DLS MRA22 - MANUAL 2, MRA31, MRA41 User Manual

How to install and operate the

DLS Marine Audio amplifiers

MRA22
MRA31
MRA41

Welcome!

This owners manual is written in easy english and
uses a lot of drawings to simply the installation and
use of the above amplifiers.

Your DLS amplifiers must be installed correctly in
order to work well. This manual will show you how
to install the amplifier like a pro. Please read the
entire manual before beginning the installation.
Install the amplifier yourself if you feel confident with
our instructions and if you have the proper tools.
However if you feel unsure, turn over the installa­tion job to someone better suited to it.

Warranty Service

This amplifier is covered by warranty, depending
on the conditions in the country where it is sold. If
the amplifier is returned for service, please include
the original dated receipt with the product.

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Technical Assistance

For technical assistance ask the shop where the
product was sold or the distributor in your very
country.You can always phone the DLS Helpdesk in
Sweden+ 46 31 84 00 60 or send an e-mail to
[e-mail] can also be found on our WEB­site www.dls.se

Contents

Installation…………………….……. 2
Tools and materials needed………. 3

Amplifier installation kit………….... 3

Wiring

Power and Remote……………..…. 3
Input and controls
Input wiring Hi & Low level……….. 4

Parallel input.................................. 4

Hi/Low input switch........................ 4

Fuses / Protect light....................... 4

Input level control........................... 5

Phase control................................. 5

Crossovers…………....................... 5

MRA 22 speaker wiring:

Front speakers…...……………….... 6

Subwoofer…………………………... 6

MRA 31 speaker wiring:

Front speakers…...……………….... 7

Subwoofer…………………………... 7

MRA 41 speaker wiring:

Four speakers…………………….... 8

Two speakers + bridged subwoofer. 8
Two way front system with
active crossover……………….……. 9

Testing……………………………….. 10
Troubleshooting……………………... 10
Professional tips…………………….. 11
Specifications………………………... 12

All models include

 RCA inputs
 High Level input
 Continuos variable low pass and high

pass crossover

 Remote turn on / off
 Automatic remote turn on/ off on high level

input without connecting any remote wire

 Electronic protection circuitry against

short-circuit, DC offset and thermal overload.
Bridgeable design to direct full power to
one or two subwoofers etc.

IMPORTANT!

While these amplifiers are specially designed
for marine applications, they are not
waterproof and should not be mounted where
it is likely to get wet.
The cover is made to resist moisture as well
as the PC-board.

DLS Svenska AB

P.O. Box 13029

SE-40251 Göteborg, Sweden

Tel: [phone]

Fax: [phone]

E-mail: [e-mail]

www.dls.se

Installation

Before you begin installation

Before you begin you need to read the manual, to have
some tools, cables and other material available. There
is one such list of material on the following page.

Amplifier location

Important
Allow air circulation around the amplifier.

2

Disconnect Battery

Before starting the instal­lation, always disconnect
the negative terminal of
the battery.

The DLS Marine Audio amplifiers have a compact
design that allows great flexibility in mounting.

Safety Considerations:

Your amplifier must be installed in a dry, well­ventilated environment and in a manner which
does not interfere with your vessel’s factory
installed electronic devices. You should also take
the time to securely mount the amplifier so that it
does not come loose in the event of a collision or
a sudden jolt to the vessel.

 Check before drilling any holes in your vessel
to make sure that you will not be drilling through
the hull, a fuel tank, fuel line, wiring harness or
other vital vessel system.
 Do not run system wiring outside or
underneath the vessel. This is an extremely
dangerous practice which can result in severe
damage to your vessel and person.
 Protect all system wires from sharp edges
(metal, fiberglass, etc.) by carefully routing
them, tying them down and using grommets
and loom where appropriate.
 Do not mount the amplifier in the engine
compartment or in any other area that will
expose the amplifier circuitry to the elements.
 Do not mount the amplifier upside down!

MRA22, MRA31, MRA41

DLS logo on amplifier cooling flange

The DLS logo on top of the amplifier is attached
with two 1 mm hex. screws. The logo can be remo­ved and twisted 90 or 180 degrees, and then
screwed back in wanted position. The logo can be
mounted in four different ways to match your in­stallation.

Removal of side flanges

In order to attach the amplifier to the surface and
connect speaker and power cables, the side
flanges must be removed. This is done by remo­ving the hex screws on top of the amplifier. Use a
3 mm hex key.

Remove these
screws using a 3
mm hex. key for
removal of side
flange. Remount
after attaching the
amplifier and
connection of the
speaker and power
cables.

This is the best way to
mount the amplifier to get
good cooling.

Tools and material needed

Tools:

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 Flat and Phillips screwdrivers
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 Wire cutter, Wire stripper
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 Electric drill with drills
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 Crimping tool
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 Digital multimeter or test lamp

Material:

 Speaker wire: minimum

12 AWG = 4 mm2 for subwoofers
13 – 16 AWG = 1,5-2,5 mm2 for other
speakers

 Stainless metal screws for mounting the

amplifier to the amplifier board and the
amplifier board to the vessel, and some
extra for fuse holder.

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 Electrical insulation tape

Amplifier installation kit:

If available, buy an amplifier installation kit. It
contains normally all you need. This is what you
have to buy if you buy the items separately.
 Power cable,minimum 8 AWG = 10 mm

2

for MRA22, 4 AWG = 21 mm2 for MRA 31/41.

 1 pc of fuseholder to install close to the

battery + fuse 50 Ampere.

 15 AWG = 1,5 mm2 wire for remote turn on /

off cable from radio / CD.

 RCA-cable for input from radio.

Different lengths are available.

 Two ring crimp terminals –one

for connection to the battery plus and one
for the battery minus connection.

 Two heavy fork crimp terminals to connect

+ and – to amplifer – but you do only need
them if you use heavy cable or to make the
installation look nicer.

 Four to ten fork crimp terminals to

connect the speaker cables – but you do
only need them if you use heavy cables or
want the installation to look nicer.

 One fork crimp terminal to connect the

remote wire to the amplifier, but you need it
only to make it look nicer.

 Four to eight splicers to connect speaker

cables to high level input cable, if high level
input is used.

 Wire ties

3

If amplifier installation kits are available with diffe­rent size of power cable, chose the most heavy
power cable to improve sound quality and to allow
more amplifiers to be installed now or later.

These are the minimum sizes we recommend for
the amplifiers:
MRA22 10 mm2 (7 AWG)
MRA31/41 21 mm2 (4 AWG)
This is for cable lengths up to 5 meters.
The ground cable must have the same size.

Wiring

Connect power and remote

Connect the fuse holder as close to the vessel
battery + as possible, using AWG 8 = 10 mm2 or
heavier cable. Use a ring crimp terminal cable to
connect to battery +. Apply silicon grease to the fuse
to prevent corrosion. Use a 50 Amp fuse for both
amplifiers.

Connect the battery cable by a crimp fork terminal
(spade ) to the +12 Volt on the amplifier. Do likewise
with the negative cable. If you use a AWG 8 = 10
mm

2

or thinner cable, you can do without the crimp
terminal and put the cable right into the connector.
Be sure to use a rubber grommet or a plastic
insulating tube where the cable passes places when
it can easily be jammed. Use wire ties to secure to
existing cables.

DLS FH1
fuse holder

To head unit
remote

For RCA cable signal input:

Connect the radio power antenna lead = remote
turn on/off from the car stereo to the amplifier remote
connection. This turns on the amplifier when the
car stereo is turned on.
You can either use the built in remote cable in the
RCA cable itself or use a separate cable.
We recommend to use a separate remote wire and
run the RCA lead separate from remote wire, power
cables and speaker cables.
You can either use a crimp fork terminal or insert
the cable directly into the amplifier terminal. If there
is no remote voltage available from the stereo, you
must connect to the ignition key through the radio
or any accessories fuse.

For High Level input:

We recommend you to connect the remote wire as
described above. The amplifier will produce soft on
/ soft off operation this way. You must set the Hi
level/Low level switch to High level position in this
case.
In the case that there is no remote voltage available
from the car stereo or you want to simplify the in­stallation, the amplifier can be turned on/ turned off
by the high level input voltage. This is done when
the Hi level/Low level switch is set to Hi level posi­tion. There is a small disadvantage that this function
gives soft turn on operation but some pop sound
when switching off.

Remote terminal ( REM )

MRA22, MRA31, MRA41

Important

On MRA22 use either the low level or high level
input, do not use both at same time.

Low level input

Use a pair of shielded stereo audio cables with RCA
type jack. RCA cables are available in different
lengths up to 5,5 meters.
Avoid placing the RCA cable
close to speaker cables,
power cables and remote
control cable. Connect to in­put socket A/B.
MRA31 has also a separate
input (C) for the mono sub
channel.

High Level Input

Connect left and right speaker wires coming from
the car stereo to the high level input as shown. You
must connect both plus and minus as the inputs
are balanced, connecting plus only gives lower level
and bad sound quality. By changing the polarity of
plus and minus, you can change the phase.

MRA 22, MRA31 High level input socket

Hi level input
plug on amp.

MRA31

On MRA31 the high level signal is fed internally to
channel C when using high level input.

Automatic turn on when using high level input.

With the Hi/Low input swich set to Hi, the amplifier
turns on automatically on high input. You dont need
to connect a separate remote wire from your head
unit.

Input and controls

Input Wiring

Inputs may be low level from the RCA output of the car
stereo or high level from the car stereo speaker out­put. Low level = RCA is to prefer for the best sound
quality.

4

RCA Output

Use RCA Outputs to
connect additional
amplifiers (not available on
MRA31).

Input Output

AA

BB

Parallel input on MRA31, MRA41

On MRA31 the PC position
internally connects the A/B input
with the input for channel C.
On MRA41 the PCD position
internally connects the A/B and
C/D inputs.

High Input
(C/D Ch)

White: A ch.+
White/Black: A ch.­Grey/Black: B ch.­Grey: B ch.+

Power
(Green)

Protect
(Red)

Power Light / Protect light

The power light (green ) comes on when
the amplifier is turned on.

The protect light ( red ) comes on
when the amplifier shuts down from
overheating, or a short circuit ( spea­ker failure)

MRA31 and MRA41 uses two
30 ampere ATC blade type
fuses.

MRA22 uses one 25 A fuse.

Fuses

Parallel Input MRA31

To ensure best possible performance from the
amplifiers a switch is installed to select between Hi
and Low input.

When using High Level input:

Push in the button to position
”Hi Level”

When using Low level input:

Push out the button to position
”Low Level”

If the switch is set to wrong position, the amplifier
still works, but the risk for disturbances or distortion

increases.

Hi / Low level input switch

Hi level
Low level

MRA22, MRA31, MRA41

Parallel Input MRA41

Off PC

Off PCD

MRA41 High level input sockets

The MRA41 four channel amplifier is connected
likewise, however we have four channels.
You can feed two channels from RCA and two
channels using high level input from rear speaker
cables.

Hi level input plug on amp for CH A/B.

Hi level input plug on amp for CH C/D.

High Input
(C/D Ch)

Violet: C ch.+
Violet/Black: C ch.­Green/Black: D ch.­Green: D ch.+

High Input
(A/B Ch)

White: A ch.+
White/Black: A ch.­Grey/Black: B ch.­Grey: B ch.+

Crossovers

Input Level control

The input level control, 5V – 0,25 V,
matches the output of your radio to
the input of the amplifier. After instal­lation is complete, make sure the in­put of the amplifier is turned down all
the way ( counter-clockwise at 5V ).

All amplifiers include high pass filter
( HPF ) and low pass filters ( LPF).
All filters are continously variable and all filters can
be switched on and off. MRA31 also include a
subsonic filter.

Low Pass Filter (LPF)

The LPF (low pass filter) mostly used for
subwoofers. It will allow low frequencies only and
blocks higher frequencies. A typical setting is 50 –
80 Hz. The filter can be switched in and out.
This is normally used for subwoofers
On MRA41 the filter can also be used for active
crossover in a 2-way speaker component kit, a
typical crocssover point is then 3,5 - 4 kHz.

5

Play a tape or CD, make sure all bass or treble
settings or equalizer are flat, and turn the volume of
the radio up until you just start to hear distortion.
Turn the volume control down just a bit. On the
amplifier increase the input level control ( clockwise
or to the right ) until you just start to hear distortion,
then back the level control just a bit. Now your radio
and amplifier levels are matched.

The phase control on MRA31 can be set
continuously from 0 - 180 degrees. This is very
useful when you want to adjust the bass sound for
best front stage image. Start on 0 and turn the control
slowly clockwise until you experience that the bass
sound is coming from the front. If you dont get the
result you want, also try to
phase reverse the subwoofer
connections and make
a new adjustment.
NOTE: This function is intended for car use and
may not be fully functional in boats. Set the control
to 0.

Phase control MRA31

0 180

PHASE

Subsonic filter MRA31

The Subsonic filter blocks the very
deepest frequencies from reaching the
subwoofers. It has a fixed frequency
of 25 Hz and can be switched On / Off.
For sub channel C only.

Level

5V

0,25V

LPF

Off On

80Hz 200Hz

50Hz

500Hz

Filter frequency range:

MRA22: 50-500 Hz
MRA31: 50 - 120 Hz

MRA41:

Ch A/B: 50(500)Hz - 500(5k)Hz

MRA22, MRA31, MRA41

Subsonic

Off On

Grand bass on MRA41

Grand Bass is used to increase the bass volume

at an interval of bass frequencies. You can select
the center frequency between 25Hz and 80 Hz and
the amplification between 0 dB ( no amplification )
and 18 dB ( full amplification ).
The slope of the filter is 10 – 12 dB at maximum
setting.
This function is used to compensate for the bass
box function and to adjust for your own taste of
bass. Set level control at 0 dB if you want it to be
inoperative.

The HPF (high pass filter) blocks very low
frequencies from reaching the speakers. It is mostly
used at say 60 Hz to protect small speakers (like 6
inch and smaller) from deep bass. It can also be
used as subsonic filter to take away the very
deepest frequencies from a bass box. The typical
setting is then around 25 – 40 Hz.
The filter can be switched off if you want to run the
amplifier in full range mode.
On MRA41 the filter can also be used for active
crossover in a 2-way speaker component kit, a
typical crocssover point is then 3,5 - 4 kHz.

High Pass Filter (HPF)

Filter frequency range:
MRA22: 15-150 Hz
MRA31: 50 - 150 Hz
MRA41:

Ch A/B: 15 - 500 Hz
Ch C/D: 15(150)Hz - 500(5k) Hz

Grand Bass

40Hz

60Hz

25Hz 80Hz

0dB 18dB

HPF

Off On

50Hz 220Hz

15Hz

500Hz