XThunder 125.4 - Receiver MTX Audio - Free user manual and instructions

Product Type	4-Channel Car Amplifier
Model	XThunder 125.4
RMS Power (14.4V, 2Ω)	4 x 125 W
RMS Power (14.4V, 4Ω)	4 x 90 W
Frequency Response	20 Hz - 20 kHz
High Pass Filter	40 Hz - 250 Hz (adjustable)
Bass Boost	18 dB @ 45 Hz (adjustable)
Input Sensitivity (Low Level)	200 mV - 5 V
Input Sensitivity (High Level)	400 mV - 10 V
Protection Circuits	Short, Thermal, High/Low Voltage
Recommended Fuse	60 A (inline)
Dimensions (H x W x D)	2.03 x 8.93 x 14.17 in (51.5 x 226.7 x 359.9 mm)
Minimum Impedance (per channel)	2 Ω
Bridged Output	Yes (rear channels)
Remote Turn-On	12 V trigger or Auto (high-level input)
Crossover Type	Low Pass, High Pass (selectable on rear)
Signal-to-Noise Ratio	> 60 dB
THD at 4Ω, 1W	< 0.2%
Construction	Double-sided PCB, Surface Mount Components, MOSFET Design
Color	Black with blue LED power indicator

Frequently Asked Questions - XThunder 125.4 MTX Audio

What is the RMS power output of the XThunder 125.4?

The amplifier delivers 4 x 125 W RMS at 2Ω and 4 x 90 W RMS at 4Ω (14.4V).

What is the minimum impedance per channel?

The minimum impedance is 2 Ω per channel for stable operation.

Can I bridge channels on this amplifier?

Yes, the rear channels can be bridged. Use the BRIDGE + R CH - terminal for bridged output.

What type of crossover does it have?

It has an adjustable High Pass Filter (40-250 Hz) on front and rear channels, and the rear channels also have selectable Low Pass or Full Range mode.

How do I power on the amplifier without a remote wire?

Set the Remote Turn On switch to Auto. The amplifier will turn on automatically when it detects a signal from the high-level input.

What fuse size is recommended?

Use a 60 A inline fuse within 18 inches of the battery.

What are the dimensions of the amplifier?

Dimensions are 2.03 x 8.93 x 14.17 inches (51.5 x 226.7 x 359.9 mm).

Does the amplifier have protection features?

Yes, it includes short circuit, thermal, and high/low voltage protection. A red LED indicates a fault.

What is the input sensitivity range?

Low-level inputs accept 200 mV to 5 V; high-level inputs accept 400 mV to 10 V.

How do I adjust the bass boost?

Use the Bass Boost control to add up to 18 dB boost centered at 45 Hz. Adjust clockwise to increase.

USER MANUAL XThunder 125.4 MTX Audio

Technical line drawing of a heat exchanger or cooling unit panel with no visible text or symbols

OWNER'S MANUAL XTHUNDER AMPLIFIERS

Use your smartphone to scan or visit youtube.com/user/MTXAudioUSA to learn how to properly install this amplifier.

PRODUCT INFORMATION

Model #

Serial #

Dealer's Name

Date of Purchase

INTRODUCTION

Thank you for purchasing this MTX Audio Hi-Performance amplifier. Proper installation matched with MTX speakers and subwoofers provide superior sound and performance for endless hours of enjoyment whether you are waking the neighbors or just out enjoying your tunes. Congratulations and enjoy the ultimate audio experience with MTX!

FEATURES

• Compact Size
• Double Sided PCB
  • Surface Mount Components
• MOSFET Design
  • LPF and HPF Crossover
• Adjustable Bass Boost
• Noise Free Design

- Short, Thermal, and High/Low Voltage Protection

CONTROL FUNCTIONS

1. Speakers - Connect speakers/subwoofers to these terminals. Be sure to check wire for proper polarity. Never connect the speaker cables to the chassis ground.
2. +BATT (+12 Volt Power) - Connect this terminal through a FUSE or CIRCUIT BREAKER to the positive terminal of the vehicle battery or the positive terminal of an isolated audio system battery. WARNING: Always protect this power cable by installing a fuse or circuit breaker of the appropriate gauge within 18 inches (45cm) of the battery terminal connection.
3. Remote - This terminal turns on the amplifier when (+) 12 volt is applied to it. Connect it to the remote turn on lead of the head unit or signal source.
4. GND - Connect this cable directly to the frame of the vehicle. Make sure the metal frame has been stripped of all paint down to the bare metal. Use the shortest distance possible. It is always a good idea to replace the factory ground at this time with a cable equal or larger than the new amplifier power cable. CAUTION: Do not connect this terminal directly to the vehicle battery ground terminal or any other factory ground points.
5. RCA Input Jacks - These RCA input jacks are for use with source units that have RCA outputs. 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.
6. Level Control - The Level, or Gain control will match the amplifier's sensitivity to the source units signal voltage. The operating range is 5V to 200mV. NOTE: This is NOT a volume control.
7. Low Pass Filter Control (Mono Block) - This control is used to select the desired low pass x-over frequency. The frequency can be adjusted from 40Hz to 250Hz for all bass mono models.
8. Subsonic Filter Control (Mono Block) - This control can filter out unwanted low frequency from 10Hz (OFF) to 50Hz. This function should only be used with vented enclosures.

9. Bass Boost Level (Mono Block) - This can boost bass level up to 18dB. The boost frequency is centered at 45Hz.

10. High Pass Filter (Full Range) - This controls the frequencies played for the front and rear channels. Low frequencies can be cut off from 40Hz to 250Hz.

11. X-Over Mode and Frequency Control (Full Range) - These controls allow control over the frequencies played for the rear channels. There is an option for Low Pass, Full Range, or High Pass. In LP or HP mode, the crossover frequency can be tuned from 40Hz to 250Hz.
12. Power Indicator - This Blue LED will light up when the amplifier is working properly.
13. Protection Indicator - This Red LED will light up and flash if there is a fault presented to the amplifier. Please disconnect the amplifier and resolve the fault before reconnecting the amplifier.
14. Remote Turn On - This unit features auto turn on technology allowing installation via high level input without the use of a remote wire. If using a factory or aftermarket radio that does not include RCA outputs, the amplifier can be connected to the source unit via high level speaker wire via the high level input. The Remote Turn On switch when placed in the "Auto" position will allow the unit to turn itself on without the need to connect a remote wire. In the "Ext" position the unit will require a remote wire connection to turn on.
15. Amplifier Strapping - Two units can be linked together to achieve a strapped 2 Ohm output. One unit must have the switch in the Master position and the other must be in the Slave position. Connect a single RCA interconnect from the Input/Output of the Master amplifier to the Input/Output of the Slave amplifier. Connect the negative speaker output terminal from the Master to the negative speaker output terminal on the Slave amplifier. Connect the positive speaker output terminal from the Master amplifier to the positive speaker input terminal on the subwoofer or terminal cup and the positive speaker output terminal from the Slave amplifier to the negative speaker input terminal on the subwoofer or terminal cup. Use caution not to connect the negative speaker output terminal on either amplifier to the ground or chassis.

PANEL LAYOUT

XTHUNDER125.4 4-Channel Amplifier Panel Layout

PANEL LAYOUT

XTHUNDER800.5 5-Channel Amplifier Panel Layout

PANEL LAYOUT

XTHUNDER1200.1 / XTHUNDER1500.1 Mono Block Amplifier Panel Layout

WIRING DIAGRAM

See page 26 for amplifier wiring diagrams.

INSTALLATION AND MOUNTING

MTX recommends your new XTHUNDER amplifier be installed by a 12 volt installation specialist. Any deviation from specified installation instructions can cause serious damage to the amplifier, speakers and/or vehicle's electrical system. Damage caused from improper installation is NOT covered under warranty. Please verify all connections prior to system turn on.

1. Disconnect the vehicle's negative battery cable.
2. Determine the mounting place for your MTX amplifier. Keep in mind there should be sufficient air flow for proper cooling. Mark the mounting holes from the amplifier to be drilled. Before drilling make sure all vehicle wires, gas lines, brake lines and gas tank are clear and will not interfere with installation. Drill the desired holes and mount the MTX amplifier.
3. Install a positive (+) power cable from the vehicle's battery through the firewall using a grommet or firewall bushing to avoid cable damage from sharp edges of the firewall. Run the cable through the interior of the vehicle and connect it to the amplifier's (+BATT) terminal. Do not connect to the battery at this time. NOTE: Use only proper gauge wire for both positive and negative connections.
4. Install a circuit breaker or fuse within 18 inches of the battery. This effectively lowers the risk of severe damage to you or your vehicle in case of a short circuit or accident. Make sure the circuit breaker is switched Off or the fuse is taken out of the fuse holder until all connections are made. Now connect your positive power cable to the positive battery terminal of the battery.
5. Grounding - Locate a proper ground point on the vehicle's chassis and remove all paint, dirt or debris to reveal a bare metal surface. Attach the ground wire to that contact point. Connect the opposite end of the ground wire to the (GND) terminal on the MTX amplifier.
6. Connect a Remote Turn-On wire from the source unit to the MTX amplifier's (REM) terminal. If the source unit does not have a dedicated Remote Turn-On lead, you may connect to the source unit's Power Antenna lead.
7. Supply the signal to your MTX amplifier by connecting the signal cables using high quality RCA to the corresponding outputs at the source unit and inputs of the amplifier.
8. Connect your speakers to your MTX amplifier's speaker terminals using the correct gauge speaker wire. Your MTX amp can drive a 2Ω (XTHUNDER125.4 & XTHUNDER800.5) or 1Ω (XTHUNDER1200.1 & XTHUNDER1500.1) minimum load for optimum power.
9. Double check all previous installation steps, in particular, wiring and component connections. Once verified, reconnect the vehicle's negative battery cable, turn the circuit breaker On or place the fuse in the fuse holder.

NOTE: Gain Levels on the amplifier should be turned all the way down (counter clockwise) before proceeding with adjustments.

INSTALLATION

For proper performance and safety, MTX recommends installing an inline fuse per the owner's manual instructions according to the following.

XTHUNDER1500.1	160A Fuse
XTHUNDER1200.1	120A Fuse
XTHUNDER800.5	80A Fuse
XTHUNDER125.4	60A Fuse

TROUBLESHOOTING

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
Power LED On, No Output	Volume on Source Unit Off	Increase Volume on Source 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	Speaker Wire L & R Reversed	Correct Speaker Wire Orientation
	RCA Inputs Reversed	Reverse RCA Inputs
Bass is Weak	Speakers Wired Out of Phase	Wire Speakers with Correct Phase
	Not Using MTX Subwoofers	Buy MTX Subwoofers
Blowing Fuses	Excessive Output Levels	Lower the Volume
	Amplifier Defective	Return for Service

SPECIFICATIONS

Model	XTHUNDER1500.1	XTHUNDER1200.1	XTHUNDER800.5	XTHUNDER125.4
Description	1 x 1500 W RMS Mono	1 x 1200 W RMS Mono	1 x 400 W RMS 4 x 125 W RMS	4 x 125 W RMS
RMS Power at 14.4V
1Ω Load	1500 W RMS	1200 W RMS	NA	NA
2Ω Load	900 W RMS	750 W RMS	1 x 400 W RMS 4 x 125 W RMS	4 x 125 W RMS
4Ω Load	600 W RMS	500 W RMS	1 x 300 W RMS 4 x 75 W RMS	4 x 90 W RMS
Features
Input Level	Low: 200mV - 5V High: 400mV - 10V	Low: 200mV - 5V High: 400mV - 10V	Low: 200mV - 5V High: 400mV - 10V	Low: 200mV - 5V High: 400mV - 10V
Frequency Response	10Hz - 250Hz	10Hz - 250Hz	10Hz - 20kHz 10Hz - 250Hz	20Hz - 20kHz
Low Pass Filter (LPF)	40Hz - 250Hz	40Hz - 250Hz	40Hz - 250Hz	NA
High Pass Filter (HPF)	NA	NA	40Hz - 250Hz	40Hz - 250Hz
Subsonic Filter	10Hz - 50Hz	10Hz - 50Hz	27Hz Fixed	NA
THD at 4Ω, 1W	<0.5%	<0.5%	<0.2%	<0.2%
Signal-to-Noise Ratio	>60dB	>60dB	>60dB	>60dB
Bass Boost	18dB @ 45Hz	18dB @ 45Hz	18dB @ 45Hz	18dB @ 45Hz
Minimum Load	1Ω	1Ω	2Ω	2Ω
Dimensions
Height	2.03" (51.5mm)	2.03" (51.5mm)	2.03" (51.5mm)	2.03" (51.5mm)
Width	8.93" (226.7mm)	8.93" (226.7mm)	8.93" (226.7mm)	8.93" (226.7mm)
Length	14.17" (359.9mm)	14.17" (359.9mm)	14.17" (359.9mm)	14.17" (359.9mm)

WIRING DIAGRAM

Mono Block Amplifier Wiring (Single Subwoofer Load)

WIRING DIAGRAM

Mono Block Amplifier Wiring (Multi-Subwoofer Load)

NOTE: Equivalent parallel woofer load cannot be less than the minimum load rating. These are monoblock amplifiers, not multi-channel amplifiers. The minimum load for the XTHUNDER1500.1 and XTHUNDER1200.1 amplifier is 1Ω. The minimum load for the Sub Channel THUNDER800.5 amplifier is 2Ω.

© 2014 Mitek Corporation. All rights reserved. MTX is a trademark of Mitek Corporation. Designed and Engineered in the U.S.A.

Due to continual product development, all specifications are subject to change without notice.

MTX Audio, 4545 East Baseline Rd. Phoenix, AZ 85042 U.S.A.

MTX004783 RevA 4/14 • 21A10130 • AW00114619