputs

• Adjustable input sensitivity

• Nickel-plated, heavy duty terminal block type connectors

• Unique rubber Insulated Iso-Feet™

Features

Specifications

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 its significant improvements
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 signifi­cantly 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 cover­to-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

[e-mail]

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

RT251D

RMS Power measured at 14.4 Volts DC:

100 Watts x 1 into a 4 Ohm load with less than 1% Thd+N
200 Watts x 1 into a 2 Ohm load with less than 1% Thd+N

Dynamic Power measured at 14.4 Volts DC:

125 Watts x 1 into a 4 Ohm load
250 Watts x 1 into a 2 Ohm load

Signal to Noise Ratio: ≥100dB A-Weighted
Frequency Response: 20Hz-85Hz
Maximum Input: 8Vrms
Bass Boost: Switchable Bass Boost 0, 6, or 12dB centered at 40Hz
Crossover: Fixed @ 85Hz, 18dB/octave low pass
Dimensions: Including Iso-Feet™

7.98" x 9.75" x 2.1" (20.3cm x 24.8cm x 5.3cm)

AMPLIFIER OWNER’S MANUAL

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1. 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.

2. Bass Boost – This equalization circuit is used to enhance the low frequency response of the vehicle’s
interior. With up to 12dB of boost and centered at 40Hz, the Bass Boost can be adjusted to meet your own
personal taste.

3. RCA Input Jacks – RCA type input jacks for use with source units that have RCA or Line Level Outputs.
A source unit with a minimum output level of 200mV is required for proper operation. However, this input
will accept levels up to 8Vrms.

4. RCA Output Jacks –

These RCA outputs allow for a signal to be sent to other amplifiers in a daisy-chain con-

figuration.

5. Speaker Level Inputs – This input will allow the RT251D 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.

Input Panel Layout

❶

❹

❷

❸

❺

AMPLIFIER OWNER’S MANUAL

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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.

RT251D - 25A

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 recom­mended 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 flow­ing through this cable can induce noise into your system. It is also very important to have a tight connec­tion to ensure maximum performance.

RT251D - 6-8 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.

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 con­dition, the amplifier will turn back on after it cools down.

Output Panel Layout

❶

❷

❸

❹

❺

❻

AMPLIFIER OWNER’S MANUAL

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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, mid­bass, midrange and tweeters are all designed to play differ­ent 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 imped­ance 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
distortion occurs.

4.

Adjust the gain control down until audible distortion
disappears.

5. The amplifier is now calibrated to the output of the

source unit.

Typical Speaker

Wiring

Configurations

Definitions of Common Terms

Read this if you wanna be a do-it-yourselfer - or give us a call at 800-CALL MTX.

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 boomy Bass Boost too high Lower setting

Bass is weak Bass Boost too low Raise setting

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

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Introduction

FELICITATIONS...

vous félicitant de votre achat d’un nou­veau amplificateur MTX Audio Road
Thunder ! MTX a été depuis longtemps
un leader dans l’industrie d’enclos
mobiles et speakers, et nous sommes
arrivés à un nouveau sommet avec le
développement des nouveaux amplifi­cateurs MTX Road Thunder. Vous n’au­riez pas pu choisir d’amplificateur plus
fiable, plus puissant ou meilleur.

Nous fabriquons chaque amplificateur
en employant la Technologie Surface

Mount le plus récent et intelligent .
Quelques advantages du nouveau dessin sont
les perfectionnements aux propriétés
mécaniques et électriques de l’amplificateur.
Les mécanismes ISMT ont de substantielle­ment plus courtes longueurs internes et
externes. Cela réduit l’inductance et la
capacitance égarées, qui résulte en une
reproduction musicale plus pure et plus
exacte avec considérablement moins d’inter­vention du bruit. Le ISMT mounter produit des
cartes d’amplificateur avec plus petits et plus
légèrs composants qui sont plus résistants
aux vibrations inhérentes dans l’environ­nement automobile.

Nous voulons tout faire pour assurer que vous
obtenez la haute performance continue de
votre amplificateur MTX Road Thunder, donc
nous vous recommandons de l’avoir installé
professionellement par votre vendeur agréé.

COMMENT UTILISER CE MANUEL

Si vous installez cet amplificateur vous­même, nous vous recommandons de lire ce
manuel de la première à la dernière page
avant de l’installer. Familiarisez-vous avec les
caractéristiques et les détails des panneaux
entrée-sortie. Vérifiez que vous avez tout
l’équipement dont vous avez besoin. Puis
suivez les instructions d’installation point par
point qui se trouvent. Vous pouvez trouver
des échantillons des diagrammes d’installa­tion sur le Web à notre site :

mtx.com

Si vous avez des questions, écrivez ou

téléphonez-nous à :

MTX Audio

4545 E. Baseline Rd.

Phoenix, AZ 85042

602-438-4545

800-CALL MTX

[e-mail]

mtx.com

FRANÇAIS

• Technologie Intelligente Surface Mount

• Source d’alimentation à découpage PWM MOSFET brevetée (5 598 325)

• Technologie d’adaptation Classe D

• Transformateur haute puissance

• Bobine superposée de forte puissance

• Dessin N-canal pur

• Double la puissance sous 2 ohms

• Circuit de protection informatisé temps réel

• Harnais métallique codifié par couleurs pour l’installation d’éntrée au niveau speaker

• Mise sous tension automatique Smart-Engage™ facilitant l’intégration avec les appareils sources
montés en usine

• Mise sous tension/hors tension acoustiquement transparente (c’est-à-dire sans bruit)

• Filtre passe-bas à fréquence de coupure de 85 Hz, 24dB/octave

• Amplificateur commutable Bass Boost @ 0, 6 ou 12dB centré sur 40 Hz

• Entrées bas niveau

• Sensibilité d’entrée réglable

• Connecteurs nickelés, d’un type bloc terminal à usage industriel

• Iso-Feet™ uniques, isolants en caoutchouc

Specifications

Caractéristiques

RT251D

RMS Power measured at 14.4 Volts DC:

100 Watts x 1 into a 4 Ohm load with less than 1% Thd+N
200 Watts x 1 into a 2 Ohm load with less than 1% Thd+N

Dynamic Power measured at 14.4 Volts DC:

125 Watts x 1 into a 4 Ohm load
250 Watts x 1 into a 2 Ohm load

Signal to Noise Ratio: ≥100dB A-Weighted
Frequency Response: 20Hz-85Hz
Maximum Input: 8Vrms
Bass Boost: Switchable Bass Boost 0, 6, or 12dB centered at 40Hz
Crossover: Fixed @ 85Hz, 18dB/octave low pass
Dimensions: Including Iso-Feet™

7.98" x 9.75" x 2.1" (20.3cm x 24.8cm x 5.3cm)