dbx 161 사용 설명서 - 페이지 13

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dbx 161에 대해서도 마찬가지입니다: 사용 설명서 (13 페이지)

페이지 인쇄

Sub Harmonic

sub-mul

ip le

the fundamental

frequency

For

ample,

a wave the frequency of

which

is half

the

fundamenta

frequency

of another

wave

cal

led the second

sub

harmonic of that

wave.

Sub Woofer

louds peaker

made specifically

reproduce the lowest of

audio

frequencies,

usu

between 20Hz and

OOHz.

Synthesizer

An ELECTRONIC

MUSIC SYNTHESIZER

an aud io

processor

at has a

-in

sound

generator (oscillator),

and

that alters

the enve lope

of the

sound

wit

voltage

contro

led

circuitry.

Synthesizers

produce

familiar sounds

and serve as

musical

strume nts, or they

can create many

uniq ue sounds

and

effects

their own.

A SUB HARMONIC

SYN

HESIZER

is a

device

whi ch

is not

used

create

usic,

but

enhance an ex isting audio

program.

In the case of

dbx Mode

l 100

, the

unit

creates a new

signa

that corresponds to

the

volume of

t he i

nput

signal

b ut

/2 t

freq uenc

the

inpu

sign

al.

Tape Saturation

T here is a

maximum

amount of energy

that

can be

recorded

any given

type

of magnetic

tape. When

a recorder "tries"

to record

energy, the signals

become

distorted,

but are not

recorded

any h igher

levels.

This

phenomenon

is called

tape

saturation

because

the

magnet

oxide

particles of the tape are literally

saturated

with

energy and can not accept any more magnetization.

T.H.D.

otal

Harmonic D

istor

ion) (See "Harmonic

Distortion")

Threshold

the

level at whic

a compressor or l

miter ceases to

have

linear gain, and begins

to perform

its

gain -changing function

(i.e., w here the output level

lo nger

rises

and fal ls

n direct

proportio

to the

nput level).

most systems, the

threshold

is a

point above wh ich

the

leve

cha

nges, al

t houg

there

are compressors

t hat

raise signal

levels be low a thresho

point.

Some

compander-

type noise reduction systems, suc

lby

* have upper

and

lower threshold

between

which

the

gai

c hanges; these systems

req

re carefu

level ca

ibration

for

proper encode/decode

perfor

mance. dbx noise reduct ion systems

have

no threshold at which

compression or

pansion factors

change,

so level

cal

ibration is

not critica

'Dolby'

trademark of Dolby

Laboratories,

Inc.

Triamplified

Similar

to biamp

ified.

sound

system

where a passive cross-

over

network

creates three frequency ranges, and

feeds three

power

amplifiers

one for bass, one for

mid,

and o ne for

igh f requencies

he amplifiers are connected direct

to the woofers, midrange

drivers and tweeters w

thout a

passive,

h igh-

level

crossover network

Tuner

unit which rece ives rad io broadcas

and conve rts t

hem

into

audio frequency signa ls. Ma

be part of a receiver

VCA

(Voltage

Controlled

Amplifi er)

raditiona

y, amplifiers

have been designed to increase signal

levels (to provide gain)

f an amp

lif

ier were

required to decrease

the

level

(to attenuate),

it could

become

unstable

and m ight even

oscillate

The gain (amount of amp

ification)

t hese traditiona

amp I

fiers wou Id be adjusted by one of three

methods

( 1) attenuat-

ing the audio signa

fed to the input of the amplif ier, (2) attenuating

the audio output

of the amplifier,

or (3) changing

the

negative feed-

back (feed

ng more or less signa

from the output

back

to the

input,

but in reversed polar

ty).

The VCA is a specia

type of amplifier

that can

used to

increase or decrease levels over a wide dynamic

range. Instead

usi

ng signal attenuation

or negative feedback, the gain (or loss) is

adjusted by means of an external

contro

voltage. dbx has a

unique,

pat ented

VCA

design that has extreme ly

low

noise and

very wide dynamic range; the

dbx VCA

is the heart of dbx no ise

reduction equipment.

Woofer

loudspeaker wh

ich rep

roduces o

ly low

frequencies.

NPUT

Tracking Accuracy

--OUT

PUT-~

Comp, cn1ori

120: 1

Co mp1eu1o

(hm

111n

g )

-Th

1e1hold

---

- -

----

Tracking

refers to the abi lity of one

rcuit to

"follow"

t he

c hanges of anot

her

circu

t. When two

volume controls are adjusted

ex actly

the

same way, the corresponding

" sam

eness" of the

output

levels can be

pressed as t he tracking accuracy of the

controls.

The level detection

circuitry

in a

dbx

encoder senses the

signal

level,

changes the

gain,

and creates an encoded signal.

he corre-

sponding

"sameness"

of the origina

signal and the encoded/

decoded signal ca

exp ressed as t he track

g accuracy of the

noise

reduction system. (dbx

systems are non-critica

for the

operator, and are

built

to close tolerances, so t hat

tracking

accuracy is exce

ent, even if the encoder and decoder are

different

pieces

of dbx equipment.)

Transition

Level

(See

Level

Match)

When a

circuit

has

uniform

compression or expansion through-

out

its

dynamic

range, there must

some level which passes

through the

unit

without

being raised or lowered (where gain is

unity).

This un

ty gain level is the transition

leve

or tra nsition point.

The trans

t ion

point

is a "window"

dB wide, in a dbx encoder

(compressor),

al I

signals above t he

transition

point are decreased in

level,

and all signa ls be low the

point

are increased in level. Con

versely,

a dbx decoder (expander), all signals above the

transition

point are increased

in level,

and al

signals below the

nt are decreased in leve l.

The

transition

level is similar to a

"threshold,"

except it does not refer to a point at which

compress ion or expansion

factors

change.

VI I l