Crown Studio Reference I Studio Reference II User manual

PROFESSIONAL STUDlO AMPLIFIERS
Studio Referenc dio Referenee
Some models may be exported under the name Asrr@rou@
O "99 8by Crown Ir~ternatit:,nal, fnc., P.O. Box t COO, Elkhart. lndizn~i 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:'@ &IrcswsT 10C? ODEP IQ S,ysl'cm.e" and
&"i.PF are registered trademarks trf Crcwn BntsrnationaY, Irx. Blher trademarks are the properv of their
respeclive owrwrs.

@Krawn"
--,,,
Stlidio Refgrence Service Manual
, , , .-. -""..."" R~K
6
*-....-
The information furnished in this manual does not Include all of the de"iaifs sf design, production, or variations of
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. BQX 4008 Elkhart lN 465?5-1000
Sbippin-ag: Pit. 2 S,W,, 171 8 W, Mishawaka Rd., Elkhark EN 4651 7
Phone: $800) 342-6939/(2 1 9) 294-8206
FAX: $2 "19) 294-8361
Web: ~w~cPQw~~u~~~~co~
TO PREVEMT ELECTRlC SMOCK 80
NQT REMOVE TOP OR BQnDM
COMERS. NQ USER SERVICWBLE
. PARTSINSIDE, REFER SERVOCtNC
TO QUALIFIED SERVICE
PERSOMNEL* DISCONNECT
POWER CORD BEFORE REMOVING
RmR ENPUT MODULE TO ACCESS
GAIN SWITCH,
A PR~VENIR LE CHOG
~LECTRIOUE N'ENLEVU
PA8 LES CQUVERTURES,
RlEM DES PART lES
UTlLES A L"INT~RIEUR,
D~BRANCHER u BORNE
AVANT DWUVRIR U
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
............................
1.3 Warranty .~.~~~~~...~.~..A~~~~~....,......... 1-1
2 Specifications ................................................................................................ -2-1
2 . "Berformance ......................................................................................2. 1
2.2 Pswei ................................................................................................. 2-1
23 Cantrofs ............................................................................................. 2-2
2. 4 f ndicators .......................................................................................... 2.2
......................................................................................
2.5 l~putsautput 2-3
2.6 Output Signal ..................................................................................... 2-3
22 Protcctisn .......................................................................................... 2.3
2.8 Construction ...................................................................................... 2.3
3 Va1tags Conversion ........................................................................................ 3-1
.................................................................................................
4 Circuit Theory 4-4
...........................................................................................
4.1 Overview 4-1
4.2 Features ............................................................................................. 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 .................................................................................. 4.2
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 Law Side (LS) ............................................................................ 4.4
....................................
4.6 Output Device Emulation Prccalectian (OBEP) 4-5
4.7 Ganliol Circuitry ................................................................................ 4-6
4.7.1 DC$LF Protect ............................................................................ 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. 1 AC kine Fiiter ............................................................................ 4-6
423.2 Soft Start ................................................................................... 4-6
4.8. 3 Over Voltage Protection ............................................................ 4-7
.............................................................................. 4.9 Display Circuitry "4-7
............................................................................................
4.9.1 1QC 4-7
4"9+2 ODEP ........................................................................................ 4.7
........................................................................
433 Signal Indicafis~s 4.7

.......
........................................................................................................... "
5 Electrical Checkout and Adjustment Procedures ,,, ....................................... 5-1
51 General Informatiow ........................................................................... 5-1
52 Standard Initiat Conditions ................................................................ 5-1
53 DC Offset .......................................................................................... 5-1
5.4 Output Bias Adjustmen$ .................................................................... 5-1
55 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
512 Slew Rate and *a OK Square Wave .................................................... 5-2
. ..........*<."...........................................................................
5 f 3 Crosstalk 5-3
5. 1-4 Output Power ................................................................................... 5-9
5.1 5 Reactive Loads ................................................................................ 5-3
5. 16 ODEP Limiting ................................................................................. 5-4
5% 17 Mute and Turn-On Delay .................................................................. 5-4
5. 18 Law Frequency Protection ............................................................... 5-4
5. 19 Signal to Noise Ratia ....................................................................... 545
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%jure 7.5 Output Assembly Exploded View ....................................... 3-1 61
Figt,i re 7% Capacitor Assembly Exploded View ................................... 7-12?
Figure 7. 7 PIP Cage Assembly Exploded View ................................... 7-15

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Stvd8"~ Reference Service Manuai @CrQWne
P, ,,
P
.................................................
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
85 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 a4301 8-3 Display Modu8e ............................................................... 8-20
8.1 Q 64331 1-2 Main Module ................................................................. 8-23
.............
8.1 1 Q43388-0 Main Module ................... .... ..,,.. ,.,
8-28
8. t 2 Q43389-8 Butput Module .............................................................. 8-33
8.13 a4331 2-0 Display Module ............................................................. 8-36

@crowne
P -..".. .......- , , , ,
Studio Reference Service pw Manusf R~K 0
P
P
Figure 2.1 Studio Wefsrence Dimensions ......................................................... 2-3
Figuss 3.1 Specific Voltage Wiring ................................................................... 3-1
Figure 32 Circuit Breaker Selection ...... .............,... ...................................... 3-11
Figure 4 . t Simplified Studio Refereilea Biock Diagram ................................... 4-1
Figure 4.2 Simplified Ampiitier Front End and Voltage Ampiifiication Stages .. 4-3
Figure 43 Simpfified Grounded Bridge ................... ,..... .............................. 4-5
Figure 5. 1 Differentiatar Circuit ........................................................................ 5-2
figure 5-2 Differentiated Square Wave .............................. ..,,,,..*+.+'......... 5-2
................................................
Figure 53 10 kHz Square Wave ................... ...
5-2
Figure 5. 4 inductive Load CoId ........................................................................ 5-3
Figure 5. 5 5~nd~etive Load Warm ...................................................................... 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. 2Top Main Assembly Parts ................................................................ 7-4
Figure 7.3 Bottom Main Assembly Parts ....................... .................................. 7-6
........................
....................
Figure 7. 4 Back Panel Assembly Parts ......... 7-8
................... ........................................
Figure 75 Output Assembly Par& ,. 7-16
Figure 73 Capacitor Asssmbly Parts ............................................................ F.12
Figure 72 PIP Cage Assembly Parts ............................................................. 7-14
Figure 8. 1 a43371 -6 Main Msdule Map .......................................................... 8-7
Figure 8.2 Q43363-8 Output Module Map ..................................................... 8-18
Figure 823 Q43383A3 Control Maduis Map .................................................... 8-13
Figure 8.4 Q843458-8 Control Madula Map ..................................................... 8-16
Figuse 825 Q4J5Q4-2 Control Module Map ..................................................... 8-19
Figuw 8. 6 64381 8-3 Bispray Module Map ..................................................... 8-22
Figure8.7 a4336 1-2 Main Module Mag .................... ...... .............................. 8-27
figure 8.8 843388-0 Main Module Map ........................................................ 8-32
Figure 83 043389-8 Output Modube Map ..................................................... 8-35
Figurs 8'16 Q43312-0 Display Msduls Map .................................................. 8-38

t .I Ths Studia Referenee
The Studio Reference amplifiers are the flagship sf
Crown Internatfsna\. They oRsr the best in sound re-
production with a dynamic range capable of accurately
reproducing 20-bit digital recardings. Super low har-
monic and intermodulation dis$or$ion provides the best
transfer function in the business. And the ultra-high
damping factor af 20,000 detivsrs superior foud-
speaker motion control for a tight and clean low-end.
1.2 Scape
This massr_eaI contains sewice information for the Grown
Studio Reference power amplifiers.. It ia designed I~P
be used with the appilcable Reference Manual' How-
ever, some important information is duplicated in this
Servica Manual in case the Reference Manual is not
readily availabls.
This Service Manual includes severaB sections, These
sectiians include Sp~cifications, Vottag~ Conversion,
Circuit Thssry? EEfectrieal Che~kout, Parts Information,
Module Information, aod Exploded View Drawings,
Schematics are included. Note that a Mexdu%e is com-
prised a$ the circuit board with the component parts
instal!@d. Crown does not sell blank (unpopulated) cis=.
cuiQ boards.
CAUTIOH: TRs infermatien in this manual Is Intsndsd to b~
ossd by an exparlenc%d t@~hnlclaa only h
1.3 Warranty
Each Reference Manual contains basic pslieies as re-
fated to %he customer. In addition, it should be staked
that this ssrviee dacumentalisn is meant ts be used
snl y by properly trained service personnel. Because
most Crawn products carry a 3 Year Full Warranty (in-
ciud~ng round trip shipping within the United States),
aft warranty service should be referred to the Crown
Factory or Authorized Warran& Sewice Center. See the
applicablsOwner's Manual for warranty details, To find
the iocation QI the nEarsst Authorired Sarvice Center,
or to obtain instructions fcar receiving Crown Factory
Service, piease contact tho Crown Technical Support
Group (within North Amerrca) or your Crown/Amcrg;bn
Importgr (outside North America),
Plant 2 S.W,
171 8 W. Mishawaka Bd,
Elkhaa, IN USA 4651 '7
Phone: [phone]
Tall Free: (8QO) M2-6939
FM: (21 9) 294-8301
Web: .er~wnaudis~com
Introduction t -7

Sf ~dio Reference Service Manual
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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 8 Ohm load, a ted full bandwidth power from 20 Hz to 480 Hz,
26dB, banless stherwise specified. rising tinearly Is better than 79 dB at 20 kb4z,
Low-.DJ&o~P@@ t kHz Psaar: Refers to maximum aver-
age power in watts at 1 kHz with 0.02% THO and noise..
Sta~d~rB 1 kHz Power: Refers ts maximum avsrage
pswer in watts at I kHz with 8.1 % TkJD and noise,
Full B~nd~idth Pawer; Refers to maximum average
pawer in watts from 20 Hm to 26 kHz with 0.1% THB
and noise.
2,l PeHormsnee
Ftgquency Response:: ~8,MdB from 20 Hs to 20 kHz at
1 watt.
Phase R~$pon%@: +5 to -75 degrees from 20 Hz ta 26
kHz at 3 w~tt~
8ignai-to-noise: (A-weighted)
reater than 120 dB belaw
rcater than 1 3 7 dB below
full bandwidth powerh
Tat@! Harmonic Dldsalon (TWO): Less than 0,02% a4
rated low-distortion I kHz pswer. Less than 0.1% af
rated full bandwidth power,
lntsrmoduEIaZlon Qiatagian {IMDf: (60 Ha & 7 kklz 4: 2)
Studio R~f~rw Less than 0,005% from full
--*
bandwidth power to 78 watts rising linearly to
8.025% at 78 milfl~atks~
Studio Ref- Less than 0.005% from ;Bull
bandwidth power ta 36 watts rising lineariy $a
0.025% at 36 mtliiwatts,
Damping Factar: Greater than 20,000 from "B BHZ to
280 Hz, and greater than 2,568 at 1 kHz.
Crosstalk: (At rated full bandwidth power,)
Sb~di~ Refer- Batter than 106 dB from
245 Hz ta 100 Hz, falling linearly to better than
70 dB at 20 kHz,
Betdef khan 180 dB from
20 ME to f 66 Hz, falling tinearly to better than
65 dB at 20 kHz,
Voltage G~in:: (With Isvel controls set far maximum ocnt-
put,) At the 26 dB garn setting, 2Q:h3% or 26 dB
~0~25 dB,
Studio m,n,&z;eL At 0.775 volt sensitivity?
'I 63: 1 k 12% or 40 dB .- 1 dB; at 1.4 volt
sensitfvity, 57: 1 k 12% or 35 dB k 1 dB.
Studio- At 0.775 volt sen%itiviby,
- ..-.
69:kj 2% aor 37 dB 41 dB; at "84 volt sensitivity,
38.1 ~12%or32dB~1 dB.
2,2 pa we^
Ps~er Bandwidth: (At standard 1 kHz power.)
&,df-rence6: -^B dB from 5 Mz to 27.5 kHz
and -3 dB from 3 Hz ta 32.8 kHz.
-1 dB from 5 Hz fa 28.6 kHz
and --3 dB from 2.3 Hz to 34.4 kHz,
tsw-Di%tofllsn f kHz Butput Power:
Sf udio .... Rcf@rea&
$t~?rea Made with both cchannsbs driven.
1,160 watts per channel into 4 ohms,
768 watts per channel into 8 ohms.
B~idge-Mono mode:
2,228 watts Into 8 ohms,
1,580 watts into 16 ohms
P8~3I/e/-Msn0 mode:
2,37 5 watts into 2 ohms,
1,565 watts into 4 ohms.
m,,B@-
StereoMode with both chag.gne!s driven:
555 watts per channel into 4 ohms,
355 watts per chanilel into 8 ohms.
Bridge-Mono mods:
"i 1 10 watts into 8 ohms.
71 5 watts into 16ohms.
Parab/e/*!dons n~ade:
1,115 watts into 2 alms.
730 watts inta 4 ohms,

Enable: A front panel push button used to turn the
Stereo mode wid)~ both ~haanneIs driven:
amplifier on and off,
1,190 watts 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 $0 CB~~FOI the output level.
Bridge-Mono mode:
2,375 watts inis 8 ohms.
Stsreomono: A three-pasitiaw back panel switch used
1,595 watts into 1 6 ohms.
to select either Stereo, Bridge-Mano or Parallel-Msns
Par~jIef-Mono mode:
2,350 watts into 2 ohms,
SsnsitivlQ: A three-position switch inside the P,l,I,p corn-
1,588 watts into 4 ohms.
partment used ta select the input sensitivity for both
ek?annefs: 6,795 ai 1.4 volts for standard 'I kHz pg;aw~r,
St~d8"oRefefcnce H:
or 26 dB voltage gain,
S!W@Q mode wifh both cchanne/s drjven:
565 waus pea channel into 4 ohms.
Mater OnfBff: A tws-position switch behind the front
360 watts per channel into 8 ohms.
pane! used to turn the front panel meters on or off,
Bridge-Mono m~d~r
3, f 45 waEs into 8 ohms,
720 wakk into 16 ohms
Par8$/@/-Mono mode:
7,135 watts into 2 ohms.
"715 waE% into 4 ohms,
Meter Display Mode: A twa-position switch behind the
frsnt panel used to set the display mudc tor ths front
panel meters. Displaymodes include dynamic range
af the output signal in dB or output levels in dB.
Ground Lift: A two-position back panel switch used to
isslatethe irrput phone jack and AC {chassis) grounds.
Full Bawdwidth Butput Pewer: (20 Hr lo 28 kHz)
Reset: A two-p~~ltion back panel switch used fa roset
the AC mains circuit b~eaker*
E@r@o made wjtfi both -lh~aanne/s drivepa:
1,075 watts per chanaal into 4 ohms.
2,4 lndicatars
768 watts per chaalnel ir3Po 8 ohms.
Enable: This indicator shows the on/M status of the
unit's How-voltage power supply
BrBdge-M~f?~
2,150 watts into 8 ohms+
"3,535 watts into f 6 ohms.
$&2dio Ref-K
St~f-sa mode wifk bath chhanng!~ db^ven:
495 watts per channel into 4 ohms.
340 watts per chaanel into 8 ohms.
Brid~e-Mgbf?~ mode:
1,020 watts into 8 ohms.
698 watts into 16 ohms.
Load Impedsn~e: Safe with all types of loads, Raked far
4 ts 8 ohms in stereo mode, 8 ts 16 ohms in Bridge-
Mona made, and 2 to 4. ohms in ParalteI-Mon~ MO~G,
Required AC Mains: 56 or 60 Hz; 106, 120, 200, 220 or
240 VA6 (k 10%)< Both units draw 90 watts or less at
idle.
Signal:: Each channel has a signalinclicatar that flashes
to show audio output.
i@C: Each channel has an 18C indicator %hat flashes if
the output waveform differs from the input wavsform
by 0.85% or more. The LED$ act as sensitive distsr-
tion indicators to provide proof of di~f~rtian-free per-
formance, In Paralfel-Mono mode the channel 2 /0@
Ilght stays an.
0DEP:Each channel has an ODEPindieatorthat shows
the channel's resewe energy status, Normally, the
LEDs are brigfatly tit to show that reserva energy is
available. In the rare event that a channel has no re-
serve, its indicator wisi dim in proportion to BDEPlim-

Dynamic Ranga/Lsuel Meter: Each Channel has a five-
segment meter that displays either the dynamic range
of the output sigrrai in dB sr the output love! in dB,
(From the factory, the amplifier is set to display dy-
namic range.) As dynamic range meters, they show
%he ratio sf peak to average power of tach channel,
As output level meters they show how high the ~~~lput
levels are relativeto standard 1 kHz powerq
2.5 llnputlOutput
input Csnneetor: Two balanced '!,is-inch jacks an the
back panel and two balanced three-pin XLR connec-
tors on the factory-installed P..B,?-FX,
lnput impsdanee: Nominally 10 K ohms, balanced
Pdornina!ly 5 K ohms, unbaianced.
I~put San%itiuiQ: Settings include 0,775 volts sr 1 A volts
for standard 1 kHz pswea:or 26 dB voleage gain.
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,s micr~henries,
DC Output 8@ssZ; (Shorted input) 32 millivslts.
2.6 Output Signal
Starsa: Unbalanced, twa-channel.
Brldgs-Mona: Balanced, singla-channel. Channel f
controis areactive; 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 $~~g;;ur
which could stress the output circuitry? the QDEPcir-
Input: Input overload prstectisn is furnished at the
amplifier input to limit current.
Turn On: The four second ~C~TM-Q~ deilay prevents dam
gerous turn-on transier~ts,
2,8 Constrvctlon
Steel chassis with durable b8ack finish, aluminum front
panel with super-glass Imron finish, lexa~, averiay? and
a specially designed flaw-through ventilation system
from front to side panels.
CoeiJng: Convection cooling with assistance from the
computerized,on-demand proportional cooling fan.
Dimen$ions: Standard 19 inch (48.3 em) rack mount
width fElA RS-316-B), 9 inch (17.8 cm) height, 16 inch
(40'6 CM) depth behind mounting surface and 2.75 inch
(7 em) prstrusion in front sf mounting surface (sea
Fig. 2.1 belaw),
Apprsxlmata WaiigM: Center of gravity is about 6 inches
(15.2 cm) behind the front mounting surface.
cuit limits the output current level until safe operating
conditions exist.
60 pounds, 11 ounces
unds, 3 ounces (332 kg)
shipping weight.
Trensformer: Transformer overheating will result in a 1
temporary shut-down due ta a ttmerrnal ~wifch in the
transformerprimary-
RF Burnout: Controlled slew-rate voltage amplifiers pro-
tect the unit agairlst RF burnouts,
56 pounds, 2 ounces
(25.5 kg) net; 69 pounds, "1 0ouncss (31 "6 kg)
shipping weight.
Specifications 2-3

Studio Reference Service ManuaI
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Studio Reference Service Manual
age Convers
The Studis Reference Ampfifiers can be wired for 100
VAC? I20 VAG, 200 VAC, 220 VAC or 240 VAC opera-
tion, This is made passible by the use of a multitap
transformer for the high energy power supplies. Per-
form the fallowing pracedure and refer %s Figures 3.3
and 3.2 ta convert the operating voltage. YOU may have
to order the approprate circuit breaker using the part
number listed in Figure 3.2.
CAUPfO#: B~eausa thare 1% a risk of slsctr!~ sheek, sniy
on gxperisne~d t~ehnician ahould aggmpfk ts altgr the line
valtage contlguratiian,
1. Remove tha tap cover of the Studio Referenee am-
plifier (held on by 8 screws).
2, With the front panel toward you, locate tka controt
module {front center) and the tab connectors (upper
- -".-
right hand corner of module).
3, Cut and remsve the wire ties to access the jumpers
and wires,
4. Refer to Figure 3,1 and make the appropriate
charrges for the desired operating voltage.
5. lnstaBI wire ties to dress the wires above the con-
nections.
6, Note the switch on the ief2 hand
side of the module and change, if necessary, for the
operating line frequency.
7, Refer "I Figure 32 and change the Circuit Breaker if
necessary+
8. On the rear 05 $he unit, change ?$"re line cord tag to
read the correct valtage. This is on the lower right hand
side of the rear panel, just above the serial tag.
9, ReassembHe the unit.
WPt 6
VOCrAGE JUMPER 1
Figure 3.1 Specific Vo1tage Wifing
Ct RCUfT BREAKER SELECTiON
30 AMP, C 7756-7
1 20
AMP. Cl 01 93-8

@ crawma
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Studio Reference Service Manuaf
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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.
, , ,
SfudjoWeference Service Manual
--,-..-.- -.".-
..,. ".,-
R~K 0
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k to interrupt around lw~=os via the Ground
" -
Studio Refereneeamplifiersutilize 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 of what is
amp stage. The inver"ring (negative) side of the bal-
essentially air conditianertechnology. 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 ofair flowpro.\rides
mod@ rejection adjnmstment (R5f 2). 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 fh~
anced signal is placsd on its iraput.) Tho BGS is a nsn-
plasticcase style. This alIo\~s for asignificantlyhigher
thermal margin for the given voltage and current rat-
ings.
Ail devices used are tested and grad~dto en-
sure
maximum reliability,Another electronic technique
used is negative feedback.Almost atl power amplifi- $put
sf the BGS, the signal goes to the
ers utilize n~gativa;.feedback 80 control gain and pro-
gain is determined by the position ofthe
vide stabifity$ but Crown uses multiple nested feed-
itch, and lev@/ is detc~mined by the level
back imps far maximum stability and greatly impag>k/ed
s an inverting stage with the input being
damping. StudioReference ampiifiers have damping
mp stage.Because gain after this stage
in @XC$S$ af 20,000 in the bassfrequencyrange. This
B (factor sf 2Q), greateramplifier sensi-
feedback, along with our compensationand ut"l3-l~~
sd $y csntrosling the ratio off~edback
distortionoutput tapol~gy~ make Grown Studio Ref-
nee, The SensitivitySwitch setsthe in-
erence amplifiersuperior* 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 toroidalEsansfsrmsr;Computer controlad,
varjable speed, whisper quiet fan; Built in AC power
fiffes; Soft start circuit Za control inrush curroot; Fuji ov-
ervodtage and internal fault protection, This ampli-
tpuX from the VGS is fed to the non-
fier can operate ineither Bridgge;!or Parallel Mans mode, the
Errof Amp op-amp stagethrough
as well as in Dual (stereo) made, A sensitivity switch
capacitor $C t 00) and input resistor
a)lowsseiectian sf input voltage required for rated &rut- output
is led back via the negative
put. Level cnr-llr~lsaremounted on the front panel and
op re~istor (W 1Q3), The ratlo of feed-
are of the rotary type, Front panel indicators let the
user know the status of amplifier enable, QDEP9 signal
tpuWof the amplifier at 26 dB, Bi-
presence (SP!), and distortion (90C), Alsa included on
revent averdrivingthe Error Amp.
the front panel is a five-segmetdisplayTor each chan-
mp amplifiesthe difference be-
riel which displays either dynamic range tn dB ar aut-
ut signals, any difference in 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 detailss~ferto the specification section,
ths Error Amp, called the Error
or
ta the appficableWaFerence Manual,
Signal (ES) drives the Voltage Translators,
4.3 Front End Operation
The front end is comprised of three stages: Balanced
Gain Stage
(BGS), Variable Gain Stage {VGS), and
the Error Amp. Figure
42 shows a simplified diagram
of the front end and voltage ampixfieation stages,
4-3,f Balanced Gain Stage (80%)
lnpk~t ts the amplifier is balanced,The shield from the
1/4" inputs may be isolated from chassis ground by
4.4 Voltage Alnplifi~ation
The Voltage Translator stage separates the output of
the Error Amp into balanced positive and negative
drive vol"s~ge?s for the Last bltage Amplifiers (LVAS)~
translating the signal from ground referenced n 15V to
kV@c referenee, LVAS provide the rnak voltage ampli-
fication and drive the High Side output stages. Be-
muse there is a slight lass of gain in the translator
stage, the gain after the translatar is a factor of 25.2,
Cir~uitTheory 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
of three deep DarDington(composite)emitter-follsw~r
stages per channel: one NPN and one PNP an the
High Side of the bridge (driving the Isad), and apse
NPN and one PMP an the Low Side of the bridge(con-
trollingthe ground referencefor %Rerails).
The output
stages arebiased taoperate class AB+B far ultra low
distortion in the signalzero-crossingregion and high
efficiency.
4,5.% High Side [NS)
Thhe High Side(HS) af the bridgeoperatesmuchlike a
conventional bipolarpush-pulloutputconfiguration, As
the input drive vsitage becomes more po%itive,the
HS NPN conducts and delivers positivevoltage to the
10ad, Eventually the NPN devices reach full conduc-
tion and +Vcc is acrsss the load, At this time the HS
PNP is biased off. When the drive signal is negative
going,"Be
HS PNP canductstodeliver-Vcc tothe load
and the HS NPN stage is off.
The
output of the +LVA drjvmthebase of $8.~ pradriver
device. Sgsgethar,the predriver and driver farm the first
two parts sf the three-deepDarlingtonandare biased
class AB, They provideoutput drive through the bias
resistorx bypassing the output devicas, at Bevels be-
Isw about 180mW, An RLC network between the
predriver and driver provide phase shift csmpensa-
tion and limitdriver base current $a safs Bevels.Output
devices are biasedclass B, Just below s%sculotf. At about
1QOmW blr~tpat they switchon to eonduct high current
to the load.Togetherwith predriver and driver?theout-
put device provides an averall cFass AB+B output,
The negativehalf
sf the HS is almsst identical to the
positive half, except that the devices are PNP One
difference is thatthe PNP bias resistoris slightly greater
in value sa that PNP output devices run closer to the
cutoM level under static (no signal) conditions, This is
because PNP devices require greater drivecurrent.
WS bias is rsgulated by Q18, the Bias Seavs, QlS is a
Vbe multipiierwhich maintair-rsapproximately 3,2V Vee
under static conditions, The positive and negative
halves of the WS output are in parallel with this 3.2V
With a full base-emitter on voltage drop across
predrivers and drivers,tha balance of voltage rasuits
inapproximately .3V drop across the bias resistorsin
the positivehalf,
and about .5V acrsss The biasresis-
tor inthe negativehalf,
Q J bn$ ~~nd~clior~ {and thus bias)
A diode suing pr~vents excessive charge build up
within the high conduction output devices whew off,
Flyback diodes shunt bask-EMF pulses from reactive
loads to the power supply to protect output devices
from dangerous reversevoltagelevels.An output ter-
minatingcircuit blocks WF on output lines from enter-
ing the amplifier through itsoutput connectors,
4,5,2 L@w Side (L8)
The towSide (LS) operates quite differently. The power
supply bridge rectifier is notgroundreferenced,nor is
the secondary of the maintransformer, in othsr wards,
tha high vsltage power supply floats with respect ta
ground, but ~Vccremaincanstantwithrespect to each
other, This allows the pswer supply to deliver +Vcc
and -Vcc from the same bridge rectifier and fiitsr as a
totaldifference io potential,regardless of theirvoltages
with respect ts ground. The LS uses inverted feed-
back from the HS output $0 control the ground refer*
ence for the rails (AVCC), Both LS quadrants are ar-
ranged
in a three-deep Darlington and are biased
AB+B in the same manner as thc WS,
When the amplifisr output swings positive, the audio
is fed to an sp-amp stage where it is inverted, This
invertedsignalisdelivereddireeIIyto the bases of the
positive (NPN) and negative (PNP) LS predrrivers. The
negative drive forces the LS PMP devices on (NPN
off), As the PNP devices coaduct, VCB af the PNP
Darlington drops. With LS dsviics emitters tied to
ground,-Vcc is pulledtowardground reference. Since
the pswer supply is not ground referenced(and the
tatai vsltage from aVcc to -Vcc is constant) +VGC is
forced higher above groundpotential. This continues
until, at the positive amplifieroutput peak, -Vcc -. OV
and +VGC eq~aIsthe total power supply potentialwith
a positive pslarily' In the Reference 1, for example,
%he power supply produces a totat af14488 from railts
rail (k72VDC me?asur@d from ground with ns signal),
therefore, the amplifieroutputcanreach a positiva peak
sf +"I 44v*
Cosrversely,duringa negativeswing af the HS output
where HS PNP devices conduct, the op-amp would
output a positive voltage forcing hS NPN devices to
canduct. This would result in +Vcc swinging tsward
ground potential and -Vcc swinging further from
groidnd patentraf. At tl-$6 negative amplifiersutpvt peak,
SVCC =z OV and -Vcc equals the tstal power supply
potentialwith
a negative pofariWy.Using the same ex-
Circuit Theory 4-4