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PROFESSIONAL STUDlO AMPLIFIERS
Studio Referenc dio Referenee
Some models may be exported under the name Asrr@rou@
O "99 8y Crown Ir~ternatit:,nal, P.O. Box t COO, Elkhart. lndizn~i
b fnc., 46575-?OQO U.S.A. Telephone: 219-244-
8000.Sfudio Refere?-9c:cawplifiers are produced by Crawn fnterrsaticsnal, Inc, xr'radernark Notice: Skrdio
Reference'*and Gronnd~d &!.idge7"are tradcrnarks and Amcnm:'@ &IrcswsT10C? ODEP IQ S,ysl'cm.e" and
&"i.PF are registered trademarks trf Crcwn BntsrnationaY, Irx. Blher trademarks are the properv of their
respecliveowrwrs.
@Krawn"
,
-
,
Stlidio Refgrence Service Manual
-
..
, , , -""...""
K
R-*. ~ 6
The information furnished in this manual does not Include all of the de"iaifs s design, production, or variations of
f
the equipment. Nor does it cover every possible 8itua"ii~n which may ariss during installation, operation sr
maintenance. if you need special assistance beyond the scope of this manuas, please eontact the Crown
Technical Suppart Group,
Mai/: P.0. BQX4008 Elkhart lN 465?5-1000
Sbippin-ag: Pit. 2 S,W,, 1718 W, Mishawaka Rd., Elkhark E 4 5 7
N 61
Phone: $800)
342-6939/(2 )
19 294-8206
FAX: $2" 9
1)294-8361
Web:~ w ~ c P Q w ~ ~ u ~ ~ ~ ~ c o ~
TO PREVEMT ELECTRlC SMOCK 80
NQT REMOVE TOP OR B Q n D M A PR~VENIRLE CHOG
COMERS. NQ USER SERVICWBLE ~LECTRIOUEN'ENLEVU
. PARTS INSIDE, REFER SERVOCtNC PA8 LES CQUVERTURES,
TO QUALIFIED SERVICE RlEM DES PARTlES
PERSOMNEL* DISCONNECT UTlLES A L"INT~RIEUR,
POWER CORD BEFORE REMOVING u
D~BRANCHER BORNE
R R ENPUT MODULE TO ACCESS
m AVANT DWUVRIR U
GAIN SWITCH, MODULE EN ARRI~RE.
f 0 REDUCE THE RISK OF ELECTRIC
SHOCK, DO NOT EXPOSE THlS
EQUIPMENT TO RAIN OR MOISTURE!
Rev. Q 12-98 Initial Printing
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Rev.
- 8.-
Studio Reference Service Manu3l @crown
1 Bntroductisn ................................................................................................... 3-1
1.1 The Stndis Referents ........................................................................ 1-1
1.2 Scope ................................................................................................ 1-1
1.3Warranty ............................. ~ . ~ ~ ~ ~ ~ . . . ~ . ~ . . A ~ ~ ~ ~ ~ . . . . , 1-1 . . . . . . . . .
2 Specifications ................................................................................................ -2-1
2."Berformance ...................................................................................... 1 2.
2.2 Pswei ................................................................................................. 2-1
23 Cantrofs ............................................................................................. 2-2
2.4 f ndicators .......................................................................................... 2.2
2.5l~putsautput ...................................................................................... 2-3
2.6 Output Signal ..................................................................................... 2-3
2 2 Protcctisn .......................................................................................... 23
.
2.8 Construction ...................................................................................... 2.3
3 Va1tags Conversion ........................................................................................ 3-1
4 Circuit Theory ................................................................................................. 4-4
4.1 Overview ........................................................................................... 4-1
4.2Features ............................................................................................. 4-2
4.3 Frant End Operation .......................................................................... 4-2
4.3.1 Balanced Gnin Stage (BGS) .....................................................4-2
4.3.2 Variable Gain Stage (VGS) ........................................................4-2
4.3.3 Error Amp ..................................................................................2 4.
4.4 Voltage Amplification ......................................................................... 4-2
4.4.1 Voltage Transfators .................................................................... 4.3
4.4.2 bast Voltage Amplifiers (LVAS).................................................. 4-3
4.5 Grounded Bridge Topology ...............................................................4-4
4.5.Wigh Side (HS) ......................................................................... -4-4
4.5.2 Side (LS)
Law ............................................................................4.4
4.6 Output Device Emulation Prccalectian (OBEP) ....................................4-5
4.7 Ganliol Circuitry ................................................................................4-6
4.7.1 DC$LFProtect ............................................................................ 4-6
4.7.2 fault Circuit ............................................................................... 4-6
4.7.3 Turn On Belay ........................................................................... 4-6
4.7.4 Fan Corjtrol ................................................................................ 4-6
4.8 Power Supply .................................................................................... 4-6
4.8.AC kine Fiiter ............................................................................
1 4-6
423.2 Soft Start ................................................................................... 4-6
4.8.Over Voltage Protection ............................................................
3 4-7
4.9Display Circuitry .............................................................................. "4-7
4.9.1 1QC ............................................................................................ 4-7
4"9+2 ODEP ........................................................................................ 4.7
4 3 3 Signal Indicafis~s ........................................................................ 47
.
".......
...........................................................................................................
5 Electrical Checkout and Adjustment Procedures ,,,....................................... 5-1
5 1 General Informatiow ........................................................................... 5-1
5 2 Standard Initiat Conditions ................................................................ 5-1
53 DC Offset .......................................................................................... 5-1
5.4 Output Bias Adjustmen$.................................................................... 5-1
5 5 OBEP Voltage Adjustment ................................................................. 5-1
5.6 AC Pawer Draw ................................................................................. 5-1
5.7 High tine Gutsue ................................................................................ 5-1
5-8 Common Mode Wejects'sn ..................................................................5-1
5.9 Voltage Gain ...................................................................................... 5-2
533 Level Controls ................................................................................. 5-2
5.1 1 Current bimi"r .. ............................................................................... 5-2
5 1 2 Slew Rate and *a OK Square Wave .................................................... 5-2
5.f 3 Crosstalk ..........*<."........................................................................... 5-3
5.1-4 Output Power ................................................................................... 5-9
5.1 Reactive Loads ................................................................................
5 5-3
5.16 ODEP Limiting .................................................................................5-4
5% Mute and Turn-On Delay ..................................................................5-4
17
5. Law Frequency Protection ...............................................................
18 5-4
5. 19 Signal to Noise Ratia ....................................................................... 4 55
5.20 Intermadulation Diskoflion ............................................................... 5-5
5.21 LED Functions ................................................................................. 5-5
5.22 Display Set-Up ................................................................................ 5-5
5.23 Turn-On Transients ........................................................................... 5-5
5.24 Turn-OM Transiep-rts..........................................................................5-5
525 Past Testing .....................................................................................5-5
6 Schematics ....................................................................................................6-1
7 Parts Information ............................................................................................ 7-1
7. 1 General lnfarmation ........................................................................... 7-1
7.2 Standard and Special Parts ............................................................... 7-1
7.3 Ordering Parts ................................................................................... 7-1
.,.....
7.4 Shipment .................... ........................................................7-1
7.5 Terms .................................................................................................7-7
7.6 Illustrated Parts List ........................ , , .. ,
, . ................................7-1
Figure 7.1 Front Panel Exploded View ................... , .........................7-2
. .
Figure 7.2 Top Main Assembly Exploded View ...................................... 7-4
Figure 7.3 Bottom Main Assembly Exploded View ................................ 7-6
Figure 7.4 Back Pans[ Assembly Exploded View ................................ 7-8
,
Fi%jure7.5 Output Assembly Exploded View ....................................... 3-1 61
Figt,ire 7% Capacitor Assembly Exploded View ................................... 7-12?
Figure 7.7 PIP Cage Assembly Exploded View ................................... 7-15
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_____ylll~1~1111__
Reference Service Manuai
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.................................................
8 Module information ........................................................................................
8-4
8.1 General information ........................................................................... 8-4
8.2 Studia Reference 1 Module lnfsrmatisn ............................................. 8-1
8.3 Studio Reference If Module Infsrmatisn ............................................8-1
8-4 Q.4397 1-6 Main Module ......................... .., . ..................................$3-2
.
8 5 Q43369-0 Outp&r"lodeelie .................................................................. 8-8
8.6 Q43183A3 Control Module .............................................................. 8-11
8.7 Q43.450-8 Control Module ...............................................................8-14
8.8 843584-2 Control Module ............................................................... 8-17
8.9 4 0 8-3 Display Modu8e ...............................................................8-20
a31
8.1Q 64331 1-2 Main Module ................................................................. 8-23
8.11 Q43388-0 Main Module ................... .,..
. .. , .............8-28
. ., . ,
8. 2 Q43389-8 Butput Module ..............................................................8-33
t
8.13 a43312-0 Display Module ............................................................. 8-36
@crowne
P "-
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Studio Reference Service Manusf
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Figure 2.1 Studio Wefsrence Dimensions ......................................................... 2-3
Figuss 3.1 Specific Voltage Wiring ................................................................... 3-1
Figure 3 2 Circuit Breaker Selection ...................,... ...................................... - 1
31
Figure 4 .t Simplified Studio Refereilea Biock Diagram ...................................4-1
Figure 4.2 Simplified Ampiitier Front End and Voltage Ampiifiication Stages .. 4-3
Figure 4 3 SimpfifiedGrounded Bridge ...................., .... .............................. 4-5
Figure 5.1 Differentiatar Circuit ........................................................................ 5-2
figure 5-2 Differentiated Square Wave .............................. ..,,,,..*+.+'......... 5-2
Figure 5 3 10 kHz Square Wave ................... .. ................................................. 5-2
Figure 5.4 inductive Load CoId ........................................................................ 5-3
Figure 5.5 5~nd~etive Warm ......................................................................
Load 5-3
Figure 56 Tartup@Yest Waveform ..................................................................... 5-4
Figure 5-4 OBEP Limiting Waveform ..................................................................... 5-4
Figure 7. 1 Front Panel Parts .............................................................................
7-2
Figure 4. Top Main Assembly Parts ................................................................7-4
2
Figure 7.3 Bottom Main Assembly Parts ....................... .................................. 7-6
Figure 7.4 Back Panel Assembly Parts ..................... .
....... ........................7-8
Figure 7 5 Output Assembly Par& ................... . , ........................................7-16
Figure 7 3 Capacitor Asssmbly Parts ............................................................F.12
Figure 7 2 PIP Cage Assembly Parts .............................................................7-14
Figure 8. 1 a43371-6Main Msdule Map ..........................................................8-7
Figure 8.2 Q43363-8 Output Module Map ..................................................... 8-18
Figure 8 3 Q43383A3 Control Maduis Map ....................................................
2 8-13
8 3 5 - Control Madula Map .....................................................8-16
Figure 8.4 Q 4 4 8 8
Figuse 8 5 Q4J5Q4-2
2 Control Module Map ..................................................... 8-19
Figuw 8. 643818-3 Bispray Module Map ..................................................... 8-22
6
Figure 8.7 a 3 6 1-2 Main Module Mag ...................... .............................. 8-27
43
figure 8.8 843388-0 Main Module Map ........................................................8-32
Figure 8 3 043389-8 Output Modube Map ..................................................... 8-35
Figurs 8 1 Q43312-0 Display Msduls Map ..................................................
'6 8-38
t .I Ths Studia Referenee Schematics are included. Note that a Mexdu%e com-
is
The Studio Reference amplifiers are the flagship s f prised a$the circuit board with the component parts
Crown Internatfsna\.They oRsr the best in sound re- Crown does not sell blank (unpopulated)cis=.
instal!@d.
production with a dynamic range capable of accurately cuiQ boards.
reproducing 20-bit digital recardings. Super low har-
monic and intermodulationdis$or$ion provides the best CAUTIOH: TRs infermatien in this manual Is Intsndsd to b~
transfer function in the business. And the ultra-high ossd by an exparlenc%dt@~hnlclaa honly
damping factor af 20,000detivsrs superior foud-
speaker motion control for a tight and clean low-end. 1.3 Warranty
Each Reference Manual contains basic pslieies as re-
1.2 Scape fated to %he customer. In addition, it should be staked
contains sewice information for the Grown that this ssrviee dacumentalisn is meant ts be used
This massr_eaI
Studio Reference power amplifiers..It ia designed I ~ P snly by properly trained service personnel. Because
be used with the appilcable ReferenceManual' How- most Crawn products carry a 3 Year Full Warranty (in-
ever, some important information is duplicated in this ciud~ng round trip shipping within the United States),
Servica Manual in case t h e Reference Manual is not aft warranty service should be referred to the Crown
readily availabls. Factory or Authorized Warran& Sewice Center. See the
applicabls Owner's Manual for warranty details,To find
This Service Manual includes severaB sections,These the iocation Q nEarsst Authorired Sarvice Center,
theI
sectiians include Sp~cifications, Vottag~ Conversion, or to obtain instructions fcar receiving Crown Factory
Circuit Thssry? EEfectrieal C h e ~ k o u tParts Information, Service, piease contact tho Crown Technical Support
,
Module Information, aod Exploded View Drawings, Group (within North Amerrca) or your Crown/Amcrg;bn
Importgr (outside North America),
Plant 2 S.W,
1718 W. Mishawaka Bd,
Elkhaa, IN USA 4651'7
Phone: (219) 294-8200
Tall Free: (8QO)M2-6939
F M : (219) 294-8301
Web: .er~wnaudis~com
Introduction t -7
Sf ~ d i Reference Service Manual
o
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introduction 4 -2
Studio Referenee Service ,Msnual
The following specifications on Bode Wajsctlon [CMR):Better than 100 dB be-
Mode, with an 8Ohm load, a ted full bandwidth power from 20 Hz to 480 Hz,
26dB, banless stherwise specified. rising tinearly I better than 79 dB at 20 kb4z,
s
t kHz
Low-.DJ&o~P@@ Psaar: Refers to maximum aver- Voltage G ~ i n :(With Isvel controls set far maximum ocnt-
:
age power in watts at 1 kHzwith 0.02% THO and noise.. put,) At the 2 d B garn setting, 2 Q : h 3 %or 26 dB
6
~ 0 ~dB,25
S t a ~ d ~ r B Power: Refers t maximum avsrage
1 kHz s Studio m , n , & z ; e LAt 0.775volt sensitivity?
pswer in watts at I kHz with 8.1% TkJD and noise, .-
'I 1 k 12% or 40 dB 1 dB; at 1.4 volt
63:
sensitfvity,57: k 12% or 35 dB k 1 dB.
1
Full B ~ n d ~ i dPawer; Refers to maximum average
th - to
S d - ..-.
ui At 0.775 volt sen%itiviby,
pawer in watts from 2 Hm to 2 kHz with 0.1% THB
0 6 6 9 : k j2% ar 37 dB 41 dB; at "84 volt sensitivity,
o
and noise. 38.1 ~ 1 2 % o r 3 2 d BdB. ~1
2,l PeHormsnee 2,2 pa we^
Ftgquency Response:: ~8,MdB 20 Hs to 20 kHz at
from P s ~ eBandwidth: (At standard 1 kHz power.)
r
1 watt. &,df-rence6: -^B dB from 5 Mz to 27.5 kHz
and - dB from 3 Hz ta 32.8 kHz.
3
Phase R~$pon%@: to -75 degrees from 20 Hz ta 2
+5 6 -1 dB from 5 Hz fa 28.6 kHz
kHz at 3 w ~ t t ~ and --3d B from 2.3 Hz to 34.4 kHz,
8ignai-to-noise: (A-weighted)
reater than 120 d B belaw
rcater than 13 7 dB below
full bandwidth powerh
tsw-Di%tofllsn f kHz Butput Power:
Tat@! Harmonic Dldsalon (TWO): Less than 0,02% a 4 S udio Rcf@rea&
f ....
rated low-distortion I kHz pswer. Less than 0.1% af $t~?reaMade with both cchannsbs driven.
rated full bandwidth power, 1,160 watts per channel into 4 ohms,
7 8watts per channel into 8 ohms.
6
lntsrmoduEIaZlon Qiatagian {IMDf: (60Ha & 7 kklz 4: 2)
Studio R ~ f ~ Less than 0,005%from full
*- - r w B~idge-Mono mode:
bandwidth power to 78 watts rising linearly to 2,228watts Into 8 ohms,
8.025% at 78milfl~atks~ 1,580watts into 16 ohms
Studio R-
e
f Less than 0.005% from ;Bull
bandwidth power ta 36 watts rising lineariy $a P8~3I/e/-Msn0 mode:
0.025% at 36 mtliiwatts, 2,37 5 watts into 2 ohms,
1,565watts into 4 ohms.
Damping Factar: Greater than 20,000
from "B BHZ
to
at
280 Hz, and greater than 2,568 1 kHz. m,,B@-
Stereo Mode with both chag.gne!sdriven:
Crosstalk: (At rated full bandwidth power,) 555 watts per channel into 4 ohms,
S b ~ dRefer-
i~ Batter than 1 6 dB from
0 355watts per chanilel into 8 ohms.
25 Hz ta 100 Hz, falling linearly to better than
4
70 dB at 20 kHz, Bridge-Mono mods:
Betdef khan 180 dB from "i110 watts into 8 ohms.
20 M E to f 66 Hz, falling tinearly to better than 715 watts into 16 ohms.
65 dB at 20 kHz,
Parab/e/*!donsn~ade:
1,115watts into 2 alms.
730watts inta 4 ohms,
Enable: A front panel push button used to turn the
Stereo mode wid)~both ~haanneIs driven: amplifier on and off,
1,190watts per channel into 4 ohms.
800 watts per chaunef iota 8 ohms, Level: A front panel rotary potentiometer far each ehan-
nel with 3 1 dstents, used $0C B ~ ~ F O I the output level.
Bridge-Mono mode:
2,375 watts inis 8 ohms. Stsreomono: A three-pasitiaw back panel switch used
1,595 watts into 16 ohms. to select either Stereo, Bridge-Mano or Parallel-Msns
Par~jIef-Mono
mode:
2,350 watts into 2 ohms, SsnsitivlQ: A three-position switch inside the P,l,I,p
corn-
1,588watts into 4 ohms. partment used ta select the input sensitivity for both
ek?annefs: 6,795 i 1.4 volts for standard 'IkHz pg;aw~r,
a
RefefcnceH:
St~d8"o or 26 dB voltage gain,
S!W@Q mode wifh both cchanne/s drjven:
565 waus pea channel into 4 ohms. Mater OnfBff: A tws-position switch behind the front
360 watts per channel into 8 ohms. pane! used to turn the front panel meters on or off,
Bridge-Mono m ~ d ~ r Meter Display Mode: A twa-position switch behind the
3 ,f 45 waEs into 8 ohms, frsnt panel used to set the display mudc tor t h s front
720wakk into 16 ohms panel meters. Display modes include dynamic range
af the output signal in dB or output levels in dB.
mode:
Par8$/@/-Mono
7,135watts into 2 ohms. Ground Lift: A two-position back panel switch used to
"715waE%into 4 ohms, isslate the irrput phone jack and AC {chassis) grounds.
Full Bawdwidth Butput Pewer: (20 Hr lo 28 kHz) Reset: A t w o - p ~ ~ l t i o n panel switch used fa roset
back
t h e AC mains circuit b~eaker*
E@r@o
made wjtfi both -lh~aanne/s drivepa:
watts per chanaal into 4 ohms.
1,075 2,4lndicatars
768watts per chaalnel ir3Po 8 ohms. Enable: This indicator shows the o n / M status of the
unit's How-voltage power supply
BrBdge-M~f?~
2,150 watts into 8 ohms+ Signal::Each channel has a signal inclicatar that flashes
" , 3watts into f 6ohms.
355 to show audio output.
$&2dio Ref-K i@C: Each channel has an 18C indicator %hat flashes if
St~f-samode wifk bath chhanng!~ db^ven: the output waveform differs from the input wavsform
495 watts per channel into 4 ohms. by 0.85% or more. The LED$ act as sensitive distsr-
340 watts per chaanel into 8 ohms. tion indicators to provide p o f of di~f~rtian-free
ro per-
formance, In Paralfel-Mono mode the channel 2 / @ 0
Brid~e-Mgbf?~mode: Ilght stays an.
1,020watts into 8 ohms.
698watts into 16 o h m s . 0DEP:Each channel has an ODEPindieator that shows
the channel's resewe energy status, Normally, the
Load Impedsn~e: Safe with all types of loads, Raked far LEDs are brigfatly tit to show that reserva energy is
4 ts 8 ohms in stereo mode, 8 ts 16 ohms in Bridge- available. In the rare event that a channel has no re-
Mona made, and 2 to 4. ohms in ParalteI-Mon~ O ~ G ,
M
serve, its indicator wisi dim in proportion to BDEPlim-
Required AC Mains: 5 or 60 Hz; 1 6 120, 200, 220or
6 0,
240 VA6 (k 10%)< Both units draw 90watts or less at
idle.
Dynamic Ranga/Lsuel Meter: Each Channel has a five- Input: Input overload prstectisn is furnished at the
segment meter that displays either the dynamic range amplifier input to limit current.
of the output sigrrai in dB sr the output love! in dB,
(From the factory, the amplifier is set to display dy- Turn On: The four second ~ C ~ T M - deilay prevents dam
Q~
namic range.) A s dynamic range meters, they show gerous turn-on transier~ts,
%he ratio sf peak to average power of tach channel,
As output level meters they show how high the ~ ~ ~ l p u t Constrvctlon
2,8
levels a r e relative to standard 1 kHz powerq Steel chassis with durable b8ack finish, aluminum front
averiay?and
panel with super-glass Imronfinish, l e x a ~ ,
2.5 llnputlOutput a specially designed flaw-through ventilation system
input Csnneetor: Two balanced '!,is-inch jacks an the from front to side panels.
back panel and two balanced three-pin XLR connec-
tors on the factory-installed P..B,?-FX, CoeiJng: Convection cooling with assistance from the
computerized, on-demand proportional cooling fan.
lnput impsdanee: Nominally 10 K ohms, balanced
Pdornina!ly 5 K ohms, unbaianced. Dimen$ions: Standard 19 inch (48.3 em) rack mount
width fElA RS-316-B),9 inch (17.8 cm)height, 16 inch
I ~ p uSan%itiuiQ:Settings include 0,775
t volts sr 1A volts (40'6 CM) depth behind mountingsurface and 2.75 inch
for standard 1 kHz pswea: or 26 dB voleage gain. (7 em) prstrusion in front sf mounting surface (sea
Fig. 2.1 belaw),
Output Canaeetam: Two sets of color-coded 5-way bind-
ing posts far each cha~3rrel(for connecting barlana
plugs, spads lugs si bare wire),
Qutput Impsdaase::Less than 10 miBliahms in sarisa with
2,smicr~henries,
DC Output 8@ssZ;(Shorted input) 3 2 millivslts.
2.6Output Signal
Starsa: Unbalanced, twa-channel.
Brldgs-Mona: Balanced, singla-channel. Channel f
controis are active; channel 2 should be turned down.
Parallai-Mono: Unbalanced, single-channel.Channel
"icontmls are active; channel 2 is bypassed.
2,7 Protection
ODEP: ff unreasonable operating conditions $~~g;;urApprsxlmata WaiigM: Center of gravity is about 6 inches
(15.2 behind the front mounting surface.
cm)
which could stress the output circuitry?the QDEPcir-
cuit limits the output current level until safe operating
60 pounds, 11 ounces
conditions exist.
unds, 3 ounces (332k g )
Trensformer: Transformer overheating will result in a
temporary shut-down due ta a ttmerrnal ~wifchin the
1 shipping weight.
transformer primary- 56 pounds, 2 ounces
(25.5 net; 69 pounds, " 0ouncss (31"6kg)
kg) 1
shipping weight.
RF Burnout: Controlled slew-ratevoltage amplifiers pro-
tect the unit agairlst RF burnouts,
Specifications 2-3
Studio Reference Service ManuaI
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/aft
Studio Reference Service Manual
age Convers
- -."-
The Studis Reference Ampfifiers can be wired for 100 right hand corner of module).
VAC? I20 VAG, 200 VAC, 220 VAC or 240 VAC opera- 3, Cut and remsve the wire ties to access the jumpers
tion, This is made passible by the use of a multitap and wires,
transformer for the high energy power supplies. Per- 4. Refer to Figure 3,1 and make the appropriate
form the fallowing pracedure and refer %s Figures 3.3 charrges for the desired operating voltage.
and 3.2 ta convert the operating voltage. YOUmay have 5. lnstaBI wire ties to dress the wires above the con-
to order t h e approprate circuit breaker using the part nections.
number listed in Figure 3.2. 6, Note the switch on the ief2 hand
side of the module and change, if necessary, for the
CAUPfO#: B~eausathare 1% a risk of slsctr!~sheek, sniy operating line frequency.
on gxperisne~d
t~ehnicianahould aggmpfk ts altgr the line 7 , Refer " Figure 3 2 and change the Circuit Breaker if
I
valtage contlguratiian, necessary+
8. On the rear 0 $he unit, change ?$"re cord tag to
5 line
1. Remove tha tap cover of the Studio Referenee am- read the correct valtage. This is on the lower right hand
plifier (held on by 8 screws). side of the rear panel, just above t h e serial tag.
2, With the front panel toward you, locate tka controt 9, ReassembHe the unit.
module {frontcenter) and the tab connectors (upper
VOCrAGE JUMPER 1 WPt 6
Figure 3.1 Specific Vo1tage Wifing
Ct RCUfT BREAKER SELECTiON
30 AMP, C 7756-7
1 20
AMP. Cl 0193-8
@.,"-crawma
-- . , . , " '
Studio Reference Service Manuaf
, -- . . . " . - .
R@K0
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Voltage Conversion 3-2
Studio Reference Service Manual
INVERTING LOW SIDE
BRIDGE OUTPUT
BWUNCE PNP STAGE
Circuit Theory 4-1
Bcrcrurn. , , ,
Sfudjo- Weference Service Manual
-,..
-- -.
.-
" .,.".-
,
R ~0
K
-
k to interrupt around lw~=os the Ground
-
"
via
Studio Referenee amplifiers utilize numerous Crown Lift Switch. The non-inverting (hot)si& of the balanced
innovations, including gf@tuflded bridge and ODEP input is fed to the non-hverting input of the; firs@ op-
teehnofogies. Cooling t~chniques make use o what is
f amp stage. The inver"ring (negative)side o the bal-
f
essentially air conditianer technology.Air flows bottom ancsd input is fed to the inverting input of the firswsp-
lo top, and front to side. Air ftsws a shafi distance amp stags. A potentiometer is provided far esmmon
across a wid@heatsink. This type of air flow pro.\rides mod@ rejection adjnmstment ( R 5 f2.Electricaiiysthe BGS
)
significantlybetter emling than the "wind $unnel'"tech- is at unity gain, (From an audio perspe~tive, however,
nology used by many other manufacturers, Output this stage actually provides +6dB gain if a fully bai-
transistors are of the metal can type, rather than f h ~ anced signal is placsd on its iraput.) Tho BGS is a n n s-
plastic case style.This alIo\~s a significantlyhigher
for
thermal margin for the given voltage and current rat-
ings. Ail devices used are tested and grad~d en- to
sure maximum reliability,Another electronic technique
used is negative feedback. Almost atl power amplifi- $puts the BGS, the signal goes to the
f
ers utilize n~gativa;. feedback8 control gain and pro-
0 gain is determined by the position of the
vide stabifity$ Crown uses multiple nested feed-
but itch, and lev@/ detc~mined the level
is by
back imps far maximum stability and greatly impag>k/ed s an inverting stage with the input being
damping. Studio Reference ampiifiers have damping mp stage. Because gain after this stage
in @XC$S$ af 20,000 in the bass frequencyrange. This B (factors 2Q),
f greater amplifier sensi-
feedback,along with our compensation and u t " l 3 - l ~ ~ s d $y csntrosling the ratio of f~edback
distortion output tapol~gy~ make Grown Studio Ref- nee, The Sensitivity Switch sets the in-
erence amplifier superior* put impedance to this stage and varies the gain such
that the overall amplifier gain is 26 dB, or is adjusted
Fsatt~res specific to the Studio Reference include: A or 0.775V ar d.4V input to attain rated
high power toroidal Esansfsrmsr;Computer controlad,
varjable speed, whisper quiet fan; Built in AC power
fiffes; Softstart circuit Z control inrush curroot; Fuji ov-
a
ervodtage and internal fault protection, This ampli- tpuX from the VGS is fed to the non-
fier can operate in either Bridgge;! Parallel Mans mode,
or the Errof Amp op-amp stage through
as well as in Dual (stereo) made, A sensitivity switch capacitor $Ct 00)and input resistor
a)lowsseiectian sf input voltage requiredfor rated &rut- output is led back via the negative
put. Level cnr-llr~ls mounted on the front panel and
are op re~istor 1 3 , ratlo of feed-
(W Q ) The
are of the rotary type, Front panel indicators let the
user know the status of amplifier enable, QDEP9signal tpuWof the amplifier at 26 dB, Bi-
presence (SP!), and distortion ( 0 )Alsa included on
9C, revent averdriving the Error Amp.
the front panel is a five-segmet display Tr each chan-
o mp amplifies the difference be-
riel which displays either dynamic range tn d B ar aut- ut signals, any differencein the
put level in dB, two waveforms will produce a near open loop gain
condition which, in turn, results in high peak auWpu&.
For addiriauai details s~fer the specification section,
to ths Error Amp, called the Error
or ta the appficable WaFerence Manual, Signal (ES) drives the Voltage Translators,
4.3 Front End Operation 4.4Voltage Alnplifi~ation
The front end is comprised of three stages: Balanced The Voltage Translator stage separates the output of
Gain Stage (BGS), Variable Gain Stage {VGS), and the Error Amp into balanced positive and negative
the Error Amp. Figure 4 2 shows a simplifieddiagram for
drive vol"s~ge?s the Last bltage Amplifiers (LVAS)~
o the front end and voltage ampixfieation stages,
f translating the signal from ground referenced n15V to
kV@c referenee, LVAS provide the rnak voltage ampli-
4-3,f Balanced Gain Stage (80%) fication and drive the High Side output stages. Be-
lnpk~t the amplifier is balanced, The shield from the
ts muse there is a slight lass of gain in the translator
1/4" inputs may be isolated from chassis ground by stage, the gain after the translatar is a factor of 25.2,
Cir~uit
Theory 4-2
ence. Their outputs drive their respechive tVA,
muting transistors, The QQEP transistors steal drive
as dictated by th@ BDEP circuitry or shunt the audio
as dietated by thg fault circuit,
Circuit Theory 4-3
Figure 4.3 is a simplified exampfe of the grounded
bridgs output topology. It consists of four quadrants A diode suing pr~vents excessive charge build up
of three deep DarDington (composite) emitter-follsw~r within the high conduction output devices whew off,
stages per channel: one NPN and one PNP an the Flyback diodes shunt bask-EMF pulses from reactive
High Side of the bridge (driving the Isad), and apse loads to the power supply to protect output devices
NPN and one PMP an the Low Side of the bridge (con- from dangerous reverse voltage levels. An output ter-
trolling the ground reference for %Rerails). The output minating circuit blocks W on output lines from enter-
F
stages are biased ta operate class AB+B far ultra low ing the amplifier through its output connectors,
distortion in the signal zero-crossing region and high
efficiency. 4,5,2 L@w Side (L8)
The tow Side (LS) operates quite differently. The power
4,5.%High Side [NS) supply bridge rectifier is not ground referenced, nor is
Thhe High Side (HS) af the bridge operates much like a the secondary of the main transformer, in othsr wards,
conventional bipolar push-pull output configuration,As tha high vsltage power supply floats with respect ta
the input drive vsitage becomes more po%itive,the ground, but ~ V c remain canstant with respect to each
c
HS NPN conducts and delivers positive voltage to the other, This allows the pswer supply to deliver +Vcc
10ad, Eventually the NPN devices reach full conduc- and -Vcc from the same bridge rectifier and fiitsr as a
tion and +Vcc is acrsss the load, At this time the HS total difference io potential, regardless of their voltages
PNP is biased off. When the drive signal is negative with respect ts ground. The LS uses inverted feed-
going, "Be HS PNP canducts to deliver -Vcc to the load back from the HS output $0control the ground refer*
and the HS NPN stage is off. ence for the rails (AVCC), Both L quadrants are ar-
S
ranged in a three-deep Darlington and are biased
The output of the +LVA drjvm the base of $ 8 . pradriver
~ AB+B in the same manner as thc WS,
device. Sgsgethar, the predriver and driver farm the first
two parts sf the three-deep Darlingtonand are biased When the amplifisr output swings positive, the audio
class AB, They provide output drive through the bias is fed to an sp-amp stage where it is inverted, This
resistorxbypassing the output devicas, at Bevels be- inverted signal is delivered direeIIy to the bases of the
Isw about 180mW, An RLC network between the positive (NPN) and negative (PNP) predrrivers. The
LS
predriver and driver provide phase shift csmpensa- negative drive forces the L PMP devices on (NPN
S
tion and limit driver base current $asafs Bevels. Output off), As the PNP devices coaduct, VCB af the PNP
devices are biased class B, below s%sculotf. about
Just At Darlington drops. With LS dsviics emitters tied to
1QOmW blr~tpat they switch on to eonduct high current ground, -Vcc is pulled toward ground reference. Since
to the load. Together with predriver and driver? out-
the the pswer supply is not ground referenced (and the
put device provides an averall cFass AB+B output, tatai vsltage from aVcc to -Vcc is constant) +VGC is
forced higher above ground potential. This continues
The negative half sf the HS is almsst identical to the until, at the positive amplifier output peak, -Vcc -. OV
positive half, except that the devices are PNP One and +VGC e q ~ a I the total power supply potential with
s
difference is that the PNP bias resistor is slightly greater a positive pslarily' In the Reference 1, for example,
in value sa that PNP output devices run closer to the %he power supply produces a totat af14488 from rail ts
cutoM level under static (no signal) conditions, This is rail (k72VDC me?asur@d from ground with ns signal),
because PNP devices require greater drive current. therefore, the amplifier output can reach a positiva peak
sf +"I44v*
WS bias is rsgulated by Q18, the Bias Seavs, Q l S is a
Vbe multipiier which maintair-rsapproximately 3,2V Vee Cosrversely, during a negative swing af the HS output
under static conditions, The positive and negative where HS PNP devices conduct, the op-amp would
halves of the W output are in parallel with this 3.2V
S output a positive voltage forcing hS NPN devices to
With a full base-emitter on voltage drop across canduct. This would result in +Vcc swinging tsward
predrivers and drivers, tha balance of voltage rasuits ground potential and -Vcc swinging further from
in approximately .3V drop across the bias resistors in groidnd patentraf. At tl-$6
negative amplifier sutpvt peak,
the positive half, and about .5V acrsss T e bias resis-
h SVCC =z OV and -Vcc equals the tstal power supply
tor in the negative half, Q J bn$ ~ ~ n d ~ c l i o rthus bias)
{and ~ potential with a negative pofariWy. Using the same ex-
Circuit Theory 4-4
E
!
t
Rev 0 Sfudio Reference Service Manual @CraUme k
-,..- ,,. , rn
I
k72VDC statically) is capable of produsing 288V
output) and +Vcc are sensed,
rent (negative amplifi~r
An iocrease in positive output signal into a load will
measurable by normal means) and the time delay from
@crown*-- ..
--.
-
Studio Refer~nce p.-p ManuaE
-
"
-
Service -
-- R@K Q, , ,-
4.7 C@~tr@l
eireuitry nal. As the outpeat transistorlheatsink increases in tem-
The Reference amplifiers have fault protect circuitry Peratu~e, ODEP voltage kvei will drop fmm
the
to guard against dangerous DC voltages and turn on/ +joVBC f3ear ~ ~If ~ 1s a dropv one of
C in
off transients, At the heart sfthis ~ir~~ifry win-
the both QDEP vsltages it will Cause the fan csntroi sig-
dew comparator ~ 1 0 2?kg fan control girc~ij:
, moni- nal to change,The fan contra& signal starts out around
tors the thermal conditions, via the OBEP eireuit, and -12.5VDC, 3rd after complete ODEP limiting, ends
regulates the fan speed accordingly, up at + 12,5VDC0Phis voltage is fed into the inverting
input of the op-amp U1B, The initial output sf U1B is
4.7,1 DCBF Pr@t@@ high $+24V), and as the fan control signal becomes
The amplifier output sigf-ralis passed through a low more positive, this output will became low, thus turn-
pass filter (R184, C1 19, R186 *and C107)ts the win- ing the fan accordin~j~~output of U1I3 drives
The
dew comparator (UJQ21, if DC campsnent ex- U4,an opts-triac, which in turn drives Q4, a triac in
ceeds a predetermined level, the output o the cam-
f AG supply forf h e fan,
parator (pins 1 and 2) goes law. The result is U302
pin 23 going to a high state which turns on the muting Ph@Gating Signadis fed into the nsn-inverting input of
transistors and disables the high energy supply by $heQP-amP Uj@+This gating signal is a p ~ ~ d uof t c
opening the relay K2. U7 A, Q 3 , and the Fan Enable signal from the display
madule., C12 and RE3 farm an RC timing circuit that,
4,7,2 Fsuft Circuit from the +15V supply, begins I charge, U1A rnoni-
s
The fau&circuitry i designed to mute
s audio and tars the tine voltage wave farm and is a O i l crossing
disa$le the high energy supply in the event of an out- detector. Every lime the line waveform crosses OV, Q4
put fault. A fau/$is defined as any time in which t h e is turned s ? discharges C12, This causesa ramp-
a and
output semicsnductars, in both the negative and posi- ing type waveform.The higher p~$i$ive portion of .&he
tive sections, draw excessive currents, waveform is used to turn off %he ~pto-triac,aven when
the fan contrkal signat itself is a a value k turn sn the
F s
The [ow side of &ridgefaultdetection consists sf Q128, has
fan.Therefare,the fancantrod curr~nt a duty cycle,
Q329 and Q130, ff both NPN and PNP output devices
are conducting excessive cajirrents,tha output af U'T82 'The f%f? Enabje %nai cQm@s the display !"nod-
from
(pin 13) is forcegs$high, This disables the high energy u!@and holds the Gating Si~flaf when the amp&
high
supply and mutes the audio path, fief is in standby<"I^'herefsfe the fan will not turn when
the amplifier is in standby*
The high side s bridge fault detection consists of
f
a126,Qf 2 and U101. This circuit compares the NPN
7
and BNP drive to the feedback signal, giving a repre- At the heart of the power supply is a muiti-tap torraidaH
sentation of output devics current. If excessive cur- power transformer, There are two ungrounded, high
wnt occurs, the window cegmparatsr U1Q2is triggered energy, secondary windings, one for each channel,
through the opto isslatsr U101. and there is one low voltaga winding for t h e 24V sup-
plies, "f?er@ also a thermal eu% switch built into
is off
4.1.3 TBFR8 n Bs%ay the transfarmer wtlich will disable the secondary wind-
During power up, the capacitor C'I 1 is charging,
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