MULTICHANNEL
AMPLIFIER
MA3
MA3
dB
1
CONTENTS (in order of appearance)
Important Safety Instructions
MA3 Manual
MA3 Data Sheet
MT6 Data Sheet
Constant-Voltage Audio Distribution Systems
Sound System Interconnection
MA3 Schematics
Warranty
22472
CHANNEL OUTPUT HEADROOM
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12
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POWER
POWER
MULTICHANNEL AMPLIFIER
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 amplifiers) 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. The wide blade or third prong is provided for your safety. If the provided plug
does not fit 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 specified by Rane.
12. Use only with the cart, stand, tripod, bracket, or table specified 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 qualified 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. The 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. This 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
amplifiers) may cause an unacceptable amount of hum or may generate too much heat and degrade the performance of this apparatus.
19. This 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 fire or electric shock, do not expose this apparatus to rain or moisture. Apparatus shall not be exposed to dripping
or splashing and no objects filled with liquids, such as vases, shall be placed on the apparatus.
WARNING
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
ATTENTION: RISQUE DE CHOCS ELECTRIQUE - NE PAS OUVRIR
To reduce the risk of electrical shock, do not open the unit. No user
serviceable parts inside. Refer servicing to qualified service personnel.
The symbols shown below are internationally accepted symbols
that warn of potential hazards with electrical products.
This symbol indicates that a dangerous voltage
constituting a risk of electric shock is present
within this unit.
This symbol indicates that there are important
operating and maintenance instructions in the
literature accompanying this unit.
WARNING: This product may contain chemicals known to the State of California to cause cancer, or birth defects or other reproductive harm.
NOTE: This 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.
These limits are designed to provide reasonable protection against harmful interference in a residential installation. This 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 off 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 different from that to which the receiver is connected.
• Consult the dealer or an experienced radio/TV technician for help.
CAUTION: Changes or modifications not expressly approved by Rane Corporation could void the user's authority to operate the equipment.
CAN ICES-3 (B)/NMB-3(B)
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 chiffon doux.
7. N’obstruer aucune évacuation d’air. Effectuez 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 modifier 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 fil, 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 spécifiés 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 afin 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 qualifié pour tout service après vente. Celui-ci est nécessaire dans n’importe quel cas où l’appareil est abimé : si le
cordon ou les fiches 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 fiche 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 suffisant pour la ventilation. Vous pouvez disposer d’autres appareils au-dessus ou en-dessous de celuici, mais certains (tels que de gros amplificateurs) 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 fixation et sécurité.
ATTENTION: afin 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,…).
ATTENTION
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
ATTENTION: RISQUE DE CHOCS ELECTRIQUE - NE PAS OUVRIR
Afin d’éviter tout risque de choc électrique, ne pas ouvrir l’appareil.
Aucune pièce ne peut être changée par l’utilisateur. Contactez un
SAV qualifié 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.
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 différent de celui sur lequel le récepteur est branché.
• Consulter un revendeur ou un technicien radio / TV expérimenté.
ATTENTION: Les changements ou modifications 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.
OPERATORS MANUAL
MA3
MULTICHANNEL AMPLIFIER
1
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0
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6
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12
12
POWER
MA3
MULTICHANNEL
AMPLIFIER
12
dB
CHANNEL OUTPUT HEADROOM
POWER
Quick Start
Speaker Connection
Sure, you say, “it’s just a three channel amp, I'm in a hurry —
I don't need to read the manual.” But at least read this little section so you really know what to expect, and your installation can
go even faster.
Be sure the amplifier is off before making any connections.
Euroblocks make amplifier connection easy. They are just like
“snap on” terminal blocks that take up to 12 guage wire.
Driving the MA3 from a balanced source is recommended.
If you must drive the MA3 Input with an unbalanced source, we
recommend using a cable that has two conductors plus a shield,
and be sure to keep cable lengths as short as possible (under 10
feet [3 meters]). See the RaneNote, “Sound System Interconnection” (contained in this booklet).
Nominal speaker loads should be no lower than 4Ω per output. If you are running series or parallel combinations, be sure
and check your total load impedance.
For constant-voltage distribution, consider using the optional TF410 or TF407 transformers with the MT6 rack panel.
Transformers may be used on any number of output channels required, and one MT6 can be used with two MA3s. If you intend
to use constant-voltage distribution transformers, you may want
to read the RaneNote “Constant-Voltage Audio Distribution
Systems” (contained in this booklet).
If you are using small speakers that could overload with bass,
you may want to activate an internal 80 Hz Filter on each channel. The MA3 is shipped from the factory with the jumpers in
the “no filter” position, as shown in the diagram on page 4.
Once Input and Output connections are completed, be sure
all rear panel LEVEL controls are all the way counterclockwise.
Now flip the POWER switch on. After a couple of seconds,
slowly turn up each channels’ LEVEL control to the desired
gain. Maximum yields the most effective dynamic range control
for the built-in Limiter). If all is well, you will hear something
pleasant. If not, re-check connections, put on a better CD, and
read more of this manual.
To reduce the risk of fire, follow these instructions:
• Connect speaker wires with the amplifier off.
• Use approved Class 2 wiring to connect speakers to the output
terminals.
• The recommended wire gauge is 12-18 AWG.
• Do not use damaged wires, and protect wires from damage.
• Strip wire 0.25 inch (about 6.3 mm).
• Twist the strands together.
• Fully insert the wire into the Euroblock connector.
• Tighten the screw.
• Make certain there are no loose wire strands.
• Use speakers with a power rating equal to or greater than the
rating of the amplifier.
• Connection at the speaker depends on the type of connector.
Follow the instructions provided by the speaker manufacturer.
WEAR PARTS: This product contains no wear parts.
Manual-1
Front Panel Description
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POWER
MA3
MULTICHANNEL
AMPLIFIER
12
dB
1
CHANNEL OUTPUT HEADROOM
POWER
2
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4
1 Heat tunnel exhaust vents are located on the left of the unit. Large aperture vent slots are used for low noise. Air is taken in at
the back of the unit and exhausts out the front. When installed in a rack, make sure there is ample room for air to exit. The sealed
heat tunnel design does not require the use of an air filter.
2 CHANNEL OUTPUT HEADROOM meters indicate the amount of remaining headroom (how much more signal can be applied before Limiting occurs).
0 dB remaining is indicated by a red indicator. When lit, any additional signal causes the Limiter to operate. It is possible to “compress” the signal as much as 20 dB with very little effect on sound quality. This gives the MA3 the overload characteristics of a
much larger amplifier, without the use of external compressors. The MA3 was designed to be driven hard (heavily compressed
signal) so it is not necessary to buy extra power to obtain the headroom required to prevent overload.
3 dB remaining is indicated by a yellow indicator. When lit, 3 dB of additional signal may be applied before Limiting.
6 dB remaining is indicated by a green indicator. When lit, 6 dB of additional signal may be applied before Limiting.
12 dB remaining is indicated by a green indicator. When lit, 12 dB of additional signal may be applied before Limiting.
3 POWER: This yellow indicator lights when power is applied to the unit. See 4 below.
4 POWER switch: This control obediently turns the MA3 on and off every time you poke it with your finger. Poking the top half
of the switch turns the unit on when it is off. Poking the bottom portion of the switch turns the unit off when it it on. All three
channels have turn-on and turn-off muting to reduce switching transients.
Manual-2
Rear Panel Description
MA3
RANE CORPORATION
WARNING
TO REDUCE THE RISK OF FIRE OR ELECTRICAL SHOCK DO
NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE. DO
NOT REMOVE COVER. NO USER SERVICEABLE PARTS
INSIDE. REFER SERVICING TO QUALIFIED PERSONNEL.
OUTPUT POWER
PER CHANNEL
40 WATTS / 8Ω
60 WATTS / 4Ω
AVIS
RISQUE DE CHOC ELECTRIQUE — NE PAS OUVRIR
OUTPUTS
CLASS 2 WIRING
COMMERCIAL AUDIO
EQUIPMENT 24TJ
CH 3
CH 2
INPUTS
CH 1
CHANNEL 3
CHANNEL 2
CHANNEL 1
12-18 AWG
+ -
+ -
+ -
+ -
+ -
+ -
+ -
+ -
+ -
+ -
R
120 V
50/60 Hz 360 WATTS
4
0
3
10
LEVEL
0
+ -
10
LEVEL
0
+ -
1
10
LEVEL
2
5
1 INPUTS are balanced Euroblock connectors, one for each channel. We recommend the use of at least 18 AWG wire for reliability.
Driving the MA3 from a balanced source is recommended. If you must drive the MA3 Input with an unbalanced source, use a
cable that has two conductors plus a shield. Connect the (+) or “hot” source to the MA3 (+) Input, the ground to the MA3 (–)
Input and connect the shield to the MA3 shield input. Do not connect the shield on the source end. Shield connections go directly
to chassis ground and should not be used as signal ground. Shield connection to chassis occurs via the screw found between the
Input and Output connectors—keep this screw tight for improved EMI protection. When operating the MA3 with unbalanced
Inputs, be sure to keep cable lengths as short as possible. Refer to the RaneNote “Sound System Interconnection” (included in this
booklet) for additional information.
2 LEVEL controls adjust the input sensitivity for each of the three Amplifiers. The internal Limiters have maximum operating range
(most amount of limiting before input overload) when the LEVEL controls are set to maximum. For best system noise performance, the input sensitivity may be reduced to send a “hotter” signal to the Amplifier. Here we go again! You get nothing for free.
There are always tradeoffs to be made (better overdrive capability or lower system noise). The choice depends on your application.
For additional information see the RaneNote “Setting Sound System Level Controls” available in the Library on our website.
3 OUTPUTS: Connect the speaker(s) or transformer(s) to each of the three channels by means of the Euroblock connectors with 12
to 18 AWG wire. See Speaker Connection on page Manual-1.
4 IEC cord socket: This connector accepts a standard IEC 3-conductor line cord (included with 120V units). Plug this into a
grounded 3-prong AC outlet of 120 VAC (or 230 VAC if the MA3 is internally wired for 230V operation).
5 Heat tunnel air intake: The fan draws air in through the finger guard on the rear of the unit. The air flow is directed down a
sealed heat tunnel and exhausts through front panel vents. No filter is required as air flow is directed through an unobstructed
sealed tunnel and will not contaminate internal circuitry.
Manual-3
TF410 & TF407 Transformers
80 Hz Highpass Filters
The MT6 rack panel holds up to six transformers installed on the
back, in any combination. Transformers are sold individually:
Internal jumpers allow independently selecting 80 Hz,
2nd-order Butterworth Filters for each channel. These Filters are
useful when using small bookshelf speakers or small constantvoltage distribution transformers.
The MA3 is shipped from the factory with the jumpers in the
“no filter” position, as shown in the diagram below. Moving the
jumper to the other position activates the 80 Hz filter. This operation requires removing the top cover and should only be done
by qualified service personel with the unit unplugged.
• The TF407 is a 40W, 70.7 V transformer with 0.5 dB insertion
loss at rated power and a frequency response of 50 Hz to 15
kHz, ±1 dB.
• The TF410 is a 40W, 100 V transformer with 0.5 dB insertion
loss at rated power and a frequency response of 50 Hz to 15
kHz, ±1 dB.
1
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0
3
3
3
6
6
6
12
12
POWER
MA 3
MULTICHANNEL
AMPLIFIER
12
dB
CHANNEL OUTPUT HEADROOM
8Ω
8Ω
70 V
OR
ZONE 1
MONO
POWER
TF 410
EXPAND
OR
LEFT
RIGHT
1
ZONE 2
MONO
2
DISTRIBUTED
3
0
0
0
3
3
3
6
6
6
12
12
POWER
MA 3
MULTICHANNEL
AMPLIFIER
12
dB
CHANNEL OUTPUT HEADROOM
POWER
MT 6
MULTICHANNEL
TRANSFORMER
70 V
70 V
70 V
DISTRIBUTED
DISTRIBUTED
DISTRIBUTED
ZONE 1
ZONE 2
ZONE 3
The MA3 is shipped with the internal 80 Hz Highpass filters in the bypassed position.
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5000 TEL 425-355-6000 FAX 425-347-7757 WEB rane.com
Manual-4
DATA SHEET
MA3
MULTICHANNEL AMPLIFIER
General Description
The MA3 is a three-channel amplifier designed to operate reliably
in commercial environments. The MA3 was specifically designed
for use in:
• Paging
• Foreground Music
• Background Music Distribution
The MA3 is an ideal amplifier with Rane’s paging and music
products, the Rane CP52S, CP64S, CP66 and DA26S.
The MA3 uses a conventional linear power supply with a toroidal transformer. This configuration minimizes the emissions associated with switching supplies and noisier transformer designs.
The power supply features independent secondary supplies for each
channel, minimizing load regulation interaction and crosstalk.
Thermal management is accomplished with a sealed heat-tunnel design incorporating low velocity forced-air and large aperture
openings. This design minimizes the noise usually associated
with forced-air cooling and eliminates the need for an air filter.
Forced-air cooling allows the amplifier to operate reliably in harsh
environments and avoid the buildup of heat in unventilated racks
associated with passive convection cooling.
The combination of a solid, conservative power supply and
forced-air cooling allows the MA3 to simultaneously deliver 40
watts of continuous average power into 8Ω and 60 watts into 4Ω.
SPiKe®* dynamic protection circuitry completely safeguards
each channel against over-voltage, under-voltage, overloads,
transients from inductive loads, thermal runaway and instantaneous temperature peaks. Biasing is not allowed to occur when
an under-voltage condition exists, reducing turn on and turn off
transients.
Fast-response limiters allow the MA3 to tolerate up to 20 dB of
overdrive into 8Ω and 4Ω loads while holding THD below 1%.
This means no loss of speech intelligibility or harsh clipping. This
feature greatly increases the dynamic range of the system without
external limiters.
Peak-responding, load-adaptive meters accurately indicate the
remaining headroom. The meters are helpful in setting system
levels and indicating signal compression.
Balanced inputs with Euroblock connectors are provided. Euroblock output connectors to speakers accept up to 12 gauge wire.
Rear panel Level controls allow amplifier sensitivity adjustment.
Internally selectable 80 Hz highpass filters for each channel offer
protection against over excursion of small bookshelf speakers and
saturation of distribution transformers at low frequencies. These
filters are shipped in the “off” position from the factory.
Features
•
•
•
•
•
3 Independent Amplifiers
60W per Channel Continuous Average Power into 4Ω, 20-20k Hz
40W per Channel Continuous Average Power into 8Ω, 20-20k Hz
Load Sensitive Dynamic Limiters and Headroom Meters
SPiKe® Protection Circuitry
•
•
•
•
•
*SPiKe is a registered trademark of National Semiconductor Corporation.
High Capacity Linear Power Supply
Sealed Heat-Tunnel Forced Air Cooling
Input Level Controls (on rear panel)
80 Hz High-Pass Filter Selection
Euroblock Connectors
Data Sheet-1
MA3
MULTICHANNEL AMPLIFIER
Features and Specifications
Parameter
Input:
Impedance
Maximum Input Level
Sensitivity
CMR
Highpass Filter
Amplifier: Gain
Power Output
Frequency Response
S/N
Crosstalk
THD+N
Slew Rate
Damping Factor
On/Off Transient Muting
Fan Cooling
Fan Noise
Tunnel Power Dissipation
SOA
Limiter: Attack Time
Decay Time
Threshold
Action
Meter: Attack Time
Decay Time
Indicators
Power Supply: Type
..........Input
..........Consumption
..........Total Load & Unit
Unit: Conformity
..........Construction
..........Size
..........Weight
Shipping: Size
..........Weight
Specification
Euroblock Connector
20k
+20
Off to 0
40
80 Hz (factory default is “off”)
27
40/60
20 - 20k
90
-60
0.05%
0.1%
0.2%
10
80
Active
Active Constant-Current
45.2
120W; 410 Btu/hr
SPiKe*
10
3000
0.1% THD+N
1% THD+N
20
500
0, 3, 6 ,12
Linear; Toroidal Transformer
100 to 240 VAC
33.6W; 115 Btu/hr
360W; 1200 Btu/hr
FCC, CULUS
All Steel
3.5"H x 19"W x 9"D (2U)
26 lb
4.25" x 20.3" x 13.75"
30 lb
Limit
Units
Conditions/Comments
min.
min.
Ω
dBu
dBu
dB
Hz
dB
watts
Hz
dBr
dB
Each leg
min.
±2.5%
±0.5
min.
min.
max.
typ.
typ.
typ.
min.
min.
Input required for full power; 8Ω
20 Hz to 20 kHz
2nd-order butterworth
1 kHz
8/4 Ω cont. avg. power, all channels driven
+0, -.5 dB
re: 40W, 8Ω, A-weighted
1 kHz, 4Ω, all channels driven
1 kHz, 40 W, 8Ω, 80 kHz BW
1 kHz, 60 W, 4Ω, 80 kHz BW
20 Hz-20 kHz, 35W, 8Ω, 80 kHz BW
V/µs
dB
typ.
typ.
typ.
max.
typ.
typ.
+0, -2
ms
ms
±10%
VAC
ms
ms
dB
8Ω, 1 kHz
Drop out 85 VAC (120 VAC unit)
Sealed tunnel
A-weighted, 6 inches from front of fan grate
60W / channel; 4Ω load; all channels driven
Safe Operating Area
10 dB step
10 dB step
@1 kHz
15 dB overdrive (max. level) @ 1 kHz
10 dB step
10 dB step
20log (Vmax/Vout) or 10log (Pmax/Pout)
Independent secondaries for each channel
C14 inlet uses C13 cord
No load (idle)
60 W/channel; 4Ω load; all channels driven
(8.9 cm x 48.3 cm x 22.9 cm)
(11.8 kg)
(11 cm x 52 cm x 35 cm)
(13.6 kg)
Note: 0 dBu = 0.775 Vrms. *SPiKe is an acronym for Self Peak Instantaneous temperature (Ke) protection circuitry.
Data Sheet-2
MA3
MULTICHANNEL AMPLIFIER
Block Diagram
HEADROOM METER
0 dB
3 dB
6 dB
12 dB
CH 1 LEVEL
CH1 INPUT
VCA
OUT
CH 1 OUTPUT
AMP
IN
40 W/8 Ω
60 W/4 Ω
80 Hz HP
Channel 1 shown, other two channels are identical
MUTE
SERVO
LIMIT
Features
The good “SPiKe”
The power amplifiers in the MA3 are protected with National
Semiconductors’ proprietary SPiKe* protection circuitry. SPiKe
protection offers a level of protection not available in conventional amplifiers. It has the ability to instantaneously monitor the
THD+N(%) & LEVEL(W) vs AMPL(dBu)
31 MAR 98 08:52:13
60
55
1
50
ois
e
45
&N
D
35
TH
0.1
40
30
25
Output Power in Watts
2
er
No bad “spikes”
The MA3 is designed to operate without interruption of signal
with as little as 85 VAC available (120 VAC unit). Even if the
Amplifier is operating at full power, the signal will not breakup as
the AC line voltage drops to 85 VAC. If the AC line drops lower
than 85 VAC the signal mutes without “spikes.” Once AC power
is restored, the signal restarts quickly without “spikes” or signal
breakup.
It’s OK to light the 0 dB Headroom indicator a lot
The high-performance limiter used in the MA3 means all the
available power can be delivered to the load and not simply held
in reserve to avoid overload. There is no need to buy up to four
times the required power just to prevent occasional system overload. The MA3 can compress a signal with 9 dB of dynamic power
range down to a signal with 3 dB of dynamic power without loss
of speech intelligibility or excessive distortion.
With typical amplifiers, when 40 watts is needed to achieve
a required average SPL of 80 dB, the contractor must buy an
amplifier rated at no less than 160 watts just to maintain 6 dB
of headroom. The figure below illustrates the performance of the
MA3 limiter.
Pow
You won't hear the other Zones
The MA3 is designed to deliver foreground music, background
music and paging signals to three different Zones without annoying crosstalk. A quiet office, for example, with a paging signal
only, will not hear foreground music playing in the lounge. The
high capacity linear power supply incorporates three independent
secondary supplies with independent bridge rectifiers and filters.
The result is exceptionally good crosstalk figures even with multiple channels driving full power into 4Ω loads.
temperature of the power device die, yielding a level of reliability
not achievable with discrete designs.
THD & Noise in %
Built to be driven hard
The MA3 Amplifier drives all three channels at the continuous
average rated power, indefinitely. It is specifically designed to
operate in demanding commercial applications. Very low emissions allow the amplifier to operate in close proximity to signal
processing equipment without causing excessive interference. The
CP52S, CP64S, CP66 and DA26S may all operate next to the
MA3 in a rack. The high efficiency “heat tunnel” design allows
the amplifier to process severely compressed signals reliably even
when installed in a rack with elevated ambient temperatures.
Forced-air cooling keeps heat away from other equipment.
20
15
0.02
-5
0
5
10
15
10
20
Input Level in dBu
*Spike is a registered trademark of National Semiconductor Corporation.
SPiKe is an acronym for Self Peak Instantaneous (Ke) protection circuitry.
Data Sheet-3
MA3
MULTICHANNEL AMPLIFIER
Rear Panel
MT6 Transformer Panel
Architectural Specifications
Constant-voltage transformers may be purchased individually,
and up to six may be mounted in any combination on the back of
a 2U high MT6 rack panel:
• TF407 is a 40W, 70.7V Distribution Transformer
• TF410 is a 40W, 100V Distribution Transformer
Both transformers rated at 40 watts, 50 Hz to 15k Hz ±1 dB,
with 0.5 dB insertion loss. Each transformer comes with crimpon tabs, wire nuts, and mounting screws.
For applications, see the RaneNote “Constant-Voltage Audio
Distribution Systems: 25, 70.7 & 100 Volts.”
The MA3 shall be a three channel amplifier. It shall deliver
40 watts continuous average power into 8 ohms and 60 watts
continuous average power into 4 ohms. The amplifier shall have
balanced inputs with Euroblock connectors and Euroblock
output connectors capable of accepting 12 gauge wire. Input level
controls shall allow adjustment of input sensitivity. An internal
means of selecting 80 Hz highpass 2nd-order butterworth filters
shall be provided. Load sensitive limiter circuits shall expand the
dynamic range of the amplifiers and prevent clipping and the associated loss of speech intelligibility.
The power supply shall use a conventional linear supply with
means of operating from 120 VAC 50/60 Hz or 230 VAC 50
Hz. An IEC connector with integral fuse and IEC cord shall be
utilized. A front panel mounted power switch shall be provided
with a “power-on” indicator.
Thermal management shall employ forced air cooling, allowing
the amplifiers to operate reliable in unventilated racks at elevated
ambient temperatures. The design shall incorporate a sealed heat
tunnel with large aperture openings and low velocity air flow to
minimize noise and eliminate the need for air filtering and the
associated maintenance.
The design shall provide protection against overvoltage,
undervoltage, overloads, transients from inductive loads, thermal
runaway and instantaneous temperature peaks. Load sensitive
headroom meters shall provide indication of 0, 3, 6 and 12 dB of
remaining headroom.
The main chassis shall be constructed of 12 gauge, cold- rolled
steel capable of reliably supporting rack mount applications. The
unit shall be UL listed and cUL certified.
The unit shall be a Rane Corporation model MA3.
MT 6
MULTICHANNEL
TRANSFORMER
MT6 front panel
MT6 rear panel with six transformers installed.
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5000 USA TEL 425-355-6000 FAX 425-347-7757 WEB rane.com
Data Sheet-4
All features & specifications subject to change without notice. 11-2014
DATA SHEET
MT6
MULTICHANNEL TRANSFORMER KIT
MT 6
MULTICHANNEL
TRANSFORMER
Front Panel
General Description
The MT6 is simply a 2U rack panel that can mount up to six
distribution transformers for Rane MA3 amplifiers.
Constant-voltage transformers are purchased individually:
• TF407 is a 40W, 70.7V Distribution Transformer
• TF410 is a 40W, 100V Distribution Transformer
Both transformers rated at 40 watts, 50 Hz to 15k Hz ±1 dB,
with 0.5 dB insertion loss. The transformer wires have insulated
female tabs. To accomodate different installation preferences,
each transformer includes:
• Four insulated crimp-on male tabs
• Four wire nuts
• Two mounting screws and nuts for the MT6 plate.
For applications, see the RaneNote “Constant-Voltage Audio
Distribution Systems: 25, 70.7 & 100 Volts.” available at rane.
com.
Rear Panel
MT6 Specifications
Parameter
Unit: Panel Construction
..........Size: 2U
Shipping Weight
Specification
12 gauge steel
3.5"H x 19"W
3 lb
Limit
Units
Conditions/Comments
8.89 cm x 48.26 cm
1.36 kg
MT6
MULTICHANNEL TRANSFORMER KIT
BLACK
From amplifier outputs
BLACK
8Ω
70.7 VOLT LINE to loudspeakers
WHITE
RED
TF407 Specifications
Parameter
Transformer Rating
..........Connectors
..........Wire
Output Tap: Voltage
Frequency Response
Insertion Loss
Shipping Weight
Specification
40
0.187" Female Insulated Terminal
10" length
70.7
50 Hz to 15 kHz
.5
3 lb
Limit
±1
typ
inch
Vrms
dB
dB
Conditions/Comments
Maximum average power
Includes male tabs and wire nuts
U.L., C.S.A., 90C grade
8Ω
1.36 kg
BLACK
From amplifier outputs
Units
Watts
BLACK
8Ω
100 VOLT LINE to loudspeakers
WHITE
RED
TF410 Specifications
Parameter
Transformer Rating
..........Connectors
..........Wire
Output Tap: Voltage
Frequency Response
Insertion Loss
Shipping Weight
Specification
40
0.187" Female Insulated Terminal
10" length
100
50 Hz to 15 kHz
.5
3 lb
Limit
±1
typ
Units
Watts
inch
Vrms
dB
dB
Conditions/Comments
Maximum average power
May be removed to use wire nuts
U.L., C.S.A., 90C grade
8Ω
1.36 kg
WARNING: This product may contain chemicals known to the State of California to cause cancer, or birth defects or other reproductive harm.
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5000 USA TEL 425-355-6000 FAX 425-347-7757 WEB rane.com
All features & specifications subject to change without notice. PN 16910
RaneNote
UNWINDING DISTRIBUTION TRANSFORMERS
Unwinding Distribution
Transformers
• High Voltage Audio Distribution
• Transformers at the Power Amp End
• Turns Ratio
• Saturation
• Insertion Loss
• Transformers at the Loudspeaker End
• Impedance Matching
• Isolation
Paul Mathews
Rane Corporation
Introduction
What could be more mundane than the transformers and autoformers that are the backbone of audio
distribution systems? This article will show you that
there is a lot more going on with these chunks of iron
and copper than you ever suspected. Learn why transformers are often the power bottleneck in distribution systems, learn how to interpret datasheets, believe
or disbelieve manufacturers’ claims, how to specify HV
components, and how to setup HV systems to deliver
the best possible power, fidelity, and bandwidth.
High Voltage Audio Distribution Systems
Although the term Constant Voltage is still in common use, this article adopts the less confusing High
Voltage (HV) terminology. HV systems are in widespread use for these principal reasons:
• HV systems minimize power losses in low-cost
wiring.
• HV systems facilitate connection of multiple loudspeakers without careful consideration of impedance
matching.
• Once an individual power adjustment on a loudspeaker has been made, the loudspeaker continually
receives the same amount of power even when other
loudspeakers are added or removed from the system,
resulting in more constant and uniform coverage.
• Volume control by transformer tap at the loudspeaker end is more efficient than resistive pads.
RaneNote 159
© 2005 Rane Corporation
Distribution Transformers-
Transformers at the Power Amp End
Boosting the Output Voltage
Solid state power amplifiers usually need a voltage boost to get to the 70.7 volt and 100 volt levels of
most HV systems, and a transformer or autoformer
will do the job. The differences between transformers and autoformers will be covered later (see the To
Isolate or Not to Isolate? section). In the meantime, the
term transformer will be used to refer to both types.
The transformer boosts the amplifier output by a fixed
ratio, called its turns ratio. The correct transformer will
provide the right amount of boost, which is simply the
desired HV system voltage, e.g., 70.7 volts, divided by
the amplifier full power output voltage.
Here is the basic procedure for selecting an output
transformer for an HV system where the amplifier
power required P has been determined using suitable
methods:
1. Determine TURNS RATIO to get proper HV level.
a) Measure the unclipped rms output voltage available from the power amplifier or calculate if from
Ohm’s Law:
VOUT = √P x R
For example, for an amplifier rated 100 watts at 8Ω:
VOUT = 28.3 Vrms
b)Calculate desired voltage boost ratio, aka turns
ratio,
N = VHV / VOUT, e.g., N = 70.7 / 28.3 = 2.5
Select candidate transformers with turns ratio
within 20% of calculated N and with datasheet
power ratings similar to amplifier output wattage.
2. Determine TRANSFORMER SIZE to prevent saturation.
a) VERY IMPORTANT: Decide on the lowest system frequency fLC for good fidelity and full power
delivery.
b)Find datasheet ratings or conduct tests to determine voltage tolerance of candidate transformers at
fLC .
c) To qualify, a transformer must not saturate when
driven with VOUT at fLC . You may or may not be able
to determine this characteristic from datasheets.
Read on.
The low frequency voltage capabilities of the
transformer will be the primary limiting
factor in system power delivery.
Distribution Transformers-
TURNS RATIO: Finding It on the Datasheet
Turns ratio does not show up on many datasheets,
but you can usually calculate it from other specifications. From the information on a transformer datasheet, find any combination of specifications that
relates primary voltage, or primary power and impedance, to secondary voltage. Use these equations, based
on Ohm’s Law and Joule’s Law, to calculate the missing
specification.
VHV
VHV = N x VPA
N = ——
VPA = √P x R
VPA
For example, from transformer datasheet specs
showing “300 watts at 4Ω” (amplifier/primary side) and
“70.7V output” (secondary), use the first equation to
calculate power amp output voltage VPA = 34.6V. Then,
use the third equation to calculate
N = 2.04.
Some transformers have what their datasheets call
voltage taps. For example, a transformer might have 25
volt, 35 volt, and 45 volt primary taps, along with 70.7
volt and 100 volt secondary taps. For any combination
of primary and secondary taps, the effective turns ratio
is simply the ratio of the secondary tap value to the
primary tap value, as given in the third equation above.
Now that we have the Turns Ratio (Step 1 above),
let’s look at the other most important performance
determining characteristic, which is voltage capability,
usually determined by transformer size and weight.
SATURATION: What’s All the Flux About?
Transformers have saturation problems that limit
their capabilities at low frequencies. In fact, a transformer that is doing a great job at 100 Hz can be an
amplifier killer just an octave lower. What happens
when a distribution transformer saturates? What does
saturation sound like? Does this mean you have to high
pass all your HV systems? These and other questions
are answered here.
What Happens When a Transformer Saturates?
Transformers transfer power from winding to winding by coupling through mutual magnetic fields. This
transfer of power is amazingly efficient, and it happens
with or without a core. However, the iron core plays
two essential roles:
1. The core contains the magnetic fields. Without a
core, significant portions of the magnetic fields balloon out around the windings, reducing mutual coupling and potentially causing interference problems.
2. The magnetic field in the core itself opposes uncoupled current flow in the primary. This is why
the transformer primary, even though it is made
of heavy copper wire, does not normally act like a
short.
is what happens when the applied voltage polarity remains the same for too long.
Saturation has nothing to do with power delivery:
the onset of saturation depends only on the
voltage waveform applied to the primary.
To reinforce this point, the next graphic shows amplifier voltage and current with an unloaded (open circuit) secondary. The current waveform stays near zero
until the volt-seconds limit of the primary is reached.
Without a core, the primary does act like a short, and
a saturated core is not much better than no core.
For audio signals, core saturation is more likely as
you lower the frequency and raise the applied voltage.
In the preceding photo, the input was 20 Vrms at 25
Hz. The onset of saturation depends on voltage and
time, so expect to see a similar problem for 40 Vrms
and 50 Hz.
Here are the primary voltage (top) and current (bottom) oscilloscope traces for a distribution transformer
entering saturation toward the end of each half cycle
of input. Both waveforms should be sinusoidal, but
the spikes on the current waveform are due to saturation. Notice that the power amplifier, in this case, is
still doing a good job of delivering a sine wave, in spite
of the current spikes. A less-robust power amplifier
would show noticeable distortion coinciding with each
spike. The coupling between primary and secondary is
not much affected by core saturation. However, during
saturation, the dc resistance of the primary suddenly
appears in parallel. The power amplifier tries to maintain its output voltage, but the load impedance has
taken a sudden dive.
Core saturation happens when the magnetic field in
the core reaches its maximum possible density, which
The saturation voltage of a transformer rises
linearly with frequency. This means that
power handling capability declines with
the inverse square of the frequency.
It should be no surprise that DC voltages are a serious problem for transformers, since DC is like zero
frequency. Indeed, dc offsets of a few tens or hundreds
of millivolts can asymmetrically saturate a transformer, meaning that saturation current spikes will
occur primarily on one signal polarity. For this reason,
some power amplifiers are a poor match to distribution
transformers, This is also one reason why some manufacturers recommend installing resistors and capacitors in series with distribution transformers, further
impacting low frequency response. Well-designed
power amplifiers have low offsets, and well-designed
transformers tolerate a reasonable level of offset.
Distribution Transformers-
Size Matters
As with most things audio, you need larger components to handle lower frequencies, and the same is
true for transformers. If other design elements are held
constant, the larger cores can tolerate higher primary
voltage levels, because magnetic fields produce lower
flux densities over their larger cross-sectional areas.
Another way to improve the voltage capability of a
transformer is to increase the number of turns in each
winding. However, unless the wire size is made smaller
(resulting in higher resistive losses), the core may still
have to be made larger to accommodate the additional
turns of wire.
Many of the distribution transformers we tested would
have much improved performance if their designers
had simply added a few turns of wire to their design.
Where Does It Say Saturation on the Datasheet?
Unfortunately, most transformer datasheets are not
much help in providing specifications for low frequency performance. Some provide a vague ‘Frequency
Response’ range. Our tests indicate that this is usually hopelessly optimistic if not dishonest: the power
bandwidth at the low end is generally much lower than
the specification. Fortunately, since no secondary load
is required to observe saturation, bench measurements
are easy. Connect a sinewave source to the primary
with a small-value resistor in series. Measure the rms
voltage across the primary with a voltmeter or an
oscilloscope. Similarly measure the voltage across the
resistor. Start at 1 kHz and sweep downwards. Across
the resistor, you should measure a small voltage (proportional to primary current) that increases slowly as
you decrease frequency. At some frequency, you will
Distribution Transformers-
observe an abrupt increase in resistor voltage, indicative of the onset of saturation. Change the drive voltage and repeat the sweep. You should be able to derive
a graph like the one shown here. This particular ‘300
watt’ transformer has a datasheet indicating “Frequency Response: 20 Hz to 20 kHz.” How would you rate it?
"300 watt" Transformer Power Handling vs Frequency
1000
Power (W)
The Sound of Saturation
When power amplifiers suddenly finds itself having
to deliver massive amounts of current, most will protect themselves by throttling back their output voltage.
On the better amplifiers, Safe Operating Area (SOA)
circuitry kicks in. On less well-designed units, the
internal power supply voltages collapse, and the amplifier circuitry is simply unable to continue to deliver a
faithful signal. Some amplifiers may blow fuses or simply fail. The sound that you hear depends very much
on how a particular amplifier responds to this type of
overload. Most likely, you will hear badly distorted bass
and/or signal drop-outs.
100
10
20
70
Pmax for THD = 0.1%
120
Frequency (Hz)
170
220
Rated P
What About High Frequencies?
From the discussion about low frequencies and saturation, you have probably guessed that saturation is not
a problem at high frequencies. However, other non-ideal characteristics come into play. Stray magnetic fields,
uncoupled between primary and secondary, show up as
leakage inductance in series with the windings. Leakage inductance reduces the voltage available to the load
at higher frequencies. Core losses are another phenomenon affecting high frequencies. The better cores use
more expensive steels and thinner laminations. Datasheet specifications are reasonably reliable indicators of
high frequency performance.
Toroidal (at right in photo) types of transformers tend to have lower leakage inductance and better
high frequency performance than most E-core models
(at left in photo). However, excellent performance is
available from either type of core: it all depends on the
details of the design.
What About Insertion Loss?
Insertion loss seems to be a mandatory specification
for distribution transformers, although we find it difficult to understand why. Losses in loudspeakers themselves totally dominate most audio systems, and audio
power is easy to find and cheap to buy. It is almost
impossible to overheat even very lossy distribution
transformers with audio program material: there is just
too much iron, copper, and surface area in a transformer that is large enough to couple at low frequencies, and
average audio power is so much lower than the peaks
that the transformer must accommodate. Finally, the
winding resistance that causes insertion loss can be a
desirable feature, since it improves the transformer’s
tolerance for DC offsets.
Insertion loss is not useful as distribution
transformer specification. Instead, focus on the
a transformer’s ability to deliver power at the
highest and lowest required frequencies.
Transformers at the Loudspeaker End
On the secondary side of the power amplifier distribution transformer, we connect HV loudspeakers in
parallel (each with its own step-down transformer),
and adjust power taps as required to achieve required
loudness in each area. System designers usually specify
HV loudspeakers with integral transformers, so you
might suppose that the drivers and transformers are
well-matched, so why worry? It turns out that ten little
10 watt transformers in parallel can be just as troublesome as one big 100 watt transformer.
The transformer characteristics discussed
above apply equally at the loudspeaker end.
Loudspeaker Step-down Transformers and Saturation
The transformers at the loudspeaker end are prone to
saturation, just like their big cousins at the amplifier
end. Imagine the effect of 10 or more transformers
all reaching voltage saturation in parallel and at the
same time. Moreover, since saturation depends only
on voltage, each loudspeaker transformer should be
able to withstand full HV voltage levels at the lowest
system frequency, regardless of the amount of power
allocated to it. This is why most HV loudspeaker modules include a series capacitor to reduce the likelihood
of transformer saturation. Note, however, that these
capacitors are perfectly suited to carrying saturation
current spikes once those spikes begin to flow.
Is Impedance Matching Important?
For best results, adjust loudspeaker taps so that they
sum to either the power amplifier output rating or to
the power amplifier distribution transformer rating,
whichever is smaller. This will present the proper rated
load impedance to the power amplifier, allowing it
to develop rated power, while minimizing saturation
effects in the transformer at low frequencies.
If additional loudspeakers are added or power tap
settings are increased beyond the amplifier or transformer rating, load impedance for the power amplifier
will go down proportionately. However, a smaller but
still linear load impedance is usually the preferred alternative to a highly nonlinear saturating transformer.
To Isolate or Not to Isolate?
Distribution transformers are available in both autoformer (non-isolating) and transformer (isolating
configurations), so you have the option of isolating the
loudspeaker wiring from the amplifier wiring. Here’s a
couple of reasons why you might want to.
Safety Isolation
Distribution transformers can provide an additional
barrier between lethal mains power potentials and accessible loudspeaker terminals. HV lines from isolating transformers have no potential relationship with
respect to earth ground, so that shocks are unlikely
except in the event of contact with both lines at once.
Some electrical inspectors require that HV lines be
isolated from power amplifier outputs.
Isolation to Break Ground Loops
For the many types of audio equipment that have
shielding potentials connected to safety ground, nonisolated HV loudspeaker lines occasionally provide a
return path for ground loops with enormous extents.
In this era of plastic loudspeaker enclosures, this is
becoming more rare.
Distribution Transformers-
Summary
1. Selecting a Distribution Transformer at the Power Amp End:
a) Select proper turns ratio to boost to HV system level and to present an acceptable impedance to the power
amplifier. You may have to derive turns ratio from other specs.
b)Select for adequate low frequency voltage capability to prevent saturation for good low frequency power
transfer. You may have to make your own measurements.
c) Verify sufficiently low leakage inductance and low core losses for good high frequency power transfer. It’s
usually OK to use datasheet information.
2. Transformers at the Loudspeaker End:
a) Suffer from the same problems and can equally become the weak link in a system.
b)Are often ‘matched’ to and included with loudspeaker modules, so be aware of inherent characteristics.
3. Toroids versus E-cores: details are more important than shape.
4. Transformer isolation: can improve safety and eliminate ground loops.
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5098 USA TEL 425-355-6000 FAX 425-347-7757 WEB www.rane.com
Distribution Transformers-
DOC 108874
RaneNote
SOUND SYSTEM INTERCONNECTION
Sound System
Interconnection
• Cause & prevention of ground loops
• Interfacing balanced & unbalanced
• Proper pin connections and wiring
• Chassis ground vs. signal ground
• Ground lift switches
Rane Technical Staff
Introduction
This note, originally written in 1985, continues to be
one of our most useful references. It’s popularity stems
from the continual and perpetual difficulty of hooking
up audio equipment without suffering through all sorts
of bizarre noises, hums, buzzes, whistles, etc.— not to
mention the extreme financial, physical and psychological price. As technology progresses it is inevitable that
electronic equipment and its wiring should be subject
to constant improvement. Many things have improved
in the audio industry since 1985, but unfortunately
wiring isn’t one of them. However, finally the Audio
Engineering Society (AES) has issued a standards
document for interconnection of pro audio equipment. It is AES48, titled “AES48-2005: AES standard
on interconnections —Grounding and EMC practices
— Shields of connectors in audio equipment containing
active circuitry.”
Rane’s policy is to accommodate rather than dictate. However, this document contains suggestions for
external wiring changes that should ideally only be
implemented by trained technical personnel. Safety
regulations require that all original grounding means
provided from the factory be left intact for safe operation. No guarantee of responsibility for incidental
or consequential damages can be provided. (In other
words, don’t modify cables, or try your own version of
grounding unless you really understand exactly what
type of output and input you have to connect.)
RaneNote 110
© 1985, 1995, 2006, 2007, 2011 Rane Corporation
Interconnection-1
Ground Loops
Almost all cases of noise can be traced directly to
ground loops, grounding or lack thereof. It is important
to understand the mechanism that causes grounding
noise in order to effectively eliminate it. Each component of a sound system produces its own ground internally. This ground is usually called the audio signal
ground. Connecting devices together with the interconnecting cables can tie the signal grounds of the two
units together in one place through the conductors in
the cable. Ground loops occur when the grounds of the
two units are also tied together in another place: via
the third wire in the line cord, by tying the metal chassis together through the rack rails, etc. These situations
create a circuit through which current may flow in a
closed “loop” from one unit’s ground out to a second
unit and back to the first. It is not simply the presence
of this current that creates the hum—it is when this
current flows through a unit’s audio signal ground that
creates the hum. In fact, even without a ground loop, a
little noise current always flows through every interconnecting cable (i.e., it is impossible to eliminate these
currents entirely). The mere presence of this ground
loop current is no cause for alarm if your system uses
properly implemented and completely balanced interconnects, which are excellent at rejecting ground loop
and other noise currents. Balanced interconnect was
developed to be immune to these noise currents, which
can never be entirely eliminated. What makes a ground
loop current annoying is when the audio signal is affected. Unfortunately, many manufacturers of balanced
audio equipment design the internal grounding system
improperly, thus creating balanced equipment that is
not immune to the cabling’s noise currents. This is one
reason for the bad reputation sometimes given to balanced interconnect.
A second reason for balanced interconnect’s bad
reputation comes from those who think connecting
unbalanced equipment into “superior” balanced equipment should improve things. Sorry. Balanced interconnect is not compatible with unbalanced. The small
physical nature and short cable runs of completely
unbalanced systems (home audio) also contain these
ground loop noise currents. However, the currents in
unbalanced systems never get large enough to affect
the audio to the point where it is a nuisance. Mixing
balanced and unbalanced equipment, however, is an
entirely different story, since balanced and unbalanced
interconnect are truly not compatible. The rest of this
note shows several recommended implementations for
all of these interconnection schemes.
The potential or voltage which pushes these noise
currents through the circuit is developed between the
independent grounds of the two or more units in the
system. The impedance of this circuit is low, and even
though the voltage is low, the current is high, thanks to
Mr. Ohm, without whose help we wouldn’t have these
problems. It would take a very high resolution ohm
meter to measure the impedance of the steel chassis or
the rack rails. We’re talking thousandths of an ohm. So
trying to measure this stuff won’t necessarily help you.
We just thought we’d warn you.
BALANCED OUTPUTS
+
–
BALANCED INPUTS
RED
BLACK
SHIELD
+
RED
BLACK
SHIELD
2-CONDUCTOR SHIELDED CABLE
–
G
MALE
G
FEMALE
RED
2
BLACK
3 C 3
SHIELD
1
1
2
T
R
S
CHASSIS
GROUND
Interconnection-2
RED
BLACK
SHIELD
2-CONDUCTOR SHIELDED CABLE
RED
BLACK
SHIELD
2-CONDUCTOR SHIELDED CABLE
RED
BLACK
SHIELD
Figure 1a. The right way to do it.
MALE
2
1
3
FEMALE
2
C 3
1
T
R
S
CHASSIS SIGNAL
GROUND GROUND
The Absolute Best Right Way To Do It
The method specified by AES48 is to use balanced lines
and tie the cable shield to the metal chassis (right where
it enters the chassis) at both ends of the cable.
A balanced line requires three separate conductors, two of which are signal (+ and –) and one shield
(see Figure 1a). The shield serves to guard the sensitive
audio lines from interference. Only by using balanced
line interconnects can you guarantee (yes, guarantee)
hum-free results. Always use twisted pair cable. Chassis tying the shield at each end also guarantees the best
possible protection from RFI [radio frequency interference] and other noises [neon signs, lighting dimmers].
Neil Muncy1, an electroacoustic consultant and
seasoned veteran of years of successful system design,
chairs the AES Standards Committee (SC-05-05)
working on this subject. He tirelessly tours the world
giving seminars and dispensing information on how to
successfully hook-up pro audio equipment2. He makes
the simple point that it is absurd that you cannot go
out and buy pro audio equipment from several different
manufacturers, buy standard off-the-shelf cable assemblies, come home, hook it all up and have it work hum
and noise free. Plug and play. Sadly, almost never is
this the case, despite the science and rules of noise-free
interconnect known and documented for over 60 years
(see References for complete information).
It all boils down to using balanced lines, only balanced lines, and nothing but balanced lines. This is why
they were developed. Further, that you tie the shield to
the chassis, at the point it enters the chassis, and at both
ends of the cable (more on ‘both ends’ later).
Since standard XLR cables come with their shields
tied to pin 1 at each end (the shells are not tied, nor
need be), this means equipment using 3-pin, XLR-type
connectors must tie pin 1 to the chassis (usually called
chassis ground) — not the audio signal ground as is
most common.
Not using signal ground is the most radical departure from common pro-audio practice. Not that there
is any argument about its validity. There isn’t. This is
the right way to do it. So why doesn’t audio equipment
come wired this way? Well, some does, and since 1993,
more of it does. That’s when Rane started manufacturing some of its products with balanced inputs and
outputs tying pin 1 to chassis. So why doesn’t everyone
do it this way? Because life is messy, some things are
hard to change, and there will always be equipment in
use that was made before proper grounding practices
were in effect.
Unbalanced equipment is another problem: it is
everwhere, easily available and inexpensive. All those
RCA and ¼" TS connectors found on consumer equipment; effect-loops and insert-points on consoles; signal
processing boxes; semi-pro digital and analog tape
recorders; computer cards; mixing consoles; et cetera.
The next several pages give tips on how to successfully address hooking up unbalanced equipment.
Unbalanced equipment when “blindly” connected with
fully balanced units starts a pattern of hum and undesirable operation, requiring extra measures to correct
the situation.
The Next Best Right Way To Do It
The quickest, quietest and most foolproof method to
connect balanced and unbalanced is to transformer
isolate all unbalanced connections. See Figure 2.
Many manufacturers provide several tools for this
task, including Rane. Consult your audio dealer to explore the options available.
The goal of these adaptors is to allow the use of
standard cables. With these transformer isolation
boxes, modification of cable assemblies is unnecessary.
Virtually any two pieces of audio equipment can be
successfully interfaced without risk of unwanted hum
and noise.
UNBALANCED
COMMON (WRONG) PRACTICE
(+)
CASE
RECOMMENDED PRACTICE
2
2
3
(–)
3
1
CHASSIS
GROUND
(+)
CASE
OPTIONAL
(–)
NOT CONNECTED
AT CHASSIS
(PLASTIC JACK)
TRANSFORMER
1/4”
TIP-SLEEVE
1
SIGNAL
GROUND
CHASSIS
GROUND
CHASSIS
GROUND
Figure 1b. Recommmended practice.
BALANCED
2
3
1
EARTH GROUNDED
METAL ENCLOSURE
CASE LUG MAY
CONNECT TO
CHASSIS
(NOT REQUIRED)
CHASSIS IS
GROUNDED TO PIN 1
Figure 2. Transformer Isolation
Interconnection-3
Another way to create the necessary isolation is to
use a direct box. Originally named for its use to convert
the high impedance, high level output of an electric
guitar to the low impedance, low level input of a recording console, it allowed the player to plug “directly”
into the console. Now this term is commonly used to
describe any box used to convert unbalanced lines to
balanced lines.
The Last Best Right Way To Do It
If transformer isolation is not an option, special
cable assemblies are a last resort. The key here is to
prevent the shield currents from flowing into a unit
whose grounding scheme creates ground loops (hum)
in the audio path (i.e., most audio equipment).
It is true that connecting both ends of the shield is
theoretically the best way to interconnect equipment
–though this assumes the interconnected equipment is
internally grounded properly. Since most equipment is
not internally grounded properly, connecting both ends
of the shield is not often practiced, since doing so usually creates noisy interconnections.
A common solution to these noisy hum and buzz
problems involves disconnecting one end of the shield,
even though one can not buy off-the-shelf cables with
the shield disconnected at one end. The best end to disconnect is the receiving end. If one end of the shield is
disconnected, the noisy hum current stops flowing and
away goes the hum — but only at low frequencies. A
ground-sending-end-only shield connection minimizes
the possibility of high frequency (radio) interference
since it prevents the shield from acting as an antenna
to the next input. Many reduce this potential RF interference by providing an RF path through a small capacitor (0.1 or 0.01 microfarad ceramic disc) connected
from the lifted end of the shield to the chassis. (This is
referred to as the “hybrid shield termination” where the
sending end is bonded to the chassis and the receiving
end is capacitively coupled. See Neutrik’s EMC-XLR
for example.) The fact that many modern day installers still follow this one-end-only rule with consistent
success indicates this and other acceptable solutions to
FEMALE
2
C
3
1
RED
BLACK
SHIELD
RF issues exist, though the increasing use of digital and
wireless technology greatly increases the possibility of
future RF problems.
If you’ve truly isolated your hum problem to a specific unit, chances are, even though the documentation
indicates proper chassis grounded shields, the suspect
unit is not internally grounded properly. Here is where
special test cable assemblies, shown in Figure 3, really
come in handy. These assemblies allow you to connect
the shield to chassis ground at the point of entry, or to
pin 1, or to lift one end of the shield. The task becomes
more difficult when the unit you’ve isolated has multiple inputs and outputs. On a suspect unit with multiple
cables, try various configurations on each connection
to find out if special cable assemblies are needed at
more than one point.
See Figure 4 for suggested cable assemblies for your
particular interconnection needs. Find the appropriate output configuration (down the left side) and then
match this with the correct input configuration (across
the top of the page.) Then refer to the following pages
for a recommended wiring diagram.
Ground Lifts
Many units come equipped with ground lift switches.
In only a few cases can it be shown that a ground lift
switch improves ground related noise. (Has a ground
lift switch ever really worked for you?) In reality, the
presence of a ground lift switch greatly reduces a unit’s
ability to be “properly” grounded and therefore immune to ground loop hums and buzzes. Ground lifts
are simply another Band-Aid® to try in case of grounding problems. It is true that an entire system of properly grounded equipment, without ground lift switches,
is guaranteed (yes guaranteed) to be hum free. The
problem is most equipment is not (both internally and
externally, AC system wise) grounded properly.
Most units with ground lifts are shipped so the unit
is “grounded” — meaning the chassis is connected to
audio signal ground. (This should be the best and is
the “safest” position for a ground lift switch.) If after
hooking up your system it exhibits excessive hum or
2-CONDUCTOR SHIELDED CABLE
RED
BLACK
SHIELD
MALE
2
3
1
TEST
WIRE
Figure 3. Test cable
Interconnection-4
GROUND CLIP
buzzing, there is an incompatibility somewhere in the
system’s grounding configuration. In addition to these
special cable assemblies that may help, here are some
more things to try:
1. Try combinations of lifting grounds on units supplied with lift switches (or links). It is wise to do this
with the power off!
2. If you have an entirely balanced system, verify all
chassis are tied to a good earth ground, for safety’s
sake and hum protection. Completely unbalanced
systems never earth ground anything (except cable
TV, often a ground loop source). If you have a mixed
balanced and unbalanced system, do yourself a favor
and use isolation transformers or, if you can’t do
that, try the special cable assemblies described here
and expect it to take many hours to get things quiet.
May the Force be with you.
3. Balanced units with outboard power supplies (wall
warts or “bumps” in the line cord) do not ground the
chassis through the line cord. Make sure such units
are solidly grounded by tying the chassis to an earth
ground using a star washer for a reliable contact.
(Rane always provides this chassis point as an external screw with a toothed washer.) Any device with
a 3-prong AC plug, such as an amplifier, may serve
as an earth ground point. Rack rails may or may not
serve this purpose depending on screw locations and
paint jobs.
Floating, Pseudo, and Quasi-Balancing
During inspection, you may run across a ¼" output
called floating unbalanced, sometimes also called psuedo-balanced or quasi-balanced. In this configuration,
the sleeve of the output stage is not connected inside
the unit and the ring is connected (usually through a
small resistor) to the audio signal ground. This allows
the tip and ring to “appear” as an equal impedance,
not-quite balanced output stage, even though the output circuitry is unbalanced.
Floating unbalanced often works to drive either a
balanced or unbalanced input, depending if a TS or
TRS standard cable is plugged into it. When it hums, a
special cable is required. See drawings #11 and #12, and
do not make the cross-coupled modification of tying
the ring and sleeve together.
Winning the Wiring Wars
• Use balanced connections whenever possible, with
the shield bonded to the metal chassis at both ends.
• Transformer isolate all unbalanced connections
from balanced connections.
• Use special cable assemblies when unbalanced lines
cannot be transformer isolated.
• Any unbalanced cable must be kept under 10 feet
(3 m) in length. Lengths longer than this will amplify all the nasty side effects of unbalanced circuitry's
ground loops.
Summary
If you are unable to do things correctly (i.e. use fully
balanced wiring with shields tied to the chassis at both
ends, or transformer isolate all unbalanced signals
from balanced signals) then there is no guarantee that
a hum-free interconnect can be achieved, nor is there a
definite scheme that will assure noise-free operation in
all configurations.
References
1. Neil A. Muncy, “Noise Susceptibility in Analog and Digital Signal Processing Systems,” presented at the 97th AES
Convention of Audio Engineering Society in San Francisco, CA, Nov. 1994.
2. Grounding, Shielding, and Interconnections in Analog
& Digital Signal Processing Systems: Understanding the
Basics; Workshops designed and presented by Neil Muncy
and Cal Perkins, at the 97th AES Convention of Audio
Engineering Society in San Francisco, CA, Nov. 1994.
3. The entire June 1995 AES Journal, Vol. 43, No. 6, available
$6 members, $11 nonmembers from the Audio Engineering Society, 60 E. 42nd St., New York, NY, 10165-2520.
4. Phillip Giddings, Audio System Design and Installation
(SAMS, Indiana, 1990).
5. Ralph Morrison, Noise and Other Interfering Signals
(Wiley, New York, 1992).
6. Henry W. Ott, Noise Reduction Techniques in Electronic
Systems, 2nd Edition (Wiley, New York, 1988).
7. Cal Perkins, “Measurement Techniques for Debugging
Electronic Systems and Their Instrumentation,” The Proceedings of the 11th International AES Conference: Audio
Test & Measurement, Portland, OR, May 1992, pp. 82-92
(Audio Engineering Society, New York, 1992).
8. Macatee, RaneNote: “Grounding and Shielding Audio
Devices,” Rane Corporation, 1994.
9. Philip Giddings, “Grounding and Shielding for Sound and
Video,” S&VC, Sept. 20th, 1995.
10. AES48-2005: AES standard on interconnections —
Grounding and EMC practices — Shields of connectors
in audio equipment containing active circuitry (Audio
Engineering Society, New York, 2005).
Band-Aid is a registered trademark of Johnson & Johnson
Interconnection-5
To Input
CABLE
CONNECTORS
MALE
BALANCED XLR
FEMALE BALANCED XLR
(NOT A TRANSFORMER,
NOR A CROSS-COUPLED
OUTPUT STAGE)
From Output
FEMALE BALANCED XLR
(EITHER A TRANSFORMER
OR A CROSS-COUPLED
OUTPUT STAGE)
¼” BALANCED TRS
(NOT A TRANSFORMER,
NOR A CROSS-COUPLED
OUTPUT STAGE)
¼” BALANCED TRS
(EITHER A TRANSFORMER
OR A CROSS-COUPLED
OUTPUT STAGE)
¼” FLOATING UNBALANCED
TRS (TIP-RING-SLEEVE)
(SLEEVE IN UNIT = NC)
¼” OR 3.5 mm
UNBALANCED
TS (TIP-SLEEVE)
UNBALANCED RCA
(TIP-SLEEVE)
BALANCED
EUROBLOCK
¼" BALANCED
TRS (TIP-RING-SLEEVE)
¼" OR 3.5mm
UNBALANCED
TS (TIP-SLEEVE)
UNBALANCED RCA
1
2
3
4
1
2
5
6
B
B
BALANCED
EUROBLOCK
+ to +
– to –
SHIELD NC
+ to +
– to –
SHIELD NC
+ to +
– to –
7
8
9
10
7
8
11
12
21
22
11
12
GROUND to GROUND
13
14
15
16
23
17
18
19
20
23
+ to +
– to –
+ to +
– to –
24
+ to +
– to –
A
SHIELD ONLY
TO XLR PIN 1
A
SHIELD ONLY
TO TRS SLEEVE
B
A
A
24
B
A
A
SHIELD ONLY
TO EUROBLOCK
+ to +
– to –
SHIELD NC
+ to +
– to –
GROUND to GROUND
Figure 4. Interconnect chart for locating correct cable assemblies on the following pages.
Note: (A) This configuration uses an “off-the-shelf” cable.
Note: (B) This configuration causes a 6 dB signal loss. Compensate by “turning the system up” 6 dB.
Interconnection-6
2-CONDUCTOR SHIELDED CABLE
2
FEMALE
1=SHIELD
RED
2
2=RED
BLACK
C 3
3=BLACK
SHIELD
1
2-CONDUCTOR SHIELDED CABLE
3
FEMALE
1=SHIELD
RED
2
2=RED
C 3
B 3=NC
SHIELD
1
1-CONDUCTOR SHIELDED CABLE
4
FEMALE
1=SHIELD
RED
2
2=RED
C 3
B 3=NC
SHIELD
1
1-CONDUCTOR SHIELDED CABLE
From Output
5
6
FEMALE
1=SHIELD
RED
2
2-CONDUCTOR SHIELDED CABLE
2=RED
BLACK
C 3
3=BLACK
SHIELD
1
CROSS-COUPLED OUTPUT ONLY: CONNECT PIN 1 TO PIN 3 AT THIS END
AND SET GROUND LIFT SWITCH TO ‘GROUNDED’ (IF PRESENT).
7
RED
BLACK
SHIELD
2-CONDUCTOR SHIELDED CABLE
8
T=RED
R=BLACK
S=SHIELD
RED
BLACK
SHIELD
2-CONDUCTOR SHIELDED CABLE
9B
T=RED
R=NC
S=SHIELD
T=RED
10B R=NC
S=SHIELD
T=RED
R=BLACK
S=SHIELD
RED
1-CONDUCTOR SHIELDED CABLE
RED
SHIELD
RED
BLACK
SHIELD
1
3
1=NC
2=RED
3=BLACK
RED
T=RED
S=SHIELD
SHIELD
RED
T=RED
S=SHIELD
SHIELD
RED
BLACK
T=RED
S=BLACK
RED
BLACK
RED
BLACK
N/C
T=RED
S=BLACK
MALE
2
1
3
1=NC
2=RED
3=BLACK
RED
BLACK
N/C
T=RED
R=BLACK
S=NC
RED
T=RED
S=BLACK
RED
1-CONDUCTOR SHIELDED CABLE
2-CONDUCTOR SHIELDED CABLE
2
T=RED
R=BLACK
S=NC
SHIELD
SHIELD
MALE
RED
BLACK
N/C
FEMALE
1=SHIELD
RED
2
2-CONDUCTOR SHIELDED CABLE
BLACK
2=RED
C 3
SHIELD
3=BLACK
1
CROSS-COUPLED OUTPUT ONLY: CONNECT PIN 1 TO PIN 3 AT THIS END
AND SET GROUND LIFT SWITCH TO ‘GROUNDED’ (IF PRESENT).
T=RED
R=BLACK
S=SHIELD
11
RED
BLACK
N/C
SHIELD
RED
BLACK
To Input
1
FEMALE
1=SHIELD
RED
2
2=RED
BLACK
C 3
3=BLACK
SHIELD
1
T=RED
S=SHIELD
T=RED
S=BLACK
CROSS-COUPLED OUTPUT ONLY: CONNECT RING TO SLEEVE
AT THIS END AND SET GROUND LIFT SWITCH TO ‘GROUNDED’ (IF PRESENT).
12
T=RED
R=BLACK
S=SHIELD
RED
RED
2-CONDUCTOR SHIELDED CABLE
BLACK
BLACK
SHIELD
CROSS-COUPLED OUTPUT ONLY: CONNECT RING TO SLEEVE
AT THIS END AND SET GROUND LIFT SWITCH TO ‘GROUNDED’ (IF PRESENT).
T=RED
S=BLACK
Interconnection-7
From Output
14
RED
BLACK
N/C
2-CONDUCTOR SHIELDED CABLE
T=RED
S=BLACK
RED
BLACK
N/C
2-CONDUCTOR SHIELDED CABLE
15A
T=RED
S=SHIELD
16A
T=RED
S=SHIELD
17
18
T=RED
S=BLACK
T=RED
S=BLACK
19A
T=RED
S=SHIELD
20A
T=RED
S=SHIELD
RED
SHIELD
RED
SHIELD
RED
BLACK
1-CONDUCTOR SHIELDED CABLE
RED
1-CONDUCTOR SHIELDED CABLE
SHIELD
1=SHIELD
3 2=RED
3=BLACK
1
2
T=RED
R=BLACK
S=SHIELD
RED
T=RED
S=SHIELD
SHIELD
RED
1-CONDUCTOR SHIELDED CABLE
2-CONDUCTOR SHIELDED CABLE
MALE
RED
BLACK
SHIELD
T=RED
S=SHIELD
SHIELD
RED
BLACK
SHIELD
2-CONDUCTOR SHIELDED CABLE
RED
BLACK
MALE
2
1
3
RED
T=RED
S=SHIELD
RED
1-CONDUCTOR SHIELDED CABLE
SHIELD
T=RED
R=BLACK
A S=SHIELD
RED
BLACK
SHIELD
2-CONDUCTOR SHIELDED CABLE
22A
T=RED
R=BLACK
S=SHIELD
RED
BLACK
SHIELD
2-CONDUCTOR SHIELDED CABLE
23
(ANY UNBALANCED CONNECTOR)
RED
BLACK
T=RED
S=BLACK
2-CONDUCTOR SHIELDED CABLE
T=RED
S=SHIELD
SHIELD
RED
BLACK
SHIELD
RED
BLACK
SHIELD
1=SHIELD
2=RED
3=BLACK
T=RED
R=BLACK
S=SHIELD
RED
BLACK
SHIELD
SHIELD
RED
21
RED
BLACK
SHIELD
To Input
13
T=RED
S=BLACK
MALE
2
1
3
1=SHIELD
2=RED
3=BLACK
T=RED
R=BLACK
S=SHIELD
(CHECK: NO STANDARD POLARITY ON EUROBLOCKS)
RED
+
BLACK
SHIELD
–
(CHECK: NO STANDARD POLARITY ON EUROBLOCKS)
24
–
+
RED
BLACK
SHIELD
RED (ANY UNBALANCED CONNECTOR)
T=RED
BLACK
S=BLACK
CROSS-COUPLED OUTPUT ONLY: CONNECT BLACK TO SHIELD AT THIS END
AND SET GROUND LIFT SWITCH TO ‘GROUNDED’ (IF PRESENT).
2-CONDUCTOR SHIELDED CABLE
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5000 USA TEL 425-355-6000 FAX 425-347-7757 WEB www.rane.com
Interconnection-8
DOC 102907
Z1
220pF
Z2
220pF
Z3
220pF
Z4
220pF
R4
1.00k
R5
1.00k
R6
1.00k
R7
1.00k
C3
470pF
R8
9.09k
R9
9.09k
C1
R10
470pF 9.09k
C4
470pF
C2
R11
470pF 9.09k
R12
+15
10.0k
2
3
C9
47pF
47pF
C10
1
4580
U4A
1
4580
U2A
-15
R14
C5
47pF 10.0k
GND
R13
+15
10.0k
2
3
-15
R15
C6
47pF 10.0k
GND
C11
0.33
C13
R22
4.42k
R24
8.45k
GND
0.33
+15
5
6
Q5
2907A
Q6
2907A
47/16v
R27
10.0k
7
R1A
2kRD
J3
1
2
3
C21
7
SHIPPED
POSITION
R44
R46
511
R42
0.1
C25
U1B
5
C33
6
7
4580
U3B
7
4580
U5B
33.2k
47pF R52
R50 C34
51.1k
4
33.2k
47pF R51
6
5
5
GND
SSM2164
D1
4148
R1B
2kRD
1
+15
U1A
5
R2C
2kRD
GND
5
GND
R2B
2kRD
GND
-15
D2
4148
R1C
2kRD
GND
R48
U3A
4580
1
+15
100k
U5A
4580
C29
-15
22/16v
C30
22/16v
+15
100k
C31
470pF
GND
22/16v 33.2k
-15
100k
R36
7.50k
2
2
3
47/16v
+C23
C27
-15
22/16v
C28
22/16v
SSM2164
2
SHIPPED
POSITION
R45
GND
R34
51.1k
GND
R30
1.00k
R38
1.00k
GND
J4
1
2
3
C22
R47
511
C26
R41
1.00k
R49
C32
470pF
GND
22/16v 33.2k
-15
R43
0.1
R37
7.50k
2
100k
2
3
+C24
47/16v
R40
1.00k
GND
R35
51.1k
GND
R32
1.00k
R33 GND
1.00k
R39
1.00k
R31 GND
1.00k
7
R2A
2kRD
4580
U4B
47/16v
R26
10.0k
5
6
4580
U2B
Q1
2907A
Q7
2222A
C17
0.0082uF
R28
R16
5.11k C15 5.11k
Q2
2222A
R20
150
R17
10.0k
-15
R23
C14
R25
8.45k
4.42k
C12
0.33
GND
0.33
+15
R29
R18
5.11k C16 5.11k
Q3
2907A
Q8
2222A
C18
0.0082uF
Q4
2222A
R21
150
R19
10.0k
-15
GND
R53
1.00k
V1+
V1C37
3
LM3886
R63
30.1k
D3
RED
D4
RED
R64
30.1k
LM3886
3
Q11
2222A
100/50v
Q9
2222A
V2+
22.1k
R61
R59
2.00k
GND
GND
10
C35
U11
150pF 9
R55
51.1k
R57
4.42k
V1-
R54
1.00k
V2C38
Q12
2222A
100/50v
Q10
2222A
22.1k
R62
R60
2.00k
GND
GND
10
C36
U12
150pF 9
R56
51.1k
R58
4.42k
V2-
7
INPUT 1
2
J1
3pin EURO
1
+
3
H1
L-BKT
GND
INPUT 2
2
J2
3pin EURO
1
+
3
H2
L-BKT
GND
6/27/2007
C:\cad projects\MA3\110689-1.SchDoc
L1
0.7uH
R65
10.0 2W
LOCATE BY AMP
L2
0.7uH
R66
10.0 2W
LOCATE BY AMP
1
L3
Meter 1
R69
D5
511k
R71
R72
R76
6.04k
R75
60.4k
Meter V1+
R73
301k
R77
4.02k
R78
5.11k
R79
5.11k
R83
5.11k
R82
4.02k
R81
6.04k
R80
60.4k
Meter V2+
C45
0.1
Meter GND
Meter GND
C43
0.33
4148
2pin EURO
1
2
D6
511k
J5
R70
4148
R74
301k
Meter GND
C44
0.33
3.01k
2pin EURO
1
2
J6
R84
5.11k
1 of 2
SHEET:
11
10
9
8
7
U8D
U8C
U8B
U8A
13
14
LM339
LM339
1
LM339
2
LM339
Meter +15
6
5
4
Meter GND
C90
0.1
Meter +15
U9B
U9C
U9D
1
LM339
14
LM339
13
Meter GND
C46
0.1
11
10
9
8
7
U9A
2
LM339
Meter +15
6
5
4
LM339
Meter GND
Q13
2907A
R85
150
H7
D11
GRN
D10
GRN
D9
YEL
D8
RED
12
6
3
0
Vr
D13
YEL
D12
RED
6
3
0
Meter GND
R87
51.1k
Meter GND
Meter GND
Meter +15
D7
RED
D14
GRN
12
H8
D15
GRN
Vr
R86 Meter +15
150
Q14
2907A
110689
MA3 - CH 1 & CH 2
Meter GND
10802 47th Avenue West
Mukilteo WA 98275-5098
OUTPUT 2
GND
OUTPUT 1
3.01k
METER BOARD
3.3uH
R67
Meter 2
OUTPUT JACK
10.0 2W
C41
0.22
GND
LOCATE BY
2
L4
3.3uH
R68
10.0 2W
GND
CHECKED BY:
OUTPUT JACK
C42
0.22
LOCATE BY
GND
ACTION:
DRAWN BY:
3
5
8
5
8
12
3
12
1
4
1
4
1
8
+
7
4
6
4
6
+
6
3
16
9
8
4
8
4
1
3
1
3
+
+
8
4
8
4
R88
1.00k
C48
470pF
R91
9.09k
R93
10.0k
C52
47pF
1
C54
0.33
C56
R98
R99
8.45k
4.42k
0.33
5
6
7
4580
U6B
R3A
2kRD
J17
1
2
3
C60
15
SHIPPED
POSITION
R109
R110
511
C65
470pF
GND
22/16v 33.2k
-15
R108
C62
R111
7
100k
C63
22/16v
C64
22/16v
U1D
13
R3B
2kRD
C66
U7A
V3+
10
C73
U13
150pF 9
GND
V3C74
100/50v
3
D20
RED
L5
0.7uH
R119
10.0 2W
3
C19
0.1
C39
0.1
Meter 3
R121
D21
511k
R122
C84
0.1
R124
60.4k
Meter V3+
R123
301k
R125
6.04k
R126
4.02k
R127
5.11k
R128
5.11k
3
1
11
10
9
8
7
13
14
LM339
U10D
U10C
1
LM339
U10A
LM339
2
LM339
U10B
Meter +15
6
5
4
2
J29
1
Meter GND
1
3
J28
2
C86
0.1
C87
0.1
Q22
2907A
Meter 1
D28
GRN
D27
YEL
D26
RED
12
6
3
0
Meter GND
D29
GRN
PWR
Vr
D25
YEL
+15
BLK
RED
Meter GND
Meter GND
Meter GND
R131
Meter +15
150
Meter V1+
Meter 2
Meter +15
Meter V2+
Meter 3
Meter V3+
10/50v
+C88
-15
1
2
3
J30
2P EURO
4
10/50v
+C89
C91
10/50v
GND
10pin FEM HDR
10
9
8
7
6
5
4
3
4
5
6
7
8
9
10
D23
MBRS140T3
D22
MBRS140T3
10pin FEM HDR
V3+
3
V2+
2
+15
V1+
Meter GND
GND
GND
U14
7815
GND
1
I O
GND
GND
+
Q21
2SC4793
R130
6.34k
V1+
20.0
R129
D24
RED
GND
2 of 2
SHEET:
110689
MA3 - CH 3 & PWR SUPPLY
2 I O3
U15
7915
10802 47th Avenue West
Mukilteo WA 98275-5098
V1-
V1+
Meter GND
C85
0.33
3.01k
2pin EURO
OUTPUT 3
1
J27
+15
-15
GND
GND
C83
0.1
4148
METER BOARD
L6
3.3uH
R120
10.0 2W
C93
0.1
2
C75
0.1
C94
0.1
GND
C92
0.1
LOCATE BY
OUTPUT JACK
C51
0.1
C59
0.1
C99
0.1
V3+
C97
0.1
C100
0.1
V2+
C95
0.1
C98
0.1
V3-
H4
H10 H11 L-BKT
C96
0.1
V2-
H12 H9
V1-
V1+
C82
0.22
GND
C7
0.1
C40
0.1
LOCATE BY AMP
C101
0.1
C20
0.1
V1-
V1+
V2-
V2+
V3-
V3+
C8
0.1
4700/50v
+C81
+C80
4700/50v
4700/50v
+C79
4700/50v
+C78
4700/50v
+C77
+C76
4700/50v
C102
0.1
R118
30.1k
LM3886
Q20
2222A
GND
D19
RS402L
3
GND
D18
RS402L
3
GND
D17
RS402L
3
22.1k
R117
R116
2.00k
GND
Q19
2222A
C72 2
0.1
C69
0.1
C70 2
0.1
C67
0.1
C68 2
0.1
V3-
R115
4.42k
R114
51.1k
R113
1.00k
GND
GND
1
33.2k
+15
47pF R112
2
3
4580
-15
1
2 J23
1
2 J22
1
2 J21
1
2 J20
1
2 J19
1
2 J18
GND
R3C
2kRD
5
GND
SSM2164
D16
4148
RED
BLK
RED
YEL
BRN
BRN
ORG
4580
U7B
0.1
6
5
100k
R105
7.50k
2
GND
GND
+C61
47/16v
R102
R104
51.1k
1.00k
R106
1.00k
R103 GND
1.00k
R107
1.00k
GND
09408
WHT
GRY
BLU
5
8
+15
U6A
4580
GND
J11
1
2
1
2
1
2
1
2
GND
1
4
2
3
-15
+15
Q17
2907A
0.0082uF
R101
R95
5.11k C57 5.11k
Q15
2907A
Q18
2222A
C58
WHT
J12
47/16v
R100
10.0k
120V BLU
J13
1
2 J24
1
2 J25
1
2 J26
7
8
4
Z5
220pF
Z6
220pF
C47
R92
470pF 9.09k
C49 R94
47pF 10.0k
GND
Q16
2222A
R97
150
R96
10.0k
-15
BLK
FRONT
PANEL
SWITCH
BLK
C55
0.01
J14
GRY
ORG
120v/230v
YEL
14
INPUT 3
+
2
J7
3pin EURO
1
3
R89
1.00k
12
2
3
YEL
120V GRY
230V BLU
1
J15 2
1
J16 2
GND
CHECKED BY:
FFC
4
6
1
3
3
12
H3
L-BKT
U1C
GND
T1
+
230V GRY
C71
0.1
ACTION:
DRAWN BY:
2
1
10
1
4
C53
0.001
2
1
8
4
IEC GND IEC GND
C50
0.001
J10
SSM2164
5.0
R90
1.5mH
1
2
GND
IEC BOARD
120V
T 3.15A 250V
H6
230V
T 1.60A 250V
F3
H13
J9
+
1
4
1
4
1
4
J8
3
H
2
G
1
N
IEC PWR
H5
IEC GND
6/27/2007
C:\cad projects\MA3\110689-2.SchDoc
11
+
-
M FAN
Declaration of Conformity
Application of
Council directive(s):
Standard(s) to which
conformity is declared:
2002/96/EC
2004/108/EC
2011/65/EU
EN60065:2002 / A1:2006
EN55103-1:2009
EN55103-2:2009
EN50581:2012
ENVIRONMENT E2
SERIAL NUMBERS: 900000 - 999999
Manufacturer:
Rane Corporation
10802 47th Avenue West
Mukilteo WA 98275-5000 USA
This equipment has been tested and found to be in compliance with all applicable standards and regulations applying to the
Electromagnetic Compatibility (EMC) directive 2004/108/EC. In order for the customer to maintain compliance with this
regulation, high quality shielded cable must be used for interconnection to other equipment. Modification of the equipment,
other than that expressly outlined by the manufacturer, is not allowed under this directive. The user of this equipment shall
accept full responsibility for compliance with the EMC directive in the event that the equipment is modified without written consent of the manufacturer. This declaration of conformity is issued under the sole responsibility of Rane Corporation.
Type of Equipment: Professional Audio Signal Processing
Brand: Rane
Model: MA3
Immunity Results:
THD+N re: 5W/8Ω, 400 Hz sine, BW: 20-20 kHz, Baseline: -66 dBr
Test Description
RF Electromagnetic Fields Immunity
80 MHz -1000 MHz, 1 kHz AM, 80% depth, 3V/m
Conducted RF Disturbances Immunity
150 kHz - 80 MHz, 1 kHz AM, 80% depth, 3V RMS
150 kHz - 80 MHz, 1 kHz AM, 80% depth, 3V RMS
Magnetic Fields Immunity
50Hz - 10kHz, 4.0 - 0.4 A/m
Results
Conditions
< -66 dBr
< -50 dBr
80 Mhz -200 MHz
200-1000 Mhz
< -66 dBr
< -66 dBr
Power Lines
Signal Lines
< -66 dBr
50 Hz - 10 kHz
I, the undersigned, hereby declare that the equipment specified above conforms
to the Directive(s) and Standard(s) shown above.
(Signature)
Michaël Rollins
Compliance Engineer
(Full Name)
(Position)
March 19, 2007
Mukilteo WA USA
(Date)
(Place)
MA3
120 V
50/60 Hz 360 WATTS
MADE IN U.S.A.
RANE CORPORATION
R
COMMERCIAL AUDIO
EQUIPMENT 24TJ
AVIS
RISQUE DE CHOC ELECTRIQUE — NE PAS OUVRIR
WARNING
TO REDUCE THE RISK OF FIRE OR ELECTRICAL SHOCK DO
NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE. DO
NOT REMOVE COVER. NO USER SERVICEABLE PARTS
INSIDE. REFER SERVICING TO QUALIFIED PERSONNEL.
+ -
+ -
CH 3
+ -
+ -
12-18 AWG
CH 2
OUTPUTS
OUTPUT POWER
PER CHANNEL
40 WATTS / 8Ω
60 WATTS / 4Ω
+ -
+ -
CH 1
+ -
10
LEVEL
0
CHANNEL 3
+ -
CLASS 2 WIRING
+ -
+ 10
LEVEL
0
CHANNEL 2
INPUTS
+ -
+ 10
LEVEL
0
CHANNEL 1
MA3
MULTICHANNEL AMPLIFIER