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AUD IOP R O AP- 3400 SERVICE M A NU A L
M10 12A THE INPUT BOARD
The inpu t board pro ces ses the audio signal from the input jac ks to the voltage amplifier board, (M1011A).
Each chann el consists of a ba lan ced gain stage , defeatable bass bo ost filter, and a preemph asis filter network.
The balanced input, (XLR Jack ) an d unbalanced input (phone jack ) are wired in parallel to the inpu t of a balanced
operational amplifier, (U1). T he g ain of this stage i s 1.6 (4dB) ba lanced and 1.6 (4dB) unbalan ced. Re sistors R1, R5
along with capacitors C1 and C2 form a radio interference elimination filter.
Switch S1 selects a flat or bass bo osted frequency respon se. The bass boo st filter provides a 20Hz high pass, high Q
filter response with a +4dB pea k at 55H z. Th e filter consists of a tee ne twork on the input of U1A along with R9, R10 ,
R11, C5 and C6. The gain is 1 (0dB ) in the pass band, (above 1 00Hz).
Ope rational amplifier U3B is a high pass shelving filter with a +2dB shelf above 20 KHz. This filter provides the p re-
emp hasis required to obtain a flat freq uen cy respon se (to 2 0KHz) on th e power amplifier output at full powe r.
M10 11A "VOLTAG E AMPLIF IERS AND SYST EM CONTRO L"
This board contains:
- Voltage amplifiers to drive the current amplifiers on the M1002A boa rds.
- The front panel volum e control circuitry.
- The EMS contr ol system with its assoc iated circuits: Pre clipping an d line curr ent sensing hea ter circu its.
- Clip a nd activity LED's. Driver circuit ry for the am plifier disable relay (used du ring amplifier turn on, turn off,
the rmal shutdown and curren t limiting).
Circuit Expla nation:
Refer to the sc hem atic of M 1011A as the section s of the circuit are explained.
The audio signa l enters the board from M101 2A through connector MS4. The two chann els are marked "L" and "R"
for left and right. The signals are to be considered as differential sources and therefore are marked as L+, L-,R+ a nd
R-. Since t he left channel has the same topology as the right channel we will only look at the left channel.
The signa l ("L+") at the terminal block (MS 4) passes through the fron t panel level control (P1) and t he de sired level
enters the inverting inp ut of U1.
Op am p U1 is an inverting amplifier wi th a set gain of 2.40 (7.6 dB). Bu ilt arou nd U1 is a du al purpo se circuit controlled
by a voltage divide r consisting of R15, R16, R17, R18 , R19, R20 and R21. Th e voltage divide r sets two refe rence
levels, (HDRM & CLP). Reference voltage levels vary wi th the voltage levels on the +/-14 4VDC supply rails. As the
amplifier?s outpu t is loaded, the supply rails voltage decreases and so do t he reference levels.
Trans istors Q1, Q3 the surrounding resistors prov ide a pre-clippin g function that trac ks the supply rails through the
HDRM volta ge referen ce and clips the audio sign al at appro ximately 11 .2V pk. The clip LED i ndicator circuit is
conne cted th rough D1 and D2 to th e ou tput of U1, The ba ses of Q2 and Q4 a re conne cted to the CLP referen ce
voltage, and when the peak outpu t voltage of U1 (+/-Vp) is enough to forward bias the transistor junctions, Q2 or Q4
will trigger the clip led circuit (Q 5), an d illuminate the clip LED.
The audio signal on the output of U1 enters U3 through R43 and RV1. Under no rmal ope rating condition s the gain of
U3 is 1(0dB). The signal then passes through U2 to the voltage amplifier.
The exclamation point within an equilatereal triangle is intended to aler t the user to the presence of impor tant operating and maintenance (servicing) instructions in the literature accompanying the appliance.
Le point dexclamation à lintérieur dun triangle équilatéral est prévu pour alerter lutilisateur de la présence dinstructions importantes dans la littérature accompag - nant lappareil en ce qui concerne lopération et la maintenance de cet appareil.
This lightning flash with arrowhead symbol, within an equilateral triangle, is intended to alert the user to the presence of uninsulated dangerous voltage within the products enclosure that may be of sufficient magnitude to constitute a risk of electric shock to persons.
Ce symbole déclair avec tête de flèche dans un triangle équilatéral est prévu pour alerter lutilisateur de la présence dun « voltage dangereux » non-isolé à proximité de lenceinte du produit qui pourrait être dampleur suffisante pour présenter un risque de choque électrique.
IMPORTANT SAFETY INSTRUCTIONS
safety-4v5.eps - April 3/2007
CAUTION : TO REDUCE THE RISK OF ELECTRIC SHOCK, DO NOT REMOVE COVER (OR BACK).
NO USER SERVICEABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED
SERVICE PERSONNEL.
FOLLOW ALL INSTRUCTIONS SUIVEZ TOUTES LES INSTRUCTIONS
Instructions pertaining to a risk of fire,
electric shock, or injury to a person
Read Instructions: The Owners Manual should be read and
understood before operation of your unit. Please, save these instruc -
tions for future reference and heed all warnings.
Clean only with dry cloth.
Packaging: Keep the box and packaging materials, in case the unit
needs to be returned for service.
Warning: To reduce the risk or fire or electric shock, do not expose
this apparatus to rain or moisture. Do not use this apparatus near water!
Warning: When using electric products, basic precautions should
always be followed, including the following:
Power SourcesYour unit should be connected to a power source only of the voltage specified in the owners manual or as marked on the unit. This unit has a polarized plug. Do not use with an extension cord or receptacle unless the plug can be fully inserted. Precau - tions should be taken so that the grounding scheme on the unit is not defeated.
HazardsDo not place this product on an unstable cart, stand, tripod, bracket or table. The product may fall, causing serious personal injury and serious damage to the product. Use only with cart, stand, tripod, bracket, or table recommended by the manufacturer or sold with the product. Follow the manufacturers instructions when installing the product and use mounting accessories recommended by the manufacturer.
The apparatus should not be exposed to dripping or splashing water; no objects filled with liquids should be placed on the apparatus.
Terminals marked with the lightning bolt are hazardous live; the external wiring connected to these terminals require installation by an instructed person or the use of ready made leads or cords.
Ensure that proper ventilation is provided around the appliance. Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus (including amplifiers) that produce heat.
No naked flame sources, such as lighted candles, should be placed on the apparatus.
Power CordDo 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 the third prong are provided for your safety. If the provided plug does not fit into your outlet, consult an electrician for replacement of the obsolete outlet. The AC supply cord should be routed so that it is unlikely that it will be damaged. If the AC supply cord is damaged DO NOT OPERATE THE UNIT.
Unplug this apparatus during lightning storms or when unused for long periods of time.
ServiceThe unit should be serviced only by qualified service personnel.
AVIS: AFIN DE REDUIRE LES RISQUE DE CHOC ELECTRIQUE, NENLEVEZ PAS LE COUVERT (OU LEPANNEAU ARRIERE) NE CONTIENT AUCUNE PIECE
REPARABLE PAR LUTILISATEUR.
CONSULTEZ UN TECHNICIEN QUALIFIE
POUR LENTRETIENT
Instructions relatives au risque de feu,
choc électrique, ou blessures aux personnes
Veuillez Lire le Manuel: Il contient des informations qui devraient
êtres comprises avant lopération de votre appareil. Conservez.
Gardez S.V.P. ces instructions pour consultations ultérieures et
observez tous les avertissements.
Nettoyez seulement avec le tissu sec.
Emballage: Conservez la boite au cas ou lappareil devait être
retourner pour réparation.
Avertissement: Pour réduire le risque de feu ou la décharge
électrique, n'exposez pas cet appareil à la pluie ou à l'humidité.
Nutilisez pas cet appareil près de leau!
Attention: Lors de lutilisation de produits électrique, assurez-vous
dadhérer à des précautions de bases incluant celle qui suivent:
AlimentationLappareil ne doit être branché quà une source dalimentation correspondant au voltage spécifié dans le manuel ou tel quindiqué sur lappareil. Cet appareil est équipé dune prise dalimentation polarisée. Ne pas utiliser cet appareil avec un cordon de raccordement à moins quil soit possible dinsérer complètement les trois lames. Des précautions doivent êtres prises afin deviter que le système de mise à la terre de lappareil ne soit désengagé.
RisqueNe pas placer cet appareil sur un chariot, un support, un trépied ou une table instables. Lappareil pourrait tomber et blesser quelquun ou subir des dommages importants. Utiliser seulement un chariot, un support, un trépied ou une table recommandés par le fabricant ou vendus avec le produit. Suivre les instructions du fabricant pour installer lappareil et utiliser les accessoires recommandés par le fabricant.
Il convient de ne pas placer sur lappareil de sources de flammes nues, telles que des bougies allumées.
Lappeil ne doit pas être exposé à des égouttements deau ou des éclaboussures et quaucun objet rempli de liquide tel que des vases ne doit être placé sur lappareil.
Assurez que lappareil est fourni de la propre ventilation. Ne procédez pas à linstallation près de source de chaleur tels que radiateurs, registre de chaleur, fours ou autres appareils (incluant les amplificateurs) qui produisent de la\
chaleur.
Les dispositifs marqués dune symbole déclair sont des parties dangereuses au toucher et que les câblages extérieurs connectés à ces dispositifs de connection extérieure doivent être effectivés par un opérateur formé ou en utilisant des cordons déjà préparés.
Cordon dAlimentationNe pas enlever le dispositif de sécurité sur la prise polarisée ou la prise avec tige de mise à la masse du cordon dalimentation. Une prise polarisée dispose de deux lames dont une plus large que lautre. Une prise avec tige de mise à la masse dispose de deux lames en plus dune troisième tige qui connecte à\
la masse. La lame plus large ou la tige de mise à la masse est prévu pour votre sécurité. La prise murale est désuète si elle nest pas conçue pour accepter ce ty\
pe de prise avec dispositif de sécurité. Dans ce cas, contactez un électricien pour faire remplacer la prise murale. Évitez dendommager le cordon dalimentation. NUTILISEZ PAS LAPPAREIL si le cordon dalimentation est endommagé.
Débranchez cet appareil durant les orages ou si inutilisé pendant de longues périodes.
ServiceConsultez un technicien qualifié pour lentretien de votre appareil.
S2125A
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2 VOLTAGE AMPLIFIER:
The voltage amplifier amplifies the audio signal?s voltage from 4.8 volts peak (at the output of U2) to approximently
97v peak which is required to drive the current amplifier board M1002A. M1002A provides the current required for the
97v peak signal to drive 1200 watts into 4 ohms out of the binding posts.
Before the circuit is described in detail here is a quick rundown on the signal?s path through the voltage amplifier
stage. Refer to the schematic of M1011A. Let's consider that a positive going AC signal is present @ test point 3. The
positive going signal will turn on the positive side of the voltage amplifier. The signal at test point 3 turns on Q12
(through R40, D14 and D13). The collector of Q12 pulls down on the base of Q14, turns this transistor on further and
allows a greater current to flow out of Q14?s collector. This increase in current passes through Q15 and it?s collector to
emitter voltage drop decreases. The collector of Q15 now being more positive in voltage turns the base of Q18 on
causing an increase in Q18?s collector current resulting in test point 5 going positive.
As the positive side of the amplifier was turning on the negative side would have been turning off. This is how test
point 5 was able to move positive following the input signal. The reverse would hold true if a negative going signal was
present on the input of the voltage amplifier.
CIRCUIT DESCRIPTION:
The voltage amplifier is a mirrored image with circuitry connected to the positive power supply rail being identical (but
opposite polarity) to the circuitry connected to the negative power supply rail.
For this reason we will look in detail at the positive side of the amplifier.
The audio signal enters the voltage amplifier at test point 3. The signal passes through R40, D14 and D13 to the base
of Q12. Diodes D13 and D14 set up the DC bias on Q12 to approximately 0.6 mA.
The first voltage gain stage consists of Q12 along with the resistor chain on its collector and the emitter resistor (R44).
Transistor Q12 drives the base of Q14 through the resistor chain. A DC current of approximately 6 mA should flow
through the collector of Q14. The voltage drop across Q14 remains constant and is derived from the voltage drop
across the voltage reference Q20, resistor R58, and the base/emitter junction of Q15. This total voltage should equal
approximately 3 VDC. Transistor Q14 is the second gain stage and its output current flows through Q15. Transistor
Q15 is a common base stage with the collector driving the base of output buffer Q18.
Diode D17 is a clamping diode that prevents the maximum peak of the audio signal from coming within 4V of the 144
VDC rail. This is to prevent the output current amplifier (board M1002A) from going into saturation during clipping and
therefore having storage delay problems.
Transistor Q18 buffers the high impedance present on the collector of Q15. The output of the buffer provides a low
output impedance at test point 5 and is current limited to 25mA through the clamping action of D19, D20 and D23.
The signal at TP-5 drives the current amp board M1002A.
DC offset on the amplifier?s output is corrected by operational amplifier U2. The DC offset forms a current through
R54, R14 and is blocked by C5 giving a DC offset correction gain of -1.
The activity L.E.D. function is a simple charge pump circuit with a transistor that redirects a constant current path
through the activity L.E.D.
3 SHUTDOWN CIRCUIT:
The last circuit on board M1011A is the shutdown relay and its associated drive circuitry. The relay circuit has two
possible operating states.
1.
Amplifier on under normal operating conditions.
2.
Amplifier power switch has just been turned OFF/ON or the amplfier is in current limit protecting the amplifier?s
output or the amplifier has overheated.
CIRCUIT DESCRIPTION
Here is how the circuit accomplishes these functions. The relay?s normally closed contacts short the output of the
voltage amplifiers to ground when the power switch is off. When the power switch is turned on, the relay remains off
(normally closed) for about 6 seconds. C52 charges to 35V and results in Q37 turning off allowing Q36 to turn on. As
Q36 turns on, it connects the negative terminal of the relay?s coil (Pin 16) to ground energizing the relay and opening
the normally closed contacts.
If prolonged current limiting occurs on the amplifier?s output transistors then D50 or D51 (depending on which channel
is current limiting) will be forward biased turning on Q38 (from its off state). Now +144VDC appears on the collector of
Q38 and through R130 and R128 turn on Q37 therefore turning off Q36 by shorting its base emitter junction. Q36
turning off will turn the relay off and the normally closed contacts (off state) will short the outputs of the voltage
amplifiers to ground so as not to continuously stress the amplifier?s output transistors. A cycle now occurs. With the
voltage amplifiers now disabled there is no signal driving the output transistors (Q14 to Q28) on board M1002A.
The current limit circuit on M1002A turns off and D50 and/or D51 are not forward biased and Q38 turns off. Through
Q37 and Q36 the relay is turned back on and the voltage amplifiers are now active again, driving the output
transistors. If current limiting still occurs, then the same cycle will occur. If the cause of current limiting (low impedance
or short on the speaker output terminals) has been removed, then the amplifier will continue to operate normally.
The third operation that the relay provides is "overheat shutdown". If for some reason the fan cannot keep the
heatsinks in a safe operating temperature area then the fan control circuit (on board M1013A) will deliver through the
"kill" signal line a positive current to turn Q37 on and turn Q36 off to turn off the relay and disable the voltage
amplifiers. When the temperature of the amplifier has been cooled down by the fan, then the kill signal will disappear
and the relay circuit will turn on the relay to resume normal operation. Anytime the relay is in the "protect" mode (due
to the abnormal states) then contact pin 8 of the relay will illuminate LD5 (the protect LED on the front panel).
M1002A CURRENT AMPLIFIER BOARD
The current amplifier board (M1002A) receives a high voltage audio signal from voltage amplifier board (M1011A) and
provides the current drive necessary to drive speaker cabinets.
The current amplifier is a two tier complimentary output driver design controlled by a complimentary mos-fet stage.
CIRCUIT DESCRIPTION - REFER TO THE SIMPLIFIED SCHEMATIC #1 ON THE FOLLOWING PAGE
