Crown MARCO-TECH 5000VZ User Manual

Notes

MACRO-TECH 5000VZ

OVERVIEW

At

first glance

the

MA-5000VZ

looks a great deal

Hke any

other

MA

Series

amplifier, except that

¡t is

physically larger

and

puts

out

more

power.

The

internal

structure

of the

MA-5000VZ

is,

however, quite

different

from

other models

in the MA

une.

To the

user, this

one is

like

the

others,

but

with a f

ew

more f eatures.

To the

technician,

this

amplifier

representsaradicaldeparturefromthe"normal"Crowndesign.

Previous

chapters covered

the

"normal," this chapter

shall

endeavorto

take

the

MA-5000VZ

as a

unique

entrty.

The

amplifier

¡s

protected

from

all

common hazards that plague high-

power

amplifiers, including

shorted,

open

or

mismatched

loads,

overloaded power

supplies,

excessive temperature,

chain-destruction

phenomena,

input-overload

damage,

and

high-frequency blowups.

The

unit

protects

loudspeakers

from

DC in the

input

signal

and

from

turn-on

and

turn-off

transients.

It

also

detects

and

prevenís

unwanted

DC

on the

outputs. Additional protection features include input current

sense,

overvoltage

(AC

mains).

A

mode

of

protection which

may

be

switched

on or

off

is

called

Loudspeaker Offset Integration (LOI).

The

LOI

circuit, when switched

on,

prevenís

excessive bass frequency

cone

excursions

below

the

audible frequency range.

It

operates essentially

as a

band-pass filter.

The

low

frequencies

are

rolled

off at

18dB/oclave

with a -3dB

córner

of

35

Hz

(Butterworth

response).

Ullra-sonics

are

rolled

off

wilh a second

order

Bessel

response

and

-3dB córner

of

SOkHz.

A

compression

circuil

in

each channel

may be

switched

off,

on

slow,

or

on

fast

by

swilches

on

Ihe

rear panel. This compressor

is

aclivaled

by

eilherinputoverloadord¡stort¡on(cl¡pping).

Compression ratio

is

infinite

(operates

as a

peak

limiter).

Thefour-quadrant

lopology

used

in the

grounded

oulpul

slages

is

called

Ihe

grounded bridge

and

makes

full

use of

Ihe

power supplies. This

patentad

lopology

also

makes

peak-lo-peak

voltages

available

lo

the

load which

are

twice

the

vollage

any

output

device

¡s

ever exposed

to.

The

grounded bridge

is

covered

in

detail

in the

BASICS

seclion

of

this

texl.

MA-5000VZ

- 1

Notes

The

two

channels

may be

used together

to

double

the

voltage (bridged-

mono)orthecurrent(parallel-mono)presentedto

the

load. Thisfeature

gives

the

User

flexibility

in

maximizing

the

power

available

to the

load.

Output

power

of the

amplifier

is

rated

as

follows (assumes

120V

60Hz

AC

mains):

StereoSohm:

1300W/CH

Stereo4ohm:

2000W/Ch

Stereo2ohm:

2500W/Ch

Bridge

Mono 8 ohm: 4000W

Bridge

Mono 4 ohm: 5000W
Parallel Mono 2 ohm: 4000W
Parallel Mono 1 ohm: 5000W

Macro-Tech amplifiers

utilize a wide

bandwidth

multiloop

design with

state

of the art

compensation

techniques.

This produces ideal behavior

and

results

¡n

ultra-low

distortion

valúes.

Aluminum

extrusions

have

been widely used

for

heatsinks

in

power

amplifiers

due to

their

low

cost

and

reasonable performance. However,

measured

on a

watts

per

pound

or

watts

per

volume

basis,

the

extrusión

technology

doesn't

perform

nearly

as

well

as the

thermal

diffuser

technology developed

for

Macro-Tech power amplifiers.

Our

thermal

diffusers

are

fabricated

from

custom

cut fin

stock

that

provides

an

extremely high ratio

of

área

to

volume,

or

área

to

weight.

All

power

devices

are

mounted directly

to

massive

heat

spreaders that

are

electrically hot. Making

the

heat spreaders electrically

hot

allows

MA-5000VZ:
CHANNEL1

SHOWN

4

(ooep)

MA-5000VZ Overall

Block

Diagram

D

(ODEP)

2 -

MA-5000VZ

improved thermal performance

by

eliminating

the

insulating

interface

underneath

the

power devices.

The

chassis

itself

is

used

as

part

of the

thermal circuit,

and

this

maximizes utilization

of the

available resources.

Air

flow

in

this

amplifier

is

front

to

rear,

also a departure

from

other

Macro-Techs.

Fan

speed

is a

function

of

ODEPIevel.

AlthoughODEP

was

covered

in

detail

in the

BASICS section

of

this text,

the

specif

ics of

the

MA-5000VZ ODEP circuit

are

unique

and

will

be

covered here.

Notes

OUTPUT

STAGE

CIRCUITRY

The

MA-5000VZ,

like

other Macro-Techs, uses

the

grounded bridge.

It

does

differ,

however,

in

certain

aspects.

For

example, quadrants

use

four

devices

¡n

parallel

ratherthan

the

normal máximum

of

three. Output

stages

are

also physically

built

in a

modular way,

for

ease

of

field

replacement.

Electrically, there

are

also

a few

differences.

Bias servo networks

consist

of two

transistor devices

per Vbe

multiplier (one

set for

high side,

one

set for low

side). Also, ODEP affects

the low

side

as

well

as the

high

side

by

stealing

low

side

bias

and

drive. Taking that a step further,

any

protective

action

which

limits,

mutes,

or

shuts down

the

amplifier will

accomplish

the

same thing

by

stealing drive.

Circuitry

on the

positive

and

negative output modules ¡nclude bias

circuitry,

current

limit

circuitry

(the MA-5000VZ

has two

speed current

limit),

last

voltage amplifiers (LVA's), pre-driyers, drivers,

and

output

devices. Temperature

sensors

are

also mounted

to the

heatsinks

vía

the

output modules. These deliver ¡nformation

to the

main

module

which

computes actual calibrated temperature

for

ODEP

and

temperature

measurement.

H-15V

R571

2.7K

Positive

(NPN) Output

Stage

Thermal

Sensor Circuitry

U50O

V.

LM334

r

L

3

R572

r£

227

O.5OW

R584

2.7K

\

+TEMP1

:

The

positive

LVA's

(Q501,

Q502,

and

Q503)convert

the

negative

output

of

the

voltage translator stage

to a

positive drive voltage

for the NPN

High

Side

(HS) predriver. There

are

three

LVAtransistorsin

parallel

due

to

the

very

high

voltages

(therefor

higher

current

and

thermal

requirements) that

are

present

when

the

power

supply

is in

high voltage

mode.

D522

prevenís

the

+LVA'sfromproducinga

high negative output

to the HS NPN

stage.

MA-5000VZ

- 3

Notes

Q507, Q508,

and

Q509

are the

-LVA's

and are

arranged

¡n

mirror

image

to

the

+LVA's,

¡ncluding

D513.

On

the

positive side D514, D515,

and

C506

vía

the

+LVA's

act to

limit

slew

rate.

D514

and

D515

also

prevent dangerously excessive current

through

the

LVA's.

D516,

D517,

and

C507

are the

negative

HS

mirror

image.
Q534

and

Q540

provide

two-speed current limiting

¡n the

output stage.

Sense

lines

are

arranged such that excessive current through

any

single

HS

output device

will

result

in

current limit protection. Q535

and

Q541

are

the

negative side mirror image.

Q503

on the

positive output module works

in

tándem with Q505

on the

negative output module

as a Vbe

multiplier

circuit.

They produce and,

with great

stabilily,

control

biasforthe

High Side

NPN

and

PNP

devices.

Potentiometer R505

is

used precisely

set

bias voltage. Bias voltage

is

easily measured

from

pin 2

(hot)

to pin 4 of ATE

ports

TP1 and

TP2.

Refer

to

section

2 for

appropriate test procedures.

Q504¡stheHSNPNpre-driverandQ511

istheHSNPNdriver.

These

devices

are

biased

class

AB for

ultra

low

distortion

in the

zero-crossing

región.
Q513, Q515,

Q517,

and

Q536

are the HS NPN

output devices. These

devices

are

biased

class

B, in

soft

cut-off,

Together

with

driver

and

pre-

driver, they function

as a

three-deep Darlington.

The

output devices

work

¡n

parallel

as a

giant composite.

The

over-all

bias topology

is

referred

to as

AB+B,

originally conceived

and

patented

by

Crown

engineers

in

1966.

This

¡s

still

the

most

efficient,

stable,

and

distortion

free

method used today.

Positive

LVA,

Portion

of HS

Bias,

&

Positive

Current

Limit

Section

VCC1

High Side

+LVA's,

Current

Limit,

and the

portion

of the

Bias

Servo

Network

on the

Positive Output

Module.

D51O

R595

3

82K

C536
O.O01

r-

R5O5

HIGH)

500

SIDE

';

BIAS

U

Emitter

Sense

Output

Audio

4 -

MA-5000VZ

D506

is

theflybackdiode

forthe

HS NPN

output quadrant.

In

the

event

that a back

EMF

(flyback) pulse exceeds power supply voltage,

the

flyback

diode

will

shunt this voltage

to the

supply

in

order

to

protect

the

output devices.

PNP

pre-drivers,

drivers,

output devices,

and

flyback diode D508

are a

mirror

image

of the NPN

side.

Overall

the

High

Side

of

bridge operates much

like a conventional output

stage,

but the Low

Side

(LS)

is

quite unique.

The LS

senses output voltage

and

common

(ground) buss potential.

The

audio output

is

inverted

by

U503.

Also

in the

U503 input

circuitry

are

static

and

dynamic balance controls.

These

controls provide a fine

balance

of the

grounded bridge. Output

of the

op-amp

drives

the LS

pre-

driver

circuits

through

the LS

bias network.

LS

bias

¡s

controlled

in a

fashion

similar

to

that

of the HS. Two

transistors, Q529

and

Q530,

along

fix LS

bias voltage

as

measured

from

pin

15(hot)topin13ofapplicableATEportTP1

orTP2. Potentiometer

R556

adjusts

bias

in the LS.

Diodes D504

and

D505 control

polarity

of

applied

LS

drive signal.

Via

the

bias transistors signal

¡s

delivered

to the

bases

of the

pre-drivers

Q527

(NPN)

and

Q528 (PNP).

Pre-drivers,

drivers,

and

output devices

in

the LS

opérate

class

AB+B,

exactly

like

the HS. The

major

difference

¡s

that

rather

than driving a load,

the NPN and PNP

stages control

the

ground reference

for the

high

voltage

rails.

As the HS

NPN's conduct,

LS

PNP's conduct,

and

vice versa

(as

explained

in

section

4.2.1).

When

the

ODEP circuit senses that limiting drive

is

necessary

to

prevent

a

dangerous thermal

condition,

¡t

provides

an

output which limits drive

Notes

+VCC1

OUTPUT POSITIVE SECTION

+VCC

BUSS

BAR

+

LVA

H-VCC1

Q513

Q515 Q517

Q536

'

C5O6

220pF

_L

C510

'

O.O1

D5O6

High Side Predrivers,
Drivers,

Output

Devices,

and

Flyback Diodes.

Notice

the

various sense

lines.

These

are

used

for

various functions

such

as VZ

switching

sense and

protection

features.

MA-5000VZ

- 5

-I-VCC1

o

I-15V

I-15V

C524
2OOpF

R552
1OO

R553
1OO

To

NPN LS

Predriver

D518

D5

J

D4

y

H

I

C52

10p

D521

N
d

RS56
500

4

1

LOW S
BIAS

6
=

f

>>[

5
5

— <

DE

A

^

D5£

r

os:

R554
1

.821

'

R555

>

1K

k

4

6

<

l

R56O
47K

_L

C534

!47pF

R547

4.99K

C52S

xH

U5O3

•

LM6364

g

JjH

—

C528
33OOpF

OUT1

B

I

COMM1

1

'

1

15V

Low

Side

of

Bridge: sensing amplifier output

and

¡nverting

the

signal,

Low

Side Bias

(portion

on

positive output module),

and

differential

circuit which clamps

Low

Side signal

¡n the

event

of

ODER

or

other

protective function.

+VCC1

+VCC1

+VCC1

Q527

I

L

tí

>

H534

¡T

D507 > 12

X

2W

C520

r-

0.022

R582

¿

0.

33

>

5W

S

Q538

V|

Q51

r

¿

R536

>

0.33

S 5W

•

i

BU

rj

S

R538

/

>

0.33

>

S

5W

S

i

Q523

R54O

0.33

5W

-*S

V"

R542

4.

0.350W

rNr^^>1^J

l-t

Ql

ice; n A

c

(

Q525

470uH

N

-

r^^V^VN

.

*T

R544

R546

51

100

C522

0.033

||

kr

R550

13K

ni

Low

Side

of

Bridge: including

P

Driver, Output Devices,

and

Fl^

Diode

on the NPN

side.

LLL

6 -

MA-5000VZ

to

the

output

stages.

For the HS,

this

limiting

¡s

accomplished

on the

main module

and

isexplained

¡nsect¡on4.4.

Forthe

LS,

ODEP provides

(via wires

labeled

±LL) a signal

which

limits bias feed

to the LS

output

devices. This

is

accomplished through current mirrors Q532

and

Q531

(LS

NPN

quadrant),

and

Q542

and

Q543

(LS PNP

quadrant).

Notes

POWER

TRANSISTOR

SPEAKER

LOAD

POWER

TRANSISTOR

VZ

POWER

SUPPLY

POWER

TRANSISTOR

SPEAKER

LOAD

POWER

TRANSISTOR

VZ

STAGEVZSTAGE

Low

Voltage, High Current Mode

VZ

POWER SUPPLY

POWER
TRANSISTOR

SPEAKER
LOAD

POWER
TRANSISTOR

VZ

STAGE

VZ

STAGE

High Voltage,

Low

Current Mode

VZ

POWER

SUPPLY

The VZ supply in the MA­SOOOVZworks,

inconcept,

very

much

like

the

MA-3600VZ.

For

the

sake

of

completeness,

some

conceptual things

will

be

duplicated

here.

VZ

means

Variable Impedance

and is the

ñame

of

Crown's

patented

articulated

power

supply technology.

It

enables

Crown

to

pack tremendous

power

into just 5.25 inches

of

vertical

rack

space.

A

power supply must

be

large

enough

to

handle

the

máximum

voltage

and

current

necessary

for

the

amplifier

to

drive

its

máximum rated power into

a

specified load.

In the

process

of

fulfilling this requirement
cónventional power supply
designs produce

lots

of

heat,

are

heavy,

and

take

up

precious

real

estáte.

And

it's

no

secret

that heat

is one of a

power

amplifiers worst enemies.
According

to

Ohm's Law,

the

bigger

the

power supply,

the

more

heai

the

power

transistors

must

dissipate.

Also,

the

lower

the

resistance

of the

power

transistors,

the

more voltage

you

can

deliverto

the

load.

But

at

the

same time that

you

lower

the

resistance

of

the

transistors,

you

increase

the

current

passing through

them,

and

again ¡ncrease

the

amount

of

heat

they must dissipate.

An

articulated power

supply,

like

VZ, can

circumvent much

of

this problem

by

reducing

the

voltage

appliedto

the

transistors

when

less

voltage

is

required.

MA-5000VZ

- 7

Notes

Reducing

the

voltage

reduces

the

heat.

Since

the

amplifier

runs

cooler,

you can

safely pack more power into

the

chassis.

The VZ

supply

is

divided ¡nto segments

to

better match

the

voltage

and

current

requirements

of the

power transistors. Remember that audio

signáis

like

music

are

complex waveforms.

For

music

the

average

level

is

always

much

less

than

the

peak

level.

This

means a power supply does

not

need

to

produce full voltage

all

the

time.
The

VZ

supply

is

divided

into

two

parís.

When

the

voltage requirements

are

not

high,

it

opérales

in a

parallel mode

to

produce less vollage

and

more current.
The

power transistors

slay

cooler

and are

nol

torced

lo

needlessly

dissipate

heal.

This

is

Ihe

normal

operaling

mode

of

Ihe

VZ

power

supply.
When

Ihe

vollage

requiremenls

are

high

VZ

swilches

to a

series mode

to

produce higher

vollage

and

less

currenl.

The

amplified

oulpul

signal

never

misses a beal

and

gels

full vollage when

it

needs

il—not

when

il

doesn't need

¡t.

Sensing

circuilry

walches

Ihe

vollage

of

Ihe

signal

lo

delermine when

GROUNDEDBRIDGE

OUTPUT STAGE

Input

VZ

Power

Supply

^

R = Switch

Resistance

8 -

MA-5000VZ

to

switch

VZ

modes.

The

switching

circuitry

is

designed

to

prevent

audible

switching

distortion

to

yield

the

highest dynamic transfer

function—you

hear

only

the

musió

and not the

amplifier.

You get not

only

the

máximum power with

the

máximum safety,

you

also

get

the

best

power

matching

to

your load.

Actual

current

flow

with power supply

and

grounded bridge operating

together

is

shown

on the

previous page.

The

individual

components

are

shown

below.

Upstream

of the

toroid

transformer,

though

not

shown,

is

where shutdown protection

and

soft-

start

circuitry taps

in to

control

AC

mains ¡nput

to the

power

supply.

The

VZ

Control circuitry senses

audio

level

and

switches

the

articulating

VZ

supplies

to

either parallel (high current) mode

for

lower

level audio,

or

series

(high voltage) mode

for

high program peaks.

Notes

Toroid

Bridge

1

In

both examples

it can be

seen that

when

the

MOSFET switch

is

off,

the

dual

supplies

are

torced

to

opérate

¡n a

parallel mode. Audio level

is

sensed

via a

line

tapping

off the

NFb

loop.

When audio level

¡s

rising

and at

about

80% of the

parallel

mode supply voltage,

the

MOSFETs

(the

switch

is

actually a three-device

composite switch)

are

turned

on.

No

current

will

flow through either

of the

control diodes

(D810

and

D811,

as

shown

for

channel

1)

because reverse polarity

is

applied through

the

MOSFET switch. Since

this

happens

to

both rectifier sources

at the

same time,

and the

negative side

of

Bridge

1 ¡s

then

shorted

to the

positive side

of

Bridge

2, the

supplies

are

forced

to

opérate

in

series

mode.

Like

two

batteries,

the

supplies will provide double voltage

in

series mode, double current

¡n

parallel mode.

Although

shipped

from

the

factory

¡n

normal

VZ

mode,

the

user

may

switch

modes

to

lock

low

voltage (high current),

lock

high voltage,

or

opérate

the

supply

in

Bi-ODEP mode. Bi-ODEP

is

similar

to

normal

VZ

MA-5000VZ

- 9