Rane MA 4 User manual

MA 4
MULTICHANNEL AMPLIFIER
CONTENTS (in order of appearance)
Important Safety Instructions
MA 4 Manual
MA 4 Data Sheet
MT 4 Data Sheet
Constant-Voltage Audio Distribution Systems
Sound System Interconnection
Warranty
Declaration of Conformity
21583
DIGITAL
AMPLIFIER
dB Headroom dB Headroom dB Headroom dB Headroom
3 6
12 24
Limit
1
Comp Exp
Fault Load Ready
3 6
12 24
Limit
2
Comp Exp
Fault Load Ready
3 6
12 24
Limit
3
Comp Exp
Fault Load Ready
3 6
12 24
Limit
4
ON
Comp Exp
Fault Load Ready
MA 4

ATTENTION: RISQUE DE CHOCS ELECTRIQUE - NE PAS OUVRIR
RISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION
To reduce the risk of electrical shock, do not open the unit. No user
serviceable parts inside. Refer servicing to qualied service personnel.
e symbols shown below are internationally accepted symbols
that warn of potential hazards with electrical products.
is symbol indicates that a dangerous voltage
constituting a risk of electric shock is present
within this unit.
is symbol indicates that there are important
operating and maintenance instructions in the
literature accompanying this unit.
WARNING
IMPORTANT SAFETY INSTRUCTIONS
1. Read these instructions.
2. Keep these instructions.
3. Heed all warnings.
4. Follow all instructions.
5. Do not use this apparatus near water.
6. Clean only with a dry cloth.
7. Do not block any ventilation openings. Install in accordance with manufacturer’s instructions.
8. Do not install near any heat sources such as radiators, registers, stoves, or other apparatus (including ampliers) that produce heat.
9. Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A
grounding-type plug has two blades and a third grounding prong. e wide blade or third prong is provided for your safety. If the provided plug
does not t into your outlet, consult an electrician for replacement of the obsolete outlet.
10. Protect the power cord and plug from being walked on or pinched particularly at plugs, convenience receptacles, and the point where it exits from
the apparatus.
11. Only use attachments and accessories specied by Rane.
12. Use only with the cart, stand, tripod, bracket, or table specied by the manufacturer, or sold with the apparatus. When a cart is used, use caution
when moving the cart/apparatus combination to avoid injury from tip-over.
13. Unplug this apparatus during lightning storms or when unused for long periods of time.
14. Refer all servicing to qualied service personnel. Servicing is required when the apparatus has been damaged in any way, such as power supply
cord or plug is damaged, liquid has been spilled or objects have fallen into the apparatus, the apparatus has been exposed to rain or moisture, does
not operate normally, or has been dropped.
15. e plug on the power cord is the AC mains disconnect device and must remain readily operable. To completely disconnect this apparatus from
the AC mains, disconnect the power supply cord plug from the AC receptacle.
16. is apparatus shall be connected to a mains socket outlet with a protective earthing connection.
17. When permanently connected, an all-pole mains switch with a contact separation of at least 3 mm in each pole shall be incorporated in the
electrical installation of the building.
18. If rackmounting, provide adequate ventilation. Equipment may be located above or below this apparatus, but some equipment (like large power
ampliers) may cause an unacceptable amount of hum or may generate too much heat and degrade the performance of this apparatus.
19. is apparatus may be installed in an industry standard equipment rack. Use screws through all mounting holes to provide the best support.
WARNING: To reduce the risk of re or electric shock, do not expose this apparatus to rain or moisture. Apparatus shall not be exposed to dripping
or splashing and no objects lled with liquids, such as vases, shall be placed on the apparatus.
NOTE: is equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules.
ese limits are designed to provide reasonable protection against harmful interference in a residential installation. is equipment generates, uses
and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio
communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful
interference to radio or television reception, which can be determined by turning the equipment o and on, the user is encouraged to try to correct
the interference by one or more of the following measures:
• Reorient or relocate the receiving antenna.
• Increase the separation between the equipment and receiver.
• Connect the equipment into an outlet on a circuit dierent from that to which the receiver is connected.
• Consult the dealer or an experienced radio/TV technician for help.
CAUTION: Changes or modications not expressly approved by Rane Corporation could void the user's authority to operate the equipment.
CAN ICES-3 (B)/NMB-3(B)
WARNING: is product may contain chemicals known to the State of California to cause cancer, or birth defects or other reproductive harm.

ATTENTION: RISQUE DE CHOCS ELECTRIQUE - NE PAS OUVRIR
RISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION
An d’éviter tout risque de choc électrique, ne pas ouvrir l’appareil.
Aucune pièce ne peut être changée par l’utilisateur. Contactez un
SAV qualié pour toute intervention.
Les symboles ci-dessous sont reconnus internationalement
comme prévenant tout risque électrique.
Ce symbole indique que cette unité utilise un
voltage élevé constituant un risque de choc
électrique.
Ce symbole indique la présence d’instructions
d’utilisation et de maintenance importantes dans le
document fourni.
ATTENTION
INSTRUCTIONS DE SÉCURITÉ
1. Lisez ces instructions.
2. Gardez précieusement ces instructions.
3. Respectez les avertissements.
4. Suivez toutes les instructions.
5. Ne pas utiliser près d’une source d’eau.
6. Ne nettoyer qu’avec un chion doux.
7. N’obstruer aucune évacuation d’air. Eectuez l’installation en suivant les instructions du fabricant.
8. Ne pas disposer près d’une source de chaleur, c-à-d tout appareil produisant de la chaleur sans exception.
9. Ne pas modier le cordon d’alimentation. Un cordon polarisé possède 2 lames, l’une plus large que l’autre. Un cordon avec tresse de masse possède
2 lames plus une 3è pour la terre. La lame large ou la tresse de masse assurent votre sécurité. Si le cordon fourni ne correspond pas à votre prise,
contactez votre électricien.
10. Faites en sorte que le cordon ne soit pas piétiné, ni au niveau du l, ni au niveau de ses broches, ni au niveau des connecteurs de vos appareils.
11. N’utilisez que des accessoires recommandés par Rane.
12. N’utilisez que les éléments de transport, stands, pieds ou tables spéciés par le fabricant ou vendu avec l’appareil. Quand vous utlisez une valise de
transport, prenez soin de vous déplacer avec cet équipement avec prudence an d’éviter tout risque de blessure.
13. Débranchez cet appareil pendant un orage ou si vous ne l’utilisez pas pendant un certain temps.
14. Adressez-vous à du personnel qualié pour tout service après vente. Celui-ci est nécessaire dans n’importe quel cas où l’appareil est abimé : si le
cordon ou les ches sont endommagés, si du liquide a été renversé ou si des objets sont tombés sur l’appareil, si celui-ci a été exposé à la pluie ou
l’humidité, s’il ne fonctionne pas correctement ou est tombé.
15. La che du cordon d’alimentation sert à brancher le courant alternatif AC et doit absolument rester accessible. Pour déconnecter totalement
l’appareil du secteur, débranchez le câble d’alimentation de la prise secteur.
16. Cet appareil doit être branché à une prise terre avec protection.
17. Quand il est branché de manière permanente, un disjoncteur tripolaire normalisé doit être incorporé dans l’installation électrique de l’immeuble.
18. En cas de montage en rack, laissez un espace susant pour la ventilation. Vous pouvez disposer d’autres appareils au-dessus ou en-dessous de celui-
ci, mais certains (tels que de gros amplicateurs) peuvent provoquer un buzz ou générer trop de chaleur au risque d’endommager votre appareil et
dégrader ses performances.
19. Cet appareil peut-être installé dans une baie standard ou un chassis normalisé pour un montage en rack. Visser chaque trou de chaque oreille de
rack pour une meilleure xation et sécurité.
ATTENTION: an d’éviter tout risque de feu ou de choc électrique, gardez cet appareil éloigné de toute source d’humidité et d’éclaboussures quelles
qu’elles soient. L’appareil doit également être éloigné de tout objet possédant du liquide (boisson en bouteilles, vases,…).
REMARQUE: Cet équipement a été testé et approuvé conforme aux limites pour un appareil numérique de classe B, conformément au chapitre 15
des règles de la FCC. Ces limites sont établis pour fournir une protection raisonnable contre tout risque d’interférences et peuvent provoquer une
énergie de radiofréquence s'il n'est pas installé et utilisé conformément aux instructions, peut également provoquer des interférences aux niveaux
des équipements de communication. Cependant, il n'existe aucune garantie que de telles interférences ne se produiront pas dans une installation
particulière. Si cet équipement provoque des interférences en réception radio ou télévision, ceci peut être detecté en mettant l'équipement sous/hors
tension, l'utilisateur est encouragé à essayer de corriger cette interférence par une ou plusieurs des mesures suivantes:
• Réorienter ou déplacer l'antenne de réception.
• Augmenter la distance entre l'équipement et le récepteur.
• Connecter l'équipement à une sortie sur un circuit diérent de celui sur lequel le récepteur est branché.
• Consulter un revendeur ou un technicien radio / TV expérimenté.
ATTENTION: Les changements ou modications non expressément approuvés par Rane Corporation peuvent annuler l'autorité de l'utilisateur à
manipuler cet équipement et rendre ainsi nulles toutes les conditions de garantie.
CAN ICES-3 (B)/NMB-3(B)
Cartons et papier à recycler.

Manual-1
MA 4
MULTICHANNEL AMPLIFIER
DIGITAL
AMPLIFIER
dB Headroom dB Headroom dB Headroom dB Headroom
3
6
12
24
Limit
1
Comp
Exp
Fault
Load
Ready
3
6
12
24
Limit
2
Comp
Exp
Fault
Load
Ready
3
6
12
24
Limit
3
Comp
Exp
Fault
Load
Ready
3
6
12
24
Limit
4 ON
Comp
Exp
Fault
Load
Ready
MA 4
OPERATORS MANUAL
Quick Start
Basic MA 4 operation is straightforward:
1. e universal switching power supply works with 100 to 240 VAC, 50/60 Hz.
2. Make sure the front panel power switch is o (the unit consumes 5 watts in standby mode).
3. Connect balanced inputs (rear panel).
4. Set SENSITIVITY controls to +22 (see why on page Manual-2) (rear panel).
5. Turn the Downward EXPander ON (rear panel).
6. Set COMPressor to 10 dB (rear panel).
7. Select the appropriate HIGH PASS lter frequency (20, 40, 60 or 80 Hz on rear panel).
8. Connect speaker loads (rear panel).
9. Make sure you have adequate ventilation around the unit – see Safety Instructions.
10. Turn ON the front panel power switch. You’re good to go!
Metering shows the status of the amplier at a glance (see page Manual-3). Headroom (with any load), dynamics control, Fault status
and Load status are indicated for each channel.
Extra Credit
For remote turn-on, fault reporting and back-up amplier operations, and remote level control wiring, see page Manual-4.
For FAULT FLAG operation (applications and reported faults), see page Manual-3.
MA 4
100-240V
50/60 Hz 500 WATTS
RANE CORP.
Class 2 Wiring
OUTPUTS
Active Low Use Rane VR 2 or 20 kΩ pot
HIGH-PASS
20Hz
40Hz
60Hz
80Hz
ON
4
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
REMOTE LEVEL 4
4FLAG 3 2 1
FAULT
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
3
2
1
MASTER
SLAVE
COMP
4
3
2
1
1
2
3
4
+
–
+
–
+
–
+
–
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
+
–
+
–
+
–
+
–
INPUTSMODE
13
22
dBu
SENSITIVITY
4
3
13
22
dBu
SENSITIVITY
4
2
13
22
dBu
SENSITIVITY
4
1
13
22
dBu
SENSITIVITY
4
EXP ON
3
INT EXT
LOAD
2
INT EXT
LOAD
1
INT EXT
LOAD
4
INT EXT
LOAD
COMMERCIAL AUDIO
EQUIPMENT 24TJ
R
4321
ON
4321
ON
+
–
+
–
+
–
+
–
SOURCE 4
SOURCE 3
SOURCE 2
SOURCE 1
WEAR PARTS: This product contains no wear parts.
Installation
• No rear mounting hardware required.
• Allow adequate ventilation to keep ambient temperature around the amplier below 104˚F (40˚C).
• Fan cooled with inset intake on left side and inset exhaust on right side (no lter)
• Amplier heat load in Btu/hr at 100/240 VAC
º 10.2 / 13.3 Btu/hr All ampliers in standby
º 112.3 / 95.5 Btu/hr All ampliers on, no signal
º 167 / 139 Btu/hr All ampliers driven, pink noise, 12 watts avg. 4:1 crest
º Note: 1 watt x 3.413 = 1 Btu/hr.

Manual-2
Description & Operation
• Each channel delivers 100 watts of power into a 4 or 8Ω load (constant power).
º Average load impedance is estimated, then used to set the limiter to confine the maximum average power to 100 watts.
• Universal voltage, power-factor-corrected power supply (see gure on data sheet).
º Switch-mode power supply operates 100 to 240 VAC, 50 Hz or 60 Hz.
º Under- and over-voltage protection with inrush current management.
º The power supply features an IEC appliance inlet.
º Must be connected to a grounded mains socket-outlet.
• Class D ampliers operate at up to 85% eciency.
º Amplifiers operate in floating Bridged configuration.
º Channels are not bridgeable.
º Balanced Inputs accept +22 dBu maximum.
• Rear panel SENSITIVITY controls allow continuous adjustment from +22 dBu to +4 dBu.
º Integrated Limiter prevents clipping regardless of input level and sensitivity setting with input levels up to +22 dBu.
º The best dynamic range is achieved when all stages in a system clip at the same time. If the signal processing in front of the ampli-
fier clips at +22 dBu, and the amplifier sensitivity is set so that it clips at + 4 dBu, you loose 18 dB of headroom.
• REMOTE DC LEVEL control inputs are provided for each channel.
º Audio taper attenuation with external linear pot (0 dB to –80 dB, –16 dB at center position).
º Clickless mute with switch (use SPST switch; connect Vc to GND to mute).
º Euroblock connector with strain relief (Vref, Vcontrol, GND).
º One pot may control all four channels by daisy-chaining the Vc of the used port to the other three ports.
• e Load-dependent Limiter eliminates voltage and current clipping, ensuring signal integrity and uninterrupted service.
º The peak signal detector for the Limiter is oversampled to insure accuracy at any frequency.
º Instantaneous attack and 3 dB per second decay.
• Average load impedance is estimated and used to determine the Limiter threshold setting.
º The front panel Load indicator (see metering) indicates the load status.
º The normal impedance range is 2 to 16 Ω. (green Load indicator on).
º Average load impedance is estimated over 180 ms and requires a minimum of 3.3 watts averaged over 180 ms.
• A soft-knee COMPressor is enabled (down) or disabled (up) for all channels using the rear panel dipswitch.
º The rms threshold is 10 dB below the Limiter threshold.
· Allows full uncompressed operation of typical program material while reducing continuous sine wave power.
· Soft knee span is 10 dB; Ratio is 3:1; Attack is 1.5 seconds; Decay is 3 dB per second.
º If the internal amplifier temperature goes above 65˚ C, the compressor is automatically set to the 10 dB setting until the
temperature drops below 55˚ C. At normal operating temperatures, the threshold setting follows the dipswitch setting.
• Downward EXPander reduces noise in the absence of signal.
º The expander is enabled (down) or disabled (up) for all channels using the rear panel dipswitch.
º Threshold is –70 dBFS; Ratio is 3:1; Attack time is 50 ms; Gain reduction 10 dB per second.
• 20, 40, 60 or 80 Hz HIGH-PASS lters are selected using the rear panel dipswitch.
º Setting affects all channels.
º Filters are 12 dB per octave, Butterworth alignment.
MA 4
100-240V
50/60 Hz 500 WATTS
RANE CORP.
Class 2 Wiring
OUTPUTS
Active Low Use Rane VR 2 or 20 kΩ pot
HIGH-PASS
20Hz
40Hz
60Hz
80Hz
ON
4
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
REMOTE LEVEL 4
4FLAG 3 2 1
FAULT
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
3
2
1
MASTER
SLAVE
COMP
4
3
2
1
1
2
3
4
+
–
+
–
+
–
+
–
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
+
–
+
–
+
–
+
–
INPUTSMODE
13
22
dBu
SENSITIVITY
4
3
13
22
dBu
SENSITIVITY
4
2
13
22
dBu
SENSITIVITY
4
1
13
22
dBu
SENSITIVITY
4
EXP ON
3
INT EXT
LOAD
2
INT EXT
LOAD
1
INT EXT
LOAD
4
INT EXT
LOAD
COMMERCIAL AUDIO
EQUIPMENT 24TJ
R
FOR CONTINUED GROUNDING
PROTECTION DO NOT REMOVE
THIS SCREW.
MA 4
ACN 001
345 482
100-240V
50/60 Hz 500 WATTS
MADE IN U.S.A.
RANE CORP. Class 2 Wiring
OUTPUTS
Active Low
Use Rane VR 2 or 20 kΩ pot
HIGH-PASS
20Hz
40Hz
60Hz
80Hz
ON
4+–+–+–+– +–+–+–+
REMOTE LEVEL 4
4
FLAG
321
FAULT
Vr Vc Vr Vc Vr Vc Vr Vc
–
+–+–+–+– +–+–+–+–
321
MASTER
SLAVE
COMP
4321
1234
+– +– +– +–
Vr Vc Vr Vc Vr Vc Vr Vc +– +– +– +–
INPUTS
MODE
13
22
dBu
SENSITIVITY
4
3
13
22
dBu
SENSITIVITY
4
2
13
22
dBu
SENSITIVITY
4
1
13
22
dBu
SENSITIVITY
4
EXP ON
3
INT EXT
LOAD
2
INT EXT
LOAD
1
INT EXT
LOAD
4
INT EXT
LOAD
COMMERCIAL AUDIO
EQUIPMENT 24TJ
R
FOR CONTINUED GROUNDING
PROTECTION DO NOT REMOVE
THIS SCREW.
4321
ON
4321
ON
MA 4
ACN 001
345 482
100-240V
50/60 Hz 500 WATTS
MADE IN U.S.A.
RANE CORP. Class 2 Wiring
OUTPUTS
Active Low Use Rane VR 2 or 20 kΩ pot
HIGH-PASS
20Hz
40Hz
60Hz
80Hz
ON
4+–+–+–+– +–+–+–+
REMOTE LEVEL 4
4FLAG 321
FAULT
Vr Vc Vr Vc Vr Vc Vr Vc–
+–+–+–+– +–+–+–+–
321
MASTER
SLAVE
COMP
4321
1234
+– +– +– +–
Vr Vc Vr Vc Vr Vc Vr Vc +– +– +– +–
INPUTS
MODE
13
22
dBu
SENSITIVITY
4
3
13
22
dBu
SENSITIVITY
4
2
13
22
dBu
SENSITIVITY
4
1
13
22
dBu
SENSITIVITY
4
EXP ON
3
INT EXT
LOAD
2
INT EXT
LOAD
1
INT EXT
LOAD
4
INT EXT
LOAD
COMMERCIAL AUDIO
EQUIPMENT 24TJ
R
FOR CONTINUED GROUNDING
PROTECTION DO NOT REMOVE
THIS SCREW.
4321
ON
4321
ON

Manual-3
• Individual FAULT FLAG ports are provided for each channel.
º When a fault is detected on power up, the channel or channels aected are not enabled, and the appropriate front
panel fault indicators are lit. A detected fault is re-tested every 10 seconds.
º When a channel develops a fault while operating, the channel shuts down and the output relay is turned OFF.
A detected fault is re-tested every 10 seconds.
º Possible faults include: supply under-voltage, over-voltage, voltage imbalance, output short to ground, output
short to supply, output short to output, clock not running, over safe temperature.
º Channels set to Master, drive the fault ag high when no fault is present. Passive pull down pulls the fault ag low
when a fault occurs or power is lost. Slave channels read the status of the fault ag (see Master/Slave below).
º The fault flag uses 5 volt logic with high-side active drive and passive pull down. No fault = +5V. Fault = 0V.
• Each channel is set for MASTER (up) or SLAVE (down) operation using the rear panel dipswitch.
º Master channels write fault flag status.
º Slave channels read fault flag status.
º The Master setting is used for remote fault reporting and/or automatic redundancy switching control.
º The Slave setting is used for individual channel remote power sequencing or automatic redundancy switching.
• Internal automatic redundancy switching is provided (see page Manual-4).
º The primary amplifier channel is set to Master. The backup amplifier channel is
set to Slave. The Master fault flag is wired to the Slave fault flag. If two different
MA 4 amplifiers are involved (recommended), also wire the fault flag grounds
together. Drive Master and Slave audio inputs from the same source, and set the
SENSITIVITY controls the same. Master and Slave front panel power switches
must be ON.
º When a fault is detected on a Master amplifier channel, that channel is shut
down, the output relay is switched to off, internally connecting the load to the
EXTernal amplifier input. The front panel fault indicator is then lit.
º The Slave channel remains in low-power standby (Ready indicator flashing) until a fault is detected (fault flag no longer driven
high by the Master channel). When a fault is detected, the Slave channel performs a self test, switches to run mode, and closes the
output relay (takes about 500 ms). The output of the Slave channel is connected to the EXTernal amplifier input on the Master
channel.
• Comprehensive front panel metering is included for each channel:
º Headroom meters are four-segment. The peak signal level is compared to the limit threshold and the difference in dB is displayed
as remaining headroom. The limiter threshold is adjusted to account for the average load impedance, resulting in load compen-
sated headroom indication.
º Red Limiter, yellow Compressor and yellow Expander indicators light when the associated dynamics control is active.
º A red Fault indicator lights when a fault is detected
º The green Load indicator is off when impedance is above 16 Ω, on when impedance is between 2 and 16 Ω and flashing when the
impedance is below 2 Ω.
º The green Ready indicator is off when the power switch is off, flashing when the power switch is on and the unit is in standby
(Slave channel with high fault flag) and on when the channel is active.
DIGITAL
AMPLIFIER
dB Headroom dB Headroom dB Headroom dB Headroom
3
6
12
24
Limit
1
Comp
Exp
Fault
Load
Ready
3
6
12
24
Limit
2
Comp
Exp
Fault
Load
Ready
3
6
12
24
Limit
3
Comp
Exp
Fault
Load
Ready
3
6
12
24
Limit
4ON
Comp
Exp
Fault
Load
Ready
MA 4
MA 4
ACN 001
345 482
100-240V
50/60 Hz 500 WATTS
MADE IN U.S.A.
RANE CORP. Class 2 Wiring
OUTPUTS
Active Low
Use Rane VR 2 or 20 kΩ pot
HIGH-PASS
20Hz
40Hz
60Hz
80Hz
ON
4
+–+–+–+– +–+–+–+
REMOTE LEVEL 4
4
FLAG
321
FAULT
Vr Vc Vr Vc Vr Vc Vr Vc–
+–+–+–+– +–+–+–+–
321
MASTER
SLAVE
COMP
4321
1234 +– +– +– +–
Vr Vc Vr Vc Vr Vc Vr Vc +– +– +– +–
INPUTSMODE
13
22
dBu
SENSITIVITY
4
3
13
22
dBu
SENSITIVITY
4
2
13
22
dBu
SENSITIVITY
4
1
13
22
dBu
SENSITIVITY
4
EXP ON
3
INT EXT
LOAD
2
INT EXT
LOAD
1
INT EXT
LOAD
4
INT EXT
LOAD
COMMERCIAL AUDIO
EQUIPMENT 24TJ
R
FOR CONTINUED GROUNDING
PROTECTION DO NOT REMOVE
THIS SCREW.
4321
ON
4321
ON
MA 4
ACN 001
345 482
100-240V
50/60 Hz 500 WATTS
MADE IN U.S.A.
RANE CORP.
Class 2 Wiring
OUTPUTS
Active Low Use Rane VR 2 or 20 kΩ pot
HIGH-PASS
20Hz
40Hz
60Hz
80Hz
ON
4
+–+–+–+– +–+–+–+
REMOTE LEVEL 4
4FLAG 321
FAULT
Vr Vc Vr Vc Vr Vc Vr Vc
–
+–+–+–+– +–+–+–+–
321
MASTER
SLAVE
COMP
4321
1234 +– +– +– +–
Vr Vc Vr Vc Vr Vc Vr Vc +– +– +– +–
INPUTSMODE
13
22
dBu
SENSITIVITY
4
3
13
22
dBu
SENSITIVITY
4
2
13
22
dBu
SENSITIVITY
4
1
13
22
dBu
SENSITIVITY
4
EXP ON
3
INT EXT
LOAD
2
INT EXT
LOAD
1
INT EXT
LOAD
4
INT EXT
LOAD
COMMERCIAL AUDIO
EQUIPMENT 24TJ
R
FOR CONTINUED GROUNDING
PROTECTION DO NOT REMOVE
THIS SCREW.
4321
ON
4321
ON

Manual-4
MA 4
100-240V
50/60 Hz 500 WATTS
RANE CORP.
Class 2 Wiring
OUTPUTS
Active Low Use Rane VR 2 or 20 kΩ pot
HIGH-PASS
20Hz
40Hz
60Hz
80Hz
ON
4
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
REMOTE LEVEL 4
4FLAG 3 2 1
FAULT
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
3
2
1
MASTER
SLAVE
COMP
4
3
2
1
1
2
3
4
+
–
+
–
+
–
+
–
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
+
–
+
–
+
–
+
–
INPUTSMODE
13
22
dBu
SENSITIVITY
4
3
13
22
dBu
SENSITIVITY
4
2
13
22
dBu
SENSITIVITY
4
1
13
22
dBu
SENSITIVITY
4
EXP ON
3
INT EXT
LOAD
2
INT EXT
LOAD
1
INT EXT
LOAD
4
INT EXT
LOAD
COMMERCIAL AUDIO
EQUIPMENT 24TJ
R
4321
ON
4321
ON
+5V
Advanced Applications
Remote Turn-on
To operate an amplier channel in low power standby with remote turn-on, set its rear panel switch to SLAVE. External +5 volts con-
nected to the FAULT FLAG holds the amplier in standby. Floating the FAULT FLAG or connecting it to ground turns the channel on.
Fault Reporting
To have an amplier channel report a fault to a control system or back up amplier, set it to Master. e
Fault Flag is held high (+5 volts) during normal operation and goes low (passive pull down) when a fault
occurs. For details on Fault Flag operation, see page Manual-3.
Remote Level Control inputs are provided for each channel. Any linear potentiometer 10k to 100k Ω
may be connected to these inputs (diagram at right).
MA 4
100-240V
50/60 Hz 500 WATTS
RANE CORP.
Class 2 Wiring
OUTPUTS
Active Low Use Rane VR 2 or 20 kΩ pot
HIGH-PASS
20Hz
40Hz
60Hz
80Hz
ON
4
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
REMOTE LEVEL 4
4FLAG 3 2 1
FAULT
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
3
2
1
MASTER
SLAVE
COMP
4
3
2
1
1
2
3
4
+
–
+
–
+
–
+
–
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
+
–
+
–
+
–
+
–
INPUTSMODE
13
22
dBu
SENSITIVITY
4
3
13
22
dBu
SENSITIVITY
4
2
13
22
dBu
SENSITIVITY
4
1
13
22
dBu
SENSITIVITY
4
EXP ON
3
INT EXT
LOAD
2
INT EXT
LOAD
1
INT EXT
LOAD
4
INT EXT
LOAD
COMMERCIAL AUDIO
EQUIPMENT 24TJ
R
4321
ON
4321
ON
MA 4
100-240V
50/60 Hz 500 WATTS
RANE CORP.
Class 2 Wiring
OUTPUTS
Active Low Use Rane VR 2 or 20 kΩ pot
HIGH-PASS
20Hz
40Hz
60Hz
80Hz
ON
4
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
REMOTE LEVEL 4
4FLAG 3 2 1
FAULT
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
3
2
1
MASTER
SLAVE
COMP
4
3
2
1
1
2
3
4
+
–
+
–
+
–
+
–
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
+
–
+
–
+
–
+
–
INPUTSMODE
13
22
dBu
SENSITIVITY
4
3
13
22
dBu
SENSITIVITY
4
2
13
22
dBu
SENSITIVITY
4
1
13
22
dBu
SENSITIVITY
4
EXP ON
3
INT EXT
LOAD
2
INT EXT
LOAD
1
INT EXT
LOAD
4
INT EXT
LOAD
COMMERCIAL AUDIO
EQUIPMENT 24TJ
R
4321
ON
4321
ON
+
–
+
–
+
–
+
–
LINEAR
POTS
ZONE 1 ZONE 2 ZONE 3 ZONE 4
SOURCE 4
SOURCE 3
SOURCE 2
SOURCE 1
MASTER
MA 4
SLAVE
MA 4
All features & specications subject to change without notice. DOC 111037
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5000 USA TEL [phone] FAX [phone] WEB rane.com
20 kΩ,
linear taper
GND
Vc
CW
Vr

Data Sheet-2
MA 4
MULTICHANNEL AMPLIFIER
Specifications
Parameter Specication Conditions/Comments
Input impedance 10 k Each leg, dierential, 1 kHz
Maximum input +22 dBu
Sensitivity range/resolution +22 to +4 dBu 256 steps
Remote level control range/resolution Attenuate only; 0 dB to –80 dB Audio taper response, 256 steps
Fault ag in/out Active 5V high-side drive, passive pull down. NO Fault = +5V; Fault = 0V
Limiter Oversampled instantaneous attack 3 dB per second decay
..........Load compensated Limit set for 7.5 amps peak Based on load Z
Compressor 50 ms rms detector reshold relative to limiter
..........reshold 10 dB re peak dBFS Rear panel dipswitch on/o
..........Attack 1.5 second
..........Decay 3 dB per second
..........Knee Span 10 dB
Expander Select on rear panel rms detector
..........reshold -70 dBFS
..........Attack 50 ms Gain reduction release time constant
..........Decay 10 dB per second Rate of gain reduction
High-pass lter 12 dB per octave, Butterworth 20, 40, 60, 80 Hz dipswitch select
Load sensing 2 to 16 normal Green Load indicator on
..........Low load detect Below 2 is low Green Load indicator ashing
..........High load detect Above 16 is high Green Load indicator o
..........Min average power 3.3 watts average required for good load estimate
Output
..........Power 100 watts 3 to 8 
..........Frequency response 20 Hz to 20 kHz +0, -3 dB
..........Dynamic range >90 dB A-weighted, typical
..........THD+N 0.1% typ 100 watts into 4, 20-20 kHz
..........Clock fundamental 310 kHz <10 mV residual
..........Relay switching Turn on mute, fault protection, redundancy switching
Fan cooling Temperature controlled, variable speed Intake left side, exhaust right side
Heat load in Btu/hr 100 / 240 volts AC 50/60 Hz
..........Standby 10.2 / 13.3
..........Run mode, no signal 112.3 / 95.5
..........All channels driven 167 / 139 pink noise, average ⅛th power, 4:1 crest
AC Mains 100 to 240 VAC ±10%, 50 or 60 Hz
PFC 100 kHz boost
DC/DC 200 kHz forward
Unit: Conformity FCC, UL
..........Construction All Steel
..........Size 1.75"H x 19"W x 9.25"D (4.4 cm x 48.3 cm x 23.5 cm)
..........Weight: 8 lb (3.6 kg)
Shipping: Size 4.5" x 20.3" x 13.75" (11.5 cm x 52 cm x 35 cm)
..........Weight: 11 lb (5 kg)
All specications typical unless otherwise noted.

Data Sheet-3
MA 4
MULTICHANNEL AMPLIFIER
MA 4
100-240V
50/60 Hz 500 WATTS
RANE CORP.
Class 2 Wiring
OUTPUTS
Active Low Use Rane VR 2 or 20 kΩ pot
HIGH-PASS
20Hz
40Hz
60Hz
80Hz
ON
4
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
REMOTE LEVEL 4
4FLAG 3 2 1
FAULT
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
3
2
1
MASTER
SLAVE
COMP
4
3
2
1
1
2
3
4
+
–
+
–
+
–
+
–
Vr
Vc
Vr
Vc
Vr
Vc
Vr
Vc
+
–
+
–
+
–
+
–
INPUTSMODE
13
22
dBu
SENSITIVITY
4
3
13
22
dBu
SENSITIVITY
4
2
13
22
dBu
SENSITIVITY
4
1
13
22
dBu
SENSITIVITY
4
EXP ON
3
INT EXT
LOAD
2
INT EXT
LOAD
1
INT EXT
LOAD
4
INT EXT
LOAD
COMMERCIAL AUDIO
EQUIPMENT 24TJ
R
FOR CONTINUED GROUNDING
PROTECTION DO NOT REMOVE
THIS SCREW.
4321
ON
4321
ON
1 24690q 578 3
1Universal voltage, power-factor corrected, switch mode power supply operates 85 to 260 VAC, 50 Hz or 60 Hz. e supply
features under and over voltage protection, low inrush current and operates with up to 85% eciency.
2INPUTS are balanced and accept up to +22 dBu via Euroblock connectors with strain-relief.
3SENSITIVITY controls allow continuous adjustment from +22 dBu to +4 dBu. Integrated limiter prevents clipping regardless of
input level and sensitivity setting.
4REMOTE DC LEVEL control ports with Euroblock strain-relief connectors allow audio taper attenuation using 10k to 100k Ω
linear pots. Clickless muting may be implemented using a switch, connecting Vr to Vc.
5A soft knee COMPressor is provided with rms threshold relative to the limit threshold. ON/o setting aects all channels. is
allows uncompressed operation with typical program material while reducing continuous sine-wave power. Ratio is 3:1; Attack is
1.5 seconds; Decay is 3 dB per second; Soft knee span is 10 dB.
6Downward EXPander reduces noise in the absence of signal. ON/o setting eects all channels.
º reshold: –70 dBFS; Ratio: 3:1; Attack: 50 ms; Gain reduction: 10dB/sec.
7Selectable 20 Hz, 40 Hz, 60 Hz or 80 Hz HIGH-PASS lters are provided. e setting aects all channels. Filters are 12 dB per
octave, Butterworth alignment.
8Each channel is set for MASTER or SLAVE operation. Master channels write Fault Flag status. Slave channels read Fault Flag
status.
• e Master setting is used for remote fault reporting and/or automatic redundancy switching control.
• e Slave setting is used for individual channel remote power sequencing or automatic redundancy switching.
9Individual FAULT FLAG ports are provided for each channel.
• e Fault Flag uses high-side active drive and passive pull down. No fault = +5 volts. Fault = 0 volts.
• Channels set to Master drive the Fault Flag high when no fault is present. Passive pull down pulls the Fault Flag low when a
fault occurs or power is lost.
• Slave channels read the status of the Fault Flag.
0Amplier outputs are oating (not ground referenced) and are not bridgeable. Each channel delivers 100 watts into a 4 or 8Ω
load. Average load impedance is estimated then used to determine the limiter threshold required to limit maximum power to 100
watts and peak current to less than 7.5 amps. Impedance estimation requires a minimum of 3.3 watts and is averaged over 180 ms.
qExternal amplier input is used for Internal, automatic redundancy switching.
wComprehensive front panel metering is included for each channel:
• Four segment, load sensitive headroom meter shows remaining headroom.
• Limiter, Compressor and Expander indicators light when the associated dynamics control is active.
• e Fault indicator lights when a fault is detected
• e Load indicator if o when impedance is above 16Ω, on when impedance is between 2 and 16Ω and ashing when the
impedance is below 2Ω.
• e Ready indicator is o when the power switch is o, ashing when the power is switch is ON and the unit is in standby
(Slave channel with high fault ag) and on when the channel is active.
dB Headroom dB Headroom dB Headroom dB Headroom
3
6
12
24
Limit
1
Comp
Exp
Fault
Load
Ready
3
6
12
24
Limit
2
Comp
Exp
Fault
Load
Ready
3
6
12
24
Limit
3
Comp
Exp
Fault
Load
Ready
3
6
12
24
Limit
4
ON
Comp
Exp
Fault
Load
Ready
w

Data Sheet-4
MA 4
MULTICHANNEL AMPLIFIER
POWER-FACTOR-
CORRECTION SWITCH-MODE
POWER SUPPLY
TUPNI
GALFTLUAF
1H
C
1
EVALS/RETSAM
Bd3 Bd6 Bd21 Bd42
COMBINATION CONTROLLER
DRAWROFWS-2
ESUF RETLIFIME HSURNI EGATLOVREVO
H3
G2
N1
CEI ECNAILPPA TELNI )zHk001( )zHk002(
CDA
TUPNI
2H
C
TUPNI
3H
C
TUPNI
4H
C
CDA
DNG
52+
52-
YTIVITISNES
SSAP-HGIH
08-06-04-02
ROSSERPMOC
RETIMILKAEP
DNAPXE
CAD
RETLIF .TTA
FILTER
CAD
RETLIF .TTA
FILTER
RETLIF .TTA
FILTER
RETLIF .TTA
FILTER
52+
52-
KLC
KLC
KLC
KLC
TIMIL PMOC TLUAF DAOL YDAERPXE Bd3 Bd6 Bd21 Bd42 TIMIL PMOC TLUAF DAOL YDAERPXE
Bd3 Bd6 Bd21 Bd42 TIMIL PMOC TLUAF DAOL YDAERPXE Bd3 Bd6 Bd21 Bd42
TIMIL PMOC TLUAF DAOL YDAERPXE
4-HC3-HC2-HC1-HC
PSD
TSOH
DNG
YTIVITISNES 4HC3HC2HC1HC DNG
A5+
LEVELETOMER
1HC 2HC 3HC 4HC
1HC
2HC
3HC
4HC
ESNESTNERRUC
4HC3HC2HC1HC
ESNESPMET
+
-
REIFILPMA
TXE
TUPTUO
1HC
4A/3A2A/1A
DNG
A5+DNG A5+ DNG
A5+
3cV1c
V4
cV2cV
4+22+
WOLEVITCA
1
COMP ON/OFF
EXP ON/OFF
00 10 01 11 zH02 ZH04 zH06 zH08 :EDOM V8.0OTV0.0:YBDNATS V0.3OTV2.2:ETUM V5.5OTV2.4:NO
1M2M3M4M
1M
2M
3M
4M
ESNESYLPPUS )52±(
TIMILTUPNI
SMR
YTIVITISNES
SSAP-HGIH
08-06-04-02
ROSSERPMOC
RETIMILKAEP
DNAPXE
TIMILTUPNI
DETECT
RMS
OUTPUT LEVEL
SMR
YTIVITISNES
SSAP-HGIH
08-06-04-02
ROSSERPMOC
RETIMILKAEP
DNAPXE
TIMILTUPNI
SMR
YTIVITISNES
SSAP-HGIH
08-06-04-02
ROSSERPMOC
RETIMILKAEP
DNAPXE
TIMILTUPNI
SMR
2HC
1HC
3HC
4HC
4+4+22+4+22+22+
yalerV
d5+
3.3+
a5+
52+
52-
52+
52-
52+
52-
+DNG
1RV
+
-
+
-
TXE
TUPTUO
2HC
+DNG2RV
+
-
+
-
TXE
TUPTUO
3HC
+DNG
3RV
+
-
+
-
TXE
TUPTUO
4HC
+DNG4RV
+
-
KCOLCYLPPUS
KCOLCYLPPUS
KCOLCPMA
KCOLCYLPPUS
DETECT
RMS
OUTPUT LEVEL
DETECT
RMS
OUTPUT LEVEL
DETECT
RMS
OUTPUT LEVEL
ETOMER LEVEL
ETOMER LEVEL
ETOMER LEVEL
ETOMER LEVEL
LOW VOLTAGE
FLYBACK
Block Diagram

Data Sheet-5
MA 4
MULTICHANNEL AMPLIFIER
POWER-FACTOR-
CORRECTION SWITCH-MODE
POWER SUPPLY
TUPNI
GALFTLUAF
1HC
1
EVALS/RETSAM
Bd3 Bd6 Bd21 Bd42
COMBINATION CONTROLLER
DRAWROFWS-2
ESUF RETLIFIME HSURNI EGATLOVREVO
H3
G2
N1
CEI ECNAILPPA TELNI )zHk001( )zHk002(
CDA
TUPNI
2HC
TUPNI
3HC
TUPNI
4HC
CDA
DNG
52+
52-
YTIVITISNES
SSAP-HGIH
08-06-04-02
ROSSERPMOC
RETIMILKAEP
DNAPXE
CAD
RETLIF .TTA
FILTER
CAD
RETLIF .TTA
FILTER
RETLIF .TTA
FILTER
RETLIF .TTA
FILTER
52+
52-
KLC
KLC
KLC
KLC
TIMIL PMOC TLUAF DAOL YDAERPXE Bd3 Bd6 Bd21 Bd42 TIMIL PMOC TLUAF DAOL YDAERPXE
Bd3 Bd6 Bd21 Bd42 TIMIL PMOC TLUAF DAOL YDAERPXE Bd3 Bd6 Bd21 Bd42
TIMIL PMOC TLUAF DAOL YDAERPXE
4-HC3-HC2-HC1-HC
PSD
TSOH
DNG
YTIVITISNES 4HC3HC2HC1HC DNG
A5+
LEVELETOMER
1HC 2HC 3HC 4HC
1HC
2HC
3HC
4HC
ESNESTNERRUC
4HC3HC2HC1HC
ESNESPMET
+
-
REIFILPMA
TXE
TUPTUO
1
HC
4A/3A2A/1A
DNG
A5+DNG A5+ DNG
A5+
3cV1cV4cV2cV
4+22+
WOLEVITCA
1
COMP ON/OFF
EXP ON/OFF
00 10 01 11 zH02 ZH04 zH06 zH08 :EDOM V8.0OTV0.0:YBDNATS V0.3OTV2.2:ETUM V5.5OTV2.4:NO
1M2M3M4M
1M
2M
3M
4M
ESNESYLPPUS )52±(
TIMILTUPNI
SMR
YTIVITISNES
SSAP-HGIH
08-06-04-02
ROSSERPMOC
RETIMILKAEP
DNAPXE
TIMILTUPNI
DETECT
RMS
OUTPUT LEVEL
SMR
YTIVITISNES
SSAP-HGIH
08-06-04-02
ROSSERPMOC
RETIMILKAEP
DNAPXE
TIMILTUPNI
SMR
YTIVITISNES
SSAP-HGIH
08-06-04-02
ROSSERPMOC
RETIMILKAEP
DNAPXE
TIMILTUPNI
SMR
2HC
1HC
3HC
4HC
4+4+22+4+22+22+
yalerV
d5+
3.3+
a5+
52+
52-
52+
52-
52+
52-
+DNG
1RV
+
-
+
-
TXE
TUPTUO
2
HC
+DNG2RV
+
-
+
-
TXE
TUPTUO
3
HC
+DNG
3RV
+
-
+
-
TXE
TUPTUO
4
HC
+DNG4RV
+
-
KCOLCYLPPUS
KCOLCYLPPUS
KCOLCPMA
KCOLCYLPPUS
DETECT
RMS
OUTPUT LEVEL
DETECT
RMS
OUTPUT LEVEL
DETECT
RMS
OUTPUT LEVEL
ETOMER LEVEL
ETOMER LEVEL
ETOMER LEVEL
ETOMER LEVEL
LOW VOLTAGE
FLYBACK

Data Sheet-6
MA 4
MULTICHANNEL AMPLIFIER
Power-Factor-Correction (PFC)
Near perfect Power-Factor with ⅓ the peak current and ½ the
average current (green) compared to non power-factor-corrected
supply with conduction of 3 ms (black). e response is mea-
sured at 100 watts.
Architectural Specifications
e unit shall be a four channel amplier. It shall deliver 100
watts of power per channel into a 4 to 8 ohm load. e ampli-
er shall incorporate load sensing with normal operation in the
range of 2 to 16 ohms. Front panel indicators shall alert presence
of a channel load outside of this range.
e amplier shall have balanced inputs with Euroblock
connectors and Euroblock output connectors capable of accept-
ing 12 gauge wire. Sensitivity controls with a range of +22 to +4
dBu shall be provided for each input on the rear panel by means
of screwdriver adjustment. Load sensitive headroom meters shall
provide indication of 3, 6, 12 and 24 dB of remaining headroom.
Euroblock connectors shall be provided as a means of con-
necting remote DC level potentiometers or switches to attenuate
the input level of each channel.
Automatic redundancy switching shall be provided in the
event of a fault of any amplier channel. Euroblock connectors
shall provide a means of connecting additional amplier outputs
for automatic backup purposes. Each channel shall have master
or slave operation determined by a rear panel dipswitch. Master
channels shall write fault ag status, and Slave channels shall
read fault ag status.
A rear panel dipswitch shall provide a selection of 20, 40, 60
or 80 Hz highpass 2nd-order Butterworth lters. Load sensitive
limiter circuits shall prevent clipping and the associated loss of
speech intelligibility. A front panel LED shall indicate limiter
activity within each channel.
Built-in compressors shall be provided with a 10 dB thresh-
old. A rear panel dipswitch shall activate or deactive the com-
pressors. A front panel LED shall indicate compressor activity
within each channel.
Built-in expanders shall be provided with a -70 dBFS thresh-
old. A rear panel dipswitch shall activate or deactive the expand-
ers. A front panel LED shall indicate expander activity within
each channel.
Euroblock connectors on the rear panel shall provide a means
of transmitting or receiving fault ag information to other
ampliers or indicators with an active 5 volt drive. A front panel
LED shall indicate a fault ag condition within each channel.
ermal management shall employ forced air cooling, allow-
ing the ampliers to operate reliable in ventilated racks at 40°C
ambient temperature. e fan speed air ow shall be controlled
by temperature. Intake shall be on the left side of the chassis and
exhaust on the right side, incorporating low velocity air ow to
minimize noise within a rack cabinet.
e universal internal switch-mode power supply shall
operate from 100 to 240 VAC, 50 or 60 Hz. e power supply
design shall provide power-factor-correction with very low inrush
current and overvoltage protection. An IEC connector and IEC
cord shall be utilized. A front panel mounted power switch shall
be provided.
e unit shall be a Rane Corporation Model MA 4.
Compressor Response
Output dB re 100W
O
u
t
p
u
t
P
o
w
e
r
Attack: 1.5 seconds
Release: 3 dB per second
Output Power
Output dB
Input dBu

Data Sheet-1
MT 4
MULTICHANNEL TRANSFORMER
Features
• Four channels, 100 watts, 100 / 70 volt
• Input 8Ω, 100 watts
• Euroblock strain-relief connectors
• 1U, 19 inch rackmount tray
• Frequency response 40 Hz to 20 kHz +0, -1 dB
• Separate mounting tray and individual transformers available
Options
• MT 4 rackmount tray with four transformers (shown below)
• KT 4 rackmount tray only
• TF 4 individual transformers
DATA SHEET
General Description
e MT 4 four-channel distribution transformer is packaged in
a space saving 1U, 19-inch rack-mount tray. e fully isolated,
high-performance toroid transformers provide at frequency re-
sponse within 1 dB from 40 Hz to 20 kHz. Each transformer is
designed for an 8Ω 100 watt input, and 100 watt 70 volt or 100
watt 100 volt output. e recommended load for the 70 volt tap
is 50 Ω. e recommended load for the 100 volt tap is 100Ω.
Convenient Euroblock connectors are provided on the rear of the
chassis.
e MT 4 comes ready-to-use with four mounted transform-
ers and strain-relief Euro connectors. e tray with Euroblock
connectors (model KT 4) and individual transformers with
mounting hardware (model TF 4) are available separately, allow-
ing the installer to build a tray with just the number of channels
required. (see the mounting in Figure 4, next page). is makes
this ideal for any rack system where high-performance 100 watt,
100 / 70 volt, isolated distribution transformers are required.
For 25 volt audio distribution systems, the TF 4 can be used
by connecting the 25V loads between its 70V and 100V taps
(green and yellow wires). ermal resistance of the TF 4 is only
1C/W and is lower when mounted in a MT 4 chassis.
Other creative combinations are possible. For example, the
yellow/green pair can drive 8Ω loads near to the amplier, with
the red/yellow pair being simultaneously used for a 70 V system.
Depending on loading of the 70 V system, this arrangement
presents an impedance between 4 and 8Ω to the amplier.
MT 4
MULTICHANNEL
TRANSFORMER
TF 4 can be used at power ratings much higher than 100 W,
provided that the low-cut frequency is moved up accordingly.
Since voltage capability doubles with each octave, power capabil-
ity quadruples each octave. See the RaneNote "Constant-Voltage
Audio Distribution Systems: 25, 70.7 & 100 Volts” available at
rane.com.

Data Sheet-2
MT 4
MULTICHANNEL TRANSFORMER
Parameter Specication Limit Units Conditions/Comments
Transformer Rating 100 Watts Maximum average power
30 Watts Maximum continuous average power
..........Connectors Chassis mounted Euroblock Strain relief
..........Chassis 1U rack-mount tray
Input voltage 28.28 Vrms 100 watts / 8 Ω
Output Tap 1: Voltage 70.7 Vrms 50 Ω load
Output Tap 2: Voltage 100 Vrms 100 Ω load
Frequency Response 40 to 20 kHz +0, -1 dB 100 watts with specied load
THD 0.1 typ % 1 kHz, 100 watts
THD 0.2 typ % 40 Hz to 20 kHz, 100 watts
Unit: Panel Construction 12 gauge steel
..........Size: 1U 1.75"H x 19"W x 9"D 4.45 cm x 48.26 cm x 22.86 cm
..........Weight 18 lb 8.2 kg
1234
RANE CORPORATION
MT 4
+
IN OUT
– 100V 70V COM +
IN OUT
– 100V 70V COM +
IN OUT
– 100V 70V COM +
IN OUT
IN OUT IN OUT IN OUT IN OUT
– 100V 70V COM
+– 100V 70V COM +– 100V 70V COM +– 100V 70V COM +– 100V 70V COM
All features & specications subject to change without notice. PN 15178 DOC 108152
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5000 USA TEL [phone] FAX [phone] WEB rane.com
Rubber
washer
Rubber
washer
KT 4
tray
Mounting
washer
#10
washer
Nut
Screw
1.5”
Max
4.2” Max
Primar
y
Black
(+)
Whit
e
(–)
Green
100
Yellow
Tap
70
Red
common
Insulation & Flammability
1. Insulation materials compatible with surface operating
tempertaures > 60°C.
2. All materials ammability rated UL94V0.
Electrical
1. Primary DC resistance: Black-White < 500 mΩ
2. Secondary DC resistance: Red-Yellow < 4Ω, Red-Green < 6Ω.
3. Magnetizing Inductance: Primary: > 1H (1V, 100 Hz)
4. Leakage Inductance: Primary (secondaries shorted): 20 µH.
Performance Specications
1. Max Output Power: 100 Vrms @ 1 Arms.
2. Average Input Power (for thermal dissapation): 30 W.
3. Maximum Power Loss: <20 W @ 100 W Output (8Ω load).
Warning: is product may contain chemicals known to the
State of California to cause cancer, or birth defects or other
reproductive harm.
Figure 1. Schematic Figure 2. Perspective Figure 3. Top View Figure 4. Mounting, Side View
TF 4 Transformer, 100 V / 100 W
Rear Panel
Figure 5. Colored leads connect
to labelled circuit board.

Constant-Voltage-1
Constant-Voltage Audio
Distribution Systems:
25, 70.7 & 100 Volts
• Background — Wellspring
• U.S. Standards — Who Says?
• Basics — What is “Constant” Anyway?
• Voltage Variations — Make Up Your Mind
• Calculating Losses — Chasing Your Tail
• Wire Size — How Big is Big Enough?
• Rane Constant-Voltage Transformers
Dennis Bohn
Rane Corporation
RaneNote 136
© 1997 Rane Corporation
Background — Wellspring
Constant-voltage is the common name given to a gen-
eral practice begun in the late 1920s and early 1930s
(becoming a U.S. standard in 1949) governing the
interface between power amplifiers and loudspeakers
used in distributed sound systems. Installations em-
ploying ceiling-mounted loudspeakers, such as offices,
restaurants and schools are examples of distributed
sound systems. Other examples include installations
requiring long cable runs, such as stadiums, factories
and convention centers. e need to do it differently
than you would in your living room arose the first time
someone needed to route audio to several places over
long distances. It became an economic and physical
necessity. Copper was too expensive and large cable too
cumbersome to do things the home hi-fi way.
RaneNote
Constant-Voltage audio distribution systems:
25, 70.7 & 100 Volts

Constant-Voltage-2
Stemming from this need to minimize cost, maxi-
mize efficiency, and simplify the design of complex
audio systems, thus was born constant-voltage. e key
to the solution came from understanding the electric
company cross-country power distribution practices.
ey elegantly solved the same distribution problems
by understanding that what they were distributing was
power, not voltage. Further they knew that power was
voltage times current, and that power was conserved.
is meant that you could change the mix of voltage
and current so long as you maintained the same ratio:
100 watts was 100 watts – whether you received it by
having 10 volts and 10 amps, or 100 volts and 1 amp.
e idea bulb was lit. By stepping-up the voltage, you
stepped-down the current, and vice-versa. erefore
to distribute 1 megawatt of power from the generator
to the user, the power company steps the voltage up
to 200,000 volts, runs just 5 amps through relatively
small wire, and then steps it back down again at, say,
1000 different customer sites, giving each 1 kilowatt. In
this manner large gauge cable is only necessary for the
short direct run to each house. Very clever.
Applied to audio, this means using a transformer to
step-up the power amplifier’s output voltage (gaining
the corresponding decrease in output current), use this
higher voltage to drive the (now smaller gauge wire due
to smaller current) long lines to the loudspeakers, and
then using another transformer to step-down the volt-
age at each loudspeaker. Nothing to it.
U.S. Standards— Who Says?
is scheme became known as the constant-voltage
distribution method. Early mention is found in Radio
Engineering, 3rd Ed. (McGraw-Hill, 1947), and it was
standardized by the American Radio Manufacturer’s
Association as SE-101-A & SE-106, issued in July 19491.
Later it was adopted as a standard by the EIA (Elec-
tronic Industries Association), and today is covered
also by the National Electric Code (NEC)2.
Basics — What is “Constant” Anyway?
e term “constant-voltage” is quite misleading and
causes much confusion until understood. In electron-
ics, two terms exist to describe two very different
power sources: “constant-current” and “constant-volt-
age.” Constant-current is a power source that sup-
plies a fixed amount of current regardless of the load;
so the output voltage varies, but the current remains
constant. Constant-voltage is just the opposite: the
voltage stays constant regardless of the load; so the
output current varies but not the voltage. Applied to
distributed sound systems, the term is used to describe
the action of the system at full power only. is is the
key point in understanding. At full power the voltage on
the system is constant and does not vary as a function of
the number of loudspeakers driven, that is, you may add
or remove (subject to the maximum power limits) any
number of loudspeakers and the voltage will remain
the same, i.e., constant.
e other thing that is “constant” is the amplifier’s
output voltage at rated power – and it is the same volt-
age for all power ratings. Several voltages are used, but
the most common in the U.S. is 70.7 volts rms. e
standard specifies that all power amplifiers put out 70.7
volts at their rated power. So, whether it is a 100 watt,
or 500 watt or 10 watt power amplifier, the maximum
output voltage of each must be the same (constant)
value of 70.7 volts.

Constant-Voltage-3
8Ω
8Ω
POWER
(LOUDNESS)
TAPS
7O.7 V @
FULL POWER
AMP
AMP
IN
IN
AMP
8Ω
8Ω
7O.7 V @
FULL POWER POWER
(LOUDNESS)
TAPS
Figure 1. Low-Inpedance Series-Parallel 8Ω Direct Drive
Figure 2. 70.7V Transformer-Coupled
Constant-Voltage Distribution System
Figure 3. 70.7V Direct-Drive Constant-
Voltage Distribution System
IN
Z = 8
Ω
8 Ω
8 Ω
8 Ω
8 Ω
8 Ω
8 Ω
8 Ω
8 Ω
8 Ω
AMP
Figure 1 diagrams the alternative series-parallel
method, where, for example, nine loudspeakers are
wired such that the net impedance seen by the ampli-
fier is 8 ohms. e wiring must be selected sufficiently
large to drive this low-impedance value. Applying
constant-voltage principles results in Figure 2. Here is
seen an output transformer connected to the power
amplifier which steps-up the full-power output voltage
to a value of 70.7 volts (or 100 volts for Europe), then
each loudspeaker has integrally mounted step-down
transformers, converting the 70.7 volts to the correct
low-voltage (high current) level required by the actual
8 ohm speaker coil. It is common, although not univer-
sal, to find power (think loudness) taps at each speaker
driver. ese are used to allow different loudness levels
in different coverage zones. With this scheme, the wire
size is reduced considerably from that required in Fig-
ure 1 for the 70.7 volt connections.
Becoming more popular are various direct-drive
70.7 volt options as depicted in Figure 3. e output
transformer shown in Figure 2 is either mounted
directly onto (or inside of) the power amplifier, or it is
mounted externally. In either case, its necessity adds
cost, weight and bulk to the installation. An alternative
is the direct-drive approach, where the power amplifier
is designed from the get-go (I always wanted to use that
phrase, and I sincerely apologize to all non-American
readers from having done so) to put out 70.7 volts at
full power. An amplifier designed in this manner does
not have the current capacity to drive 8 ohm low-im-
pedance loads; instead it has the high voltage output
necessary for constant-voltage use — same power;
different priorities. Quite often direct-drive designs
use bridge techniques which is why two amplifier sec-
tions are shown, although single-ended designs exist.
e obvious advantage of direct-drive is that the cost,
weight and bulk of the output transformer are gone.
e one disadvantage is that also gone is the isola-
tion offered by a real transformer. Some installations
require this isolation.

Constant-Voltage-4
Voltage Variations — Make Up Your Mind
e particular number of 70.7 volts originally came
about from the second way that constant-voltage
distribution reduced costs: Back in the late ’40s, UL
safety code specified that all voltages above 100 volts
peak (“max open-circuit value”) created a “shock
hazard,” and subsequently must be placed in conduit
– expensive – bad. erefore working backward from a
maximum of 100 volts peak (conduit not required), you
get a maximum rms value of 70.7 volts (Vrms = 0.707
Vpeak). [It is common to see/hear/read “70.7 volts”
shortened to just “70 volts” – it’s sloppy; it’s wrong; but
it’s common – accept it.] In Europe, and now in the
U.S., 100 volts rms is popular. is allows use of even
smaller wire. Some large U.S. installations have used as
high as 210 volts rms, with wire runs of over one mile!
Remember: the higher the voltage, the lower the cur-
rent, the smaller the cable, the longer the line. [For the
very astute reader: e wire-gauge benefits of a reduc-
tion in current exceeds the power loss increases due
to the higher impedance caused by the smaller wire,
due to the current-squared nature of power.] In some
parts of the U.S., safety regulations regarding conduit
use became stricter, forcing distributed systems to
adopt a 25 volt rms standard. is saves conduit, but
adds considerable copper cost (lower voltage = higher
current = bigger wire), so its use is restricted to small
installations.
Figure 4. Transformer & Line Insertion Losses
Calculating Losses — Chasing Your Tail
As previously stated, modern constant-voltage am-
plifiers either integrate the step-up transformer into
the same chassis, or employ a high voltage design to
direct-drive the line. Similarly, constant-voltage loud-
speakers have the step-down transformers built-in as
diagrammed in Figures 2 and 3. e constant-voltage
concept specifies that amplifiers and loudspeakers need
only be rated in watts. For example, an amplifier is
rated for so many watts output at 70.7 volts, and a loud-
speaker is rated for so many watts input (producing a
certain SPL). Designing a system becomes a relatively
simple matter of selecting speakers that will achieve
the target SPL (quieter zones use lower wattage speak-
ers, or ones with taps, etc.), and then adding up the
total to obtain the required amplifier power.
For example, say you need (10) 25 watt, (5) 50 watt
and (15) 10 watt loudspeakers to create the coverage
and loudness required. Adding this up says you need
650 watts of amplifier power – simple enough – but
alas, life in audioland is never easy. Because of real-
world losses, you will need about 1000 watts!
Figure 4 shows the losses associated with each trans-
former in the system (another vote for direct-drive),
plus the very real problem of line-losses. Insertion loss
is the term used to describe the power dissipated or
lost due to heat and voltage-drops across the internal
transformer wiring. is lost power often is referred to
as I2R losses, since power (in watts) is current-squared
(abbreviated I2) times the wire resistance, R. is same
mechanism describes line-losses, since long lines add
substantial total resistance and can be a significant
source of power loss due to I2R effects. ese losses oc-
cur physically as heat along the length of the wire.
You can go to a lot of trouble to calculate and/or
measure each of these losses to determine exactly how
much power is required3, however there is a Catch-22
involved: Direct calculation turns out to be extremely
difficult and unreliable due to the lack of published in-
sertion loss information, thus measurement is the only
truly reliable source of data. e Catch-22 is that in
order to measure it, you must wait until you have built
it, but in order to build it, you must have your amplifi-
ers, which you cannot order until you measure it, after
you have built it!
e alternative is to apply a very seasoned rule of
thumb: Use 1.5 times the value found by summing all
of the loudspeaker powers. us for our example, 1.5
times 650 watts tells us we need 975 watts.
IN AMP
TRANSFORMER
INSERTION LOSS
(TIL) I
2
R LINE LOSS (TIL)

Constant-Voltage-5
Wire Size – How Big Is Big Enough?
Since the whole point of using constant-voltage dis-
tribution techniques is to optimize installation costs,
proper wire sizing becomes a major factor. Due to
wire resistance (usually expressed as ohms per foot, or
meter) there can be a great deal of engineering involved
to calculate the correct wire size. e major factors
considered are the maximum current flowing through
the wire, the distance covered by the wire, and the
resistance of the wire. e type of wire also must be
selected. Generally, constant-voltage wiring consists of
a twisted pair of solid or stranded conductors with or
without a jacket.
For those who like to keep it simple, the job is rela-
tively easy. For example, say the installation requires
delivering 1000 watts to 100 loudspeakers. Calculating
that 1000 watts at 70.7 volts is 14.14 amps, you then
select a wire gauge that will carry 14.14 amps (plus
some headroom for I2R wire losses) and wire up all 100
loudspeakers. is works, but it may be unnecessarily
expensive and wasteful.
Really meticulous calculators make the job of select-
ing wire size a lot more interesting. For the above ex-
ample, looked at another way, the task is not to deliver
1000 watts to 100 loudspeakers, but rather to distribute
10 watts each to 100 loudspeakers. ese are different
things. Wire size now becomes a function of the geom-
etry involved. For example, if all 100 loudspeakers are
connected up daisy-chain fashion in a continuous line,
then 14.14 amps flows to the first speaker where only
0.1414 amps are used to create the necessary 10 watts;
from here 14.00 amps flows on to the next speaker
where another 0.1414 amps are used; then 13.86 amps
continues on to the next loudspeaker, and so on, until
the final 0.1414 amps is delivered to the last speaker.
Well, obviously the wire size necessary to connect the
last speaker doesn’t need to be rated for 14.14 amps! For
this example, the fanatical installer would use a differ-
ent wire size for each speaker, narrowing the gauge as
he went. And the problem gets ever more complicated
if the speakers are arranged in an array of, say, 10 x 10,
for instance.
Luckily tables exist to make our lives easier. Some of
the most useful appear in Giddings3as Tables 14-1 and
Table 14-2 on pp. 332-333. ese provide cable lengths
and gauges for 0.5 dB and 1.5 dB power loss, along with
power, ohms, and current info. Great book. Table 1
above reproduces much of Gidding’s Table 14-24.
Table 1: 70.7V Loudspeaker Cable Lengths and Gauges for 1.5 dB Power Loss
Wire Gauge > 22 20 18 16 14 12 10 8
Max Current (A) > 5 7.5 10 13 15 20 30 45
Max Power (W) > 350 530 700 920 1060 1400 2100 3100
Load
Power
Load
Ohms Maximum Distance in Feet
1000 5 0 0 0 0 185 295 471 725
500 10 0 93 147 236 370 589 943 1450
400 12.5 0 116 184 295 462 736 1178 1813
250 20 117 186 295 471 739 1178 1885 2900
200 25 146 232 368 589 924 1473 2356 3625
150 33.3 194 309 490 785 1231 1962 3139 4829
100 50 292 464 736 1178 1848 2945 4713 7250
75 66.6 389 618 981 1569 2462 3923 6277 9657
60 83.3 486 774 1227 1963 3079 4907 7851 12079
50 100 584 929 1473 2356 3696 5891 9425 14500
40 125 729 1161 1841 2945 4620 7363 11781 18125
25 200 1167 1857 2945 4713 7392 11781 18850 29000

Constant-Voltage-6
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5000 TEL [phone] FAX [phone] WEB rane.com
DOC 103210 3-16
Rane Constant Voltage Transformers
Rane offers several models of constant-voltage trans-
formers. e design of each is a true transformer
with separate primary and secondary windings – not
a single-winding autotransformer as is sometimes
encountered.
MA3 Transformers
e MA3 had a design change in February 2007 affect-
ing whether the transformers are mounted internally
or externally.
For MA3 amplifiers manufactured after February
2007, use the MT 6 rack panel, which can hold up to six
transformers.
For MA3 amplifiers manufactured before Febru-
ary 2007, transformers are mounted internally. If you
aren't sure, the older MA3 has six transformer mount-
ing holes above the input jacks. TF 410 transformers
are sold individually for either rack-mounting or direct
mounting inside the MA3 chassis.
TF 410 rated 40 watts, 100 volts.
MT 4 Transformers
e MT 4 high performance toroidal transformers set
a new standard for wideband frequency response and
small size. MT 4 transformers come assembled in a 1U
rack-mount open tray chassis or individually as follows:
MT 4 Four channels: 100W, 100V or 70.7V (tapped sec).
TF 4 Rated 100W, 100V or 70.7V (tapped secondary).
KT 4 Open 1U tray chassis with connectors, mounts four TF 4
transformers.
Use MT 4 transformers with any standard power
amplifier and any combination of constant voltage
loads up to 100 watts to improve frequency response
and power handling. MT 4 transformers use premium
toroidal cores and windings to deliver excellent full-
power bass and a flat frequency response well above the
audio range. Distributions systems noticeably deliver
better audio fidelity. MT 4 transformers are also small-
er and lighter than other distribution transformers.
For 25 volt audio distribution, the TF 4 can be used by
connecting the 25V loads between its 70V and 100V taps.
See the MT 4 Multichannel Transformer Data Sheet.
References
1 Langford-Smith, F., Ed. Radiotron Designer’s Handbook, 4th
Ed. (RCA, 1953), p. 21.2.
2 Earley, Sheehan & Caloggero, Eds. National Electrical Code
Handbook, 5th Ed. (NFPA, 1999).
3 See: Giddings, Phillip Audio System Design and Installation
(Sams, 1990) for an excellent treatment of constant-volt-
age system designs criteria; also Davis, D. & C. Sound Sys-
tem Engineering, 2nd Ed. (Sams, 1987) provides a through
treatment of the potential interface problems.
4
Reproduced by permission of the author and Howard W. Sams & Co.
1234
RANE CORPORATION
MT 4
+
IN OUT
– 100V 70V COM +
IN OUT
– 100V 70V COM +
IN OUT
– 100V 70V COM +
IN OUT
IN OUT IN OUT IN OUT IN OUT
– 100V 70V COM
+– 100V 70V COM +– 100V 70V COM +– 100V 70V COM +– 100V 70V COM
MT 6 rack panel, rear view, with six transormers installed.