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Full text of "MTX Thunder4250D Troubleshooting guide"

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on your purchase of a new MTX 
Thunder Amplifier! MTX has long 
been the industry leader in mobile 
enclosures and speakers, and we 
have reached new heights with the 
development of the new MTX Thunder 
amplifiers. You couldn't have chosen 
a more reliable, powerful, or better 
performing amplifier - In fact, we 
back up every Thunder amplifier with 
a three-year warranty if installed by 
an authorized MTX retailer (see the 
warranty statement on page 34). 

Your new MTX Thunder amplifier was 
designed, built and thoroughly tested at our 
state-of-the-art electronics manufacturing 
facility in Phoenix, Arizona. We manufacture 
every amplifier using the latest Intelligent 
Surface Mount Technology. Some of the 
advantages of the new design are its signifi¬ 
cant improvements to the amplifier's electri¬ 
cal 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 repro¬ 
duction with significantly less noise interfer¬ 
ence. The ISMT mounter produces amplifier 
boards with smaller and lighter components, 
which are more resistant to vibrations inher¬ 
ent in the automotive environment. 

A word about power ratings. It is important for you 
to know how they stack up. MTX has chosen the 
most honest, most conservative way to rate our 
amps. We show you the RMS power, at 12.5 volts, 
and dynamic power at 14.4 volts. However, we go 
above and beyond the call of duty. We test each 
amplifier. The technician records the "actual" 

power output, and records this number on your 
Certified Performance Certificate. The amplifier 
must meet or exceed the rated specification 
before we'll ship it. No questions. No exceptions. 

We want to ensure you get continuous 
high performance from your MTX Thunder 
amplifier, so we recommend that you 
have it professionally installed by your 
authorized MTX dealer. 


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. Sample installa¬ 
tion diagrams may be found on our website: 

If you have any questions, write or call us at: 


4545 E. Baseline Rd. 

Phoenix, AZ 85040 
* 1-800-CALL-MTX 
Register your warranty online 

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 on Thunder4250D and 6500D 
Smart-Engage™ auto turn on for easy integration with factory head units Thunder4250D and 6500D 
Acoustically Seamless Turn-on/Turn-off (i.e. no noise) 

Variable frequency low-pass crossover, 40Hz to 200Hz, 24dB/octave low pass 
Defeatable compression circuit included on Thunder6500D and Thunder81000D 
Continuously adjustable and defeatable Bass EQ enhancement circuitry, centered at 40Hz 
Low level inputs 

EBC - External Bass Control Port with an additional 3dB of gain when used, and 23dB attenuation 
Adjustable input sensitivity 

Buffered RCA Outputs for daisy-chaining additional bass amplifiers 
Nickel-plated, heavy duty terminal block type connectors 
Unique rubber Insulated Iso-Feet™ 


RMS Power measured at 12.5 Volts DC: 

125 Watts x 1 into a 4 Ohm load with less than 1% Thd+N 

250 Watts x 1 into a 2 Ohm load with less than 1% Thd+N 

Dynamic Power measured at 14.4 Volts DC 

200 Watts x 1 into a 4 Ohm load 

350 Watts x 1 into a 2 Ohm load 

Signal to Noise Ratio: >1G0dB A-Weighted 

Damping Factor: >200 

Frequency Response: 20Hz-2Q0Hz 

Maximum Input: 8Vrms 

Thunder EQ: Variable Bass Boost (0-18dB) centered at 40Hz 
Crossover: Variable 40Hz to 200Hz, 24dB/octave low pass 
Dimensions: 7" x 9.75" x 2" (17.8cm x 24.8cm x 5.1cm) 

9.9" x 9.75" x 2.1" (23.6cm x 24.8cm x 5.3cm) Including IsoFeet™ 


RMS Power measured at 12.5 Volts DC: 

250 Watts x 1 into a 4 Ohm load with less than 1% Thd+N 

500 Watts x 1 into a 2 Ohm load with less than 1% Thd+N 

Dynamic Power measured at 14.4 Volts DC 

450 Watts x 1 into a 4 Ohm load 

775 Watts x 1 into a 2 Ohm load 

Signal to Noise Ratio: >100dB A-Weighted 


RMS Power measured at 12.5 Volts DC: 

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

1000 Watts x 1 into a 2 Ohm load with less than 2% Thd+N 

Dynamic Power measured at 14.4 Volts DC 

850 Watts x 1 into a 4 Ohm load 

1500 Watts x 1 into a 2 Ohm load 

Signal to Noise Ratio: >100dB A-Weighted 

Damping Factor: >100 

Frequency Response: 20Hz-200Hz 

Maximum Input: 8Vrm$ 

Thunder EQ: Variable Bass Boost (0-18dB) centered at40Hz 
Crossover: Variable 40Hz to 200Hz, 24dB/octave low pass 
Dimensions:15.4" x 9.75" x 2".(40.1cm x 24.8cm x 5.1cm) 

17.8” x 9.75” x 2.1" (45.2cm x 24.8cm x 5.3cm) Including IsoFeet™ 
Recommended Fuse = 150A 

Damping Factor: >200 
Frequency Response: 20Hz-200Hz 
Maximum Input: 8Vrms 

Thunder EQ: Variable Bass Boost (0-18dB) centered at40Hz 
Crossover: Variable 40Hz to 200Hz, 24dB/octave low pass 
Dimensions: 11.5" x 9.75" x 2" (29.2cm x 24.8cm x 5,1cm) 

13.9" x 9.75" x 2.1" (36.6cm x 24.8cm x 5.3cm) Including IsoFeet™ 

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 IVrms. 

2. Thunder EQ - This equalization circuit is used to enhance the low frequency response of the vehicle's 
interior. With up to 18 dB of boost and centered at 40Hz, the Bass EQ can be adjusted to meet your own 
personal taste. 

3. Frequency Control - This control is continuously adjustable from 40Hz through 200Hz at 24dB per octave. 
Factory setting is at 40Hz. 

4. 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. 

5. EBC 2- The EBC, or Electronic Bass Control, allows a remote bass control to be adjusted from the dri¬ 
ver's seat. If the optional EBC is installed, the bass level will be able to be adjusted to overcome noise and 
other interference. With EBC 2 multiple amplifiers can be controlled. 

6. RCA-Output Jacks - These RCA outputs allow for a signal to be sent to other amplifiers in a daisy-chain 
configuration. The RCA outputs also allow for multiple bass amplifiers to be level controlled using one EBC. 

7. Speaker Level Inputs - This input will allow the Thunder425D and 6500D 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 units right negative (-) White / Black = Source units left negative (-) 

Solid Grey = Source units right positive (+) Solid White = Source units left positive (+) 

With the Smart-Engage™ auto-turn 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. 

8. Compression Circuit - This new circuit, found on the Thunder6500D and Thunder81000D, 
prevents the amplifier from going into clipping, even at high SPL levels. The compression circuit allows the 
listener to play the amplifier at high volume levels, yet protects the speakers against the potential damage 
that can occur during dynamic musical passages. The circuit is switchable on/off, for those SPL competi¬ 
tors who run their amplifiers into clipping on purpose. Warning : Damage to speakers may occur when the 
compression circuit is in the off position. 

Inout Panel Layout 

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. 

Thunder4250D - 20Ax 2 
Thunder6500D - 25A x3 
Thunder81000D -150 Amps (not supplied) 

2. Power Terminal - This terminal is where the power source of the vehicle is connected. The 12V+ must be con¬ 
nected directly to the positive battery post It is highly recommended that you place an additional fuse within 18" 
of the battery connection. Be sure to use the correct gauge of power cable! If wire of insufficient size is used, 
there will be a voltage drop and the amp will starve, causing poor performance. In an extreme case, the amp may 
shut down due to the low battery voltage protection feature. The terminal closest to the fuse(s) is where the power 
cable with connector should be installed. Be sure to make your connection clean to avoid any shorting to the other 
terminals. Always double check all of the connections for any discrepancies..08 

Thunder4250D - 6-8 Gauge 
Thunder6500D - 4-6 Gauge 
Thunder81000D - 1/0 Gauge only 

3. Remote Terminal - This is the wire that turns the amplifier on and off. This terminal connects to the amp turn-on lead 
or the power antenna lead coming from the source unit. If the source unit doesn't have one of these wires, you can 
either run a wire to the battery with a switch or use an ignition controlled wire to power up the amp. If you use the 
ignition controlled wire, be aware that the amplifier will be on, as long as the car is on. When using the Smart 
Engage™ feature, a high powered radio, and speaker level inputs it is not necessary to connectthe Remote Terminal. 

4. Ground Terminal - The ground terminal connects the amplifier to the vehicle ground. Be sure to use the same size 
wire gauge or larger as the +12V connection. A strong ground point is very important. A little screw through the body 
is not acceptable. The cable should be as short as possible and connected to the chassis of the vehicle. The contact 
point should be free of paint and debris for best results. All precautions for the 12V+ connection apply to this con¬ 
nection as well. 

5. Power LED (top of heatsink)- Alighted LED indicates that power has been applied to the amplifier. +12V from the 
battery to the +BATT terminal (#10) 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. 


6. 4 Term Block- The + and - terminals connect the speaker to the amplifier. 2 ohm minimum 
impedance is allowed. 

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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 dis¬ 

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

Mono Amplifier 
Impedance Requirement 

2 ohm minimum 

Definitions of 
Common Terms 

The following list of terms with their definitions is offered as 
help in understanding the set-up and operation of your 

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 

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} 

Troubleshooting Guide 

Bead this if you wanna be a do-it-yourselfer - or give us a call at 1-800-CALLMTX. 


No LED indication 

LED on, no output 

Output distorted 

Balance reversed 

Some balance reversed 

Bass is boomy 
Bass is weak 



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 

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 

Head unit volume set too high 

Lower head unit volume 

Amplifier gain set too high 

Lower amplifier gain 

Speakers wired L + R reversed 

Wire speakers with correct orientation 

RCA inputs reversed 

Reverse RCA inputs 

Some Speakers wired L + R 

Wire speakers with correct orientation 


Some RCA inputs reversed 

Reverse appropriate RCA inputs 

Thunder EQ too high 

Lower setting 

Thunder EQ too low 

Raise setting 

Speakers wired out 

Wire with correct phase 

of phase 

Not using MTX woofers 

Buy MTX woofers 

Excessive output levels 

Lower volume 

Amplifier defective 

Return for service 

Blowing fuses 


All MTX Thunder Amplifiers purchased in the USA are guaranteed against defects in 
material and workmanship for a period of three years from the date purchased by the 
end user, if the amplifier is installed by an authorized MTX dealer (one year, if 
installed by the consumer). This warranty is limited to the original retail purchaser of 
product. MTX disclaims any liability for the other incurred damages resulting from 
product defects. Any expenses incurred in the removal and reinstallation of 
amplifiers are not covered by this warranty. MTX's total liability will not exceed the 
purchase price of the amplifier. This warranty is valid only in the USA. 

To ensure efficiency and full benefit on any warranty claim during the warranty 
period stated above, MTX requests the return of the warranty registration card, 
completed in full immediately following purchase. Proof of purchase must be 
provided at time of warranty claim. If there is no proof of purchase provided with the 
warranty claim, MTX reserves the right not to honor the warranty set forth above. 
Therefore, labor and parts may be charged to you. 

This warranty does not apply to product exterior and cosmetics. Misuse, abnormal 
service or handling, improper alterations or modifications in design or construction 
void this warranty. 

No sales personnel of the seller, or any other person is authorized to make any 
warranties other than those described above or to extend the duration of any 
warranties on behalf of MTX beyond the time period described above. 

For Warranty Inquiries, please call: 




4545 E. Baseline Rd. 
Phoenix, Arizona 85040 

Register Warranty On-line: 





The Pointe at South Mountain 
^ 4545 East BaseBne Road 
Phoenix, AZ 85040 

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Please fold and seal with tape 










1. WAS THIS UNIT: □ Purchased for personal use □ Received as a gift 


□ Dealer □ Radio □ TV □ Newspaper □ Catalog 

□ Friend/Family □ Store display 

□ Magazine (Circle the magazine) Motor Trend Car and Track Rolling Stone Lowrider 

Truckin’ Autosound and Security Car Sound Car Audio and Electronics Car Stereo Review 

□ Other_ 

3. IS THIS: □ Your first car stereo □ Replacement/Upgrade 


□ Dealer recommendation □ MTX Name/reputation □ Friend/family recommendation 

□ Product Appeal □ Sound □Price □ Other_ 


□ Styling □ Sound Quality □ Power handling □ Bass Reproduction 

□ Durability □ Installation Flexibility 


□ Very Satisfied □ Satisfied Q Neutral □ Not Satisfied 





■ Connect to Car Stereo 
Remote/Power Antenna 
Turn-On Wire 



Minimum Wire Size: 

Power: 1/0 AWG. Ground: 1/0 AWG. 

Battery Negative (-) Cable 
Prior to Installing Amplifier 

Remove Paint 
from Metal 

CAUTION: This amplifier may draw in excess of 150 Amps of current 

Upgrading the vehicle’s factory battery and alternator is required. 

(For specific details, contact your local authorized MTX dealer, or call 1-800-CALL-MTX.) 

For installation options go to