Bryston 11b User manual

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1

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-TftPt

OUTPUTS-IQW

FIlTER-MUTE-

-84UWCE-

INSTRUCTION

MANUAL

FOR

11B/12B

PRE-AMPLIFIER

Congratulations

on

your

selection

of

the

very

finest

sound

equipment.

Your

Bryston

preamplifier

has

been

engineered

to

provide

many

years

of

trouble-free,

highly

musical

lis¬

tening

enjoyment.

This

instruction

manual

refers

to

the

Model

12B.

With

the

exception

of

the

phono

inputs,

the

Model

11B

preamplifier

is

identical,

and

the

instructions

pertain

to

it

in

exactly

the

same

way.

Where

a

difference

occurs,

it

will

be

noted

in

the

text.

The

Model

12B

is

a

basic

signal

preamplifier

with

switching

facilities

for

all

the

sources

likely

to

be

used

by

even

the

most

elaborate

domestic

sound

system,

including

dubbing

capability

for

two

tape

recorders,

and

the

convenience

of

recording

from

any

source

while

simultan¬

eously

listening

to

any

other

through

the

speakers.

The

included

diagram

will

illustrate

the

switching

functions

of

the

Bryston

Model

12B

preampli¬

fier.

Phono

Inputs;

Including

Moving

Coil

The

Model

12B

is

supplied

with

an

internal

moving-coil

step-up

transformer.

This

extremely

wide¬

band

transformer,

with

almost

no

added

noise

or

distortion,

increases

the

voltage

gain

through

the

phono

section

by

22.5dB,

and

adjusts

the

in

put

i

m

pedance

to

suit

the

vast

ma¬

jority

of

moving-coil

cartridges.

(It

is

available

on

special

order

with

6dB

less

gain,

and

a

higher

input

im¬

pedance,

for

those

few

high-output

MC

cartridges

which

may

perform

better

with

these

settings).

The

12B

will

also

accept

moving-

magnet

cartridges

by

switching

the

MC

transformer

out

via

a

switch

on

the

front

panel.

In

this

case,

the

cartridge

is

plugged

into

the

MM

inputs

on

the

rear

panel.

The

MM

inputs

(only)

are

equipped

with

input

loading

capacitors

of

about

275

pf

per

channel.

When

added

to

the

normal

turntable

wiring

capacitance,

this

yields

about

300-400

pf,

which

is

in

the

optimum

range

for

most

cartridges.

(This

internal

phono

capacitance

may

be

special-ordered

to

any

value

at

no

extra

charge).

The

Model

11B

is

identical

to

the

Model

12B

except

that

it

is

not

equipped

with

the

MC

transformer.

Thus

both

.phono

inputs

become

MM

inputs,

as

above.

They

may

be

selected

between

Phono

1

and

Phono

2

via

the

switch

on

the

front

panel.

(The

MC

tranformer

may

be

retrofitted

at

any

time,

converting

the

preamp

to

a

12B).

Since

the

phono

stage

on

the

Model

12B

in¬

verts

absolute

phase,

the

MC

trans¬

former

is

connected

to

invert

phase

also.

Thus,

MC

cartridges

play

in

proper

phase

with

no

special

con¬

nection

necessary.

In

case

of

MM

cartridges,

reversing

the

hot

and

ground

leads

on

the

cartridge

pins

is

a

convenient

way

of

obtaining

the

same

function.

Tape

Monitor

Function

Although

the

12B's

tape

monitor

function

is

arranged

differently

from

most

standard

preamplifiers,

it

is

not

complicated

to

use.

The

two

selector

switches

operate

independently,

and

affect

only

the

outputs

to

which

their

labels

refer.

Thus

the

“MAIN

OUTPUT”

switch

is

used

as

the

tape

monitor,

also.

Include

yourtape

deck

in

the

preamp’s

tape

loop

in

the

normal

way

(i.e.,

its

record

head

is

connected

to

Tape

1

output,

and

its

playback

head

is

plugged

back

into

Tape

1

input).

To

monitor

the

recording,

just

move

the

MAIN

OUTPUT

switch

to

“Tape

1

”

A

sec¬

ond

tape

deck

may

be

included

in

the

tape

loop

in

a

similar

manner,

using

Tape

2

input

and

output,

and

“Tape

2”

selector

position

for

mon¬

itoring.

Two

Tape

Recorders;

Dubbing

Facility

Plug

in

the

playback

and

record

heads

of

the

two

decks

to

their

res¬

pective

tape

inputs

and

outputs,

as

above.

Normally,

both

decks

will

receive

the

same

signal

for

record¬

ing

When

“Tape

1”

is

selected

on

the

TAPE

OUTPUT

switch,

how¬

ever,

the

playback

head

of

deck

1

is

connected

to

the

record

head

of

deck

2,

via

Tape

2

output.

This

obviously

allows

direct

dubbing

from

Tape

Deck

1

to

Tape

Deck

2.

Selecting

“Tape

2”

on

the

TAPE

OUTPUT

switch

allows

dubbing

in

the

opposite

direction

by

reversing

these

connections.

External

Equalizer,

Noise

Re¬

duction,

or

Other

Audio

Pro¬

cessor

An

equalizer,

noise

reducer,

etc.,

may

be

included

in

the

tape

loop

(as

shown

in

the

diagram)

by

con¬

necting

its

input

to

one

of

the

tape

outputs,

and

its

output

back

to

(the

same

numeral)

tape

input.

Turn

the

MAIN

OUTPUT

switch

to

(that

numeral)

"Tape”

position

whenever

you

wish

to

use

the

audio

proces¬

sor

in

the

signal

path.

During

that

time,

the

TAPE

OUTPUT

switch

is

used

as

the

selector

for

whichever

source

is

to

be

processed.

Turning

the

MAIN

OUTPUT

switch

back

to

this

source

position

will

bypass

the

processor.

Headphone

Jack

The

Model

12B

is

equipped

with

a

headphone

jack

for

convenient,

private

listening.

The

signal

is

taken

directly

from

the

output

circuit

which

normally

feeds

the

power

amplifier,

and

is

thus

controlled

by

the

volume

knob.

This

output

will

drive

head¬

phones

of

any

type,

but

lower

impedance

headphones

may

re¬

quire

somewhat

more

volume

control

rotation

for

the

desired

loudness.

To

facilitate

headphone

listening

without

disturbing

others,

the

preamplifier

automatically

dis¬

connects

thedirect

feed

to

the

power

amplifier.

(This

is

indicated

by

the

green

pilot

light

on

the

front

panel

changing

to

red

whenever

the

out¬

put

relay

is

opened).

This

circuit

does

not

disconnect

the

remote

outputs.

(See

under“RemoteOutput”).

Since

sqme

headphones

may

require

substantial

volume

control

rotation,

be

sure

to

reduce

the

volume

before

removing

the

headphone

plug,

or

you

may

be

startled

by

the

high

sound

level

when

the

relay

re-connects

the

amplifier.

Remote

Output

The

12B

preamplifier

is

equipped

with

a

special

remote

output,

which

is

switched

via

the

“Main

Output”

selector,

but

which

exits

ahead

of

the

volume

control.

This

line-level

output

may

then

be

used

to

drive

amplifiers

in

remote

locations,

with

local

volume

controls.

This

allows

remote

systems

to

function

inde¬

pendently

of

the

volume

level

set

in

the

main

system.

The

automatic

amplifier

disconnect

which

is

part

of

the

headphone

circuit

does

not

affect

these

remote

outputs.

(As

an

option,

this

function

may

be

replaced

by

a

second

set

of

main

outputs,

connected

in

parallel

with

the

first.

Thisallowstheconvenientconnec-

tion

of

two

amplifiers

which

are

desired

to

be

controlled

together,

such

as

subwoofer

installations,

or

passively

biamplified

systems).

Low

Filter

The

inflection

point

of

the

rumble

filter

has

been

chosen

at

31.7Hzto

correspond

to

the

lowestsignal

fre¬

quencies

likely

to

be

found

in

re¬

corded

music,

and

to

a

suggested

revision

to

the

RIAA

recording

curve

for

LP

discs.

For

these

reasons,

and

for

the

more

important

reason

of

avoiding

low

frequency

transient

overshoot,

ringing

and

phase

mis¬

alignment,

the

low

filter

is

a

“minimum”

type,

with

a

6dB/octave

slope

below

cutoff.

This

is

quite

effective

in

reducing

subsonic

woofer-wooble

and

its

attendant

intermodulation

effects,

however,

since

the

most

problematic

turntable

and

warp-induced

rumble

frequen¬

cies,

in

the

area

of

2-5Hz,

are

reduced

an

average

of

about

20dB

or

a

factor

of

100

in

terms

of

power

demand.

The

low

filter

switch

is

active

in

the

In’

position,

and

affects

only

the

phono

inputs.

Mute

Switch

The

listener

often

is

called

momentarily

away

from

critical

lis¬

tening,

to

answer

the

phone

for-

example,

and

wishes

to

reduce

the

gain

for

a

short

time

without

disturb¬

ing

the

volume

control

setting.

The

mute

switch

reduces

preamp

gain

by

20dB.

Thus

the

music

may

still

be

heard,

but

at

a

background

level.

This

is

also

useful

for

changing

records,

cueing

the

stylus

manually

to

a

particular

song,

cleaning

the

stylus

with

a

brush,

etc.

The

mute

switch

is

active

in

the

'In’

position

and

affects

only

the

main

outputs

without

disturbing

the

tape

outputs.

Mono

Function

Occasionally

a

system

will

display

some

offset

in

gain

favouring

one

channel

over

the

other

due

to

slight

differences

in

speaker

efficiency,

differences

in

room

loading,

or

a

somewhat

off-center

listening

pos¬

ition

dictated

by

room

decor.

Thus

it

is

convenient

to

"mo.no”

the

signal

to

obtain

the

most

unambiguous

center

image,

convenient

to

adjust¬

ing

the

balance

control.

For

reasons

of

simplicity,

rather

than

having

a

separate

switch

for

this

function,

the

"Mute”

switch

also

connects

the

two

channels

in

Mono.

Obviously,

the

listener

may

wish

to

advance

the

volume

control

to

pro¬

vide

sufficient

level

for

establishing

center

image.

Do

not

forget

to

reduce

the

volume

control

again

before

deactivating

the

mute

switch

in

this

case,

or

you

may

be

startled

by

the

sudden

increase

in

sound

level.

The

balance

control

is

a

tailored

inflection

type

which

has

very

gradual

action

near

the

center

of

rotation

for

fine

adjustments

to

the

left-right

balance

of

the

stereo

image.

Turn

On

Delay

The

Model

12B

contains

an

output

relay

with

an

approximate

3-second

delay

at

turnon,

to

allow

any

transient

thumps

to

settle.

The

relay

opens

instantly

when

the

preamp

is

switch¬

ed

off

to

prevent

any

power-supply

decay

artifacts

from

appearing

at

the

outputs.

The

relay

is

hermetically

sealed

in

an

inert

atmosphere

to

completely

eliminate

contact

con¬

tamination

and

provide

nearly

infinite

lifetime

(rated

in

tens

of

billions

of

cycles).

This

same

relay

is

employed

in

the

automatic

amplifier

disconnect

function

which

is

part

of

the

head¬

phone

circuit,

and

in

the

protection

mechanisms

connected

into

the

power

supply.

Whenever

the

pre¬

amplifier

is

under

power,

and

the

relay

is

open

for

any

reason,

the

green

pilot

light

on

the

front

panel

changes

to

red.

(Since

the

power-

supply

filter

capacitors

are

quite

large,

the

red

LED

indication

will

fade

slowly

after

fhe

preamp

is

switched

off).

Accessory

Outlets

The

12B

includes

three

3-prong

grounded,

120

volt

receptacles

on

the

rear

panel,

two

switched,

one

unswitched.

Please

observe

the

caution

printed

below

the

re¬

ceptacles

regarding

maximum

power

draw

from

these

outlets.

Large

power

amplifiers,

especially

including

the

Bryston

Models

3B

and

4B

should

not

be

plugged

into

these

receptacles.

To

do

so

may

damage

the

preamp’s

power

switch.

It

is

permissible

to

plug

the

Bryston

2B-LP

into

these

outlets,

however,

or

any

class

AB

amplifier

up

to

50,

(or

class

A

amplifier

up

to

15)

watts

per

channel.

In

general,

it

is

inadvisable

to

switch

large

power

amplifiers

on

and

off

by

the

switch

in

a

preamplifier,

for

the

above

rea¬

son,

and

also

because

it

is

likely

to

cause

a

fluctuating

voltage-drop

on

the

preamplifier's

line

cord,

which

in

worst

case

conditions

can

become

an

audible

problem.

DC

Power-Supply

Output

On

the

rear

panel

of

the

Model

12B

(and

11B)

there

is

a

DIN

con¬

nector

which

provides

±24V

DC

of

regulated

power.

This

is

provided

for

future

Bryston

products,

such

as

equalizers,

electronic

crossovers

and

the

like,

which

will

be

available

with

or

without

power

supply,

for

reasons

of

economy.

This

output

is

fully

protected,

and

contains

a

circuit

which

opens

the

output

relay

auto¬

matically

if

excessive

current

is

drawn.

The

Twelve-B

has

been

designed

from

a

rational,

function-oriented

ideal

of

maximum

musical

accuracy,

with

an

absolute

minimum

of

use¬

less

gadgetry

or

extraneous

con¬

trols.

The

signal-handling

circuit

is

novel

and

fundamentally

correct,

both

electrically

and

more

important,

sonically.

We

believe

you

will

find

a

renewed

sense

of

awareness

of

the

listening

pleasure

in

your

music

collection,

played

through

your

Bryston

preamplifier.

All

your

signal

sources

will

sound

cleaner

and

more

muscially

transparent

than

you

may

have

experienced

before.

Please

do

not

hesitate

to

write

us

if

you

have

any

questions

or

com¬

ments

about

any

of

our

products.

Your

opinion

is

of

paramount

im¬

portance

to

us.

Af

\

\

-

Y

V

J

LTD.

LTEE

57

WESTMORE

DRIVE,

REXDALE,

ONTARIO,

CANADA

M9V

3Y6

TELEPHONE:

416-746-1800,

TELEX:

06-989548

IN

THE

U.S.A.

TELEPHONE

802-223-6159

Printed

in

Canada

VIOLET

POWER

AMPLIFIER

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AMPLIFIER

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RECEPTACLES

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300993

300993

ASSEMBLED

BY:

CHASSIS

CONNECTORS

RESISTORS

CAPACITORS

SEMICONDUCTORS

2

JULY

86

Assembly

Notes

for

11B/12B

Preamps

with

Balanced

Outputs

Component

placement

for

Balanced

Output

11B/12B

Preamps

Hookup

for

Balanced

Output

board

and

XLR

board

Foil

side

view

5

CONDUCTOR

CABLE

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1>

Assemble

Balanced

Output

Board

(BALOUT

2v2)

2>

Five

conductor

cable

is

prepared

and

soldered

on

to

balanced

output

board.

3>

Install

balanced

output

board

on

mother

(main)

board.

4->

Feed

five

conductor

cable

through

hole

in

power

supply

shield

and

soldered

onto

2XLR—M

board.

5>

Insert

male

XLR

jacks

through

power

supply

shield

(from

outside)

&

solder

on

to

2XLR—M

board.

XLR

jacks

are

NOT

screwed

down;

they

will

be

sandwiched

between

the

main

board,

the

chassis

rear

panel

and

the

top

panel

and

thus

held

sucurely

without

any

need

for

screws.

6>

Apply

self-ahesive

label

to

outside

surface

of

rear

panel

over

XLR

jacks

Component

side

view

12B-BAL

WRP

JULY

89