Ov ervie w, Pr eamplifier, Insert point – Joemeek three Q Desktop Channel User Manual

Page 4

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background image

7

6

Ov

ervie

w

The

JOEMEEK

threeQ

is

like

having

one

channel

of

a

professional

record

-

ing

studio

in

a

small

box.

It

takes

a

microphone

or

instrument,

amplifies

it,

compresses

and

equalizes

it

ready

to

be

recorded.

Simple

to

use

yet

extremely

powerful,

the

threeQ

will

bring

out

the

best

in

any

microphone

or

instrument

and

give

the

gloss

of

a

professional

studio

production

to

all

your

performances.

As

well

as

recording

it

will

also

be

found

useful

for

live

work.

Think

of

the

threeQ

as

four

separate

items

of

equipment:

The

Preamplifier

The

JOEMEEK

Optical

Compressor

The

Meequalizer

The

Fader

Pr

eamplifier

This

is

the

all-important

front

end

to

the

threeQ.

Its

job

is

to

accept

any

type

of

microphone,

instrument

or

other

source

of

audio

signal,

and

make

it

loud

enough;

microphones

often

need

rather

a

lot

of

amplification,

while

guitars,

keyboards

and

CD

players

need

less.

Mics

need

to

be

connected

to

low

impedance

inputs,

while

instruments

prefer

high

impedance

inputs.

To

ensure

correct

impedance

matching,

the

inputs

are

split

into

an

XLR

connector

for

Mics,

and

a

jack

“Line”

connector

for

everything

else.

A

switch

on

the

front

panel

decides

which

input

connector

is

active.

The

LED

under

-

neath

the

switch

lights

to

show

that

the

Line

input

(jack)

is

selected.

In

other

words:

Switch

out

(LED

of

f)

=

“Mic”

Switch

in

(LED

on)

=

“Line”

Both

Mic

and

Line

inputs

are

electronically

balanced.

Note:

although

the

Line

input

is

not

normally

used

for

microphones,

it

can

be

suitable

for

some

high

output

unbalanced

microphones,

such

as

battery

pow

-

ered

Electret

types.

The

Line

Input

(jack)

is

balanced

and

wired

as

follows:

T

ip:

+

(hot)

Ring:

-

(cold)

Sleeve:

ground

The

Mic

Input

(XLR)

is

balanced

and

wired

as

follows:

Pin

2:

+

(hot)

Pin

3:

-

(cold)

Pin

1:

ground

PHANT

OM

POWER

Most

high-quality

studio

mics

are

“Phantom

powered”,

which

is

to

say

they

have

electronics

inside

them,

which

get

their

power

from

the

preamp.

Most

mics

require

a

supply

of

48

V

olts,

so

Phantom

Power

is

often

labelled

“48V”.

There

is

a

switch

on

the

back

of

the

threeQ

(next

to

the

XLR

mic

connector)

to

turn

this

power

on

or

of

f.

A

red

LED

lights

when

this

power

is

on.

When

switching

the

Phantom

Power

on,

quite

a

loud

thump

may

be

produced,

so

it

is

a

good

idea

to

turn

down

the

Output

Gain

(or

to

momentarily

select

the

Line

input),

when

pressing

the

switch.

When

using

dynamic

or

ribbon

mics,

do

not

turn

this

on.

It

probably

won’t

do

any

harm

but

it

certainly

won’t

do

any

good,

so

leave

it

of

f!

Consult

the

microphone

handbook

if

you

are

unsure

what

kind

of

mic

you

have.

There

is

just

one

other

control,

labelled

“Input

Gain”,

which

covers

a

range

of

amplification

from

10dB

to

60dB.

In

many

other

preamps

the

action

of

the

Gain

control

is

rather

uneven,

with

the

40dB

to

60dB

range

being

crammed

into

the

last

1/6th

of

a

turn.

All

Joemeek

preamps

use

a

specially

designed

control

that

ensures

smooth

operation

over

the

whole

range

of

rotation.

The

(0

)

symbol

next

to

the

25dB

mark,

means

unity

gain,

or

0dB,

for

a

signal

in

the

Line

input.

Hence

for

Line

inputs

the

range

of

gain

adjustment

either

side

of

this

mark,

is

+35dB,

-15dB.

The

PEAK

LED

lights

6dB

below

clipping,

so

occasional

brief

flashes

are

OK

but

if

it’

s

on

all

the

time

you

need

to

back

the

Input

Gain

of

f!

TECHNICAL

STUFF

V

ery

low

noise

-

does

it

matter?

Y

es

and

no,

it

all

depends

what

you

are

doing

-

what

really

matters

is

“signal-to-noise

ratio”.

All

electronics

produce

a

certain

amount

of

background

noise

-

it’

s

in

the

nature

of

things.

Providing

there

is

only

a

relatively

small

amount

of

noise,

the

signal

will

cover

it

up,

or

“mask”

it.

So

providing

the

signal

is

much

bigger

than

the

noise,

you

won’t

be

aware

of

the

noise.

So

in

other

words

the

“signal-to-noise

ratio”

needs

to

be

a

big

number

,

ideally

such

as

80dB

or

90dB.

So

how

do

you

achieve

that

in

practice?

The

trick

is

to

keep

the

microphone

as

close

to

the

sound

source

as

possible

without

overloading

it,

so

as

to

get

as

much

signal

out

of

it

as

possible.

Then

you

set

the

Gain

control

to

give

only

as

much

gain

as

is

needed

to

get

a

decent

level

into

the

recorder

.

Of

course

when

there

is

no

signal

going

on,

you

may

hear

the

background

no

is

e

of

t

he

e

le

ct

ro

ni

cs

.

In

t

ha

t

ca

se

,

gi

ve

n

th

e

am

ou

nt

o

f

ga

in

in

t

he

s

tu

di

o

m

o

n

ito

ri

n

g

s

ys

te

m

,

th

is

n

o

is

e

flo

o

r”

s

h

o

u

ld

i

d

e

a

lly

b

e

i

n

t

h

e

r

e

g

io

n

o

f

-8

0

d

B

u

or

lower

,

in

order

for

it

not

to

be

noticed.

The

threeQ

microphone

preamplifier

uses

state-of-the-art

electronics

and

has

an

equivalent

input

noise

of

around

-128dBu

(with

150ohm

in

pu

t l

oa

d)

. D

es

pi

te

a

ll

th

e

hy

pe

rb

ol

ae

a

nd

o

bf

us

ca

tio

n,

th

e

th

eo

re

tic

al

best

possible

performance

for

silicon-based

electronics

is

about

-132dBu.

So

the

preamplifier

design

used

in

the

threeQ

and

all

other

NextGen

Joemeek

products

approaches

this

limit.

To

improve

significantly

on

this

would

require

highly

specialised

electronics

and

probably

a

vat

of

liquid

Nitrogen

to

cool

it!

The

maximum

gain

available

from

the

preamp

is

60dB,

in

which

case

the

noise

floor

will

be

-68dBu.

This

is

actually

quite

noisy

-

if

you

record

that

noise

onto

a

digital

recorder

and

play

it

back

you

can

definitely

hear

it.

In

practice

of

course,

you

do

not

record

and

play

back

“silence”

and

the

rest

of

the

mix

will

probably

be

more

than

70dB

louder

than

this

noise

and

will

mask

it

completely

.

Even

so

it

is

generally

a

good

idea

not

to

use

gains

greater

than

40dB

or

50dB

and

indeed,

it

should

rarely

be

necessary

to

do

so.

Insert

Point

This

is

simply

an

unbalanced

“Send

and

Return”

jack

on

the

rear

panel.

It

allows

you

to

patch

any

other

pieces

of

equipment

into

the

signal

path,

such

as

an

ef

fects

processor

or

noise

gate.

To

use

it

you

will

need

a

“Y”

lead

wired

as

follows:

T

ip:

send

Ring:

return

Sleeve:

ground

When

no

jack

is

inserted,

the

socket

is

internally

linked,

or

“normalled”,

so

that

the

signal

flows

uninterrupted.

Note

that

the

Insert

Point

is

after

the

Preamp

but

before

the

Compressor

and

EQ.

three q manual.indd

3/9/04, 4:19 PM

8-9

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