MOSFET POWER AMPLIFIERS

Installation Instructions / Owner's Manual

MDS GP2 MDS GP3 MDS GP4

MDS - Multi Dynamic Systems of Sweden AB

Midsommarv. 8-10
126 35 Hägersten
+46(08)556 00 740
www.mds.se

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 1

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 INTRODUCTION
Congratulations on your purchase of a MDS state-of-the-art power amplifier. Your
selection of a MDS product indicates a true appreciation of fine musical reproduction.
Whether adding to an existing system or including your MDS amplifier in a new system,
you are certain to notice immediate performance benefits.

KEEP YOUR SALES RECEIPT

Take this time to attach your sales receipt to the manual and put in a safe place. In case
of any unforeseen reason this product may need warranty service, your receipt will be
necessary to establish purchase date.

RECOMMENDATION
A power amplifier’s performance is only as good as its installation. Proper installation will
maximize the system’s overall performance. It is recommended that you have our
product installed by an authorized MDS retailer. However, if you decide to install it
yourself, please carefully read through this manual and take your time to do a quality
installation.

IMPORTANT! Before making any connections, disconnect the car’s battery until
the installation is completed to avoid possible damage to the electrical system.

WARNING!
Exposure to high power sound system can cause hearing loss or damage.
Listening to your system at loud levels while driving, will impair your ability to
hear traffic sounds and emergency vehicles. Use common sense when listening
to your system.

Serial # Model #

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 SAFETY PRECAUTIONS
Fuse amplifiers power wire at the battery.
Be sure to fuse the power wire within 12” of the car's battery. This will protect the car's
battery in case of a short circuit between the power amplifier and battery. THIS IS A
MUST, the amplifier's built-in fuse will only protect the power amplifier not the car's
battery!

Use high grade wire connectors.

To ensure maximum power transfer and secure safe connections, it is recommended to
use high grade barrier spades (for connection at amplifier) and terminal rings (for
connection at battery).

Do not run any wires underneath vehicle.

Exposed wires have a chance of being cut or damaged. It is best to run all wires through
the vehicle under the carpet and/or side panels. This lends to a cleaner installation and
less risk of damage.

Use caution when mounting amplifier.

Remember there are many electrical wires, gas lines, vacuum lines, brake lines as well
as a gas tank in the automobile. Make sure you know where they are when mounting the
amplifier to avoid puncturing lines, shorting wires or drilling holes in the gas tank.

Run signal wires away from electrical wires.

To avoid possibility of induced noise from the car's electrical system (i.e. popping noises
or engine noise), run wires away from the car's electrical wiring.

Make all ground wires as short as possible and at the same point.
In order to reduce the chance of ground loops (i.e. engine noise), make the grounding
wire as short as possible to reduce the wire's resistance. Also, when using multiple
components, make sure all units are grounded at the same point.

Avoid sharp edges when running the wires.

To avoid the possibility of power, signal or speaker shorts, be careful not to allow the
amplifiers wires to come in contact with sharp edges. Use a grommet to protect the wire
when running through the fire wall .

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 FEATURES AND BENEFITS
DC Offset Protection
This circuit protects the output of the amplifier against DC voltage. If for some reason DC
voltage is detected at the output stage, the amplifier will shut down protecting the
speakers from direct current.

Short Circuit Protection

The circuit protects the amplifier from damage due to a short found in the speakers or
wiring. If one of the speakers or its wiring comes in contact with ground, the amplifier will
shut down. To resume normal operation, correct the problem and turn the head unit off,
then back on. The amplifier will reset and play again.

Thermal Protection

To protect the amplifier circuitry against damage caused by prolonged exposure to high
temperatures, a thermal protection circuit is activated if the amplifier reaches excessively
high operating temperature. Once the thermal circuit is activated, the amplifier will shut
down to cool off. The amplifier will automatically turn back on once it cools down to a safe
operating temperature.

Power & Protection Indicator

The power L.E.D. Illuminates when the amplifier is on and receiving power. The protect
LED Illuminates when the amplifier has gone into the protection mode (Please refer to our
trouble shooting section).

Tri Mode Capable

If so desired, the amplifier may be run in stereo and mono at the same time. For example,
this feature would allow you to run a pair of mid and tweeters in stereo and a sub-woofer
mono.

Built-in Crossover

The MDS amplifiers include a built-in variable **high and low pass crossovers. The
crossover features a variable frequency selection (40Hz ~ 400Hz) for precise high or low
pass filtering.

Bass Boost
For added low frequency performance the amplifiers are equipped with a variable
0~12 dB bass boost @ 45Hz.

Line Output

One set of full range line outputs have been provided for convenient connection to
additional amplifiers in the system.

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 Power Fusing

This protects the amplifier against short circuits and excessive current.

Remote Turn-on
Automatically turns amplifier on when connected to the head unit's remote output. The
amplifier will turn on and off with the head unit to save current consumption. This control
also operates the reset circuit for the amplifier's protection. It must be connected with the
head unit in order to reset protection circuits.

Adjustable Input Sensitivity

Allows you to fine-tune the level matching between your source and the power amplifier.

High Level Input

Allowing for integration with “Factory Sound Systems”.

Stable To 2 Ohm Stereo Mode

Stability to 2 ohm in stereo mode, 4 ohms bridged.

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 MOUNTING LOCATION
Before you start the installation, it will be necessary to find a mounting location for the
amplifier. Find a location in which the amplifier will receive adequate ventilation in order
to dissipate the heat it develops during operation. Two popular mounting locations are in
the trunk or under the seat.

Select the location in which you wish to mount the amplifier. Use caution when mounting
amplifier, there are many wires, gas lines, vacuum lines, brake lines as well as a gas tank
in the automobile. Make sure you know where they are when mounting the amplifier to
avoid puncturing lines, shorting wires or drilling holes in the gas tank. Once you are
ready, use a pencil to mark the mounting holes in the bottom panel. After you have
marked the locations of the holes move amplifier out of the way and drill small starter
holes to make the tapping screws easier to install. Use provided screws to tighten down
the amplifier.

INPUT
REMOTE HI-INPUT FRONT REAR OUTPUT HI-INPUT
POWER PROTECT
GAIN GAIN
+L- +R-
L +L- +R-
X-OVER X-OVER
BASS BOOST MIN MAX MIN MAX BASS BOOST
FILTER FILTER
R
40Hz 400Hz 40Hz 400Hz
HPF FULL LPF HPF FULL LPF
OdB 12dB OdB 12dB

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 POWER CONNECTIONS

FUSE
SPEAKERS POWER
L+ R+ +12V REM GND

20A
BRIDGE

IN-LINE POWER FUSE

MOUNTED WITHIN 12"
FROM BATTERY RECOMMENDED
(NOT PROVIDED)

RADIO'S REMOTE
TURN-ON OUTPUT

+ -
94.7 CAR BATTERY
+12V

IMPORTANT! Before making any connections, disconnect the car’s battery until the
installation is completed to avoid possible damage to the electrical system.

Connect the amplifier to the car's battery.

At times, the amplifier will need to draw large levels of current that cannot be provided by
any circuit in the car's fuse box. We recommend using a 4 to 8 gauge power wire for your
connections depending on the amplifier and length of the wire. Strip one end of the wire
and crimp on a barrier spade connect to the terminal on the amplifier marked “+12V”.
Loosen screw terminal and connect barrier spade and tighten. Use caution to make sure
no stray wire stands come in contact with surrounding terminals causing short circuits.
Run the wire directly to the positive terminal of the car's battery. Make sure to use an in-
line fuse within 12” of the car's battery to protect the electrical system and amplifier
against short circuits and/or power surges.

Connect the ground terminal of the amplifier to the car's chassis.

For the ground connection, use an 4 to 8 gauge wire (black) to connect to the terminal
marked GND and then connect it to the car's chassis. Try to keep the length of the cable
as short as possible, preferably less than 6". Also make sure that the point on the car
where the connection is to be made is free of paint and dirt.

Connect the remote terminal of the amplifier to a switchable +12V source.

This connection allows the amplifier to be turned on and off with the power control of the
radio. If the radio has a REMOTE output terminal, connect it to the amplifier's terminal
marked REMOTE (using a 16 gauge wire or heavier). Now when the radio is turned on,
the amplifier will automatically turn on. This connection can also be made to the radio’s
Power Antenna wire.

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 SIGNAL CONNECTIONS
Connect the RCA output of the head unit (AM/FM cassette player, CD, or DAT) to
the RCA input terminals of the amplifier.

To make these connections, we recommend high quality RCA cables, which are
available at your local car audio retailer. Run signal wires away from electrical wires to
avoid possibility of induced noise from the car's electrical system (i.e. popping noises or
engine noise). Please note that when making these connections the signal inputs
correspond with the speaker outputs.

INPUT OUTPUT HI-INPUT

FILTER
BASS BOOST X-OVER GAIN
L L +L- +R-
HPF FULL LPF
REMOTE POWER
OdB 12dB 40Hz 400Hz MIN MAX
R R PROTECT

L R

TWO CHANNEL SIGNAL CONNECTIONS

INPUT
REMOTE HI-INPUT FRONT REAR OUTPUT HI-INPUT
POWER PROTECT
GAIN GAIN
+L- +R-
L +L- +R-
L
X-OVER X-OVER
BASS BOOST MIN MAX MIN MAX BASS BOOST
FILTER FILTER
R
40Hz 400Hz R 40Hz 400Hz
HPF FULL LPF HPF FULL LPF
OdB 12dB OdB 12dB

L R R L
Optional full range line out connection
FRONT REAR to additional amplifiers in the system.

FOUR CHANNEL SIGNAL CONNECTIONS

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 HIGH LEVEL CONNECTIONS (OPTIONAL)
High Level inputs have been included to connect the amplifier to a radio without low-level
outputs (i.e. factory radio). This connection will allow you to connect directly to the
speaker output of the radio with out the need of an external adapter.

Determine the type of radio you have and make one of the following connections.
CAUTION! Before making any connections determine the type of radio to avoid possible
damage to amplifier and/or radio.

INPUT OUTPUT

L L POWER
REMOTE BASS BOOST X-OVER GAIN

FILTER PROTECT
R HI-INPUT
R
OdB 12dB 40Hz 400Hz MIN MAX
HPF FULL LPF
+L- +R-

94.7

LEFT + WHITE
LEFT - WHITE/BLACK
(NOT USED) BLACK (GROUND)
RIGHT + GRAY
RIGHT - GRAY/BLACK

TWO CHANNEL CONNECTIONS:

FLOATING GROUND RADIO (MOST COMMON TYPE)

INPUT OUTPUT

L L POWER
REMOTE BASS BOOST X-OVER GAIN

FILTER PROTECT
R HI-INPUT
R
OdB 12dB 40Hz 400Hz MIN MAX
HPF FULL LPF
+L- +R-

94.7

LEFT + WHITE
WHITE/BLACK (NOT USED)
BLACK GROUND
RIGHT + GRAY
GRAY/BLACK (NOT USED)
TWO CHANNEL CONNECTIONS:
COMMON GROUND RADIO

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 INPUT
REMOTE HI-INPUT FRONT REAR OUTPUT HI-INPUT
POWER PROTECT
GAIN GAIN
+L- +R-
L +L- +R-
X-OVER X-OVER
BASS BOOST MIN MAX MIN MAX BASS BOOST
FILTER FILTER
R
40Hz 400Hz 40Hz 400Hz
HPF FULL LPF HPF FULL LPF
OdB 12dB OdB 12dB

94.7

GRAY/BLACK RIGHT - LEFT + GREEN

GRAY RIGHT + LEFT - GREEN/BLACK
BLACK (GROUND) (NOT USED) (NOT USED) BLACK (GROUND)
WHITE/BLACK LEFT - RIGHT + PURPLE
WHITE LEFT + RIGHT - PURPLE/BLACK

FOUR CHANNEL CONNECTIONS:

FLOATING GROUND RADIO (MOST COMMON TYPE)

INPUT
REMOTE HI-INPUT FRONT REAR OUTPUT HI-INPUT
POWER PROTECT
GAIN GAIN
+L- +R-
L +L- +R-
X-OVER X-OVER
BASS BOOST MIN MAX MIN MAX BASS BOOST
FILTER FILTER
R
40Hz 400Hz 40Hz 400Hz
HPF FULL LPF HPF FULL LPF
OdB 12dB OdB 12dB

94.7

GRAY/BLACK (NOT USED) LEFT + GREEN

GRAY RIGHT + GREEN/BLACK (NOT USED)
BLACK GROUND BLACK GROUND
WHITE/BLACK (NOT USED) RIGHT + PURPLE
WHITE LEFT + PURPLE/BLACK (NOT USED)

FOUR CHANNEL CONNECTIONS:

COMMON GROUND RADIO

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 SPEAKER CONNECTIONS
Make the speaker connections using speaker wire that is at least 16 gauge or heavier.

As with any audio component, proper phasing of the amplifier and speakers is essential
for strong bass response. When connecting, make sure that positive (+) from the
amplifier is connected to the positive (+) of the speaker, and the same for negative (-).

FUSE
SPEAKERS POWER
L+ R+ +12V REM GND

20A
BRIDGE

+ - 4 Ohm Speakers + -
(2 Ohm Minimum)

TWO CHANNEL
SPEAKER CONNECTIONS

BRIDGE FUSE
+ LF - + RF - POWER
+12V REM GND

30A 30A
+ LR - + RR -
BRIDGE

4 Ohm Speakers 4 Ohm Speakers

(2 Ohm Minimum) (2 Ohm Minimum)

FOUR CHANNEL SPEAKER CONNECTIONS

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 SPEAKER CONNECTIONS (BRIDGED)
The MDS amplifiers are capable of being bridged in a mono configuration. This feature
allows you the flexibility of using the amplifier to drive a ** subwoofer or a center channel.
In this configuration the amplifier sums the right and left channel to deliver one channel
(mono) output.

Please note: in order for the amplifier to sum right and left signal information, both right
and left RCA connections must be made.

**CAUTION! In the bridged mode, the amplifier must see a 4 Ohm load or higher. Any
lower than 4 Ohms will cause the amplifier to overheat and possibly cause permanent damage
to the amplifier!

FUSE
SPEAKERS POWER
L+ R+ +12V REM GND

20A
BRIDGE

+
4 Ohm Speaker

TWO CHANNEL BRIDGED SPEAKER CONNECTIONS

BRIDGE FUSE
+ LF - + RF - POWER
+12V REM GND

30A 30A
+ LR - + RR -
BRIDGE

4 Ohm Speaker 4 Ohm Speaker

FOUR CHANNEL BRIDGED SPEAKER CONNECTIONS

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 SPEAKER CONNECTIONS (TRI-MODE)
The amplifier is capable of running in a Mono / Stereo mode. This feature gives the
amplifier the ability to run stereo satellites (midbass & tweeter) simultaneously with a
mono subwoofer.

These connections are more complicated because they require the use of passive
crossover networks (Not provided) to divide the frequencies to the speakers. We have
included a sample diagram for 4 Ohm connections. If you wish to use multiple speakers
to achieve a lower impedance and higher power, it is strongly recommended that you
seek professional advice from your MDS retailer before attempting to make these
connections.

Please Note: In the Tri-mode configuration, the amplifier’s built-in crossover must be set
to the ”FULL” position so the speakers receive full range output.

FUSE
SPEAKERS POWER
L+ R+ +12V REM GND

20A
BRIDGE

100 F
-
-

100 F
4 mH

Right
Left
Mid / Tweeter
Mid / Tweeter
4 Ohm
4 Ohm
(2 Ohm Minimum)
(2 Ohm Minimum) + -

L E G E N D

Mono Woofer
8 Ohm NON-POLAR
CAPACITOR
INDUCTOR
(COIL)
(4 Ohm Minimum)

CAUTION! In Tri- mode operation, the amplifier must see a 2 Ohm load or higher for the
stereo satellites and no lower than 4 Ohms for the subwoofer(s). Any lower than the above
mentioned impedance will cause the amplifier to overheat and possibly cause permanent
damage to the amplifier.

13

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 REMOTE BASS CONTROL MODULE (OPTIONAL)
Before connecting the remote, it will be necessary to find a mounting location that will be
easy to access for adjustment. Once you select your mounting location, you will need to
run the control wire from the remote to the amplifier. To avoid possibility of induced noise
from the car's electrical system (i.e. popping noises or engine noise), run the cable from
the remote to the amplifier away from the car's electrical wiring.

Please note: Once the remote is plugged in, it overrides the bass boost on the amplifier
and becomes the primary bass adjustment.

INPUT OUTPUT HI-INPUT

FILTER
BASS BOOST X-OVER GAIN
L L +L- +R-
HPF FULL LPF
REMOTE POWER
OdB 12dB 40Hz 400Hz MIN MAX
R R PROTECT

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 ADJUSTING THE X-OVER AND BASS
.
(Please note: If you intend to use the amplifier in the Tri-mode configuration, it is
necessary to set the crossover control to the “FULL” setting in order to receive full range
output)

The amplifiers are equipped with a built-in variable crossover network allowing you to
select the crossover type (i.e. Low-Pass or Hi-Pass) and the desired crossover point.
For example if you wish to drive a pair of subwoofers, you can select the “Low Pass”
setting on the amplifier to filter out high frequencies. This will send only low frequencies
to your subwoofers (see example settings below). The crossover point should be
determined by the speakers operating range. Please refer to speaker manufactures
recommended crossover point.
Select the crossover type on the You can add up to 12dB bass boost by
amplifiers side panel. increasing the Bass Boost control.
(Low-pass is selected in this example for subwoofers)

FILTER X-OVER BASS BOOST

HPF FULL LPF

OdB 12dB
40Hz 400Hz

Select the crossover point

for your speakers.

FINE TUNE THE SYSTEM

Fine tune the amplifier's input sensitivity.
GAIN The gain sensitivity control for the MDS
amplifier is located on the side panel. This gain control
has been included to allow adjustment to properly
match the output of the radio. This is one of the most
misunderstood adjustments. By rotating the control in
MIN MAX the clockwise direction, the amplifier‘s input will
become more sensitive and the music will play louder. This
is not a volume control and you will not get more power out of the amplifier in the
maximum position! It may seem to deliver more output, but actually the system is only
playing louder faster as you turn the volume control on the radio. Ideally, to properly level
match the system the goal is to achieve maximum output from the amplifier without
distortion at about 3/4 of the volume control.

To determine if the amplifier’s gain is set properly, turn the system on and slowly increase
the volume control. You should be able to use about 3/4 volume before the system gets
loud but not distorting. It is very important when making these adjustments that you do
not over drive the speakers (at point of distortion) this will cause permanent damage to
the speakers. If you are unable to achieve 3/4 volume before distortion you will need to
adjust gain control (in this case you would reduce the gain). The gain controls should be
adjusted very slowly. It may help to have another person to assist you by adjusting the
gain controls while you listen for distortion.

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 TROUBLE SHOOTING THE SYSTEM
We have put together this trouble-shooting guide if you experience problems after
installing the amplifier. Please keep in mind that the majority of problems incurred are
caused by improper installation and not the equipment itself. In addition, there are many
components in the system that could cause various signal problems such as inducted
electrical noise and engine noise.

Before you can properly address the problem, you must first find the component that is
causing the problem. This will take patience and a process of elimination.

LOOK FOR.... SOLUTION

No Output

Blown fuse Replace

Bad RCA Cable(s) Replace
+12V at power terminal Check connection
+12V at remote terminal Check connection
Grounding point clean and tight Check for ground w/meter
Head Unit's fader not in center position Set to center position

Low Output

Check level adjustments Re-adjust

Bad RCA cable(s) Replace
Improper level matching Re-adjust

Engine Noise

Grounding points are clean and tight Check for ground w/meter
Ground all components at same point Ground at same point
Try different grounding point Change for better ground
Bad RCA cable(s) Replace
Use High Quality shielded RCA cables Rejects inducted noise
Low Vehicle charging system and/or battery Fix and/or replace

Protection L.E.D. Illuminated

Speaker short Check speakers connection

for short circuit
Speaker grounding out Make sure speaker wires
do not touch chassis ground
Impedance too low Check speaker impedance
(Min 2 ohm Stereo, 4 Mono)
Overheating Check mounting location
for Adequate air Circulation
Speaker impedance too low

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 SPECIFICATIONS
MDS GP2 MDS GP3 MDS GP4
Output Power @ 14.4 VDC :
Max Output 100W x 2 max 240W x 2 max 140W x 4 max
4 ohm 50W x 2 120W x 2 70W x 4
2 ohm 75W x 2 180W x 2 105W x 4
Bridged 4ohm 150W x 1 380W x 1 210W x 2
Frequency Response 10Hz-25KHz 10Hz-25KHz 10Hz-25KHz
S/N Ratio (A-weight) >75dB >75dB >75dB
THD with 20k filter .30% .30% .30%
Channel Separation 45dB 45dB 45dB
Low Input Level 200mV-5V 200mV-5V 200mV-5V
Hi Input Level 1.5V-14V 1.5V-14V 1.5V-14V
Battery Voltage Range 10.5VDC-16VDC 10.5VDC-16VDC 10.5VDC-16VDC
Crossover Type HPF/FULL/LPF HPF/FULL/LPF HPF/FULL/LPF
Crossover Frequency 40Hz-400Hz 40Hz-400Hz 40Hz-400Hz
Crossover Slope 12dB/Oct 12dB/Oct 12dB/Oct
Bass EQ at FULL/LP 0-12dB @ 45Hz 0-12dB @ 45Hz 0-12dB @ 45Hz
Fuse 1 x 20A 2 x 25A 2 x 30A

Due to continuing product improvement, specifications subject to change without notice.

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 18

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 MDS - Multi Dynamic Systems of Sweden AB
Midsommarv. 8-10
126 35 Hägersten
+46(08)556 00 740
www.mds.se
Manual By

www.extremeconcepts.com
MDS AMP REV 1.31.04

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