MB QUART Discus - Manual

System Design
The success of any car stereo system relies on several factors,
such as the system design, execution of the installation, and
system setup. Please remember that any system is only as good
as its weakest link.
Please remember that higher power systems are not necessarily
useful purely for high sound pressure levels, but also to establish
a headroom capability, to reproduce musical peaks cleanly without
distortion.
Lower power amplifiers will clip earlier than their more powerful
cousins, and cause loudspeaker failure when overdriven, due to
the harmonics generated by a clipped signal, thus overheating
voice coils.
Amplifiers should be mounted with the fins running horizontally for
best convection cooling, to minimize overheating. Purchase the
best quality RCA cables you can afford, for reliability and less
engine noise interference in the audio system.
It is highly recommended that the amplifier be mounted to a board
of MDF or other solid structure using the 4 mounting screws
provided. Avoid mounting the amplifier to metal as this can
introduce noise and other unwanted issues. When mounting the
amplifier, ensure that it is mounted HORIZONTALLY, as shown in
the diagram above, for optimal heat dissipation. Mounting
amplifiers to speaker enclosures is not recommended as this can
cause damage to the amplifier components. When choosing a
location for mounting the amplifier, ensure that you check for
clearance from wires, gas tank, electrical devices and brake lines
etc.
Congratulations!
By purchasing an amplifier from MB Quart, you have decided on a
product of the highest technical quality. MB Quart wishes you
great enjoyment with your amplifier. Should you have any
questions about this system or other MB Quart products, please
email us at [email protected]
General:
Run the wiring so that RCA cables are at least 18“ away from power and speaker
cables. Keep RCA cables away from electrical devices in the vehicle that can
cause electrical noise, such as electric fuel pumps, emission control modules and
other on-board electronic modules.
Power and ground connections:
(See table below)
Use a sufficient gauge power cable and ground cable using the chart below as
reference to what size wire you require. Discus series amplifiers require at least 4
gauge power wire. In a multi amplifier system, add the total value of the
manufacture recommended fusing to get your total system amperage. Some
applications may require multiple runs of power wire to meet the system
requirements. In multi amplifier systems it is advisable to mount a large enough
fuse right at the battery, and run one or multiple +12 volt power cables to a fused
distribution block near the amplifiers. It is then a simple matter to connect the +12
volt terminal of each amplifier to the distribution block. During this process, please
ensure that the main power fuse is removed to avoid shorting the electrical system.
The main fuse must be within 12” of the vehicles battery.
Ground each amplifier with as short a ground lead as possible directly to the
vehicle chassis using at least 4 gauge wire or equivalent to the size of the
amplifiers’ power wire. Use a ground distribution block, if you wish, but it is
extremely important to keep the main ground lead from this distribution block to the
chassis as short as possible , not more than 12“. The ground connection integrity
to the chassis is very important, and the best way to achieve a good, solid
electrical and mechanical contact is to use a large round crimp lug, crimped and
soldered to the ground cable. The next step is to scrape the paint off the vehicle
chassis , slightly larger than the ground lug, at the connection point. Drill a
clearance hole in the chassis, the same size as the lug hole, and use a bolt, spring
washer and nut to securely fasten the ground lug. Use petroleum jelly to coat the
bolt/lug connection, to prevent oxidization with time.
TIP: Use the same approach when installing head units, equalizers or any audio
equipment for that matter - run short individual grounds from each piece directly to
the vehicle chassis, to minimize ground loops and system noise. All power, ground
and speaker connections should be crimped and soldered for reliability. Make sure
that none of the cable insulation can chafe against exposed metal in the vehicle,
causing short circuits to the chassis.
Safe connection sequence:
After all cables are run, connect speaker wires to the speakers and amplifiers, then
run and plug in RCA cables. Next, connect all power, ground, and remote turn on
leads. Now connect all +12 volt cables to the amplifier/s and distribution blocks
and fuse holders. Finally, connect the main +12 volt cable to the battery, with the
main fuse removed, and we are almost ready to power up the system.
Power up the system:
The following procedure may seem like overkill, but there is nothing more
frustrating when turning on a system for the first time, and it does not work properly
immediately.
First, make sure the head unit is off, and turn all level controls to minimum
(counterclockwise), including the head unit volume control. Set all equalizers to 0
dB (no boost), and all crossover frequency controls at approximate frequencies, as
recommended by the loudspeaker manufacturer. Set all input selector and
crossover switches as required for the application. Remove all amplifier fuses, and
insert the main fuse at the battery. If the fuse does not blow, you can insert the
fuse in one of the amplifiers, and we are ready to turn on the system. Turn the
head unit on, insert a CD, or select a radio station, and increase the head unit
volume control. If the system sounds fine, turn off the head unit, and install fuses in
the remaining amplifiers, one by one, till the complete system is powered up and
functioning properly.
SETTING UP SYSTEMS AFTER INSTALLATION FOR
BEST PERFORMANCE
General:
At this point you are ready to get more specific on the settings for your amplifier.
High Pass:
-When in Hi Pass operation, this setting acts as a low frequency cut off for your
system reproduction. The point that you set it at cuts off any frequencies from
reproduction beyond this point. The 12 o’clock position is a great starting point.
EXAMPLE: If you adjust the High Pass to 100Hz, the amplifier will not play
frequencies below 100Hz but will play frequencies from 100Hz to the chosen Low
Pass frequency.
-When in Low Pass/Bandpass operation, this setting acts as a low frequency cut
off for your system reproduction aka Subsonic Filter. The point that you set it at
cuts off any frequencies from reproduction beyond this point. The 12 o’clock
position is a great starting point. EXAMPLE: If you adjust the High Pass to 25Hz,
the amplifier will not play frequencies below 25Hz but will play frequencies from
25Hz to the chosen Low Pass frequency.
-When in Flat/Full operation, the High Pass crossover is bypassed.
Bass EQ:
This setting is a fixed bass boost at 45Hz that is variable from 0-9dB. This feature
provides impact to your bass, but if not adjusted correctly, it can be over used and
cause damage to your speakers and amplifiers. It is best to slowly turn this setting
clockwise until the desired punch is felt. It is not recommended to exceed the 12
o’clock position unless listening at a low volume or a low recording quality as this
can result in high distortion and possibly clipping.
Low Pass:
The Low Pass control acts as a ceiling and doesn’t allow frequencies to the right of
the desired setting to be reproduced. Turning the potentiometer all the way to the
right is a great starting point. EXAMPLE: If you adjust the Low Pass to 120Hz, the
amplifier will not play frequencies above 120Hz but will play frequencies from
120Hz to the chosen Hi Pass or Subsonic frequency.
-When in Hi Pass operation, this setting is bypassed.
Level Control Setup:
Ensure that the Level is turned completely to the left prior to turning the system on.
Next you should insert a CD or cassette that you are familiar with to use as a
reference, and turn the head unit volume control to about 80% of its full setting.
The system sound level will of course be very low, and the following procedures
will help you to match the amplifier input sensitivities properly to the head unit
output signal level.
It is important to match the amplifier LEVEL input sensitivity to the Radio/CD
output sensitivity. This can be located in the Radio/CD manual.
If the Radio/CD output sensitivity is 2 volts, then adjust the amplifier LEVEL input
to 2 volts.
If you are not sure what the Radio output sensitivity is, follow these general guide
lines:
Turn the level control up slowly, till you hear distortion, then back off a few degrees
on the control. If at any point your amplifier goes into protection, you will need to
turn the Level to the left a bit and then try again. If you reach a point where the
output does not increase, stop turning the Level control to the right as the
amplifier/speaker combo has reached its maxx output in this application.
2 or 3 way active systems (all):
Always start with the bass, or low frequency amplifier as a reference, by turning its
control up to the point where distortion is audible, and back it off some.
Now adjust the level control for the highs or tweeter channels in a 2 way active system,
to balance the highs to lows.
In a 3 way active system, match the midrange level to the bass, and then the highs to
the midrange and bass. It may be necessary to perform a few iterations of the
midrange and highs level control settings to achieve a satisfactory sound balance.
The key to finding the problem in a misbehaving sound system is to isolate
parts of that system in a logical fashion to track down the fault.
Description of the Diagnostic system built into all MB Quart amplifiers
The diagnostic system will shut down the amplifier, until reset by turning the head unit
off, and back on. This state of affairs will be indicated by the front panel PROTECT
LED lighting up under the following conditions:
1 - A short circuit on the loudspeaker leads.
2 - An internal amplifier fault that causes a DC offset on the loudspeaker output.
Should the amplifier go into diagnostic mode, simply disconnect all RCA and speaker
leads, while keeping +12 volt, power ground and remote leads connected.
1. Now turn the amplifier back on, and if the diagnostic LED lights, the amplifier has an
internal fault.
2. If not, plug the RCA cables back, and reset the amplifier. If it goes into diagnostic
now, the fault lies in the input, either with bad cables or source unit.
3. If the amplifier seems fine with RCA cables plugged in, connect the speakers, one at
a time, and if one of the speakers or its wiring is faulty, it will activate the diagnostic
system.
Amplifier heatsink overheating
The amplifiers will shut down when the heatsink temperature reaches 80 degrees
centigrade, and turn back on once the unit has cooled down below that point.
Causes of overheating:
1 - Inadequate cooling - relocate or remount to provide better natural airflow over the
fins.
2 - Driving high power levels into low impedances - back off on the volume control,
and/or make sure you are not loading the amplifier with less than the recommended
loudspeaker impedance.
Low output power
1 - Check that level controls have been set up properly.
2 - Make sure that the battery voltage, as measured at the amplifier’s +12 volt and
ground terminals, is 11 volts or more.
3 - Check all +12 volt and ground connections.
Fuses blowing
1 - The use of loudspeaker impedances below the recommended minimums will draw
more current - check.
2 - A short on the main +12 volt cable from the battery to the vehicle chassis will cause
the main fuse to blow.
3 - If an amplifier fuse blows continually, with only +12 volt, ground and remote leads
connected, the amplifier may be faulty.
System does not turn on
1 - Check all fuses.
2 - Check all connections.
3 - Measure the +12 volt and remote turn on voltages at the amplifier terminals. If
these are non existent or low, take voltage measurements at fuse holders, distribution
blocks, the head unit’s +12 volt and remote leads to localize the problem.
Noise problems
System noise can be divided into two categories, hiss, and electrical interference.
Hiss, or white noise
1 - High levels of white noise usually occurs when amplifier level controls are turned
up too high - readjust according to the procedures in section ”Setting up systems after
installation for best performance”
2 - Another major problem that can cause excessive hiss, is a noisy head unit - unplug
the amplifier input RCA cables, and if the hiss level reduces, the source unit is at fault.
Electrical interference
The inside of an automobile is a very hostile electrical environment. The multitude of
electrical systems, such as the ignition system, alternator, fuel pumps, air
conditioners, to mention just a few, create radiated electrical fields, as well as noise on
the +12 volt supply and ground. Remember to isolate the problem - first unplug
amplifier input RCA cables, if the noise is still present, check the speaker leads, if not,
plug the RCA’s back, and investigate the source driving the amplifier, one component
at a time.
A ticking or whine that changes with engine RPM:
1 - This problem could be caused by radiation pickup of RCA cables too near to a fuel
pump or a distributor, for instance, - relocate cables.
2 - Check that the head unit ground is connected straight to the vehicle chassis, and
does not use factory wiring for ground.
3 - Try to supply the head unit with a clean +12 volt supply directly from the battery +,
instead of using a supply from the in dash wiring/fusebox.
A constant whine:
This type of noise can be more difficult to pinpoint, but is usually caused by some kind
of instability, causing oscillations in the system.
1 - Check all connections, especially for good grounds.
2 - Make sure that no speaker leads are shorting to exposed metal on the vehicle
chassis.
3 -RCA cables are notorious for their problematic nature, so check that these are
good, in particular the shield connections.
Installation Manual
Installation Instructions
Trouble Shooting
DISCUS
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