Crown Studio Reference I Studio Reference II, Studio Reference I, Studio Reference II Service 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:c awplifiers

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

.

PARTS INSIDE,

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

This

page

intentionally

left

blank

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

R@K

0

.

-..,

_____ylll~1~1111__

.

, ,

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.

2 Top

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

Figure 8.7

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

applicabls Owner'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:

(21

9) 294-8200

Tall

Free:

(8QO)

M2-6939

FM:

(21

9)

294-8301

Web:

.er~wnaudis~com

Introduction

t

-7

Sf

~dio

Reference

Service

Manual

This

pa@@

intentionally

left

blank

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@-

Stereo Mode

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

16 ohms.

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"o Refefcnce

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.

Display modes

include

dynamic

range

af

the

output

signal

in

dB

or output

levels

in

dB.

Ground

Lift:

A

two-position

back

panel

switch

used

to

isslate the

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 signal inclicatar

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

ODEPindieator that

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

relative to

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

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;;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

transformer primary-

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

This

page

inten&ianally

/aft

blank

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

--.,."---

. , .

, " '

Studio

Reference

Service

Manuaf

-."...--,

.

R@K

0

This

page

intentionally

left

blank

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~K

0

-

k

to interrupt around

lw~=os

via

the

Ground

"

-

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

of

what

is

amp stage. The

inver"ring

(negative)

side

of the

bal-

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

(R5f

2).

Electricaiiys the

BGS

significantly better 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-

plastic case

style.

This

alIo\~s

for

a significantly higher

thermal

margin

for

the given voltage

and

current rat-

ings.

Ail

devices

used

are tested

and

grad~d to 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

of the

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.

Studio Reference ampiifiers

have

damping

mp

stage. Because

gain

after this

stage

in

@XC$S$

af

20,000

in

the bass frequency range.

This

B

(factor

sf

2Q),

greater amplifier sensi-

feedback,

along

with

our compensation and

ut"l3-l~~

sd

$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;

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

in either

Bridgge;! or Parallel Mans mode,

the

Errof

Amp

op-amp

stage through

as

well

as

in

Dual

(stereo)

made,

A

sensitivity

switch

capacitor

$C

t

00)

and

input

resistor

a)lows seiectian

sf

input voltage

required

for

rated &rut-

output

is

led

back

via

the

negative

put.

Level

cnr-llr~ls are mounted

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 averdriving the Error

Amp.

the

front panel is a five-segmet display Tor each chan-

mp

amplifies the 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

details s~fer to the specification section,

ths

Error

Amp,

called the Error

or

ta

the appficable WaFerence 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~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

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-

trolling

the ground reference for %Re rails).

The

output

stages

are biased

ta operate

class

AB+B

far ultra

low

distortion

in

the signal zero-crossing region and

high

efficiency.

4,5.%

High

Side

[NS)

Thhe

High

Side (HS)

af the bridge operates much like

a

conventional

bipolar push-pull output configuration,

As

the input drive vsitage becomes more po%itive, the

HS

NPN

conducts

and

delivers positive voltage

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

canducts to deliver -Vcc to the load

and

the

HS

NPN

stage

is

off.

The

output

of

the

+LVA

drjvm the base

of

$8.~

pradriver

device.

Sgsgethar, the predriver

and

driver farm

the

first

two parts

sf

the three-deep Darlington and are

biased

class

AB,

They

provide output 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

limit driver

base

current

$a

safs Bevels. Output

devices

are biased class

B,

Just

below

s%sculotf.

At about

1QOmW

blr~tpat

they

switch on

to

eonduct

high

current

to

the

load. Together with predriver

and

driver? the out-

put

device provides

an

averall cFass

AB+B

output,

The

negative half

sf

the

HS

is

almsst

identical

to

the

positive half, except that

the

devices are

PNP

One

difference

is

that the

PNP

bias

resistor is

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 drive current.

WS

bias

is

rsgulated

by

Q18,

the

Bias

Seavs,

QlS

is

a

Vbe

multipiier which maintair-rs approximately

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

in approximately

.3V

drop across

the

bias

resistors in

the positive half,

and

about

.5V

acrsss

The

bias resis-

tor in the negative

half,

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 reverse voltage levels. An output

ter-

minating circuit blocks

WF

on

output

lines

from

enter-

ing

the

amplifier

through its output connectors,

4,5,2

L@w

Side

(L8)

The

tow Side

(LS)

operates

quite

differently.

The

power

supply

bridge

rectifier

is not ground referenced, nor

is

the

secondary

of

the main transformer,

in

othsr

wards,

tha

high

vsltage power supply

floats

with respect

ta

ground,

but

~Vcc remain canstant with respect

to

each

other,

This

allows

the pswer

supply

to deliver

+Vcc

and

-Vcc

from

the

same

bridge

rectifier

and

fiitsr

as

a

total difference

io

potential, regardless

of

their voltages

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

inverted signal is delivered direeIIy to

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

pulled toward ground reference.

Since

the pswer supply

is

not ground referenced (and the

tatai

vsltage from

aVcc

to

-Vcc

is

constant)

+VGC

is

forced

higher

above

ground potential.

This

continues

until,

at

the

positive

amplifier output peak,

-Vcc

-.

OV

and

+VGC

eq~aIs the total

power

supply potential with

a

positive pslarily'

In

the

Reference

1,

for

example,

%he

power

supply

produces

a

totat

af14488

from rail ts

rail

(k72VDC

me?asur@d

from

ground

with

ns

signal),

therefore,

the

amplifier output can reach a positiva

peak

sf

+"I

44v*

Cosrversely, during a negative swing

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

amplifier sutpvt

peak,

SVCC

=z

OV

and

-Vcc

equals

the tstal power supply

potential with

a

negative pofariWy. Using

the

same

ex-

Circuit

Theory

4-4

E

!

t

Rev

0

k

-..,-

,,.

,

Sfudio

Reference

Service

Manual

@CraUme

rn

I

k72VDC

statically)

is

capable

of

produsing

288V

rent (negative

amplifi~r

output)

and

+Vcc

are

sensed,

An

iocrease

in

positive

output

signal

into

a

load

will

measurable

by

normal

means)

and

the

time

delay

from

@crown*

--

Studio

Refer~nce

Service

ManuaE

-..-.-.

-"-

p..-.p

---

, , ,-

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, the

ODEP

voltage

kvei

will

drop fmm

to

guard

against dangerous

DC

voltages

and

turn

on/

+joVBC

f3ear

~~~Cv

If 1s

a

drop

in

one of

off

transients,

At

the

heart

sf

this

~ir~~ifry

the

win-

both

QDEP

vsltages

it

will

Cause

the

fan

csntroi

sig-

dew

comparator

~102,

?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

+

1

2,5VDC0

Phis

voltage

is fed

into

the inverting

input

of

the

op-amp

U

1

B,

The initial output

sf

U1

B

is

4.7,1

DCBF

Pr@t@@

high

$+24V),

and

as

the

fan

control

signal

becomes

The

amplifier output sigf-ral

is

passed

through

a

low

more

positive,

this output

will

became

low,

thus

turn-

pass filter

(R184,

C

1

19,

R186

*and

C107)

ts

the

win-

ing

the

fan

accordin~j~~ The output of

U1

I3

drives

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 of the

cam-

AG

supply for

fhe

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

$he

QP-amP

Uj@+

This

gating signal

is

a

p~~duct

of

opening

the

relay

K2.

U7

A,

Q3,

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

Is

charge,

U1A

rnoni-

The

fau&

circuitry

is

designed

to

mute

audio

and

tars

the

tine

voltage

wave

farm

and

is

a

Oil

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

the

is

turned

sa?

and

discharges

C12,

This

causes

a

ramp-

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

aF

a value

ks

turn

sn

the

The

[ow

side

of

&ridge

fault detection consists

sf

Q128,

fan.

Therefare, the

fan cantrod curr~nt

has

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

from

the

display

!"nod-

(pin

13)

is

forcegs$

high,

This

disables

the

high

energy

u!@

and

holds the

Gating

Si~flaf

high

when

the

amp&

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

sf

bridge

fault

detection

consists

of

a126,

Qf

27

and

U101.

This

circuit compares the

NPN

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

U

1

Q2

is

triggered

energy,

secondary

windings,

one

for

each channel,

through the

opto isslatsr

U101.

and

there

is

one

low voltaga winding

for

the

24V

sup-

plies,

"f?er@

is

also

a

thermal

eu%

off

switch

built into

4.1.3

TBFR

8n

Bs%ay

the

transfarmer

wtlich

will

disable the

secondary

wind-

During

power

up,

the

capacitor

C'I

18

is charging,

ings in

the

event

of the transformer overheating.

which

causes %he

nan-inverting

input

{pin

-4

09

of U 182

to

be

!OW

and

the output

(pin

13)

$0

be

high,

With

pin

4,8,1

AC

tin@

Filter

13

high,

the

high

energy

taik

are

disabled by

the

re-

824

and

025

are

ir-t

the

AC

primary,

They

are

wired

lay

K2,

and

the

audio

is

mutsd

by

the muting transis-

such

that they

null

out

any

DC

compo9-ren"in

the

AC

tors.

Aft~r

approximately

4

seconds,

C1

"I

Qis

fully

pawere

This

done

because

the tarriodiat

transformer

charged

and

pin

10

is

pulled

high,

thus

causing

pin

may

develop

a

mechanical

buzz

if

them

is

any

DC

13

to

go

low

and

the

amplifier

to

:,cams

out of

standby-

shift

in

the

AC

waveform

applied

to

the

transfarmer

4,7,4

Fsn

Centre!

The

F8n

ContrdSi~na$is

t.aken

from

the

positive

ODE$

bias

valfages.

Both

channel

1

and

channel

2

ODEP

inrush current that

is

possible

with

the

voltages

are

eambined

to

create

the

fan

c~rrtrsl

sig-

rmer, a SO%$

Start

Circuit

has

been

in-

Circuit

Theov

4-6

and

power

is

applied

diractty

to

the

transformer.

4,9.3

Signal

Indlcatlan

4,8.3

Over

Voltage

Proteetion

Ul

El

serves

as

a

window

comparator

for

the

purpose

of

over line

voltage

cantro!, In the

event that

the

line

vslfags

sxceeds

10%

over

the

rated

line

voltage,

the

high

energy

power

supplies

are

disabled,

W7

%up-

plies

the

regulated

+

I

SV

to

pin

"I

of

U

1

B

and

serves

as

the

window

reference

level.

With

pin

10

in

csntrof

of

U1

D,

&he

output:

(pin

13)

has

a

logic

law

which

is

applied

across

033

and

014,

This

prevents

csndue-

tisn

and

allows

Q1

to

remain

on,

which

thus

allows

K2

to

remain

ensrgired

Resistors

W3,

W4,

R5

and

R6

serve

a$

a

resistor

drop-

ping

neWsrk

from

the

unregulated

+24V

supply

to

ground,

As

the

line

voltage

incraas~s,

the

unregulated

supply

will

increase,

The

voltage

iievsD

sn

the

wiper

of

R4

is

applied

to

Pin

1

1

(non-inverting

input).

When

the

Hevel

exceeds

%he

window

level

of

pin

-10,

the

circuit

switches

states,

This

allows

Dl

3

and

0

14

to

canduet,

incorporated

on

the

display

module are three

modes

ef signal

indication.

SB

(Signal

Presence

Bndicnfiow)

U

1 A and

D3

serve

to

rectify the

amplifier

output

sig-

nal.

U1

B

takes

this

rectified signal

and

drives

the

LED,

E3,

which

illuminates

any

timg

there

is

signal

pre~ent

at

the

autpkdt of

the

amplifier

channel,

Dynamic

Range

With

the

switch

51

in

the

Dynamic

position,

this

recti-

fied

audio

signal

is

placed

on

the

invsrtin~

inputs

of

a

sequence

of

window

comparators.

This

signal

is

recti-

fied

but

unfiltered,

therefore

it

contains

ah@

peak

value

of

%he

audio

waveform,

U3C,

U3D,

USA,

U5B

and

U5B

serve

as

the

current

sources

for

the

five

Dynamic

Range

LEDs.

R29,

R3t

R33,

W35,

R37

and

R39

pro-

vide

a resistor

dropping

network

for

the

inverting

in-

puts

"l

athe

LED

drivers,

placing

a

logic

high

on

the

base

0%

01%

This,

iu

turn,

This

same

reclifisd

signal

is

placed

an

the

non-invert-

biases

off

Q

1

and

de-energizes

K2.

ing

i~lputs

via

the

filtering

Function

of

C3

and

the

op-

amp,

U1

C.

This

filtered

sigr~al

is

of

an

RMS

value,

With

4.9

Display

Circuitry

the

nan-inverting

inputs

receiving

the

RMS

value, and

the

inverting

inputs

receiving

th~

peak

value,

the

aut-

4.9.1

ilOC

pull

of

each

LED

comparator

equals

the

dynamic

U3A

and

U3B

serve

as a

voltage comparator

with

R13,

ranga

of

tha

signal,

R15

and

R'W

7s

the

r@sistor

dropping

newark.

Pin

'7'

has

a

window

level

of

+7V

and

pin

4

has a window

of

Output

Leved

-7V

U3A

and

U38

have

a

logic

high

which

turns

off

With

the

switch,

$1,

in

the

Level

positian,

the

peak

a1

and

the

10~

LEO

El,

when

ths

Signal

fro.cam

signal

is

still

placed

on

the

inverting

inputs

af

the

corn-

the

error

amp

appears,

the

7V

window

is

overcame

paratsr

drivers.

A

small

DC

level

is

piaced

ow

all

of

the

and

switches

the

state

of

U3A

and

U3B.

Q1

is

then

non-inverting inputs,

This DC

level

serves

as a cali-

biased

on

and

the

tOC

LED,

El,

iliuminates.

The

ca-

$rated

reference

far

comparatofs.

W78

calibrates

the

pacitor

C27

makes

sure

the

LED

is

lit

long enough

for

display

balance between

the

two

channels

sf

the

am-

the

human

eye

to

see

it.

plifier"

4,9,2

60EP

U1

B

on

the

display

module

is

the

curr@nt

source

far

the

OBEP

LED

E15,

Under

normas

operating

condi-

tions

pin

14

of

Uf

D

is

a

negative

vsitags.

This

allows

BY

ts

conduct

and

El5

to

illuw~inate.

As

the

ODEP

signal

drops

ts

the

point

wkiiere

OBfP

limiting

takes

Circuit

Theory

4-7

@crmwmx

-""...."-

St~~dia

Reference

Servjce

Manuaf

-,.-

" ""

-...--

This

page

intentianally

left

blank

Circuit

Theory

4-8

R@K

0

----...,

...-

-

,,, ,, ,

-...I.....YIIIIIIIIIIllllYllllllYl

Studio

Reference

Service

, , ,,

Manual

-.,-

mcrmwn*

Checkou

Procedures

t8,9

-10.31

1039

28.0

--10"26

10+26

21.7

.-.18.28

18.20

22.2

--16.14

1Qs?4

23.3

.-"i.09

1Q,$39

25.0

--toO~W

1O.W

25,6

--9.97

9.97

26.7

--8,9l

9.91

2723

-.9+86

9.86

28,9

-9.80

9.80

30.0

-9.94

9.44

31.1

-9.69

9-69

5,2

Standard

initial

Cowdltigns

32.2

-9.63

9.63

Level

controls

fully

clockwise.

StereoBMano

switch

in

Stereo.

Sensitivity

switch

in

26

dB

fixed

gain

pasition.

It

is

assumed,

in

each

step,

that

Ehe

conditions

of

the

amplifier

are

per

these

initial

conditions

unless

other-

wise

specified,

-ODEP

Proe8Bure:

Measure

pin

3

of

3500

and,

if

news-

sary,

adjust

R121

to

obtain

V

,,,,

as

specified

above.

Measure

pin

3

of

J700

and,

if

necagsarx

adjust

R22t

to

obtain

V

,,,,

as

s~ecifred

above,

5,3

QC

Offset

+OOEP

~rocgiite:

~easure

pin

4

of

3500

and,

if

neces-

sary,

adjust

R132

to

obtain

V+,,,,

as

specified

above.

Spgc;

8 WBC,

k2

rnV

Measure

pin

4 of

J700

and,

if

necessary,

adjust

R232

lnltial

Ce~dttOax~gr

Controls

per

standard,

mputs

shorted

oblasn

v+OL)EP

as

Preeadurs:

Msasure

DC

voltage

at

the

sutput

canncc-

tors

(rear

panel).

There

is

ns

adjustment

for

output

off-

set.

If

spec

is

not

met,

there

is

an

afectricai

rnaifunc-

tian,

Sligh8fy

out

of

spec

measurEment

is

usually

due

to

U"iQiU204

0165:

of

tolerance,

5.4

Output

Bias

Adjustment

Spec:

300

ta

320

rnVDC,

ilnitiall

Gandstiaa$::

Contrais

per

standard,

healsink

tern-

peratare

less

than

40°C

P~oeedurs:

Measwe

DC

voltages

or?

the

output

mod-

ule

across R02,

adjust

R26

if

B-eecessary,

Measure

DC

voltages

on

the

output

module

across

R21,

adjerst

R23

if

necessary.

Repeat

for

second

channel.

5,6

BC

Power

Draw

Spbc::

70

Wazrs

nmaximkam

quiescent.

initial

Csnditions:

Controls

per

standard.

Procedure:

With

no

input

si~nal

and

BBQ

16ad,

measure

AC

line

wattage

draw.

if

current

draw

is

excessive,

check.

far

high

AC

Iim

voltage

or

high

bias

vsitaga.

5.7

High

Line

Gutout

Spec:

Unit

goes

into

standby

when

the

AC

line

voftage

goes

^f

8%

to

to

12%

aabw

onominal,

lnltial

Gondltionsl:

Controls

par

standard.

Proeedgre:

No

load,

no

signal,

Bring

up

AC

line

volt-

age

with a variac

10%

to

12%

high.

Far

120VAC

units

5.5

ODEP

Voltage

Adjustment

this

is

132VAC

is

334.4VAC.

Unit

should

go

into

Spat:

Bias

Per

Chart,

~6,4V

DC.

standby.

Adjust

R4

sn

the

control

module

if

neees-

sary.

InltiaiP

@oiaridition%:

ContnaSs

per

standard,

heatsink

at

room

temperature

20

to

30°C

(68

to

86°F)"

Note:

This

adjustrnerr"rh8ufd

nsrmaliy

be

performed

wilhin

2

r~rintsts%

07

turn

an

from

ambient

(esfd)

cornditions,

If

possible,

measure

healsink

temperature;

if

not,

msa-

sure

ambient

room

temperature.

Use

this

infarmation

when referencing

the

$.a/lawing

chart,

5.8

Common

Mode

Reje~tion

Spac:

>70

dB

at

1

kHz,

initial

Cendilions:

Controls

per

standard,

Prosgdure:

No

load,

Inject

a

0

dBil(.775VRMS),

1

kHz

sine

wav@

into

each

channel,

one

channel

at

a

time,

wieh

inverting

and

non-inverting

inputs

shorted

to-

getkaer.

Adjust

R512

(Chl)

and

RE12

(Ch2)

for

less

than

4,9mVRMS

(-44

dBu)

at

the

amplifier

output.

Elcctrfcal

Checkout

5-1

Gheckou

Procedures

5.9

Voltage

Gain

Spee

2666

Gg%n;

Gain

of

20,8

k3%.

Spac

0.775V

5e~%itlvi~:

REF

I

."---Gain

at

'508.65

&3%,

REF

!i

-~~~~~~~~~Eain

af

68,28

~3%.

Spec

1.4V

S~nsltivlQ:

REF

I

---Gain

of

5521

&3%.

REF

t

l

----Gain

st

37

.SO

a3%,

Inibtia%l

Eondlti@n%:

Controls

per standard.

26

dB

Procsduf@:

Inject

a

0,775

VAC

1

kHz

sine

wave

with

the Sensitivity

Switch

in

ths

26

dB

position,

Mea-

sure

15.5

VAC

f0.S

VAC

at

the

amplifier

skstpu2.

0,775V

Prosedut~::

Inject

a

0.775

VAC 1 kHz

sins

wave

with

the

Sensitivity

Switch

in

the

8.975V

position*

REF

i

measure

78

VAC,

f2.3

VAC,

at

Zh@

amplifies output.

REF

II

measure

52.9

VAC,

;s;.

"1.6

VACt

at

the

amplifier

output.

1

.@V

Bros@dure:

lnject

a

1,4

VAC

1

kHz

sine

wave

with

the

S~n~itisgify

Switch

in

the

1.4V

position.

REF

1

mea-

Figufe

5.2

DiF@r@nZia$ed

Square

Wave

sum

778

VAC,

&2,3

VAC,

st

the

amplifier

output.

REF

I!

measure

52.9

VACF A 1.6

VAC,

at

the amplifier

output*

5,10

Level

C~ntrsls

S@@s:

kevef

cantroiled

by

level

controls,

Inltlairl

Conditiows:

Controls

per

standard.

Bre@adur@:

No

Laad,

lnject

a

%

kHz

sine

wave.

With

level

controls

fully

clockwise

you

should

see

futf

gain,

As

controts

are

rotated

eountercixkwise,

sbsewe

sirni-

Iiar

gain

reduetisn

in

each

channel,

&$hen

complete,

return

!eve8

contrsls

$0

fully

clockwise

pssitian,

5,lf

Current

Limit

Spec:

REF

1

---Current

fimit

at

43

amps,

323

amps.

REF

II

-Current

limit

at

30

amps,

k3

amps,

lnrtlal

Csndftians:

ConWols

per

standard.

Procad&~s:

Load

each

channel

ta

7

Ohm.

Inject

at

"I

kHz

differentiated

&ear

38%

duty

cycte)

square

wave.

See

Figure

5%

f

.

Insrease

output

level

until

current

lim-

iting

occurs,

Refer

$0

Figure

52

for

wave

Form.

REF

f

will

limit

(clip)

at

43

vstt

peak,

2~3

voltss.

REF

II

will

limit

(clip)

at

38

v~iwpeak,

k3

volts,

In

-I

Out

5.12

Slsw

Rate

&

10

kHz

Square

Wave

Spac:

REF

1

-23

d3

V/pS.

REF

If

-1

9

~3

V&S.

lnltrai

eondltlo~s:

Cantrsls

per

standard,

F~ecedurg:

Laad

each

~hawwel

to

8

sk~rns.

inject

a

10

kHz

square

wave

at

a

level

of

2

ts

5

volts

below

clip.

Observe

the slope

af

the

waveform

and

catculate

the

sllew

rate,

Any

ringing

must

die

out

in

lass

than

"44

of

the

period,

and

its

amplitude

must

be

less

then

2%

aOf

%be

waveform

amplitude.

See

Figure

5.3.

Figure

5.3

IQ

kHz

Square

kVave

Electrical

Checkout

5-2