Adcom S.A.F.E. GFA-7705 User manual

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2

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1

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G

FA-

7

70

5

GFA-7/0/

s.a.f.e:

HIGH

CURRENT,

MULTI-CHANNEL

POWER

AMPLIFIERS

GFA-7705/07

Features

•

Precision-matched

devices

used

throughout

the

signal

path.

•

Independent

power

supplies

for

each

channel.

•

Fewer

gain

stages

improve

signal

reproduction

accuracy.

•

Custom

toroidal

power

transformer

provides

better

regulation

and

greater

peak

current

capability.

•

ADCOM-Universal

pre-prepped

chassis

and

internal

power

supplies

for

easy

in-field

upgradeability

from

5

to

7

channel

configuration.

•

Independent

thermal-overload

and

distortion

LEDs

for

all

5

(to

7)

channels.

•

S.A.F

E.®

Circuit:

Self

Annealing

Fuse

Equipped—automatic

reset

protection

circuit

in

the

event

of

speaker

or

speaker

wire

dead-short.

•

High

quality,

gold-plated

5-way

binding

posts.

•

High

quality,

gold-plated

RCA

jacks.

•

Large

independent,

internal

heatsinks

for

greater

cooling

capability

of

output

devices.

•

Convenient

12

VDC

power

ON/OFF

triggering.

•

Heavy

gauge,

anodized

aluminum

front

panel.

•

Cooling

vents

for

greater

efficiency

and

cooler

operation

while

driving

low

impedance

loads.

Table

of

Contents

Introduction

Warranty

Information.

4

Description

of

Unit—

20-Amp

Device

Notification

.4

Rear

Panel..

Front

Panel..

Installation

&

Hookup

Unpacking

the

GFA-7705/07.

9

Placement

of

the

GFA-7705/07.9

Quick

Connection

Diagram.

1

0

Connecting

the

GFA-7705/07.

H

Caring

for

your

GFA-7705/07.

12

Troubleshooting

Resolving

Problems.

1

3

Service

Information...

1

4

Specifications.

1

5

3

Introduction

Congratulations

on

your

decision

to

purchase

the

GFA-7705/07

multi-channel

power

amplifier.

The

GFA-7705/

07

integrates

very

well

with

any

other

home

theater

system,

such

as

Dolby

ProLogic

™

or

Dolby

Digital

™

You

have

made

a

wise

choice

that

will

reward

you

with

exceptionally

accurate

and

musical

sound

reproduction

for

years

to

come.

To

realize

the

full

potential

of

your

new

amplifier,

please

read

these

operating

and

installation

instructions

thoroughly

before

attempting

to

make

any

connections

to

it.

ADCOM

Protection

Plan

(NORTH

AMERICA

ONLY)

ADCOM

offers

the

enclosed

valuable

Limited

Warranty.

Please

read

the

details

on

the

Warranty

Card

carefully

understand

the

extent

of

the

protection

offered

by

the

Warranty,

its

reasonable

limitations,

and

what

you

should

do

in

order

to

obtain

its

benefits.

Be

sure

to

verify

that

the

serial

number

printed

on

the

rear

panel

matches

the

serial

number

on

the

outer

carton.

If

any

number

is

altered

or

missing,

you

should

notify

us

immediately

in

order

to

ensure

that

you

have

received

a

genuine

ADCOM

product

which

has

not

been

opened

mishandled,

or

tampered

with

in

any

way.

Always

retain

your

original

sales

receipt

as

a

proof

of

purchase.

Description

of

Unit

The

GFA-7705/07

is

a

20-Amp

Device.

GFA-7705/07

is

high-power,

high-current,

wide-bandwidth

design

employing

ADCOM’s

Fast

Analog

Transform

(F.A.T.)

circuitry

with

direct-coupled

Power

Rig

output

stages.

All

channels

are

completely

monaural

from

transformer

secondaries

through

the

output

stages.

In

order

for

this

product

to

achieve

its

actual

rated

power

output

on

all

channels

and

to

avoid

repeatedly

throwing/popping

the

related

electrical

service

panel

circuit

breaker,

it

is

critical

that

the

amplifier

be

professionally

installed

on

a

20-Amp

household

AC

circuit

and

outlet,

preferably

dedicated

but

at

minimum

one

not

shared

with

other

large

current-draw

appliances

or

devices.

Common

15-Amp

household

circuits

are

easily

and

inexpensively

converted

to

20

Amp

configuration

by

any

high

voltage

licensed

electrician.

5

y

1

s

For

this

reason,

the

GFA-7705/07

ships

Factory-equipped

with

a

hard-wired,

20-Amp

Plug

on

the

AC

Power

Cord.

nnfr^p^AMnliDun^I

P

LUG

°

R

HARDWIRED

AC

POWER

CORD

TO

EMPLOY

EITHER

A

15

AMP

OUTLET

OR

“AUDIOPHILE”

TYPE

DETACHABLE

POWER

CORD.

■

r^|^^7^^^^^^~^^^^~P

R

000-0

T

'

^^

ARRA

~'^^

^^^0^^^0—THE

PRODUCTAN

D

PUCE

THE

USER

AT

EXTRFMF

RISKflF

INJUR

Y

OR

DEATH.

4

Rear

Panel

Inputs

(1)

The

audio

inputs

for

the

GFA-7705

and

7707

are

through

high-quality,

gold-plated

RCA

jacks

to

minimize

hieh

RCA

-T

■

*»

~*

«*

SZ5!S££1L

L

manvc

e

b

l

FA

wh

05

h

/07

'*

P

[

eSerVed

’

you

should

use

the

quaUt^shiJ^

C0,Or

‘

C

°S

a

1

Specmca

"

y

*

*****

,

OT

«

*WfcaUoo.

YourZSca^Mp

select

the

best

cable

for

your

needs.

(See

Connecting

the

GFA-7705/07

for

more

information.)

P

Inputs

(1b)

Chassis

knock-out

for

future

expansion

channel-card

input

jack

(GFA-7705

only).

Outputs

(2)

EssjSassisHssS®*

“

■

™

S

1

vxzv

(See

CONNECTING

THE

GFA-7705/07

for

more

information.)

Outputs

(2b)

Chassis

knock-out

for

future

expansion

channel-card

output

binding

posts

(GFA-7705

only).

5

WARNING

THERE

ARE

NO

USER-SERVICEABLE

PARTS

OR

FUSES

INSIDE

THE

GFA-7705/07.

In

the

event

that

the

amplifier’s

rear-panel

circuit

breaker

fails

to

reset

(opens

again

when

power

applied

to

unit

and

unit

turned

on)

you

must

refer

the

amplifier

to

ADCOM

Factory

Service

or

ADCOM

Authorized

Service

Center.

Do

not

open

the

amplifier

nor

remove

the

topcover-Hazardous

and

Potentially

Lethal

Voltage

Present

and

Warranty

may

be

voided.

12VDC

Triggering

(3a)

ADCOM

has

provided

the

installer

the

ability

to

control

the

OFF/ON

function

of

the

GFA-7705/07

by

a

12Volt

DC

output

jack

on

the

rear

of

certain

pre-amplifiers

and

tuner

pre-amplifiers.

When

using

this

feature

the

front

panel

Power

Switch

must

be

left

in

the

in

“on”

position.

To

connect,

you

will

need

a

monaural

mini

phone

plug

to

monaural

mini

phone

plug

cable

of

appropriate

length

(not

included)

to

reach

from

the

rear

panel

of

the

amplifier

to

the

rear

panel

of

the

pre-amplifier.

Contact

your

dealer

for

information

on

using

this

feature

with

ADCOM

and

other

brand

pre-amplifiers.

Although

12VDC

is

optimal,

the

circuit

will

operate

from

approx.

5

to

30VDC.

Center

conductor

(tip)

is

positive

(+).

AC

Circuit

Breaker

(3b)

The

15-Amp

AC

Breaker

protects

the

electronic

circuits

of

the

GFA-7705/07.

Normally,

this

breaker

will

open

only

if

there

is

an

overload

or

a

component

failure

within

the

GFA-7705/07.

If

the

Power

LED

(7)

does

not

glow,

it

may

be

an

indication

that

the

AC

Breaker

has

blown.

If

you

are

using

the

12VDC

Triggering

feature

(above)

it

may

be

possible

that

there

is

no

trigger

voltage

present

or

a

problem

exists

with

that

connection.

To

determine

if

the

problem

is

caused

by

a

malfunction

in

the

12VDC

system,

remove

the

small

plug

inserted

into

the

12VDC

Triggering

jack.

Press

the

front

panel

power

switch

to

turn

off

the

amp,

and

immediately

re

press

the

power

switch.

If

the

problem

is

caused

by

the

12VDC

triggering

circuit

the

amp

will

turn

on

and

the

LED

will

glow.

DO

NOT

attempt

repair

of

the

12VDC

system.

If

you

are

not

sure,

or

the

amplifier

displays

other

symptoms,

please

consult

the

RESOLVING

PROBLEMS

section

on

page

13.

AC

Power

Cord

(4)

The

AC

cord

provides

power

to

operate

all

the

GFA-7705/07’s

circuits.

The

GFA-7705/07

is

a

very

high

power

amplifier

and

as

such

must

be

directly

connected

to

the

wall

outlet

or

an

appropriate

(non-

current

limiting)

surge

protector

or

AC

line

conditioner

of

20-Amp

service

capability.

NOTE:

As

previously

described

on

Page

4,

the

attached

plug

is

a

20-Amp

fitting

which,

in

order

for

the

amplifier

to

deliver

its

rated

power

output,

should

not

be

defeated

in

order

to

accomodate

standard

15-amp

household

wall

outlets.

Please

consult

with

your

dealer

and/or

licensed

electrician

for

conversion

of

a

15

amp

outlet

and

panel

circuit

to

a

20

amp

circuit.

6

(5)

(6)

(7)

(8a,

8b)

Front

Panel

On/Off

Switch

(5)

™

e^v“S,F.

h

™

r

/n7

et

t0

frrr

t,ansfor

™

r

.«*

»*

Power

LED

(6)

seconds

to

fully

extinguish.

t

me

t0

fade

001

com

Ptetely.

It

may

take

up

to

30

“

'

he

GFA

-

7

705,

°

7

.

«*

P°«r

LED

will

no.

triggering,

source

*—«

-

7

Distortion

Alert

LEDs

(7)

The

Distortion

Alert

circuit

is

a

unique

ADCOM

distortion

detection

system

which

reads

all

forms

of

non¬

linear

distortion

such

as

THD,

IM,

slew-induced,

“clipping,”

etc.

The

Distortion

Alert

LEDs

will

light

when

distortion

reaches

approximately

1%

regardless

of

impedance,

voltage/current

phase

angle

or

the

reactance

of

the

loudspeakers

which

the

amplifier

is

driving.

Sometimes,

when

the

amplifier

is

in

use,

the

LEDs

may

occasionally

flicker

during

high

volume

listening,

particularly

if

you

are

driving

low

impedances.

This

flickering

is

no

cause

for

concern.

The

LEDs

are

simply

warning

you

that

the

amplifier

is

approaching

its

maximum

power

output

into

the

particular

loudspeakers

you

are

using.

If,

however,

the

Distortion

Alert

LEDs

glow

brightly

or

are

illuminated

most

of

the

time

during

playback,

you

are

over

driving

the

amplifier

and

should

turn

down

your

volume

control

to

reduce

the

listening

level,

otherwise

it

may

cause

the

Thermal

Protection

to

be

activated

or,

in

extreme

cases,

damage

vour

loudspeakers.

Thermal

Protection

LEDs

(8a)

The

GFA-7705/07

is

provided

with

both

a

thermal

protection

circuit

and

a

current

overload

circuit

which

will

shut

down

the

individual

amplifier's

channels

if

its

heatsink

temperature

reaches

85°

C

or

the

amplifier’s

outputs

are

shorted.

The

Thermal

Protection

LEDs

will

light

when

either

of

these

protection

circuits

are

on

its

respective

channel

has

been

triggered

and

the

amplifier

is

inoperative.

The

thermal

protection

circuitry

will

typically

be

triggered

by

very

high

power

demands

into

impedances

much

lower

than

the

amplifier

is

capable

of

driving

at

those

levels.

If

any

amplifier

channel’s

output

through

the

loudspeaker(s)

ceases

abruptly,

and

its

Thermal

Protection

LED

glows,

you

will

know

that

its

heatsink

temperature

has

become

unacceptably

high

and

the

circuitry

is

protecting

the

amplification

devices.

Please

note

that

the

Power

LED

(7)

will

remain

on

and

the

amplifier

will

still

be

energized.

Once

the

temperature

of

the

heatsink(s)

drops

to

a

safe

operating

level,

that

amplifier

will

automatically

resume

operation.

Activation

of

the

Thermal

Protection

circuitry

in

any

of

the

amplifiers

in

the

GFA-7705/07

is

an

indication

that

the

amplifier

has

been

over

driven

or

that

the

load

the

loudspeakers

are

presenting

to

the

amplifier

is

unreasonably

low.

If

you

wish

to

prevent

recurrent

activation

of

the

thermal

protection

circuitry,

you

must

reduce

the

volume-level

demands

or

correct

the

load-impedance

condition

which

may

be

causing

activation

of

this

circuitry.

S.A.F.E.®

Protection

Circuit

(8b)

Self-Annealing

Fuse

Equipped:

Instead

of

blowing

internal

protection

rail

fuses

in

the

event

of

a

dead-

short

to

either

a

loudspeaker

or

speaker

cable

leads,

the

GFA-7705/07

will

enter

into

a

self-protect

SAFE

mode.

If

the

output

of

any

channel

of

the

amplifier

becomes

shorted

the

protection

circuit

will

trip

and

the

individual

Thermal

Protection

LED

for

that

channel

will

light.

The

Protection

LED

will

blink

approximately

every

5

seconds

as

the

circuit

will

attempt

to

reset;

if

the

short

has

been

corrected

the

amplifier

will

resume

proper

operation.

If

the

short

is

still

present

the

channel

will

cycle

off

again.

The

cycling

of

the

protection

circuit

will

continue

until

the

short

is

corrected

or

the

amplifier

power

is

switched

off.

8

WARNING

Whenever

connections

to

or

from

the

GFA-7705/07

are

being

made,

be

certain

that

the

AC

On/Off

Switch

(5)

of

the

amplifier

is

in

the

OFF

position,

the

AC

Power

Cord

(4)

of

the

amplifier

is

disconnected

from

the

AC

wall

outlet

and

that

all

associated

components

are

turned

off.

Installation

&

Hookup

Unpacking

the

GFA-7705/07

Before

your

new

GFA-7705/07

left

our

factory,

it

was

carefully

inspected

for

physical

imperfections

and

tested

for

all

electrical

parameters

as

a

routine

part

of

ADCOM’s

systematic

quality

control.

This,

along

with

full

operational

and

mechanical

testing,

should

ensure

a

product

flawless

in

both

appearance

and

performance.

After

you

have

unpacked

the

GFA-7705/07

inspect

it

for

physical

damage.

Save

the

shipping

carton

and

all

packing

material

as

they

are

intended

to

reduce

the

possibility

of

transportation

damage,

should

the

amplifier

ever

need

to

be

shipped

again.

In

the

unlikely

event

damage

has

occurred,

notify

your

dealer

immediately

and

request

the

name

of

the

carrier

so

a

written

claim

to

cover

shipping

damages

can

be

initiated.

THE

RIGHT

TO

A

CLAIM

AGAINST

A

PUBLIC

CARRIER

CAN

BE

FORFEITED

IF

THE

CARRIER

IS

NOT

NOTIFIED

PROMPTLY

IN

WRITING

AND

IF

THE

SHIPPING

CARTON

AND

PACKING

MATERIALS

ARE

NOT

AVAILABLE

FOR

INSPECTION

BY

THE

CARRIER.

SAVE

ALL

PACKING

MATERIALS

UNTIL

THE

CLAIM

HAS

BEEN

SETTLED.

Placement

of

the

GFA-7705/07

During

normal

home

operation

the

internal

heatsinks

of

the

GFA-7705/07

may

become

warm.

However,

there

are

instances

during

high-level

playback

into

low

impedances

when

the

heatsinks

will

become

much

warmer

than

usual.

To

ensure

the

amplifier's

long-term,

trouble-free

operation,

it

is

necessary

to

provide

adequate

ventilation

for

the

heatsinks.

Therefore,

the

GFA-7705/07

should

be

kept

away

from

external

sources

of

heat

such

as

radiators

and

hot-air

ducts.

The

GFA-7705/07

should

never

be

placed

with

other

heat-producing

components

in

a

cabinet

or

enclosure

lacking

free

air

flow.

The

top

and

bottom

panels

of

the

amplifier’s

chassis

have

been

provided

with

vents

to

allow

the

necessary

cooling

of

the

internal

components.

It

is

imperative

that

these

vents

are

not

obstructed

in

any

way.

We

recommend

that

you

do

not

stack

other

components

on

top

of

the

GFA-7705/07.

Not

only

will

heat

generated

by

the

amplifier

affect

the

performance

of

equipment

stacked

on

top

of

the

GFA-7705/07,

but

the

free

flow

of

air

through

the

ventilating

slots

in

the

amplifier

may

be

partially

obstructed.

This

is

particularly

important

if

your

system

includes

low-impedance

loudspeakers

which

are

difficult

to

drive,

or

you

will

consistently

demand

high

volume

levels

from

the

amplifier

and

speaker

system.

If

you

observe

these

recommendations,

the

GFA-7705/07

will

perform

reliably

in

any

reasonable

environment.

You

should

also

pay

attention

to

such

normal

considerations

as

protection

from

excessive

dust

and

moisture.

Occasional

vacuuming

of

accumulated

dust

on

the

chassis,

panels

and

around

the

ventilating

slots

should

be

all

that

is

required.

The

optimal

performance

of

your

new

GFA-7705/07

will

ultimately

depend

on

the

care

with

which

you

make

the

connections

between

the

amplifier,

preamplifier,

surround

sound

decoder

and

the

loudspeakers.

All

input

and

output

signal

connections

should

be

made

only

with

high

quality,

low

capacitance,

shielded

cables

following

the

recommendations

in

the

Inputs

and

Outputs

section

of

CONNECTING

THE

GFA-7705/07.

Quick

Connections

For

those

of

you

who

are

in

a

hurry

to

hook

up

your

amplifier

into

your

system,

we

have

included

this

quick-connection

section.

The

wiring

is

straight

forward

and

expeditious

if

you

use

the

proper

cables

and

follow

this

diagram

exactly.

If

you

have

any

difficulties

or

questions,

please

refer

to

the

appropriate

section

of

this

manual

for

complete

descriptions

and

instructions.

9

Connecting

the

GFA-7705/07

Remember,

that

the

Left

and

Right

designations

are

as

you

are

sitting

down

in

your

listening/viewing

area

Theyareas

fdSs

”***

and

°

UtpUtS

are

gr

°

Uped

in

5

or

7

bracketed

sets,

one

set

for

each

channel.'

LB

-

Left

Back

(GFA-7707

only)

LS

—

Left

Surround

LF

—

Left

Front

C

—

Center

RF

—

Right

Front

RS

—

Right

Surround

RB

-

Right

Back

(GFA-7707

only)

Inputs

(1)

To

preserve

the

correct

effects,

be

certain

to

connect

the

RCA

cables

to

the

proper

RCA-input

connector.

If

the

cables

are

color

coded,

then

use

this

sequence

for

the

connections:

^

ue

..Left

Front

fted...Right

Front

G

feen

...Center

White

with

Blue

Stripe....Left

Surround

White

with

Red

Stripe.Right

Surround

The

recommended

maximum

RCA

cable

capacitance

should

be

less

than

or

equal

to

30pF

per

foot

when

measured

between

the

two

conductors,

and

less

than

or

equal

to

50pF

per

foot

when

measured

between

one

conductor

and

the

shield.

Outputs

(2)

NOTE.

The

GFA-7705/07

is

“polarity

correct”.

That

is,

it

does

not

invert

phase

from

input

to

output.

Any

positive

signals

at

its

inputs

will

appear

as

a

positive

signal

at

its

outputs.

In

connecting

the

amplifier

to

the

loudspeaker,

it

is

vital

to

maintain

proper

polarity

(positive

to

positive,

negative

to

negative).

On

the

GFA-7705/07,

the

positive

terminal

is

color

coded

RED

and

labeled

“+,”

and

the

negative

is

color

coded

BLACK

and

labeled

The

positive

terminal

on

the

corresponding

loudspeaker

will

be

color

coded

RED,

or

will

be

labeled

“+,”

“pos,”

"positive,”

“8

ohms,”

or

“A

ohms.”

The

negative

terminal

on

the

speaker

will

be

color

coded

BLACK,

or

will

be

labeled

“neg,”

negative,”

“C,”

“Common,”

“G,”

or

“ground.”

It

is

necessary

that

your

speaker

cables

be

terminated

with

“U”-

the

most

contact

area

insuring

long-term

reliability.

The

spade

connector

should

have

a

maximum

width

of

0.57

inches

and

an

opening

width

of

no

less

than

0.25”

(see

diagram

on

right).

type

spade

connectors.

These

will

give

To

properly

connect

the

speaker

cable

to

the

binding

posts

turn

the

insulated

head

of

the

binding

post

clockwise

until

the

wire

or

connector

is

firmly

secured.

Finger

pressure

is

sufficient

and

you

should

not

use

pliers

or

other

tools

which

could

damage

or

over

tighten

the

binding-post

assembly.

The

binding

posts

have

been

designed

in

such

a

way

that

finger

pressure

is

all

that

is

required

to

cause

a

“pinching”

action

among

the

different

metal

surfaces

to

ensure

proper

connection.

It

is

very

important

to

use

the

correct

size

of

wire

in

order

to

avoid

unnecessary

loss

of

amplifier

power

in

the

cable,

reduction

of

amplifier

damping

factor

and

other

undesirable

conditions.

Recommended

capacitance

of

the

speaker

wire

should

not

exceed

50pF

per

foot.

This

insures

high

frequencies

will

not

be

rolled-off.

11