Harman Kardon TD302 Owners Manual - Page 4

DOLBY

NR

AND

HX

PRO

SYSTEMS

Dolby

B

and

C

Noise

Reduction

(NR)

Systems

The

TD302

provides

both

the

Dolby

B

and

the

Dolby

C

noise

reduction

systems.

Dolby

B

has

become

a

standard

feature

on

many

decks.

Dolby

C

is

a

newer,

more

effective

system

that

virtual

ly

el

iminates

noise

from

cassette

recordings.

What

causes

tape

noise

Tape

noise

is

inherent

to

some

extent

in

al

l

magnetic

re-

cordings.

With

cassette

tapes,

the

most

objectional

noise

is

in

the

midrange

and

high

frequencies

and

is

perceived

as

"hiss".

The

amount

of

"hiss"

is

affected

by

many

factors,

such

as

the

tape

speed,

the

size

of

the

magnetic

particles

on

the

tape

and

the

level

of

the

recorded

signal

.

The

tape

speed

is

standardized

and

the

TD302

is

optimized

for

popular

low

noise

tape

formulations.

The

operating

principle

of

Dolby

noise

reduction

In

short,

the

Dolby

noise

reduction

systems

boost

weak

midrange

and

high

frequency

signals

during

the

record

mode,

and

then

reduce

them

to

their

original

level

during

playback.

This

enables

the

weak

signals

to

be

recorded

at

higher

levels

and

therefore

be

played

back

at

higher

levels

relative

to

the

"hiss".

Dolby

C

has

twice

the

noise

reduction

effect

as

Dolby

B.

Neither

system,

however,

is

capable

of

removing

noise

from

the

signal

source.

Response

(dB)

50

40

30

20

10

0

20

50

100

200

500

1000

2000

5000

10000

20000

NR

OFF

B

-Type

C

-Type

Frequency

(Hz)

Noise

Spectra

Dolby

HX

PRO

Headroom

Extension

System

The

TD302

is

equipped

with

the

Dolby

HX

PRO

headroom

extension

system.

It

operates only

during

the

record

mode

and

does

not

require

the

user

to

"turn

it

on"

or

make

adjustments.

It

is

compatible

with

any

low

noise

(standard),

chromium

dioxide

(CrO2),

or

metal

audio

cassette

tape.

The

effect

of

HX

PRO

is

that

is

extends

the

high

frequency

saturation

(overload)

level

of

the

tape

being

recorded.

Therefore,

many

of

the

high

level,

high

frequency

music

signals

that

would

be

compressed

or

distorted

with

a

conventional

cassette

deck

wi

ll

be

recorded

accurately

by

the

TD302.

In

order

to

determine

the

optimum

record

level,

see

"Recording

Level

Adjustment"

section

on

page

7.

The

advantages

of

HX

PRO

are:

1

.

The

perfomance

of

low

noise

and

chromium

dioxide

tapes

almost

equals

that

of

the

more

expensive

metal

tapes.

2.

A

major

improvement

is

made

in

high

frequency

dynamic

range.

3.

The

higher

record

levels

result

in

an

increased

signal-to-

noise

ratio.

4.

No

decoding

is

necessary.

The

improved

recording

accuracy

can

be

appreciated

with

any

high

qual

ity

tape

player,

including

a

portable

or

car

stereo

unit.

5.

It

can

be

used

with

or

without

Dolby

B

and

C

noise

reduction

circuitry.

Response

(dB)

2

1

—10

20

—30

—40

.

.

HX

Dolby

PRO

and

C

ON

---.

0.

-..

\

•

HX

PRO

Dolby

FIX

Dolby

ON,

C

OFF

PRO

and

C

OFF

i

I

•

I

%

\

.

•

‘

I

1000

2000

5000

10000

20000

Frequency

(Hz)

Frequency

Response

50000

3

Harman Kardon TD302 Owners Manual - Page 4

Dolby, Systems

Page 4 highlights