Altair MF8 SERIES User manual

PROFESSIONAL POWER AMPLIFIERS
MF SERIES
OWNERS MANUAL
MF8,12,16,24
EQUIPOS EUROPEOS ELECTRÓNICOS, S.A.L.
AVDA. DE LA INDUSTRIA, 50. 28760 TRES CANTOS (MADRID)
ALTAiR
www.altairaudio.com
91-8043265 91-8044358 [email protected].

CONTENTS
1. INTRODUCTION 3
2. SWITCHES, INDICATORS, ATTENUATORS AND CONNECTORS. 5
MF8 AND MF12 FRONT PANEL 5
MF16 AND MF24 FRONT PANEL 5
MF8 AND MF12 REAR PANEL 6
MF16 AND MF24 REAR PANEL 6
3. WORKING PRECAUTIONS 7
4. INSTALLATION 7
UNPACKING 7
MOUNTING 7
CHANGING THE FUSE 8
CONNECTING TO THE MAINS 8
INPUT CONNECTION 9
UNBALANCEDINPUT 10
BALANCED INPUT 10
OUTPUT POWER CONNECTION. MODES OF OPERATION 11
STEREOMODEOPERATION 12
MONO MODE OPERATION 12
BRIDGE MODE OPERATION 13
EARTH LINK 14
5. OPERATION 14
POWER UP 14
INPUT ATTENUATORS 15
BRIDGE MODE INDICATOR 15
CLIP INDICATORS (INPUT SIGNAL OVERLOAD) 15
SIGNAL INDICATORS 15
ERROR INDICATORS 16
THERMALINDICATORS 16
ON/STBY INDICATORS 16
POWER SWITCH 17
FAN 17
LOADIMPEDANCES 17
MAINTENANCE 18
AMPLIFIER CONDITIONS 19
6. SPECIAL OPERATIONS 21
CHANGING XLR INPUT CONNECTORS POLARITY 22
INPUT ATTENUATOR CONFIGURATION IN MODE MONO (MF16 AND MF24 ONLY) 23
LIMITER ON/OFF 23
INPUT SENSIBILITY/GAIN ADJUST 24
7. DISTRIBUTED SYSTEMS APPLICATION (PUBLIC ADDRESS) 25
8. TECHNICAL SPECIFICATIONS 26
9. GRAPHS 27
10. WARRANTY 28
2
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES

ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 3
1. INTRODUCTION
Congratulations on your purchase of the ALTAIR power amplifier MF series. Our dilated
experience in the design and manufacture of great power amplifiers culminate with the pre-
sentation of this new generation of amplifiers MF series.
There is a lot the characteristics that make of the ALTAIR power amplifiers MF series,
one of the most highlighted of the audio professional market, here enumerated some:
Flexibility in the input connections
They had a input system that is configured by means of a panel that integrates two XLR
connectors male-female per channel (a female XLR + Jack in the models MF8 MF12 over the
own chassis) and a switch of work mode. By means of this system, one could change the
polarity and the sensibility of the power amplifier in order to allow its integration in any sound
system. This segregation of the elements corresponding to the input signal opens the possibil-
ity of incorporating remote control circuits easily, crossovers, as well as simplify the mainte-
nance works .
Multiple protection
As global protection, incorporates turn on switches with thermal breaker (models MF16
MF24). These switches, located at the front panel substitute to the old fuses with the rising
advantages: its holds their own curve indefinitely, it that is unchanged with the temperature,
show the shooting by means of the lever state and avoids locating and substitute the typical
blended fuse.
Has improved the circuits of DC output protection with the incorporation of CROW-BAR
circuits or solid state relays. The conventional relays incorporate contacts associated with
electromechanical elements that with the time are subject to failures. This is no longer with the
solid state device. Guiding directly the power transistors output to the loudspeakers binding
post has improved several qualities of the signal quality, the damping factor and the global
reliability.
Equally, the conventional thermal switches (based on contacts) has been substituted of
the power modules by solid state sensors whose information completes the double condition
of speed fan control and discharge the thermal protection.
The power supply transformer is protected also in front of excessive heating, discon-
necting both inputs until their normal temperature of operation is reached.
All the protection situations are displayed in the power amplifier front panel.
Clipping circuit limiter
Since most of the damage caused to loudspeakers, and even in the power amplifiers,
is normally the result of the permanence of the power unit during long periods of time in
clipping, it is necessary to be able to have limiter mechanisms that assure their reliable opera-
tion.

For this purpose, all the MF series power amplifiers has a “soft-clipping” circuit that acts
on the output power by comparing the input and output signals. Once it detects a distortion or
other noticeable cut, it stabilizes the integrity of the output signal thereby avoiding overloading
and saturation levels that might damage the system.
Monoblockchassis
The chassis is of construction of a single piece: the efforts of the different subsets of the
equipment fall on an only piece of laminate steel of great thickness and reinforced toward their
union with the wings. Avoids the breaks and the “loss of screws” because of the own vibrations
give them teams in continuous tour.
Under control
The conception of the new loudspeakers, especially the uses for low frequencies is
based on that the amplifiers that govern them behave as ideal tension amplifiers, is say with
zero output impedance. The MF series approaches to this value nearly zero presenting a
damping factor better than 700 what redounds in a perfect control of the position of the reels
along all their excursion.
Naturally, you want to use your power amplifier, but before beginning is important that
you read this manual. This manual will help you to install and use your new power amplifier. It
is very important that you read it carefully, mainly the paragraphs marked as NOTE,
PRECAUTION and DANGER, for your security.
Save the original packing, you could use if you need to transport the power amplifier.
NEVER SHIP THE POWER AMPLIFIER WITHOUT IT'S ORIGINAL PACKING.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 4

2. SWITCHES, INDICATORS, ATTENUATORS AND CONNECTORS.
These are the switches, indicators, attenuators and connectors that you could find in
your power amplifier. The description and explanation of each one of them, you will find it in
the corresponding section.
MF8 AND MF12 FRONT PANEL
MF16 AND MF24 FRONT PANEL
INPUTATTENUATOR.
BRIDGE MODE INDICATOR.
INPUTSIGNALOVERLOADINDICATOR.
SIGNALINDICATOR.
ERROR INDICATOR (D.C. OR TURN ON).
THERMALPROTECTIONINDICATOR.
TURN ON / STAND BY INDICATOR.
POWER SWITCH.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 5
COOLINGVENTS
COOLINGVENTS

MF8 AND MF12 REAR PANEL
MF16 AND MF24 REAR PANEL
OUTPUT POWER SPEAKON®CONNECTOR.
BINDINGPOST.
FAN (ONLY MF16 AND MF24).
FUSEHOLDER.
MAINSCORD.
EARTH LINK SWITCH.
INPUTSIGNALCONNECTORXLR-3-31.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 6
COOLINGVENTS

JACK 1/ 4" INPUT SIGNAL LINK CONNECTOR.
(ONLY MF8 AND MF12).
XLR-3-32 INPUT SIGNAL LINK CONNECTOR.
(ONLY MF16 AND MF24).
MONO/STEREO/BRIDGESWITCH.
3. WORKING PRECAUTIONS
The manufacturer cannot be held responsible for any damage which is incurred by not
using the power amplifier in compliance with the warranty or working precautions.
DANGER: High voltage inside the amplifier. ! Do not open !. The power amplifier
doesn't contain parts that can be repaired by the user. The power amplifier could
have electric power stored in their interior even disconnected it from the mains.
CAUTION: Protect the power amplifier from the rain and moisture. Ensure that
no objects or liquids enter it. If liquid is spilled into the power amplifier, disconnect
the power amplifier from the mains and consult a qualified service technician.
Don't place the power amplifier close to sources of heat. Also make sure that the front
and the rear panel there are free of obstructions, since the fan could not work properly and
cause the thermal protection work.
DANGER: The power amplifier output connectors could have high voltage. Make sure of
turning off the power amplifier before handling on these output connectors.
4. INSTALLATION
UNPACKING
Before leaving from factory, each power amplifier was carefully inspected and tested.
Unpack and inspect the power amplifier for any damage that may have occurred during
shipment. If any damage is found, doesn't connect the power amplifier to the mains, notify
the salesperson immediately, because the unit must be inspected by a qualified service
technician.
Save the original packing, you could use if you need to transport the power amplifier.
NEVER SHIP THE POWER AMPLIFIER WITHOUT IT'S ORIGINAL PACKING.
MOUNTING
It is always advisable mount the power amplifiers in rack, either for mobile or fixed
installations, for protection, safety, aesthetics, etc.
The MF series power amplifiers are designed for standard 19" rack mounting, and
occupy 2u (MF8 and MF12) or 3u (MF16 and MF24) high rack space .
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 7

Due to the weight of the unit, it should be securely fastened at the front and the back of
the cabinet. If the racks are carriage ones, it is advisable that have trays in order to allow the
power amplifier to rest on its base and in an elastic cradle, if possible. It is advisable, leave a
separation space between amplifiers and other units in order to facilitate its cooling, upon
mounting the amplifier in a rack.
In the mounting, either fixed or in rack, the cooling vents placed in the front panel (MF8
and MF12 also in the rear panel) and the fan, placed in the rear panel (only for MF16 and
MF24) should be free, so that the air circulates freely, and the amplifier could have a better
heat dissipation. In the same way, make sure that there are no heat sources near the front
cooling vent, because the fan exhaust cool air through this vent.
Also, the mains transformer of the models MF16 and MF24, has a cooling vent in the left
side of the power amplifier. This cooling vent may correspond with another one in the rack.
CHANGING THE FUSE
The power amplifiers are designed to work with slow blow fuses of 6x32, whose values
in order to work with a mains voltage of 230V 50-60 Hz are specified in the following list:
MODELS FUSE (230V. 50-60 Hz)
MF8 T8A.
MF12 T12A.
MF16 T16A.
MF24 T20A.
Make sure that the power amplifier is disconnected from the mains.
At the power amplifier rear panel is placed the fuse holder. Unscrew the most external
part of the fuse holder.
Upon unscrewing the most external part of the fuse holder, the fuse will appear. Re-
move it and change for new one.
Screw the external part of the fuse holder.
CAUTION: Always make sure upon changing the fuse, that this is the adequate.
CONNECTING TO THE MAINS
The connection of the power amplifier to the mains takes place by means of a three-
wire cord provided by the factory. The European standard color code is: Brown-Live, Blue-
Neutral and Yellow/Green-Earth, keeps in mind this mains configuration, whenever handle
the power amplifier plug.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 8
1
2
4
3

In the connection of several devices to the same AC distribution board and extension
cables, keeps in mind the maximum current of the power amplifier, and make sure that the
mains connector, as well as the AC distribution board, are of enough current capacity, since
could take place in the mains connector, and in the same AC distribution board a overheat-
ing, with the risk of fire and/or short circuit. The following list shows the maximum current
requirement of the different models of power amplifiers:
MODELS MAXIMUM CURRENT REQUIREMENT
MF8 6A.
MF12 10A.
MF16 14A.
MF24 18A.
Make sure that the power amplifier power switch, is at position 0 (turned off).
Insert the male connector of the three-wire cable into the mains plug.
Turn on the power amplifier power switch. Right now the power amplifier will turn on.
CAUTION: Make sure that the mains voltage is 230V. 50-60 Hz., as well as their fuse is the
adequate.
INPUT CONNECTION
Each power amplifier's channel incorporates one XLR-3-31 female connector. The
inputs are balanced, with a nominal impedance of 20 KΩ(10 KΩunbalanced). On the other
hand, the amplifier according to models has two JACK connectors 1/ 4" (MF8 and MF12) or
two XLR-3-32 males connectors (MF16 and MF24), one per channel (LINK) that allows us to
link the input signal from the power amplifier, to other units. The XLR male connectors and
those of LINK are internally wired in parallel.
The input connections depends on two factors, the first is the type of input signal bal-
anced or unbalanced, and the second the ground configuration of the sound source (floating
or ground-referenced). The next pictures shows some of the different possibilities of connec-
tion, relying on the type of input signal, balanced or unbalanced and according to the
ground configuration of the equipment (floating or ground-referenced).
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 9
1
2
3

ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 10
SOUND
SOURCE +
-
+
-
+-
POWER
AMPLIFIER
SOUND
SOURCE +
POWER
AMPLIFIER +
+-
SOUND
SOURCE
-
+
+
POWER
AMPLIFIER +
-
ONLY MF8 AND MF12
Floating sound source ( / ) : Close.
Ground-referenced sound source ( / ) : Open.
Floating sound source ( / ) : Close.
Ground-referenced sound source ( / ) : Open.
ONLY MF8 AND MF12
Floating sound source ( / ) : Close.
Ground-referenced sound source ( / ) : Open.
UNBALANCED INPUT:This type of connection will be used when the sound source doesn't
provide balanced output. If it is possible, will be employed the connection type 1.
1) Using twin-lead shielded cable:
2) Using single conductor coax cable:
BALANCED INPUT:
NOTE: The previous pictures, has been carried out supposing that the power amplifier is
configured in the standard A.E.S.: pin 2 of the XLR connector as positive (later on will explain
how changing this power amplifier configuration). If the power amplifier is configured with
the pin 3 of the XLR connector as positive, change the pin 2 by the 3 in the previous pictures.
ONLY MF8 AND MF12

OUTPUT POWER CONNECTION. MODES OF OPERATION
Each channel includes a pair of five-way binding post and a SPEAKON
®connector.
These connectors are wired inside in parallel. The red binding post is positive and the black
is ground. The SPEAKON®connector, following NEUTRIK recommendations, has the next
polarity: PIN 1+ positive, and PIN 1- ground. Keep in mind the polarity upon connecting the
speakers since change the a speaker polarity of a system reduces the output power of the
power amplifier, upon remaining this speaker with other phase with regard to the others.
In the output connection it is necessary to keep in mind a series of important precau-
tions in order to don't produce an accidental short circuit or a possible damage in the equip-
ment:
Consider the power-handling capacity of your speakers before connecting it to the power
amplifier. Equipos Europeos Electrónicos is not liable for damage occurred by the connection
of speakers to the power amplifier with less nominal power that the power amplifier.
Turn off the power amplifier and turn down the input attenuators, whenever takes
place a output power connection. The output power connectors could have high
voltage, with the rising danger of short circuit.
Never put the output power connectors in parallel. This connection doesn't in-
crease the power and could cause the break of the power amplifier.
Do not connect the power amplifier output connectors to the output connectors of
any other power amplifier. This connection could cause the break of one or both
power amplifiers.
Do not connect the output connector ground (black binding post or PIN 1- of the
SPEAKONr connector) to input connector ground (PIN 1 of the connector XLR-3-31 or
sleeve of the Jack connector 1/ 4" in the case of the models MF8 and MF12). This
could create a ground loop and could cause feedback oscillations.
Use loudspeaker cables capable to resist the output current of the power amplifier.
The selection of a good loudspeaker cable, with a good quality and an adequate
diameter is very important, and is often one of the things that less is kept in mind.
The next list shows us the maximum output currents of the power amplifiers according
to the model:
MODELS MAXIMUM OUTPUT CURRENT
MF8 16A.
MF12 19A.
MF16 23A.
MF24 28A.
There are many factors that determine the loudspeaker cable diameter: the length of
the cable, the type of signal that is going to circulate for it, the output power of the power
amplifier etc. A cable with high resistance, reduces the damping factor, limiting the power
amplifier capacity for control to the speakers accurately.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 11

The possible output connections, depends on the configuration of the switch MONO/
STEREO/ BRIDGE of the power amplifier:
CAUTION: Do not change the configuration of MONO/STEREO/BRIDGE switch unless the
power amplifier is first turned off. Before turn on the power amplifier, make sure that the
mains, input and output connections are correct. If doesn't follow these recommendations,
could cause a power amplifier and/or loudspeakers breakdown.
STEREO MODE OPERATION: In this mode the two channels of the power amplifier are totally
independent, for what the two inputs signal, and the two power outputs will be wiring inde-
pendently. In order to configure the power amplifier in STEREO mode, turn the amplifier off,
slide the MONO/ STEREO/ BRIDGE switch to the center position, and wire the input and output
connections according to the next picture:
MONO MODE OPERATION: In the mode MONO, the input signal should be carried out for one
any of the XLR connectors or Jack 1/ 4" (only for MF8 and MF12) of the CHANNEL 1 (CH1). The
input signal is routed to both channels, being the power outputs totally independent. In the
models MF16 and MF24, the input attenuators could configure internally, so that the CH1
input attenuator governs both channels, or that each input attenuator affects to their corre-
sponding channel (for more information consults the section SPECIAL OPERATIONS - INPUT
ATTENUATORS CONFIGURATION IN MONO MODE), in the models MF8 MF12 the input attenu-
ators of the two channels are totally independent in MONO mode. In order to configure the
power amplifier in MONO mode, turn the amplifier off, slide MONO/ STEREO/ BRIDGE switch
toward the left (as you face the rear panel), and wire the input and output connections
according to the next picture:
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 12
CHANNEL2.
CHANNEL1. SOUNDSOURCE.
*THELOUDSPEAKERSCONNECTIONCOULD
BE ACHIEVE TO THE BINDING POST OR TO
THESPEAKON®CONNECTOR,SINCETHESE
CONNECTORSAREWIREDINTERNALLYIN
PARALLEL.
+ +
- -
PIN1+
PIN1- PIN1- PIN1+
*LOUDSPEAKERSWIREDTO
BINDINGPOST
- -
+ +
*LOUDSPEAKERSWIREDTO
SPEAKON® CONNECTORS
CHANNEL2.
CHANNEL2.
CHANNEL1.
CHANNEL1.

+ +
- -
PIN1+
PIN1- PIN1- PIN1+
--
+ +
-
+
PIN1+PIN1+ +
-
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 13
CHANNEL1.
*THELOUDSPEAKERSCONNECTIONCOULD
BE ACHIEVE TO THE BINDING POST OR TO
THESPEAKON®CONNECTOR,SINCETHESE
CONNECTORSAREWIREDINTERNALLYIN
PARALLEL.
*LOUDSPEAKERSWIREDTO
BINDINGPOST
*LOUDSPEAKERSWIREDTO
SPEAKON® CONNECTORS
CHANNEL2.
CHANNEL2.
CHANNEL1.
CHANNEL1.
SOUNDSOURCE.
CHANNEL1.
*THELOUDSPEAKERSCONNECTIONCOULD
BE ACHIEVE TO THE BINDING POST OR TO
THESPEAKON®CONNECTOR,SINCETHESE
CONNECTORSAREWIREDINTERNALLYIN
PARALLEL.
*LOUDSPEAKERSWIREDTO
BINDINGPOST
*LOUDSPEAKERSWIREDTO
SPEAKON® CONNECTORS
SOUNDSOURCE.
BRIDGE MODE OPERATION:In BRIDGE mode, the input should be insert for any of the XLR
connectors or Jack 1/ 4" (only for MF8 and MF12) of CH1. In this mode the power of the two
channels will be added over a single load. The CH1 input attenuator controls both channels,
remaining the CH2 input attenuator disabled. The output in BRIDGE mode, must be taken
between the red binding post (positive pole is the red binding post of CH1 and the ground,
the red binding post of CH2) or for the SPEAKON
®connectors (positive pole is the PIN 1+ of
CH1 and the ground is the PIN 1+ of CH2). To put the power amplifier in BRIDGE mode, turn
the power amplifier off, slide the MONO/ STEREO/ BRIDGE switch toward the right (as you
face the rear panel), and wire the input and output connections according to the following
picture:

EARTH LINK
In some installations, it might be necessary to isolate the power amplifier electric
ground, from the system mains earth, in order to avoid ground loops, that could generate
unwanted noises, for this reason, the power amplifier provides an EARTH-LINK switch placed
at the rear panel in order to lift the mains earth from the power amplifier electric ground.
MAINS EARTH LINKED WITH THE POWER AMPLIFIER ELECTRIC GROUND.
MAINS EARTH LIFTED FROM THE POWER AMPLIFIER ELECTRIC GROUND.
CAUTION: Sometimes, lift the mains earth, using a ground-lift connector, the one
which undoes the ground loop also, but this is very dangerous, since if for any
circumstance part of the mains signal is derived to the chassis, could cause a
short circuit through our body, upon having eliminated one of the working pre-
cautions of the unit. For this circumstance,NEVER lifts the mains earth (use the
EARTH-LINK switch of the unit) in order to avoid possible accidents.
5. OPERATION
POWER UP
Plug in all input and output connectors (following the recommendations of the
sectionsINSTALLATION-INPUTCONNECTIONANDINSTALLATION-OUTPUTCON-
NECTION). Ensure that both power amplifier's input attenuators are turned fully
counter-clockwise to the -∞position. At this time could switch the power amplifier
on.
Upon switch the power amplifier on, acts the delay turn on system, that minimizes the
effect of the transitory currents in the transformer. In a few seconds, the delay turn on system
stops working (a RELAY will be listened to). In the models MF16 MF24, if this circuit doesn't
work correctly, would light the ERROR indicators of both channels at the same
time, and the power amplifier would not start up, at the same time the ON/STBY indicator
would not pass to green colour.
When turning on a rack of power amplifiers they should be switched on individually. The
practice of leaving all power amplifiers in a rack switched on and powering up the whole
rack by connecting it to the mains is dangerous and likely to blow the mains fuse of the rack
power supply, if with good approach, the rack has one. In a rack of power amplifiers, switch
the power amplifiers on one by one.
Note that upon switching the power amplifier on, the ON/STBY indicator lights in
red (indicating that the power amplifier is cutting the input signal), and after a few second
change to green (indicating that the power amplifier connected the input signal). At this time
could turn on the power amplifier input attenuators.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 14

INPUT ATTENUATORS
Each power amplifier channel has a input signal attenuator, gauged. The
calibration is measured between ±0.5 dBu.
The input attenuators are independent for each channel in STEREO
mode. In the models MF16 and MF24 in mode MONO it is selectable the control
of the input attenuators over the channels (independent or both channels depen-
dent on the CH1 input attenuator) (for more information see section SPECIAL OPERATIONS -
INPUTATTENUATIONCONFIGURATIONINMONOMODE).
In the models MF8 and MF12 in mode MONO, the input attenuators are independent for
each channel. In mode BRIDGE both channels depend on the CH1 input attenuator.
BRIDGE MODE INDICATOR
The red BRIDGE LED illuminates when the power amplifier is working in BRIDGE
mode.
CLIP INDICATORS (INPUT SIGNAL OVERLOAD)
The CLIP red LED , illuminates when the power amplifier starts to saturate,
moreover, if the limiter is ON, this LED indicates that the circuit limiter starts to work (for more
information see section SPECIAL OPERATIONS- LIMITER CONFIGURATION). The CLIP indicators
are independent in each channel, and indicates a real saturation, by comparing
input and output continuously, and are independent of the mains voltage.
The CLIP indicators also illuminates when there is a output short-circuit or
when a protection (DC or thermal) of the power amplifier disconnects the input, whenever
one input signal is being introduced to the power amplifier.
To make the loudspeakers life longer, avoid this situation of overload during for ex-
tended periods of time.
If the input signal level is too high, don't turn the power amplifier limiter off, because it is
an efficient protection for the loudspeakers.
In general, the loudspeakers resist high peaks of instantaneous power, but when
exposed power to extended saturations they lose any guarantee of good operation.
The saturation measuring circuit is sensitive to peaks, it has a quick attack time and a
slow release time.
SIGNAL INDICATORS
The SIGNAL green LEDs illuminates when the output signal of the corre-
sponding channel reaches 25 dBu before saturation.
These LEDs indicate signal presence in the power amplifier input.
This SIGNAL measurement circuit is sensitive to peaks, it has a quick attack
time and a slow release time to indicate the average power.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 15

ERROR INDICATORS
The power amplifier load protection circuit, work when a continuous voltage appears in
the power amplifier output connectors, shorcutting the power amplifier output, disconnecting
the input signal (the ON/STBY LED of the corresponding channel illuminates on
red) and indicating this situation with the ERROR red LED of the corresponding
channel. When the continuous voltage disappear, the load protection circuit automatically
release the power amplifier's output shortcut, connect the power amplifier's input, the ERROR
red LED turns off and the ON/STBY LED turns green. By this shortcut in
the power amplifier's output, if the continuous voltage remains, the thermal protection could
activate. This protected circuit is know by CROW-BAR.
The power amplifier has an independent load protection circuit and an ERROR
indicator for each channel.
How spoke previously in the section OPERATION - POWER UP, the ERROR red LED
, could also indicate a failure in the delay turn on circuit in the models MF16 and
MF24, in that case would light the ERROR red LED of both channels at the same
time. The failure in the delay turn on circuit could take place for three circumstances, a very
low mains voltage, in which case it is necessary to solve the problem in the mains and
power up the power amplifier again, a shortcut in the power amplifier, or the break of the
own delay turn on circuit. In these last two cases, should order to revise the power amplifier
for a qualified technician.
THERMALINDICATORS
When the power amplifier output transistors reach the 90ºC, begin to work the thermal
protection circuit, lighting the THERMAL orange LED of the corresponding channel.
The thermal protection, disconnects the power amplifier input signal, turning red the ON/
STBY LED of the corresponding channel. This only happens under the most severe
conditions of continuous overload; in such a case, it is essential to localize and to rectify the
cause of this overheating condition. The thermal protection circuit returns automatically to its
normal position when the power amplifier output transistors drops under the security of
security, connecting the input signal again, and turning green the ON/STBY LED .
The mains transformer, has a thermal breaker, which protect it from overheating. When
work this thermal breaker, the power amplifier input signal of both channels is opened,
changing to red the ON/STBY LED of both channels and start flash the THERMAL
orange LED of both channels, indicating that the mains transformer has reached
the 100ºC. As in the case of the power amplifier output transistors, it is essential to localize
and rectify the cause of this overheating condition. When the mains transformer temperature
drops under the security level, the thermal protection circuit returns automatically to their
normal condition connecting the power amplifier input signal of both channels again, turning
off the THERMAL LED of both channel , and changing to green the ON/ STBY LED
of both channels.
ON/STBY INDICATORS
The ON/STBY LED indicates the connection or disconnection of the power amplifier input
signal. The three colors LED ON/STBY illuminates in red when the power amplifier
input signal is disconnected and it illuminates in green when the power amplifier input signal
is connected.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 16

Therefore, whenever this indicator is in red, will indicate us that the power amplifier
input signal is disconnected, and the power amplifier is not operative at that moment. This
occurs when the power amplifier is turned on, and when the ERROR or THERMAL protections
are activated.
The power amplifier has two ON/STBY LED indicators, one per channel.
POWER SWITCH
The power switch of the models MF16 and MF24 has a thermal breaker
inside. This thermal breaker acts interrupting the mains supply of the power
amplifier, when the mains current is high or equal to 20 amperes. When the
thermal breaker work, the power switch is placed in the OFF position, for what it is
necessary to turn on the power amplifier in order to use it again. It is important to
know what circumstance happen and correct this, before power up the power amplifier
again.
The models MF8 and MF12 incorporates power switches without thermal
breaker.
FAN
The power amplifier includes a thermally controlled system, which continuously regu-
lates the fan speed depending on, the heat energy it has to evacuate. This variable speed
circuit, avoids abrupt changes of temperature and substantially extents the working life of the
components builds in. At power amplifier turn on, the fan rotates with his top velocity, in
order to exhaust the maximum dust possible. Soon after, the fan's speed drops to normal.
The power amplifier fan rotates with its top velocity also, in an overheating situation (when a
thermal protection work) so that the heat drops under the security level quickly.
In the models MF16 and MF24, the fan is protected with a grid, that avoids objects
inserted between its wheels, as well as a possible accident with the same. It is important that
nothing obstruct the airflow to the fan at any time.
The models MF8 and MF12 have the fan inside, for what doesn't have protection grid,
however incorporates some cooling vents in the rear panel for which the air is evacuated, for
what it is important make sure that the cooling vents are always free so that the air could
circulate with freedom.
LOADIMPEDANCES
The power amplifiers MF series, are designed to drive a 2Ωor higher load impedances
load in MONO or STEREO mode (4Ωor higher in mode BRIDGE), without current limiting.
However, using several speakers in parallel in order to get these 2Ωit could be an imped-
ance of load of less than 2Ω.
The speaker load impedance is variable with the frequency, and in fact, connect four
speakers in parallel, with a nominal impedance of 8Ωeach one, gives a less impedance like
result that the theoretical 2Ω. Therefore high signal levels associated with a compressed
signal source can cause the power amplifier to reach its thermal limits and disconnects its
load.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 17

If you want that your power amplifier works with 2Ωload impedances, you should
consult the speaker impedance curves that is going to connect and study each case in
particular. It is very advisable enable the power amplifier limiter, whenever it is working with
2Ωload impedances.
The ability to drive 2Ωload impedances is primarily intended to insure that the power
amplifier will never be pushed beyond its current limits when driving nominal 4Ωload im-
pedances that may reach a minimum of only 2Ωat some frequencies.
When the power amplifier is working in BRIDGE mode, the load impedance must be of
4Ωor higher, with the same consideration that in MONO or STEREO mode with 2Ωload
impedance. This is because in BRIDGE mode, it is as if each channel is driving with the half
load impedance.
MAINTENANCE
Periodically, and in a technical service, should clean the dust and dirt accumulated
inside the power amplifier, especially in the heatsinks, the fan and the cooling vents, with a
vacuum cleaner or with an air-compressor gun. The dirt diminishes considerably the capac-
ity of radiation and ventilation.
The input attenuators (potentiometers) are sensitive to the dust accumulated, and
therefore for they will be cleaned with an air compressor gun or be changed if they are very
wrong.
NOTE: Equipos Europeos Electrónicos don't recommend the use of spray cleaners because
they could damage the lubricant layer of the potentiometers. Use compressed air to clean
them or replace with similar parts.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 18

AMPLIFIER CONDITIONS
INDICATORS AMPLIFIER CONDITION
The power amplifier has just been turned on (it is still in the
initial mute delay) and it is receiving an input signal. In this
case the ON/STBY indicators of both channels would be
illuminated in red. OR
A protection was activated (ERROR or THERMAL) and this
condition has been corrected. The power amplifier is
receiving an input signal. In this case would be illuminated
in red the ON/STBY indicator of the channel in which the
protection has been activated.
The power amplifier has just been turned on (it is still in the
initial mute delay) and it is not receiving an input signal. In
this case the ON/STBY indicators of both channels would be
illuminated in red. OR
A protection was activated (ERROR or THERMAL) and this
condition has been corrected. The power amplifier is not
receiving an input signal. In this case would be illuminated
in red the ON/STBY indicator of the channel in which the
protection has been activated.
The thermal protection of one channel has been activated.
In this case, the THERMAL indicator (amber) and the ON/
STBY indicator (red) of the channel in which the protection
has been activated would be illuminated. The power
amplifier is receiving an input signal.
OR
The transformer thermal protection has been activated.
The THERMAL indicators (amber) of both channels will be
blinking and the ON/STBY indicators of both channels will
be illuminated. The power amplifier is receiving an input
signal.
The thermal protection of one channel has been activated.
In this case, the THERMAL indicator (amber) and the ON/
STBY indicator (red) of the channel in which the protection
has been activated would be illuminated. The power
amplifier is not receiving an input signal.
OR
The transformer thermal protection has been activated.
The THERMAL indicators (amber) of both channels will be
blinking and the ON/STBY indicators of both channels will
be illuminated. The power amplifier is not receiving an
input signal.
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 19

INDICATORS AMPLIFIER CONDITION
The DC protection of one channel has been activated. In
this case, the ERROR indicator (red) and the ON/STBY indi-
cator (red) of the channel in which the protection has been
activated will be illuminated. The power amplifier is receiv-
ing an input signal.
The DC protection of one channel has been activated. In
this case, the ERROR indicator (red) and the ON/STBY indi-
cator (red) of the channel in which the protection has been
activated will be illuminated. The power amplifier is not
receiving an input signal.
INDICATORS RED AMBER GREEN
ALTAiR PROFESSIONAL POWER AMPLIFIERS MF SERIES 20
MF16 AND MF24 ONLY.The delay turn on protection circuit
has been activated. The ERROR indicators (red) of both
channel will be illuminated. This could happen for a very low
mains voltage or for a failure or overheating on the delay
turn on circuit, when the amplifier has been turned on.
The channel with this indicator status is not receiving an
input signal, but is ready in order to receive it.
There is no power to the amplifier, either because it is not
plugged or because the power switch is in the OFF position.
Normal operation. The channel with this indicator status is
receiving an input signal, and amplifying it.
The channel with this indicator status is receiving an input
signal too high. If the limiter is connected, it will be working,
and if it is not connected, the output signal will be saturated.