National Horizon 20 Manuale utente

INSTRUCTION

BOOK

FOR

The

National

The

latest

in

audioengineeringtechniques,plus

careful

attention

to

design

details,

make

the

Hqrizon

20

an

instrumentunparalleled

for

superb

performance

and

operatingefficiency.

Its

excellentcharacteris-

tics

are

due,

in

largemeasure,

tothe

uniqueoutput

stage

in

which

the

couplingbetween

the

outputtubes

is

unity,independent

ofthe

outputtransformer.

This

permits

the

useof

highefficiency

class

ABj

operation

without

the

impulsedistortion

commonly

associated

with

conventional

circuits

whichrelyupon

the

output

transformer

for

couplingbetween

the

tubes.

Unity

coupling

hasthe

additional

advantage

of

requiring

a

TWENTY

WATT

AMPLIFIER

far

lowerimpedance

ratio

between

the

outputtubes

and

the

load

with

attendantreduction

in

leakage

in-

ductance

and

increased

power

bandwidth.

In

addition

toits

superlative

performance,

theNa-

tionalHorizon

20

incorporates

the

unique

plug-in

faci-

lity

forthe

accommodation

ofthe

Horizon

5

Preampli-

fier

—

ControlUnit.Thisfeaturealoneexemplifies

the

advanceddesign

ofthe

National

high

fidelity

line

resulting

in

optimum

flexibility

of

installation

and

operation.

The

following

specifications

indicatesome

of

the

other outstandingfeatures

ofthe

Horizon

20.

Please

use

this

manual.

Ithas

been

prepare*/

with

the

prime

p

urpose

of

enabling

the

user

to

obtain

full

satisfaction

from

this product.

NATIONAL

COMPANY,

INC.,

MAIDEN

&

MELROSE,MASS.

FEATURES

HARMONIC

DISTORTION:0.3%

at

ratedoutput

of

20

watts.

0.6%

at25

watts.

INTERMODULATION

DISTORTION:

1%at20

watts,

measured

with

400

cps.

and7 kc.ata

ratio

of

4:1.

FREQUENCY

RESPONSE:±0.1

db

from

20

cps.

to

20

kc.±1db

from

10

cps.

to100kc.

POWER

RESPONSE

AT20

WATTS:

±0.15

db

from

20

cps.

to20kc.±1db

from

10

cps.

to60kc.

HUM

AND

NOISE:

80db

below

20

wattsoutput.

SENSITIVITY:

1.6

volts

for20

wattsoutput.

OUTPUTIMPEDANCE:

8

and

16

ohms

nominal.

INPUT

IMPEDANCE:

500,000ohms.

INPUTLEVELCONTROL:accommodates

a

wide

range

of

input

signal

levels.

RUMBLE

FILTER:built

into

minimizeturntable

rumble

and

noise.

ACCESSORY

OUTLET:

117

volt

AC,3

amp.con-

venienceoutlet

for

energizing

associated

equipment.

PREAMP

COMPARTMENT:contains

multiconnector

wired

to

associated

rear-paneljacks

to

convert

the

Horizon

20toa

single-unitequipment

when

the

Hori-

zon

5

preamp

is

plugged

in.

POWER

INPUT:

117

VAC,50-60cps,

1

amp,

110

watts.

PREPARING

TO

OPERATE

Examine

the

amplifier

immediately

after

unpacking

to

make

certainthat

no

apparentdamage

has

been

in-

curred

duringshipment.

A

cardboard

padis

placed

around

the

tubes

to

protect

them

in

transit.

This

must

be

removed.

Todosoitis

necessary

to

remove

the

cabinet.

Since

the

Horizon

20hasno

operatingcon-

trols,

itmaybe

installed

inany

convenientlocation

so

long

as

there

will

bea

free

circulation

ofairto

allowventilation.

The

above

would

holdtrue

when

the

Horizon

5

preamp

is

used

with

the

amplifier,

pro-

vided

that

the

preamp

is

located

ata

pointremote

from

the

amplifier.

When

the

NationalHorizon

5

preamp

is

plugged

into

the

Horizon

20,the

unitmust

be

installed

with

con-

trol

accessibility

in

mind.

The

attractive

overall

appearance

ofthe

amplifiermakes

it

well

suited

for

useona

tabletop,shelf

orany

convenient

location.

Once

the

input,power

and

speakerconnectionshave

beenmade,

the

Horizon

20

with

the

Horizon

5

preamp

becomes

a

versatile

controlcenter

forthe

custom

high

fidelity

installation.

Ifitis

desired

to

make

this

combination

part

ofa

custom

installation,

refer

tothe

paragraph

on

Cabinet

Installation.

ELECTRICAL

CONNECTIONS

Allthe

input

and

outputconnections

ofthe

Horizon

20

amplifier

are

located

onthe

backdrop

ofthe

chas-

sis.

See

Figure

1.

Connections

tothe

variousjacks

and

terminalsshould

be

made

inthe

following

manner:

1.

HORIZON

20

AMPLIFIER

WITHOUT

HORIZON

5

PREAMP

PWR.

AMP.INPUT:

The

output

ofthe

National

Criterion

or

similar

AM-FM

tuner

orthe

output

ofa

preamp

otherthan

the

Horizon

5 is

connected

to

this

jack.Singleconductorshielded

cable

must

be

used,

the

lengthdictated

bythe

recommendationsaccompany-

ing

the

particularequipment.

Associated

equipment

should

have

an

output

level

of1.6

volts

or

more.

All

other

jacks

are

unused.

SPEAKER

OUTPUT:

A

highfidelityloudspeaker

system

having

an

impedance

of

either

8 or16

ohms

may

be

connected

to

these

terminals.

The

terminal

marked

G isthe

common

connection

andmaybe

grounded

if

desired.

Shieldedcable

isnot

required

for

speakerconnections

andthe

length

isnot

critical.

Number

18

wire

(size

of

ordinarylampcord),

or

larger,

is

recommended.

117V

3A

OUTLET:

This

convenienceoutlet

is

supplied

forthe

purpose

of

providinginputvoltage

for

otherunits

ofthe

system

as

desired.

Itis

ener-

gized

when

the

amplifier

is

pluggedinto

the

117-volt

line.

2.

HORIZON

20

AMPLIFIER

WITH

HORIZON

5

PREAMP

PWR.

AMP.INPUT:

When

the

Horizon

5

preamp

is

used

with

the

Horizon

20,

eitherpluggedinto

the

unit

or

connected

by

means

ofan

interconnecting

cable,

the

Pwr.Amp.Inputjack

isnot

used.

The

interconnectingcablecompletewithmatingconnec-

tors

maybe

procured

in

either

4 or

15-footlengths.

When

the

interconnecting

cable

is

used,

remove

one

of

the

thumbscrews

from

the

preamp

compartment

coverplate

and

thread

the

screwinto

the

tappedhole

atthe

rightedge

ofthe

preampcompartment.

This

must

be

done

in

order

to

close

the

interlockswitch.

TV

INPUT:

AnyTV

tunerhaving

an

output

of1.6

volts

or

more

maybe

connected

to

this

jack.

This

jack

will

also

accommodate

the

standardhigh-level

ceramic

or

crystaltypephonopickup.Shieldedcable

must

be

used.

TAPE

PLAYBACK

INPUT:

A

tapereproducing

unit

maybe

connected

to

this

jack,

orany

piece

of

-2-

II7VAC

60

~

GAIN

HUM

BALANCE

TAPE

PHONO

PLAYBACK

OUTPUT

REAR

VIEW

Figure

I.

Electrical

Connections

audio

equipment

having

an

output

of

approximately

1.6

volts.

Thisjackwill

also

accommodate

the

cera-

mic

or

crystalpickup.

TUNER

INPUT:

The

NationalCriterion

AM-FM

tuner

orany

high

qualitytuner

maybe

connected

at

this

point.

When

the

Criterion

is

used,

the

four-foot

length

of

audiointerconnectingcable

maybe

used.

If

another

tuner

is

employed,

the

cableusedshould

be

ofthe

single-conductor

shieldedtype.

The

length

must

be

determined

bythe

instructionsaccompanying

the

tuner.Cables

in

excess

ofthe

recommended

length

may

cause

serious

attenuation

ofthe

higher

frequencies.

PHONO

INPUT:This

jack

accommodates

all

types

of

high

fidelitylow-levelphonopickup

cartridges.Shield-

ed

cable

ofthe

type

and

length

recommended

bythe

pickup

manufacturer

should

be

used.

A

slide

switch

is

incorporated

in the

Horizon

5 to

select

the

proper

circuitry

for

either

the10mv.or30mv.

type

of

cart-

ridge.(Seeinstruction

manual

supplied

with

the

Horizon

5

preamp).

SPEAKER

OUTPUT

AND

117V,

3A

OUTLET:

The

instructionsgiven

in

paragraph

1.

also

apply

when

the

preamp

is

used.

OPERATING

INSTRUCTIONS

When

the

Horizon

20

amplifier

is

usedwithout

the

preamp

installedthere

areno

operationalcontrols

to

be

adjusted.

The

linecordshould

be

pluggedinto

a

117-volt

sourcethatwill

be

switchedwithsomeother

unit

ofthe

highfidelity

installation.

No

ON-OFF

switch

is

provided

onthe

amplifier

since

itmaybe

installed

inan

inaccessible

location.

If

the

Horizon

5

preamp

is

installed

inthe

preamp

compartment

ofthe

amplifier

or

connected

tothe

am-

plifier

by

means

ofthe

interconnecting

cable;

all

the

operational

functions

ofthe

amplifier-preamp

com-

bination

are

handled

atthe

controlpanel

ofthe

pre-

amp.

Thisincludes

the

ON-OFF

switch,

program

Se-

lectorswitch,Loudness-Volumecontrol,

Bass

and

Treble

controls

andthe

full

range

of

phonoequaliza-

tion

selection.

The

function

of

thesecontrols,

to-

gether

with

instructions

for

their

proper

adjustment,

is

described

inthe

Horizon

5

instructionmanual.

-3-

FRONTPANEL

OF

CABINET

BRACKET

NOTE:

FELT

FEET

DIMENSIONS

OF

OPENING

IN

FRONTPANEL

14"X

4"

Figure

2.

Custom

Cabinet

Installation

-4-

CABINET

INSTALLATION

If

desired,

the

Horizon

20

Amplifier

maybe

mounted

ina

woodencabinet

as

part

ofthe

custom

installation.

Thisrequires

a

shelf

and

cutout

as

illustrated

in

Figure

2.

Locate

the14by4

inchhorizontalcutout,

making

certainthat

itis

square

with

the

sides

ofthe

cabinet.

Prime

consideration

should

be

given

tothe

location

in

regard

to

accessibility

of

controls

and

sufficient

clearancebetween

thetopofthe

amplifier

and

the

inside

ofthe

cabinet

topto

allowventilation.

A

12by15

inchshelf

must

be

installed

within

the

cabinet,

with

itstop

surface

flush

with

the

bottom

edge

ofthe

cutout.Thisshould

be

made

of

stock

at

least

1/2

inchthick

and

supported

by

shelf

mounting

brackets

sufficiently

rigid

to

maintain

the

weight

of

the

Horizon

20.

Remove

the

metaldustcover

from

the

amplifier

as

described

inthe

followingparagraph.

Before

placing

the

amplifier

inthe

cabinet

it

must

be

equipped

with

the

ornamental

bezel.

Thisbezel

maybe

procured

from

your

Nationaldealeralong

with

the

necessary

brackets,

mounting

hardware

and

A.C.

linecord.

The

bezel

hastwo

mounting

holes

onthetop

flange

and

three

holes

onthe

bottom

flange.

Thetop

flange

is

securedusing

the

brackets,

screws,

washers

and

nuts

suppliedwith

the

bezel.

The

bottomflange

is

secured

by

first

withdrawing

thetwo

feltfeet

and

self-tapping

screw

atthe

front

ofthe

amplifier

and

thenreplacing

them

through

the

flange.

Slide

the

Horizon

20

through

the

cutoutuntil

the

bezelmeets

the

front

ofthe

cabinet.

The

weight

of

the

amplifier

is

sufficient

to

hold

the

unit

inthe

cabinet.

REMOVALFROMCASE

The

Horizon

20

amplifier

is

enclosed

ina

ventilated

protective

metal

dust

coverequippedwith

a

safety

interlock.

The

cover

must

be

removed

to

gain

access

tothe

tubesand/orcomponents.

Todoso,

remove

thetwo

hex-headscrews

atthe

front

corners

ofthe

bottom

plate

and

remove

thetwo

Phillips-headscrews

atthe

ends

ofthe

reardrop

ofthe

dustcover.

Slide

the

coverstraightback

far

enough

to

disengage

the

interlockplug

and

then

lift

the

cover

from

the

ampli-

fier.

Thisprocess

is

reversed

when

replacing

the

dustcover.

Use

care

in

engaging

the

interlock

to

prevent

distortion

ofthe

plug.

HUM

BALANCE

ADJUSTMENT

Thehum

balancingadjustment

has

beenmade

atthe

factory

for

satisfactoryperformance

ofthe

power

am-

plifier

itself

butmay

requirereadjustment

after

the

input

equipment(Horizon

5

preamp

etc,)

has

been

connected.

To

accomplish

this,

turn

onthe

equipment

and

turn

the

loudness

or

volume

control

ofthe

preamp

to

maximum.

Any

tonecontrols,such

asthe

Bass

and

Treblecontrols

ofthe

Horizon

5,

should

beset

atthe

Flat

position.

With

no

signal

input,adjust

the

Hum

Balancecontrol

onthe

rear

chassis

drop

ofthe

Horizon

20for

minimum

hum

from

the

loudspeaker.

GAINADJUSTMENT

The

Gaincontrol

atthe

back

ofthe

chassis

requires

no

adjustment

when

the

Horizon

5

preamp

is

used

with

the

amplifier.

Itis

always

left

atthe

maximum

clockwiseposition

(full

gain).

When

the

Horizon

20is

usedwithout

a

preamp,

the

Gain

control

is

adjusted

toseta

limit

of

maximum

volume

level

as

follows:

Setthe

volume

control

ofthe

deviceconnected

to

the

amplifier

at

maximum.

Setthe

Gaincontrol

of

the

amplifier

to

provide

the

maximum

volume

forthe

specific

installation.

Make

this

adjustment

using

program

material

with

a

high

audio

level.

Thereafter

the

level

is

controlled

bythe

volumecontrol

onthe

associated

device.

-5-

TABLE

1.

TUBESOCKETVOLTAGES

CONDITIONS

All

voltages

measuredbetween

tube

pinand

chassis

except

as

noted.

VTVM

used

forall

measurements.

117

VAC,

60

cycle

input.

No

input

signal.

Tolerance

±1.0%.

TUBE

VI

V2

V3

V4

1

140

0

NC

2

0

32

#

32

#

400H

3

1.5

380

117V

tie

point

4

32*

380

350AC

5

32*

-26

-35

NC

6

250

-26

-35

350AC

7

»*

32

#

32

#

5

8

-270

5

0

400

«

9

32*

—

*6.3

AC

between

pins

4 or5 and9.

**-3.6

betweenpins

7 and8.

#6.3

AC

betweenpins

2 and7.

##5

AC

betweenpins

2 and8.

I6db

FEEDBACK-

PWR.AMP.,

INPUT

c

CONNECTED

WHEN

HORIZON

5

IS

USED

TAPE

PLAYBACK

PHONO

TUNER0

•>0/60cps

SPEAKER

OUTPUT

Figure

3.

Functional

Block

Diagram

-6-

PARTS

LIST

5YMBOL

CR1

El

E2

Jl

J2

J3

J4

J5

J6

LI

PI

R3

R19

SW1

Tl

T2

Wl

XF1

DESCRIPTION

SeleniumRectifier

Dummy

Panel

Terminal

Panel,

speakerconnection

Phono-jack,

single,

CinchMfg.

Co.

type8171

Receptacle,

A.C.

Alden

Products

type

402ACE

Receptacle,

A.C.powercordinterlock;CordsLtd.,Inc.typeCC-2

Phono-jack,

double,CinchMfg.

Co.

type8113

Jack,

16

contacts,

Amphenol

type

26-4200-16S

modified

Phono-jack,double,CinchMfg.

Co.

type8113

Filter

Choke,

1.5

hy,

200ma,

StancortypeC2327

Dummy

Plug

Variable,500,000ohms,

C

taper,

IRC

type

RQ13-133

Variable,1,000ohms,

A

taper,

IRC

typeRQ11-108

Switch,interlock

Output

Transformer,

two

primary

windings

Power

Transformer,

primary

117v AC,60

cycles;

secondaries

360-0-360

v at

120

ma,5 v at3

amps,

6.3v at3.5

amps

Power

Cord,

2

conductor,interlock;Phalo

Plastics

typeCSR-606RTV

or

equivalent

Fuseholder,

Littlefuse

type34201

NATIONAL

CO.

DRAWING

NO.

T657-1

T671-2

E259-6

T458-1

T452-1

L283-1

T579-1

T448-1

T579-1

T685-1

SB:2800

T013-1

T013-5

T755-1

T665-1

T658-1

A

10927

E510-1

Standard

Form

Warranty

Adopted

by

die

Radio

Manufacturers

Association,

Inc.

This

equipment

is

warranted

tobe

free

from

defective

material

and

workmanship

and

repair

or

replacement

will

be

made

ofany

part

which

under

normal

in

stall

at

ion,

useand

service

discloses

defect,

provided

the

unit

is

delivered

bythe

owner

tothe

manufacturer

or

through

the

authorized

radiodealer

or

wholesaler

from

whom

purchased,

intact,

for

examination,

with

all

transportation

chargesprepaid

tothe

factory,within

ninety

days

from

the

date

of

sale

to

originalpurchaser,and!

provided

that

such

examination

discloses

in

the

manufacturer's

judgment

that

itis

thus

defective.

This

warranty

does

not

extend

to

any

radio

products

which

havebeen

subjected

to

misuse,

neglect,

accident,

incorrect

wiring,

improper

installation,

ortousein

violation

of

instructions

furnished

by

the

man-

ufacturer,

nor

extend

to

units

which

have

been

repaired

or

altered

outside

ofthe

factory,

norto

cases

where

the

serial

number

thereof

has

been

removed,

defaced

or

changed,

norto

accessories

used

therewith

of

other

manufacture.

Any

part

ofa

unit

approved

for

remedy

or

exchange

hereunder

will

be

remedied

or

exchanged

bythe

authorized

radio

dealer

or

wholesaler

without

charge

tothe

owner.

This

warranty

isin

lieu

ofall

other

warranties

expressed

or

implied

andno

representative

or

person

is

authorized

to

assume

forthe

manufacturer

any

otherliability

in

connection

with

the

sale

of

theirradioproducts.

National

Company,

Inc.reserves

the

right

to

make

any

change

in

design

orto

make

add'

tanto,

or

im-

provements

in,its

products

without

imposing

any

obligations

upon

itself

to

install

them

inits

productspre-

viously

manufacturered.

-7-

Figure

4.

Schematic Diagram

-8-

M-4000-ER418

10-54

National Horizon 20 Manuale utente

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