9303 / 9505
®
Insta lla tion & Ope ra tion
®
MADE
IN THE
USA
nova
trans
PROFESSIONAL POWER AMPLIFIER
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P E R F O R MANC E S P E C IF IC ATIO NS
9303/9505
Full Power Bandwidth: 0.15Hz to 300kHz
Signal-to-Noise:
Slew Rate:
CMRR:
>100dB “A” Weighted
150 V/µs
75dB at 1kHz
+29dB max.
Gain:
9303
Power Rating:
Distortion:
150 wpc @8 Ω, 225 wpc @ 4Ω, 450 Watts mono @ 8Ω
0.07% THD 20-20Hz, Typically 0.005% THD 1kHz, at rated power into 8Ω
800 (to 1kHz); 80 (to 20kHz); 20 (to 100kHz) into 8Ω
Damping Factor:
Input Sensitivity Range: 1.22 Vrms for 150W into 8Ω, 1.06Vrms for 225W into 4Ω
Dimensions:
19"W x 12-1/2"D x 3-1/2"H (excluding feet)
36 lbs. (16.4kg)
Weight:
Power Consumption:
Quiescent, 84 VA; at rated power, 612 VA (150W into 8Ω, both channels driven)
9505
Power Rating:
Distortion:
250 wpc @8 Ω, 375 wpc @ 4Ω, 750 Watts mono @ 8Ω
0.1% THD 20-20Hz, Typically 0.005% THD 1kHz, at rated power into 8Ω
1000 (to 1kHz); 100 (to 20kHz); 20 (to 100kHz) into 8Ω
Damping Factor:
Input Sensitivity Range: 1.58 Vrms for 250W into 8Ω, 1.37Vrms for 375W into 4Ω
Dimensions:
19"W x 12-1/2"D x 5-1/4"H (excluding feet)
50 lbs. (22.7kg)
Weight:
Power Consumption:
Quiescent, 132 VA; at rated power, 1020 VA (250W into 8Ω, both channels driven)
– ii –
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T AB L E O F C O N T E N T S
SAFETY PRECAUTIONS ........................................................................................................................................... i
PERFORMANCE SPECIFICATIONS ......................................................................................................................... ii
INTRODUCTION ................................................................................................................................................... 1
INSTALLATION
Location ........................................................................................................................................................... 1
AC Line ............................................................................................................................................................ 1
Input................................................................................................................................................................. 2
Balanced Input: 1/4" Tip Ring Sleeve .......................................................................................................... 2
Balanced Input: XLR................................................................................................................................... 2
Unbalanced Input ...................................................................................................................................... 2
Unbalanced Source with Balanced Input ................................................................................................... 2
Output Connections ......................................................................................................................................... 2
Monophonic Use .............................................................................................................................................. 2
OPERATION
Power Switch ................................................................................................................................................... 3
Balanced/Unbalanced Input Switch .................................................................................................................. 3
Ground Switch ................................................................................................................................................. 3
Mono Switch .................................................................................................................................................... 3
Load Fault Protection ........................................................................................................................................ 3
Warm Up ......................................................................................................................................................... 3
Cleaning and Maintenance ............................................................................................................................... 3
Schematic Diagram .......................................................................................................................................... 4
PC Board Layout............................................................................................................................................... 6
Parts List ........................................................................................................................................................... 7
9303/9505 Functional Block Diagram .............................................................................................................. 8
TECHNICAL INFORMATION
Theory and Operation of trans• nova ................................................................................................................ 9
Circuit Implementation ..................................................................................................................................... 9
Calibration ..................................................................................................................................................... 10
Common Mode Rejection ........................................................................................................................ 10
Bias .......................................................................................................................................................... 10
WARRANTY ......................................................................................................................................................... 11
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I N T R O D U C T I O N
Th e Hafler 9303 an d 9505 are two ch an n el profession al power am plifiers. Passive coolin g with large h eatsin ks
is used for low m ech an ical n oise. Our paten ted tran s• n ova circuit topology an d MOSFET output stage en sures
trouble free, lon g term operation an d is backed by our seven year warran ty.
Th is m an ual con tain s in form ation on usin g th e 9303 an d 9505 am plifiers. It is organ ized in to th ree m ain
section s. “In stallation ” covers th e location an d con n ection of th e am plifier in th e system . Like m an y precision
com pon en ts careful atten tion to th e in itial setup can yield dividen ds in h igh er perform an ce an d trouble-free
use. “Operation ” covers th e con trols an d features of th e am plifiers an d h ow to use th em to get th e best effect.
Th e “Tech n ical In form ation ” section con tain s in form ation on th e circuit im plem en tation an d th e sch em atic
diagram an d parts list. We stron gly urge readin g over th e In stallation an d Operation portion s of th is m an ual
before puttin g th e am plifier in to service.
Th e circuitry used in th e 9303 an d 9505 is th e latest refin em en t of our tran s•n ova (TRANScon ductan ce NOdal
Voltage Am plifier, US Paten t 4,467,288) circuit. Th e 9303 an d 9505 utilize our proprietary DIABLO (paten t
application in progress) tran scon ductan ce driver stage wh ich com bin es th e lin earity of Class A operation with
th e curren t h eadroom of a Class B system . Wh en used in com bin ation with th e robust output stage used with
th ese m odels, DIABLO yields lower h igh frequen cy distortion with out th e son ic pen alties associated with
in creasin g th e n egative feedback.
Th e 9303 an d 9505 h ave fully differen tial in puts for use in balan ced lin e system s. Th e balan ced in put term in als
work with eith er 1/4" TRS ph on e or XLR plugs. Gold-plated RCA ph on o jacks are available for use with
un balan ced source com pon en ts. Th e output term in als are gold-plated bin din g posts, spaced on 3/4" cen ters
for use with dual ban an a plugs. For h igh power application s, th e am plifier can run in bridged m on o for double
th e output voltage. Usin g state-of-th e-art surface m oun t assem bly equipm en t in our m an ufacturin g facility
en sures con sisten cy an d reliability.
I N S T A L L A T I O N
LOCATION
Th e 9303 an d 9505 can produce con siderable h eat in n orm al operation so th e prim ary con sideration wh en
determ in in g a location for th e am plifiers is to allow for adequate ven tilation . Th e large h eatsin ks provide
un restricted airflow, but care m ust be taken to keep th e slots in th e bottom pan el an d top cover clear, as well.
If th e am plifier is m oun ted in an equipm en t rack, m ake sure adjacen t equipm en t does n ot im pede cool air flow
th rough th e am plifier bottom an d out th e top. Th e attach ed feet provide sufficien t clearan ce for th e bottom
wh en th e am plifier is restin g on a h ard surface. In adequate ven tilation can sh orten com pon en t life, especially
wh en oth er equipm en t raises th e am bien t air tem perature, so a circulatin g fan sh ould be con sidered in tigh t
quarters. Th e power tran sform er can gen erate a substan tial m agn etic field, so caution sh ould be exercised in
th e placem en t of low level com pon en ts such as a tape deck, m ixer or m ic pream p to avoid in ducin g n oise in
th e low level circuitry.
AC LINE
Th e 9303 an d 9505 operate from a 120 volt, 60Hz AC power lin e. Con n ection is m ade by an IEC Type 320,
groun ded lin e cord. For safety con sideration s on ly a properly groun ded (earth ed) receptacle sh ould be used.
If a groun ded circuit is n ot available do n ot break off th e groun d pin ; use th e proper adapter plug for a two wire
receptacle. Located in side th e am plifier is th e lin e fuse wh ich in terrupts th e power to th e am plifier. If th is fuse
blows replace it on ly with th e sam e type an d ratin g fuse. Th e correct replacem en t fuse value is in cluded in th e
parts list in th e “Tech n ical In form ation ” section of th is m an ual. If th e replacem en t fuse blows, th is is an
in dication of a fault with th e am plifier. Servicin g sh ould be perform ed on ly by a qualified tech n ician .
– 1 –
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INPUT
Th e 9303 an d 9505 h ave in put jacks for both balan ced an d un balan ced in put sign als. Th e un balan ced in puts
use con ven tion al RCA ph on o jacks. Wh en usin g th e RCA in puts, th e rear pan el BALANCED/UNBALANCED
switch m ust be set to th e UNBALANCED position . Th e balan ced in put jacks are dual fun ction con n ectors wh ich
accept 1/4" TRS (Rip Rin g Sleeve) ph on e or XLR plugs. Set th e BALANCED/UNBALANCED switch to th e
BALANCED Position to use th ese jacks. Th e con n ector pin -out is prin ted on th e rear pan el of th e am p.
Ba la n ced In put: 1/4" Tip Rin g Sleeve
Th e 1/4" balan ced in put jack is con n ected accordin g to con ven tion al usage with th e Tip h igh (+), Rin g
return (–) an d th e Sleeve groun d sh ield.
Ba la n ced In put: XLR
Th e XLR balan ced in put jack is con n ected accordin g to th e IEC In tern ation al Stan dard, with pin 2
h igh (+), pin 3 return (–) an d pin 1 groun d sh ield. Wh en preparin g to use th e am plifier, ch eck th e
output con figuration of th e source un it to m ain tain th e proper sign al polarity.
Un ba la n ced In put
Man y popular m ixers use un balan ced RCA ph on o jacks for th e m on itor outputs. For sh ort cable run s
RCA audio patch cable can be used with out an y system perform an ce pen alty. Ch eck th e m ixer specs
for th e m axim um cable len gth it will drive. Make sure th e BALANCED/UNBALANCED switch is set
for UNBALANCED operation .
Un ba la n ced Source with Ba la n ced In put
Better n oise rejection for lon g cable run s can be ach ieved by usin g a twisted pair balan ced cable from
th e un balan ced source. At th e source en d of th e cable, con n ect an RCA plug with th e return (–) wire
an d sh ield con n ected to th e groun d sh ell of th e plug. Wire th e plug at th e am plifier en d of th e cable
th e sam e as for th e regular balan ced in put con n ection .
OUTPUT CONNECTIONS
Th e speaker output con n ectors are dual bin din g posts. Th ese bin din g posts will directly accept 12 AWG wire
or ban an a plugs an d are spaced on 3/4" cen ters to accept dual ban an a plugs.
MONOPHONIC USE
For system s with h igh power requirem en ts, th e am plifiers can be con figured for sin gle ch an n el bridged m on o
operation . To bridge th e am plifier, set th e rear pan el STEREO/MONO switch to th e Mon o position ; use on ly
th e left ch an n el in put, an d con n ect th e speaker to th e red output bin din g posts. Wh en th e am plifier is bridged,
th e output is floatin g. An y speaker wh ich requires a com m on groun d from th e am plifier output can n ot be used
in th is application . Sin ce a bridged am plifier sh ares th e load between th e two ch an n els, th e am plifier will
effectively drive h alf of th e load. Th erefore, for bridged m on o operation we recom m en d usin g an eigh t oh m
load as th e m in im um im pedan ce.
– 2 –
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O P E R A T I O N
POWER SWITCH
Th e POWER switch is located on th e fron t pan el of th e am plifier. An in tern al lam p in dicates wh en it is turn ed
on . Stan dard practice is to turn th e am plifier on last an d off first wh en switch in g com pon en ts in dividually to
preven t sen din g dam agin g tran sien ts, gen erated in th e source com pon en ts, to th e speakers. It is possible to
leave th e power switch in th e on position an d switch th e am plifier rem otely th rough a power distribution
block or pream p switch ed outlet. Wh en doin g so m ake sure th e switch is rated for th e curren t required by th e
am plifier.
BALANCED/ UNBALANCED INPUT SWITCH
Th e BALANCED/UNBALANCED switch con figures th e in put groun din g wh en usin g th e RCA ph on o in put
jacks. In th e UNBALANCED position th e balan ced differen tial in put return (–) port is groun ded in side th e
am plifier. Th is preven ts n oise pickup or un stable am plifier operation caused by th e open in put. In th e
BALANCED position th e differen tial am plifier in puts are con n ected to th e h ot (+) an d (–) in com in g sign al
con n ectors.
GROUND SWITCH
Groun d loops are ch aracterized by a h um or buzz in th e system an d are caused by a voltage poten tial differen ce
between two poin ts in a groun d circuit. Groun d loops are aggravated wh en m ultiple path s exist for a given
circuit. Moun tin g com pon en ts in a rack with m etal rails m ay in troduce groun d loops between associated
equipm en t, because th e rails can establish an addition al groun d path . Th e CHASSIS/FLOAT switch allows you
to select th e am plifier groun din g sch em e for best system com patibility. With th e switch in th e CHASSIS
position all sign al groun ds are referred to th e ch assis an d power lin e groun d. In th e FLOAT position th e sign al
groun d is decoupled from th e ch assis. Th e position of th e switch is determ in ed by th e overall n oise in th e
system ; ch oose th e position wh ich gives th e lowest h um .
MONO SWITCH
Con ven tion al two-ch an n el stereo operation is obtain ed with th e STEREO/MONO switch in th e STEREO
position . For h igh powered sin gle ch an n el use, set th e switch to MONO an d use th e left ch an n el in put an d
th e RED bin din g posts on ly for th e output. For th erm al con sideration s we do n ot recom m en d usin g less th an
an eigh t oh m load on th e am plifier wh en run n in g it in m on o. Wh en th e switch is set in th e m on o position
th e left ch an n el (+) an d (–) in puts are con n ected to th e righ t ch an n el in reversed polarity, wh ich in verts th e
righ t ch an n el output.
LOAD FAULT PROTECTION
Because of th e self-protectin g properties an d fault toleran ce of th e lateral MOSFETs used in th e 9303 an d 9505,
elaborate voltage an d curren t lim itin g protection sch em es are n ot n ecessary. To preven t dam age to th e
am plifier from a fault in th e loudspeaker load, th e power supply B+ an d B– rails are fused. Ch eck th ese fuses
if th e soun d is garbled or th ere is n o output. Th e fuses sh ould n ot blow un der n orm al use an d a blown fuse
is usually an in dication of a fault. Th e fault could be a bad con n ection , a problem with th e speaker or a sh ort
in th e speaker lin e. Discon n ect power to th e am plifier before rem ovin g th e cover.
WARM UP
In order to ach ieve th e best son ic perform an ce from th e am plifier, we recom m en d lettin g it warm up for 1 h our
before begin n in g an y critical listen in g. Th e am plifier will n ot deliver its full poten tial soun d quality before th is
tim e h as passed.
CLEANING AND MAINTENANCE
Th ere is n o requirem en t for regular m ain ten an ce on th e electron ic com pon en ts of th e am plifier. If th e case
becom es soiled it can be clean ed usin g a soft cloth an d a m ild detergen t, such as spray win dow or glass clean er.
If th e am plifier is located in a particularly dusty en viron m en t clean in g th e in side with com pressed air or
vacuum in g every 18 to 24 m on th s is sufficien t.
– 3 –
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S C HE MATIC DIAG R AM
NOTES: Unless specified otherwise
1. All resistors in ohms
2. All capacitors in microfarads
3. Component Designators:
1-99:
Left Channel
101-199: Right Channel
201-299: Common Parts
301-399: Chassis/Power Supply
4. Left Channel Only Shown
5. Stereo/Mono Switch Shown in Stereo
6. Balanced/Unbalanced Switch Shown in Balanced Position
7. Chassis/Float Ground Switch Shown in Float Position
– 4 –
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– 5 –
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P C BO ARD LAYO UT
– 6 –
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P AR TS LI S T
DESIGNATOR VALUE
PART #
DESIGNATOR VALUE
PART #
ALL RESISTORS IN OHMS
R213
R214
R215
220, 1/4W, 5%
220, 1/4W, 5%
10k, 1/4W, 5%
RM/4-221C
RM/4-221C
RM/4-103C
R1, R101
R2, R102
R3, R103
R4, R104
R5, R105
R6, R106
R7, R107
R8, R108
R9, R109
R10, R110
R11, R111
R12, R112
R13, R113
R14, R114
R15, R115
R16, R116
R17, R117
R18, R118
R19, R119
R20, R120
R21, R121
R22, R122
R23, R123
R24, R124
R25, R125
R26, R126
R27, R127
R28, R128
R29, R129
R30, R130
R31, R131
R32, R132
R33, R133
R34, R134
R35, R135
R36, R136
R37, R137
R38, R138
R39, R139
R40, R140
R41, R141
R42, R142
R43, R143
R44, R144
R45, R145
R46, R146
R47, R147
R48, R148
R49, R149
R50, R150
R51, R151
R52, 152
R53, R153
R54, R154
R55, R155
R56, R156
R57, R157
R58, R158
R202
47.5k, 1/4W, 1%
47.5k, 1/4W, 1%
1k, 1/4W, 5%
1k, 1/4W, 5%
2.2M, 1/4W, 5%
100, 1/4W, 5%
22k, 1/4W, 5%
100, 1/4W, 5%
100, 1/4W, 5%
332, 1/4W, 1%
100, 1/4W, 5%
332, 1/4W, 1%
22.1, 1/4W, 1%
22.1, 1/4W, 1%
22.1, 1/4W, 1%
22.1, 1/4W, 1%
1k, 1/4W, 5%
28k, 1/4W, 1%
909, 1/4W, 1%
100, 1/4W, 5%
332, 1/4W, 1%
475, 1/4W, 1%
332, 1/4W, 1%
56, 1/4W, 5%
56, 1/4W, 5%
3.32k, 1/4W, 1%
2k, 1/4W, 5%
10k, 1/4W, 5%
100, 1/4W, 5%
1k, 1/4W, 5%
100, 1/4W, 5%
100, 1/4W, 5%
2k, 1/4W, 5%
1k, 1/4W, 5%
1k, 1/4W, 5%
1k, 1/4W, 5%
100, 1/4W, 5%
1k, 1/4W, 5%
100, 1/4W, 5%
28k, 1/4W, 5%
100, 1/4W, 5%
100, 1/4W, 5%
1k, 1/4W, 5%
47.5, 1/4W, 1%
1k, 1/4W, 5%
100, 1/4W, 5%
100, 1/4W, 5%
47.5, 1/4W, 1%
475, 1/4W, 1%
475, 1/4W, 1%
475, 1/4W, 1%
475, 1/4W, 1%
56.2k, 1/4W, 1%
220, 1/4W, 5%
220, 1/4W, 5%
220, 1/4W, 5%
220, 1/4W, 5%
0, 1/4W, 1%
RM/4-4752C
RM/4-4752C
RM/4-102C
RM/4-102C
RM/4-225C
RM/4-101C
RM/4-223C
RM/4-101C
RM/4-101C
RM/4-3320C
RM/4-101C
RM/4-3320C
RM/4-0221C
RM/4-0221C
RM/4-0221C
RM/4-0221C
RM/4-102C
RM/4-2802-03
RM/4-9090C
RM/4-101C
RM/4-3320C
RM/4-4750C
RM/4-3320C
RM/4-560C
RM/4-560C
RM/4-3321C
RM/4-202C
RM/4-103C
RM/4-101C
RM/4-102C
RM/4-101C
RM/4-101C
RM/4-202C
RM/4-102C
RM/4-102C
RM/4-102C
RM/4-101C
RM/4-102C
RM/4-101C
RM/2802-03
RM/4-101C
RM/4-101C
RM/4-102C
RM/4-0475C
RM/4-102C
RM/4-101C
RM/4-101C
RM/4-0475C
RM/4-4750C
RM/4-4750C
RM/4-4750C
RM/4-4750C
RMP/4-5622-03
RM/4-221C
RM/4-221C
RM/4-221C
RM/4-221C
RM/4-000C
RM/4-3921C
RM/4-3921C
RM/4-223C
RM/4-223C
RM/4-223C
RM/4-223C
RM/4-6043C
RM/4-474C
RM/4-102C
RM/4-102C
P1, P101
P2, P202
200, Trim Pot
200 Trim Pot
RVH-201
RVH-201
D1, D101
D2, D102
D3, D103
D4, D104
D5, D105
D6, D106
D7, D107
D201
BAV99L
BAV99L
BAV99L
BAV99L
BAV99L
BAV99L
BAV99L
1N5245B 15V
BAV99L
SS-260SM
SS-260SM
SS-260SM
SS-260SM
SS-260SM
SS-260SM
SS-260SM
SS-212
D202
D203
D204
SS-260SM
SS-212
SS-212
1N5245B 15V
1N5245B 15V
U1, U101
U9, U109
U201
U202
U203
NPDS5566
NPDS5566
TL072CD
LM337
SS-0865
SS-0865
SS-143SM
SS-240-056
SS-240-056
LM317
C1, C101
C2, C102
C3, C103
C4, C104
C5, C105
C6, C106
C7, C107
C8, C108
C9, C109
C10, C110
C11, C111
C12, C112
C13, C113
C14, C114
C15, C115
C16, C116
C17, C117
C18, C118
C19, C119
C20, C120
C21
C201, 202
C203
C204
C205
C206
C207
C208
C209
C210
330pF, 500V
330pF, 500V
0.47µF, 50V
0.1µF, 50V
CM-331-024
CM-331-024
CYV-474
CYV-104-024
CER-107C-024
CYV-104-024
CER-107C-024
CYV-104-024
CYV-104-024
CM-070-024
CM-101-024
CM-101-024
CYV-473-024
CM-220-024
CM-681-024
CM-470-024
CPP-475MC
CPP-475MC
CER-209E
100µF, 50V
0.1µF, 50V
100µF, 50V
0.1µF, 50V
0.1µF, 50V
7pF, 500V
100pF, 500V
100pF, 500V
0.047µF, 50V
22pF, 500V
680pF, 500V
47pF, 500V
4.7µF, 160V
4.7µF, 160V
20,000µF, 100V
20,000µF, 100V
0.01µF, 1000V
0.1µF, 50V
CER-209E
CD-103/20-024
CDS-104CCDB
CER-108C-024
CER-108C-024
CYV-104-024
CYV-104-024
CER-107C-024
CER-107C-024
CER-106C-024
CTR-475A-024
CTR-475A-024
CD-103A-024
1000µF, 50V
1000µF, 50V
0.1µF, 50V
0.1µF, 50V
100µF, 50V
100µF, 50V
10µF, 50V
4.7µF, 160V
4.7µF, 160V
0.01µF, 1600V
C211
C215
SW1
SW2
SW3
DPDT Switch
DPDT Switch
DPDT Switch
SW-0280
SW-0280
SW-0280
3.92k, 1/4W, 1%
3.92k, 1/4W, 1%
22k, 1/4W, 1%
22k, 1/4W, 1%
22k, 1/4W, 1%
22k, 1/4W, 1%
604k, 1/4W, 1%
470k, 1/4W, 4%
1k, 1/4W, 5%
1k, 1/4W, 5%
R203
R205
R206
R207
R208
R209
R210
R211
S201
Power Switch
Inrush Limiter
SWH-152B
SSH-618
TS-201
Q2, Q102
Q3, Q103
Q4, Q104
Q5, Q105
Q6, Q106
Q7, Q107
MMBT5088L
MMBT5088L
MMBT5088L
MMBT5087L
MMBT5088L
MMBT5087L
SS-0114
SS-0114
SS-0114
SS-0115
SS-0114
SS-0115
R212
– 7 –
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DESIGNATOR VALUE
PART #
SS-0115
SS-0114
SS-0115
SS-0114
SS-0115
SS-101A
SS-101A
SS-102A
SS-102A
SSH-741T
SSH-741T
SSH-741T
SSH-741T
SSH-740T
SSH-740T
SSH-740T
SSH-740T
SS-0115
DESIGNATOR VALUE
PART #
SS-222
SSH-609
SSH-609
Q8, Q108
Q10, Q110
Q11, Q111
Q12, Q112
Q13, Q113
Q14, Q114
Q15, Q115
Q16, Q116
Q17, Q117
Q45, Q145
Q46 Q146
Q47, Q147
Q48, Q148
Q49, Q149
Q50, Q150
Q51, Q151
Q52, Q152
Q201
MMBT5087L
BR201
BR301
BR-302
Bridge Rectifier
Bridge Rectifier
Bridge Rectifier
MMBT5088L
MMBT5087L
MMBT5088L
MMBT5087L
MPS-A56
MPS-A56
MPS-A06
MPS-A06
2SK1058
2SK1058
2SK1058
2SK1058
2SJ162
2SJ162
2SJ162
2SJ162
MMBT5087L
MMBT5088L
MMBT5088L
IEC Connector
IEC Line Cord
Dual Binding Post
MOSFET Insulator
CC-0918
FA-0209
CC-0867
HWH-442
9303 Differences
IEC Line Cord
FAH-146
C19, C119
C20, C120
15000µf, 75V
15000µf, 75V
CER-159ES
CER-159ES
F201
10A, Slo/Blo
FS-010SM
Q202
Q203
SS-0114
SS-0114
Not Used
2SK/1058
2SJ/162
Q47, Q147
Q50, Q150
F1, F101
F2, F102
F201
AGC 10A Fuse
AGC 10A Fuse
15A Slo/Blo
FS-010
FS-010
FS-015SB
FS-0390
F203, F204
2.5A Fast Mini
9303 / 9505 FUNCTIONAL BLOCK DIAGRAM
SERVO
INTEGRATOR
(+)
(+) BUFFER
(+)
LEFT INPUT
(–)
LEFT CH.
LEFT
AMPLIFIER
OUTPUT
(–)
(–) BUFFER
BALANCED/
UNBALANCED
SWITCH
SERVO
INTEGRATOR
(+)
(+) BUFFER
(+)
RIGHT INPUT
(–)
RIGHT CH.
AMPLIFIER
RIGHT
OUTPUT
(–)
(–) BUFFER
STEREO/MONO
SWITCH
RIGHT CH.
LEFT CH.
HIGH VOLTAGE
POWER
SOFT
TURN ON/OFF
SYSTEM
HIGH VOLTAGE
POWER
LOW VOLTAGE
POWER SUPPLY
SUPPLY
SUPPLY
– 8 –
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TE C HNIC AL RE F E R E NC E
THEORY AND OPERATION OF trans• nova
The (TRANSconductance NOdal Voltage Amplifier) principle is based on our 1984 U.S. Patent 4,467,288. This patent
describes the advantages of audio power amplifiers in which a MOSFET output stage is connected in a grounded source
configuration. In this connection the output stage has its full voltage gain of typically 20dB (ten times), instead of the
usual 1dB loss of voltage follower designs.
It is an inevitable result of electrical physics that this output with gain inherently increases the power gain (for the same
bandwidth) of the output stage by typically ten times over the conventional follower connection, using exactly the same
MOSFET devices.
The output stage is thus now ten times less wasteful of its incoming drive power. The driver stage can now be of a low
voltage (±24 volts) nature and be designed along the same principles always used in high quality preamplifiers: Class
A operation, high linearity, and wide bandwidth. A topology utilizing an output stage with gain yields a much simpler,
shorter total signal path than that of the usual high voltage driver designs. The number of serial stages is reduced from
five or more, to only three.
But all of the above does not make an amplifier trans• nova. The output stage is further refined into a trans-impedance
stage (current-to-voltage converter), to achieve extremely short loop (fast) negative feedback. The output stage is driven
cooperatively by a transconductance stage (voltage-to-current converter).
The 9303and 9505are the most sophisticated amplifiers we have yet developed utilizing the basic trans• nova principle.
And, although the measured specifications are very good, the numbers do not describe the realistic sound of the
amplifiers.
CIRCUIT IMPLEMENTATION
Earlier models of amplifiers we have offered using the trans• nova topology have earned the reputation for clean, natural
sounding reproduction. A conservative, purist design approach was used to avoid compromising the desirable
characteristics of the trans• nova circuits. Circuit innovation was not prevented by this conservatism; as is evident in the
discoverieswhich resulted in developmentofthe DIABLO circuitryto be discussed shortly, and the novelbalanced input
system.
Many “balanced” amplifiers are merely conventional unbalanced designs with a Balanced-to-Unbalanced converter
(usuallyICop-amp based)precedingthe poweramplifier. The 9303 and 9505, however, are true differentialinputpower
amplifiers. Each (+) and (–) input port has been buffered to allow direct signal access to the differential amplifier, without
conversion to unbalanced form. Deactivating the Balanced Mode is accomplished via a rear panel switch that grounds
the (–) inputs, effectively converting the amplifier to unbalanced operation.
The input stage is a JFET differential amplifier. This circuit configuration results in excellent front end headroom and
extremely low intermodulation effects. The ultra low noise characteristic of the JFETs virtually eliminates noise “mixing”
(intermodulation) with the music signal, reducing discordant product frequencies known as “noise grain” or “noise
fuzz.” A servo integrator has been employed to establish minimal DC offset. This circuit monitors the DC offset at the
output of the amplifier, and injects an equal but opposite DC voltage into the (+) port of the differential input, thereby
cancelling the offset. This method eliminates the need for a sonically degrading electrolytic capacitor in the audio path,
and provides superior subsonic frequency response.
– 9 –
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The final output stage utilizes lateral MOSFETs; four pairs are used for each channel in the 9505 and three pairs in the
9303. These devices, unlike conventional bipolar transistors do not exhibit “thermal runaway.” Thermal runaway is a
phenomenon whereby a transistor heats up as it draws more current, which causes it to get hotter, and conduct more
current, and so on until the device self destructs. Since the MOSFETs are inherently self protecting, no sonically
degrading, complexcircuitryisrequired to monitorand protectthe devices. The lateralMOSFETsalso have a linearinput
to output transfer function. Their connection in circuits and their operating characteristics are very similar to vacuum
tubes, which is perhaps responsible for their widely recognized sonic trait of being “musical” and non-fatiguing.
Operation of the transconductance stage is a major factor in the reproduction quality of the amplifier. The number of
MOSFETs used at the output stage of the 9303 and 9505 imposes sufficient capacitive load on the transconductance
stage thatifa conventionalClassAstage were used (havingintrinsicallya 2:1 limiton peak-to-quiescentcurrent)itwould
begin to show “stress” at the higher audio frequencies. The newly perfected DIABLO driver system (Dynamically
Invariant A-B Linear Operation; patent application in progress) satisfies the current headroom requirement by smoothly
and continuously varying the current transfer ratios of the two transconductance paths, under the control of the signal
current itself. This implementation allows the current transfer ratio of one path to be smoothly and continuously reduced
to zero while the other is smoothly and continuously increased by a factor of two. What is remarkably new here is that
when this normally-limiting 2:1 value is reached there is now about 14dB of additional, perfectly linear current
headroom left to drive the MOSFETs! The result is a dramatic decrease in high-frequency distortion combined with
higher ultrasonic stability – the “Holy Grail” of amplifier design.
The power supply utilizes a UI style transformer with a separate primary for each channel. The transformer has a separate
secondary for each channel high voltage power supply, each feeding a conventional split full wave bridge rectifier. High
voltage power supply capacitance is 20,000µF per rail for each channel for the 9505 and 5,000 for the 9303. The third
transformer secondary feeds a regulated supply for the input stage and driver circuitry. Low voltage power supply
capacitance is 1,000µF per rail, with additional decoupling for each channel.
CALIBRATION
Common Mode Rejection:
The input common mode null is adjusted by the trim pot R1 (R101 for the left channel). The CMRR should be greater
than 75dB below rated output. If the CMRR requires adjustment, feed the amplifier input with a common mode signal
and adjust R1. Disconnect the power to the amplifier before removing the cover. Use a sinewave generator set to 1
volt output at 1kHz. Connect the generator signal output to the tip and ring of a 1/4" plug and ground to the sleeve. Plug
this into the amplifier input. Connect an AC voltmeter to the amplifier output binding posts. Adjust R1 to give the lowest
voltage output from the amplifier. For a temporary adjustment when a signal generator and voltmeter are not available,
use an FM tuner and tune it to an unused station as your signal source, and connect the output to the amplifier as
described above. Connect the amplifier output to a small full range speaker and adjust R1 for the lowest output from
the speaker.
Bias:
The bias control establishes the quiescent Class AB output current of the amplifier. The bias should not need
readjustment from the factory setting; however, if the amplifier is repaired and output devices have been changed, or
if the two channels of the amplifier do not run at the same temperature, calibrating the bias is necessary. Disconnect
the power to the amplifier before removing the cover. To adjust the bias, disconnect the input and speakers and remove
the B+ fuse for that channel. Connect an amp meter across the now vacant fuse clips and adjust R45 (R145 for the left
channel) to get a current reading of 300mA for the 9303, 400mA for the 9505.
– 10 –
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S ERVICE P O LICY AND LIMITED WARRANTY
If you encounter any difficulty or have any question concerning your 9303 and 9505 Amplifier, please call our Technical
Support Department weekdays, 8:00 a.m. to 3:30 p.m., Mountain Standard Time, at 800-795-2385.
Should you have any doubts as to whether the amplifier is malfunctioning and requires service, please call us before
sending it in for repair. All units being returned (regardless of warranty status) must receive a Return Authorization (RA)
number. In addition, we can offer troubleshooting assistance that may simplify or even eliminate the need for factory
service.
The Hafler 9303 and 9505 Amplifiers are warranted to the original owner (non-transferrable) for seven years from the
date of purchase, including parts, labor, and return shipping costs within the Continental United States, Alaska, and
Hawaii. This warranty applies only to products sold in the United States Of America.
For warranties outside the U.S.A., please contact your local agent.
It is the owner’s responsibility to pay shipping (preferably United Parcel Service, UPS) to the factory: collect shipments
will not be accepted. Units under warranty should be accompanied by a copy of the dated Bill Of Sale. Use the original
carton and all packing material, with the RA number clearly marked on the outside of the package. Be sure to include
a return address, the RA number, a daytime telephone number, and a brief description of the difficulty, including whether
it occurs continuously or intermittently.
This warranty gives you specific legal rights. You may also have other rights which may vary from state to state.
– 11 –
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HAFLER PROFESSIONAL
A DIVISION OF
ROCKFORD CORPROATION
546 SOUTH ROCKFORD DRIVE
TEMPE, ARIZONA 85281 U.S.A.
IN U.S.A. (602) 967-3565
IN EUROPE, FAX (49) 4207-801250
IN JAPAN, FAX (81) 559-79-01265
MAN-0587-D
4/95
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