Adcom GFA-5500 User manual

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3

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AXXM

details

you

can

hear

G

FA-5500

High

Current

Power

Amplifier

OWNER’S

MANUAL

THE

FOLLOWING

PRECAUTIONS

AND

SAFETY

INSTRUCTIONS

ARE

REQUIREMENTS

OF

UL

AND

CSA

SAFETY

REGULATIONS

Warning:

To

reduce

the

risk

of

fire

or

electric

shock,

do

not

expose

this

unit

to

rain

or

moisture.

CAUTION

RISK

OF

ELECTRIC

SHOCK

DO

NOT

OPEN

AVIS:

RISQUE

DE

CHOC

ELECTRIQUE-NE

PAS

OUVRIR,

The

graphic

symbol

of

a

lightning

flash

with

an

arrow

point

within

a

triangle

signifies

that

there

is

dangerous

voltage

within

the

unit

and

it

poses

a

hazard

to

anyone

removing

the

cover

to

gain

access

to

the

interior

of

the

unit.Only

qualified

service

personnel

should

make

any

such

attempt.

The

graphic

symbol

of

an

exclamation

point

within

an

equilateral

triangle

warns

a

user

of

the

device

that

it

is

necessary

to

refer

to

the

instruction

manual

and

its

warnings

for

proper

operation

of

the

unit.

Do

not

place

this

unit

on

an

unstable

cart,

stand,

tripod,

bracket,

or

table.

The

unit

may

fall,

causing

serious

injury

to

a

child

or

adult,

and

serious

damage

to

the

unit.

Use

only

with

a

cart,

stand,

tripod,

bracket,

or

table

recommended

by

the

manufacturer,

or

sold

with

the

unit.

Any

mounting

of

the

device

should

follow

the

man¬

ufacturer's

instructions,

and

should

use

a

mounting

ac¬

cessory

recommended

by

the

manufacturer.

Read

all

the

safety

and

operating

instructions

before

connecting

or

using

this

unit.

Retain

this

notice

and

the

owner’s

manual

for

future

reference.

All

warnings

on

the

unit

and

in

its

operating

instructions

should

be

adhered

to.

All

operating

and

use

instructions

should

be

followed.

Do

not

use

this

unit

near

water:

for

example,

near

a

bathtub,

washbowl,

kitchen

sink,

laundry

tub,

in

a

wet

basement,

or

near

a

swimming

pool.

The

unit

should

be

installed

so

that

its

location

or

position

does

not

interfere

with

its

proper

ventilation.

For

example,

it

should

not

be

situated

on

a

bed,

sofa,

rug,

or

similar

surface

that

may

block

the

ventilation

openings;

or

placed

in

a

built-in

installation,

such

as

bookcase

or

cabinet,

that

may

impede

the

flow

of

air

through

its

ventilation

openings.

The

unit

should

be

situated

away

from

heat

sources

such

as

radiators,

heat

registers,

stoves,

or

other

devices

(including

amplifiers)

that

produce

heat.

The

unit

should

be

connected

to

a

power-supply

outlet

only

of

the

voltage

and

frequency

marked

on

its

rear

panel.

The

power-supply

cord

should

be

routed

so

that

it

is

not

likely

to

be

walked

on

or

pinched,

especially

near

the

plug,

convenience

receptacles,

or

where

the

cord

exits

from

the

unit.

Clean

unit

only

as

recommended

in

its

instruction

manual.

The

power-supply

cord

of

the

unit

should

be

unplugged

from

the

wall

outlet

when

it

is

to

be

unused

for

a

long

period

of

time.

Care

should

be

taken

so

that

objects

do

not

fall,

and

liquids

are

not

spilled,

into

the

enclosure

through

any

openings.

This

unit

should

be

serviced

by

qualified

service

personnel

when:

A.

The

power

cord

or

the

plug

has

been

damaged;

or

B.

Objects

have

fallen,

or

liquid

has

been

spilled,

into

the

unit:

or

C.

The

unit

has

been

exposed

to

rain,

or

liquids

of

any

kind;

or

D.

The

unit

does

not

appear

to

operate

normally,

or

exhibits

a

marked

change

in

performance:

or

E.

The

device

has

been

dropped,

or

the

enclosure

damaged.

DO

NOT

ATTEMPT

SERVICING

OF

THIS

UNIT

YOURSELF.

REFER

SERVICING

TO

QUALIFIED

SERVICE

PERSONNEL

ATTENTION

POUR

PREVENIR

LES

CHOCS

ELECTRIQUES

NE

PAS

UTILISER

CETTE

FICHE

POLARISEE

AVEC

UN

PROLONGATEUR,

UNE

PRISE

DE

COURANT

OU

UNE

AUTRE

SORTIE

DE

COURANT,

SAUF

SI

LES

LAMES

PEUVENT

ETRE

INSEREES

A

FOND

SANS

EN

LAISSER

AU-

CUNE

PARTIE

A

DECOUVERT.

CAUTION

TO

PREVENT

ELECTRIC

SHOCK

DO

NOT

USE

THIS

POLARIZED

PLUG

WITH

AN

EXTENSION

CORD,

RECEPTACLE

OR

OTHER

OUTLET

UN¬

LESS

THE

BLADES

CAN

BE

FULLY

INSERTED

TO

PREVENT

BLADE

EXPOSURE.

CAUTION

POWER

LINES

Any

outdoor

antenna

must

be

located

away

from

all

power

lines.

OUTDOOR

ANTENNA

GROUNDING

If

an

outside

antenna

is

connected

to

your

tuner

or

tuner-preamplifier,

be

sure

the

antenna

system

is

grounded

so

as

to

provide

some

protection

against

voltage

surges

and

built-up

static

charges.

Section

810

of

the

National

Electrical

Code,

ANSI/NFPA

No.

70-1984,

provides

information

with

respect

to

proper

grounding

of

the

mast

and

supporting

structure,

grounding

of

the

lead-in

wire

to

an

antenna

discharge

unit,

size

of

grounding

conductors,

location

of

antenna

discharge

unit,

connection

to

grounding

electrodes,

and

requirements

for

the

grounding

electrode.

a.

Use

No.10

AWG

(5.3

mm^)

copper,

No.8

AWG

(8.4

mm^)

aluminum,

No.17

AWG

(1.0

mm")

copper-clad

steel

or

bronze

wire,

or

larger,

as

a

ground

wire.

b.

Secure

antenna

lead-in

and

ground

wires

to

house

with

stand-off

insulators

spaced

from

4-6

feet

(1.22-1.83

m)

apart.

c.

Mount

antenna

discharge

unit

as

close

as

possible

to

where

lead-in

enters

house.

d.

Use

jumper

wire

not

smaller

than

No.6

AWG

(13.3

mm")

copper,

or

the

equivalent,

when

a

separate

antenna-grounding

electrode

Is

used.

See

NEC

Section

810-21

(j).

EXAMPLE

OF

ANTENNA

GROUNDING

AS

PER

NATIONAL

ELECTRICAL

CODE

INSTRUCTIONS

CONTAINED

IN

ARTICLE

810

-

RADIO

AND

TELEVISION

EQUIPMENT.

NOTE

TO

CATV

SYSTEM

INSTALLER

This

reminder

is

provided

to

call

the

CATV

system

installers

attention

to

Article

820-22

of

the

National

Electrical

Code

that

provides

guidelines

for

proper

grounding

and,

in

particular,

specifies

that

the

cable

ground

shall

be

connected

to

the

grounding

system

of

the

building,

as

close

to

the

point

of

cable

entry

as

practical.

INTRODUCTION

Congratulations

on

your

decision

to

purchase

the

GFA-5500

Stereo

Power

Amplifier.

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

connect

it.

Furthermore,

it

is

a

good

idea

to

keep

this

manual

handy

for

future

reference.

FEATURES

•

Precision

matched

MOSFETs

used

throughout

the

signal

path.

•

80,000

pF

of

power

supply

filter

capacitance

with

low

ESR

for

greater

reserve

capacity.

•

Low

number

of

gain

stages

improves

signal

reproduction

accuracy.

•

Custom

toroidal

power

transformer

provides

better

regulation

and

greater

peak

current

capability.

•

High

quality,

gold

plated

binding

posts.

•

Independent

thermal

overload

and

distortion

LEDs

for

each

channel.

•

Gold

plated,

brass

RCA

jacks

with

Teflon

insulators.

•

Large,

exposed

heatsinks

for

greater

cooling

capability

of

output

devices.

•

Heavy

gauge,

anodized

aluminum

front

panel.

•

Powder

coated,

baked

chassis

and

top

cover

for

greater

durability.

•

Increased

cooling

vents

on

top

cover

for

greater

efficiency

and

cooler

operation

while

driving

low

impedance

loads.

IMPORTANT

NOTICE

ADCOM

PROTECTION

PLAN

(USA

ONLY)

ADCOM

offers

the

enclosed

valuable

Limited

Warranty.

Please

read

the

details

on

the

Warranty

Card

carefully

to

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,

or

if

the

ADCOM

Warranty

Card

is

not

included

in

the

carton,

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.

1

UNPACKING

Before

your

new

GFA-5500

left

our

factory,

it

was

carefully

inspected

for

physical

imperfections

and

tested

for

all

electrical

parameters

as

a

routine

part

of

ACCOM'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-5500

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.

INSTALLING

THE

GFA-5500

During

normal

home

operation

the

external

heatsinks

of

the

GFA-5500

will

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-5500

should

be

kept

away

from

external

sources

of

heat

such

as

radiators

and

hot-air

ducts.

The

GFA-5500

should

never

be

placed

with

other

heat-producing

components

in

a

cabinet

or

enclosure

lacking

free

air

flow.

If

you

require

that

the

GFA-5500

be

mounted

in

an

enclosed

cabinet,

it

is

recommended

that

the

rear

panel

of

the

cabinet

be

provided

with

ventilation

openings

at

the

top

and

bottom

to

allow

air

to

circulate

freely

in

the

cabinet.

The

top

and

bottom

panel

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-5500.

This

is

particularly

important

If

your

system

includes

low-impedance

loudspeakers

which

are

difficult

to

drive,

or

if

you

will

consistently

demand

high

volume

levels

from

the

amplifier

and

speaker

system.

Not

only

will

heat

generated

by

the

amplifier

affect

the

performance

of

equipment

stacked

on

top

of

the

GFA-5500,

but

the

free

flow

of

air

through

the

ventilating

slots

in

the

amplifier

may

be

partially

obstructed.

If

you

observe

these

recommendations,

the

GFA-5500

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,

heatsinks,

panels

and

around

the

ventilating

slots

should

be

all

that

is

required.

The

optimal

performance

of

your

new

GFA-5500

will

ultimately

depend

on

the

care

with

which

you

make

the

connections

between

the

amplifier,

preamplifier

and

the

loudspeakers.

All

input

and

output

signal

connections

should

be

made

only

with

high

quality,

low-loss,

low

capacitance

cables

following

the

recommendations

in

the

following

relevant

sections.

Please

refer

to

the

rear

panel

diagram

to

identify

all

the

connector

locations.

WARNING

DO

NOT

EXPOSE

THE

AMPLIFIER

TO

RAIN,

WATER,

OR

MOISTURE

OF

ANY

KIND.

RIGHT/LEFT

INPUT

(D

The

audio

inputs

to

the

GFA-5500

are

through

two

high

quality,

gold

plated

RCA

jacks

to

minimize

high

frequency

losses,

noise,

etc.

They

will

accept

standard

RCA

type

plugs,

one

for

each

channel,

LEFT

and

RIGHT,

usually

supplied

at

the

ends

of

interconnecting

cables.

To

ensure

that

the

performance

designed

into

the

GFA-5500

is

realized,

you

should

use

the

highest

quality

cables

feasible.

There

are

many

cables

which

are

designed

specifically

for

these

applications

and

your

ADCOM

dealer

can

be

of

help

in

selecting

the

best

cable

for

your

application.

Whatever

cable

you

finally

select,

it

should

have

low

capacitance.

This

is

particularly

important

if

you

use

a

long

run

between

the

preamplifier

and

amplifier.

Generally

speaking,

a

cable

with

a

capacitance

of

less

than

100

pF

will

work

best

The

load

impedance

which

the

GFA-5500

inputs

present

to

the

source

preamplifier

or

tuner-preamplifier

is

49.9k

ohms.

This

load

impedance

results

in

minimal

amplifier

noise

when

used

with

a

source

component

of

low

output

impedance

such

as

an

ADCOM

preamplifier

or

tuner/preamplifier.

To

preserve

the

correct

stereophonic

effects,

please

be

certain

to

connect

the

left

output

of

the

preamplifier

or

tuner-

preamplifier

to

the

RCA

jack

on

the

GFA-5500

labeled

LEFT

INPUT

and

the

right

output

of

the

source

component

to

the

RIGHT

INPUT

jack.

2

GFA-5500

Rear

Panel

Diagram

WARNING

WHENEVER

CONNECTIONS

TO

OR

FROM

THE

GFA-5500

ARE

BEING

MADE,

BE

CERTAIN

THAT

THE

AC

ON/OFF

SWITCH

OF

THE

AMPLIFIER

IS

IN

THE

OFF

POSITION.

THE

AC

CORD

OF

THE

AMPLIFIER

IS

DISCONNECTED

FROM

THE

AC

WALL

OUTLET

AND

THAT

ALL

ASSOCIATED

COMPONENTS

ARE

OFF.

RIGHT/LEFT

OUTPUT

(D

The

GFA-5500's

connection

to

the

loudspeakers

are

made

through

two

high

quality,

five-way,

gold

plated

binding

posts

located

on

the

rear

panel.

These

terminals

will

accommodate

either

bare

wire,

tinned

wire,

terminal

pins,

spade

lugs

or

banana

plugs,

both

single

and

dual.

These

output

terminals

are

color

coded

RED

and

BLACK

to

indicate

polarity.

To

ensure

correct

stereo

phasing,

you

must

connect

the

RED

output

terminal

(labeled

“+")

to

the

loudspeaker

input

terminal

color

coded

RED

(or

labeled

POSITIVE,

POS,

8

OHMS

or

4

OHMS).

The

BLACK

binding

post

terminal

on

the

amplifier

(labeled

should

be

connected

to

the

loudspeaker

input

terminal

color

coded

BLACK

(or

labeled

NEGATIVE,

NEC.

C,

COMMON,

G.

or

GROUND).

The

RIGHT

OUTPUT

should

be

connected

to

the

right

channel

loudspeaker,

as

you

face

the

pair

of

loudspeakers,

and

the

LEFT

OUTPUT

to

the

left

channel

loudspeaker.

In

order

to

ensure

that

connections

to

the

loudspeakers

are

correct,

you

must

be

able

to

identify

each

wire

conductor

of

the

loudspeaker

cables

at

both

ends

of

the

cables.

This

is

relatively

easy

to

do

since

most

loudspeaker

cables'consist

of

two

parallel,

stranded

conductors

in

a

flexible

insulation,

with

a

coding

system

for

wire

identification.

Sometimes

there

is

a

colored

“tracer"

wrapped

around

one

of

the

conductors;

some

cables

have

one

of

the

conductors

colored

silver

and

the

other

copper;

some

have

a

“ridge"

molded

on

the

insulation

of

one

of

the

conductors,

while

others

are

imprinted

with

*+"

and/or

markings.

Your

ADCOM

dealer

also

sells

special

loudspeaker

cables

and

these

are

most

often

labeled

with

respect

to

polarity.

3

NOTE

THE

GFA-5500

IS

POLARITY

CORRECT

AND

DOES

NOT

INVERT

PHASE,

THAT

IS,

ANY

POSITIVE

GOING

SIGNAL

AT

ITS

INPUT

WILL

APPEAR

AS

A

POSITIVE

GOING

SIGNAL

AT

ITS

OUTPUT,

Generally

speaking,

when

making

connections

to

the

loudspeakers

from

the

amplifier

it

is

very

important

to

use

the

correct

type

and

size

of

wire

in

order

to

avoid

unnecessary

loss

of

amplifier

power

in

the

cable,

reduction

of

amplifier

damping

factor

and

other

undesirable

conditions.

For

runs

up

to

twelve

feet,

ordinary

“zip”

or

lamp

cord,

made

up

of

AWG18

stranded

wire

and

available

in

a

variety

of

insulation

colors

may

be

used.

For

runs

up

to

forty

feet,

AWG16

stranded

wire

should

be

used

as

a

minimum

to

prevent

power

losses.

For

lengths

over

forty

feet

and

not

exceeding

sixty

feel,

use

at

least

AWG14

stranded

wire.

Runs

exceeding

sixty

feet

require

the

use

of

heavier

conductors

such

as

AWG12,

Regardless

of

the

cables

you

select

to

connect

your

loudspeakers,

there

are

some

additional

requirements

which

you

should

observe

in

order

to

ensure

maximum

performance

from

your

amplifier.

It

is

most

important

that

you

make

certain

the

wiring

you

have

selected

has

as

low

a

capacitance

as

possible.

All

amplifiers,

particularly

wide

bandwidth

audio

amplifiers

are

susceptible

to

the

capacitance

cables

present

to

their

outputs

at

extremely

high

frequencies.

This

capacitance,

in

conjunction

with

the

inductance

of

the

wire

itself

and

the

reactive

load

of

the

loudspeakers,

can

create

anomalies

at

ultrasonic

frequencies

which,

although

inaudible,

can

affect

performance

in

the

audible

range.

There

are

several

different

ways

to

connect

the

wiring

to

the

RIGHT

and

LEFT

OUTPUTS,

The

methods

used

will

depend

on

the

specific

type

of

connectors

supplied

with

the

loudspeakers,

the

speaker

cables,

etc.

As

a

matter

of

course,

we

prefer

to

use

banana

plugs

because

it

is

generally

the

most

secure

method

of

connection.

Also,

the

springs

of

the

banana

plugs

create

a

self-cleaning

action

which

ensures

the

best

contact

between

the

binding

posts

and

the

connectors

themselves.

There

are

“sockets”

provided

in

the

center

of

the

binding

posts’

studs

which

permit

secure

seating

of

the

banana

plugs.

Before

inserting

the

banana

plug

into

the

binding

post,

ensure

the

binding

post

is

securely

hand

tightened

in

a

clockwise

direction.

Additionally,

when

connecting

the

cables

to

the

amplifier

and

loudspeakers,

it

is

important

that

you

“tin”

the

wires

with

good

quality

electronic

solder

in

order

to

minimize

contact

resistance.

Tinning

prevents

the

buildup

of

surface

compounds

which

can

form

on

copper

wire

and

increase

its

contact

resistance.

It

is

partly

for

this

reason

that

banana

plugs

are

preferred.

However,

make

sure

that

the

cable

ends

are

tinned

before

you

make

the

cable

connections

to

the

banana

plugs.

Alternatively,

you

can

use

“crimped”

pins

or

other

lugs

to

ensure

low

contact

resistance

at

the

connection

to

the

amplifier

and

loudspeakers.

If

you

prefer

to

use

other

methods

of

connection,

unscrew

the

insulated

head

of

the

binding

post

until

the

hole

in

the

binding

post

stud

is

accessible.

You

can

then

insert

the

bare

or

tinned

wire,

or

terminal

pin,

through

the

hole.

You

can

also

use

the

many

variety

of

spade

lugs

available

by

simply

placing

the

tines

of

the

spade

lug

onto

the

binding

post

stud.

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

post

has

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.

All

loudspeakers

having

a

nominal

impedance

down

to

4

ohms

can

be

connected

to,

and

driven

by

the

GFA-5500,

The

amplifier

can

drive

these

low

impedances

at

more

than

adequate

power

levels

with

no

difficulty.

It

should

be

noted

here

that

many

loudspeaker

systems

which

are

nominally

rated

at

4

ohms

drop

in

impedance,

in

some

parts

of

their

frequency

range,

to

as

low

as

2

ohms

(and

some

others

to

even

less

than

2

ohms).

You

will

not

experience

difficulties

even

with

these

very

low

impedance

loads

unless

you

demand

excessively

high

volume

levels

from

the

system.

In

most

applications,

you

can

drive

two

or

more

sets

of

loudspeakers.

You

should

note,

however,

that

when

loudspeakers

are

paralleled,

the

impedance

presented

to

the

amplifier

is

lower

than

the

nominal

impedance

of

each

loudspeaker.

In

other

words,

if

you

parallel

two

8

ohm

sets

of

loudspeakers,

the

resultant

impedance

presented

to

the

amplifier

will

be

4

ohms.

If

8

ohm

and

4

ohm

loudspeakers

are

paralleled,

the

resultant

impedance

will

be

approximately

2,6

ohms.

In

this

last

situation,

depending

upon

the

lowest

impedance

of

the

nominally

4

ohm

speakers,

and

if

excessive

power

demands

are

placed

on

the

amplifier,

you

may

trigger

the

THERMAL

PROTECTION

on

the

amplifier

or

blow

one

of

the

EXTERNAL

PROTECTION

FUSES,

See

its

respective

section

for

more

information.

For

convenient

switching

of

multiple

sets

of

speakers

with

impedance

protection

for

the

amplifier,

you

should

consider

the

use

Of

an

ADCOM

speaker

selector.

These

are

available

from

your

local

ADCOM

dealer.

4

AC

LINE

CORD

(T)

NOTE

The

GFA-5500’s

power

cord

is

supplied

with

a

"polarized"

AC

plug

as

required

bv

UL/CSA

stanri;,rH^

=,nH

fho

i

r,"if

«^«ncal

Shock

and

to?n

™

re

mlnlji;?

h

i

frSm

[?!

etedric^s'hS-k^H

‘’“T"’'

P'“9

(“hP

«*«e

“afe

and

one

narrow

blade)

To

prevent

foil,

ihserSl

prevent

b"Setp’’ot^^^^^^^

""

AC

POWER

FUSE

®

^o^rXrl"g'^o';?he

not

c^V^tLe

the

amplifier

is

energized,

the

POWER

LED

will

blown

Unpluq

the

AC

LINE

CORn

fmm

Ar

n

‘he

AC

POWER

FUSE

is

vt

WARNING

U«PbUO

TH.

*C

Exf

rr^

K^hXrrXr

£

cap

in

the

fuse

holder

body

should

be

easily

accomplished

without

excessive

force

THREADS.

Seating

of

the

„

,

,

WARNING

SffERe“;^^^^^^

USE

SUBST^TUTfFUSEl"vJ?S

Circuits,

MAY

CREATE

A

FIRE

Ha'^R^AND

MA^wfc

?h^

AC

POWER

FUSE

For

115

Volt

operation:

12

AMP

ABC/250V

_

POWER

FUSE

For

230

Volt

operation:

6

AMP

ABC/250V

AC

ON/OFF

SWITCH

©

5

POWER

LED

0

This

LED

will

glow

whenever

the

AC

ON/OFF

switch

is

turned

on

and

the

GFA-5500

is

energized.

If

the

AC

LINE

FUSE

blows

the

POWER

LED

will

cease

to

glow.

The

POWER

LED

indicates

that

there

is

AC

voltage

being

fed

to

the

amplifier,

but

it

does

not

signify

that

all

the

amplifier's

circuits

are

in

operation.

If,

for

example,

you

have

blown

one

or

more

of

the

EXTERNAL

PROTECTION

FUSES,

the

amplifier

will

not

operate.

That

is,

the

amplifier

will

not

produce

any

audio

signal

even

though

the

POWER

LED

is

glowing.

Similarly,

if

the

THERMAL

PROTECTION

LED

glows,

the

amplifier

will

not

produce

sound

even

though

the

POWER

LED

may

still

glow.

Additionally,

the

internal

power

transformer

is

provided

with

a

thermostat

which

will

interrupt

power

into

the

transformer

if

its

temperature

exceeds

125°C.

This

high

temperature

will

seldom,

if

ever,

be

encountered

unless

the

amplifier

is

subjected

to

abnormal

conditions,

such

as

operation

into

loads

of

less

than

3

ohms

at

very

high

listening

levels,

etc.

If

the

AC

POWER

FUSE

is

not

blown,

the

POWER

LED

is

out,

the

THERMAL

PROTECTION

LED

is

out

and

the

EXTERNAL

PROTECTION

FUSES

are

intact,

this

would

indicate

that

the

thermostat

within

the

transformer

has

opened.

Once

the

temperature

within

the

transformer

decreases

to

a

normal

level,

the

thermostat

will

reset

itself

automatically

and

normal

operation

will

resume.

If

you

are

to

avoid

continually

tripping

the

thermostat

in

the

transformer,

you

must

reduce

the

sound

level

demands,

correct

the

load

impedance

of

the

loudspeakers,

or

both.

INSTANTANEOUS

DISTORTION

ALERT

LEDs

®

The

INSTANTANEOUS

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

INSTANTANEOUS

DISTORTION

ALERT

LEDs

will

light

when

distortion

reaches

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

INSTANTANEOUS

DISTORTION

ALERT

LEDs

glow

brightly

or

are

illuminated

most

of

the

time

during

playback,

you

are

overdriving

the

amplifier

and

should

turn

down

your

volume

control

to

reduce

the

listening

level

or

you

may

blow

one

or

more

of

the

EXTERNAL

PROTECTION

FUSES,

cause

the

THERMAL

PROTECTION

to

be

activated

or,

in

extreme

cases,

damage

your

loudspeakers.

GFA-5500

Front

Panel

Diagram

6

THERMAL

PROTECTION

LEDs

(S

The

GFA-5500

is

provided

with

a

thermal

protection

circuit

which

will

shut

down

the

amplifier

if

either

heatsink's

temperature

reaches

85”C.

The

THERMAL

PROTECTION

LEDs

will

light

Whenever

the

thermal

prWL^on

drcufon

its

tnggered

and

the

amplifier

is

inoperative.

The

thermal

protection

circuitry

will

typically

be

eSSs

f

demands

into

impedances

much

lower

than

the

amplifier

is

capable

o7drivin^at

thoL

p

„

channel

s

output

through

the

loudspeaker(s)

ceases

abruptly,

and

one

or

both

the

THERMAL

h

^

‘'^^t

its

heatsink

temperature

has

become

unacceptably

high

and

the

circuitry

is

eneS

n

note

that

the

POWER

LED

will

remain

on

and

the

amplifirwTlI

st^be

resume

oper?t"oa

heatsink(s)

drops

to

a

safe

operating

level,

the

amplifier

will

automatically

NOTE

ACTIVATION

OF

THE

THERMAL

PROTECTION

CIRCUITRY

IN

THE

GFA-5500

IS

AN

INOICATinM

tuat

tuiit

AMPLIFIER

HAS

BEEN

OVERDRIVEN

OR

THAT

THE

LOAD

THE

LOUDSPEAKERS

ARE

PRESENTING

TO

THP

AMPLIFIER

IS

UNREASONABLY

LOW.

IF

YOU

WISH

TO

PREVENT

CIRCUITRY.

YOU

MUST

REDUCE

THE

VOLUME

LEVEL

DEMANDS

OR

CORRECT

THE

LOAD-IMPEDANCE

CONDITION

WHICH

MAY

BE

CAUSING

ACTIVATION

OF

THIS

CIRCUITRY,

OR

BOTH

EXTERNAL

PROTECTION

FUSES

(D

There

is

an

additional

protection

provided

to

the

GFA-5500

in

the

form

of

EXTERNAL

PROTECTION

FUSES

for

thP

nr

are

rnade

of

me

ampKeV

e«heMoa

f^m

or

Short

term,

and

are

meant

to

protect

not

only

the

loudspeakers,

but

the

power

output

devices

as

well.

^

If

the

amplifier

ceases

to

operate

from

either

one

or

both

channels,

particularly

during

high

level

passaaes

or

Iona

tPrm

high

volume

playback,

and

the

POWER

LED

glows

while

the

THERMAL

PROTFotiom

i

pi^o

^

^

one

or

more

of

the

EXTERNAL

PROTECTION

FUSES

are

blLn

PROTECTION

LEDs

are

out,

chances,

are

that

Your

GFA-5500

is

designed

to

activate

its

protection

devices

reliably,

particularly

when

the

amolifier

is

rareipsdu

-®<^

a^P'-«er

usuallj

WARNING

SUBSTITUTE

serious

damage

to

the

amplifier

circuits,

MAY

CREATE

A

FIRE

HAZARD,

AND

MAY

VOID

THE

WARRANTY^

_EXTERNAL

PROTECTION

FUSE

VALUE/TYPE:

8

AMP

AGC/250

VOLT

WARNING

THERE

ARE

POTENTIALLY

LETHAL

VOLTAGES

WITHIN

THE

GFA-5500

AMPLIFIFR

RFMnx/iwr

tuc

COVER

GREATLY

INCREASES

YOUR

CHANCE

OF

INADVERTENTLY

EXPOSING

YOURSFI

F

TO^FXTRpmp

DANGER.

REFER

ALL

SERVICING

TO

QUALIFIED,

ADCOM

AUTHORIZED

no

hot

ATTEMPT

TO

SERVICE,

REPLACE,

OR

REPAIR

ANY

INTERNAL

COMPONENT

YOURSELF.

7

CARING

FOR

YOUR

GFA-5500

Great

care

has

been

taken

by

ADCOM

to

ensure

that

your

amplifier

Is

as

flawless

In

appearance

as

it

is

eiectronically.

The

front

panel

is

a

heavy

gauge,

high-grade

aluminum

extrusion

carefully

finished

and

anodized

for

durability.

The

chassis,

top

cover

and

rear

panels

are

heavy

gauge

steel,

that

has

been

powder

coated

and

baked

to

ensure

a

lasting

finish.

If

the

front

panel,

top

or

sides

become

dusty

or

finger

printed,

they

can

be

cleaned

with

a

soft

lint

free

cloth,

slightly

dampened

with

a

very

mild

detergent

solution

or

glass

cleaner.

WARNING!

Do

not

spray

or

pour

liquids

of

any

kind

on

the

GFA-5500

SERVICING

ADCOM

has

a

Technical

Service

Department

to

answer

questions

pertinent

to

the

installation

and

operation

of

your

unit.

In

the

event

of

difficulty,

please

contact

us

for

prompt

advice.

If

your

problem

cannot

be

resolved

through

our

combined

efforts,

we

may

refer

you

to

an

authorized

repair

agency,

or

authorize

return

of

the

unit

to

our

factory.

To

aid

us

in

directing

you

to

a

convenient

service

center,

it

would

be

helpful

if

you

indicate

which

major

city

is

accessible

to

your

home.

Please

address

mail

inquires

to;

Phone,

Fax

or

E-mail

inquires

to:

ADCOM

Service

Corporation

Tel.:

732-683-2356

10

Timber

Lane

Fax;

732-683-9790

Marlboro,

NJ

07746

USA

Monday

through

Friday

9:00

AM

to

5:00

PM

EST

E-Mail:

[email protected]

For

Fax

inquires,

please

include

a

return

Fax

number

for

the

reply.

When

calling

or

writing

about

your

GFA-5500,

be

sure

to

note

and

refer

to

its

serial

number

as

well

as

the

date

of

purchase

and

the

dealer

from

whom

it

was

purchased.

It

is

helpful

in

any

communications

to

us,

please

include

a

daytime

phone

number

where

we

may

reach

you.

In

the

event

the

unit

must

be

returned

to

our

factory

for

service,

you

will

be

instructed

on

the

proper

procedure

when

you

cail

or

write

for

a

Return

Authorization.

UNDER

NO

CIRCUMSTANCES

SHOULD

YOUR

UNIT

BE

SHIPPED

TO

OUR

FACTORY

WITHOUT

PRIOR

AUTHORIZATION,

OR

PACKED

IN

OTHER

THAN

ITS

ORIGINAL

CARTON

AND

FILLERS.

if

the

original

shipping

carton

and

its

fillers

have

been

lost,

discarded,

or

damaged,

a

duplicate

carton

may

be

obtained

from

our

Service

Department

for

a

nominal

charge.

Always

ship

PREPAID

VIA

UNITED

PARCEL

SERVICE

(UPS)

OR

OTHER

APPROVED

CARRIER.

DO

NOT

SHIP

VIA

PARCEL

POST,

since

the

packing

was

not

designed

to

withstand

rough

Parcel

Post

handling.

FREIGHT

COLLECT

SHIPMENTS

WILL

NOT

BE

ACCEPTED

UNDER

ANY

CIRCUMSTANCES.

8