Crown MARCO-TECH 5000VZ User manual

Notes
MACRO-TECH5000VZ
OVERVIEW
At firstglance the MA-5000VZ looks a greatdeal Hkeany other MA
Series amplifier,exceptthat ¡tis physicallylarger and puts out more
power. The internal structure ofthe MA-5000VZ is, however,quite
different from othermodels intheMA une. Tothe user,this oneis like
the others, but with a f ew more f eatures. Tothe technician, this amplifier
representsaradicaldeparturefromthe"normal"Crowndesign. Previous
chapterscovered the "normal,"thischapter shall endeavorto take the
MA-5000VZ asa unique entrty.
The amplifier ¡s protected from all commonhazardsthatplaguehigh-
power amplifiers,including shorted, open or mismatched loads,
overloadedpower supplies, excessivetemperature, chain-destruction
phenomena, input-overload damage, and high-frequencyblowups.
The unit protects loudspeakers from DCinthe input signal and from
turn-on and turn-off transients. It also detects and prevenís unwanted
DC onthe outputs.Additionalprotectionfeaturesincludeinputcurrent
sense, overvoltage (AC mains).
A mode of protectionwhich may be switched onor off is called
LoudspeakerOffsetIntegration(LOI). The LOI circuit,whenswitched
on, prevenís excessivebassfrequency cone excursions below the
audiblefrequencyrange. It operatesessentially asa band-passfilter.
The low frequencies are rolled offat 18dB/oclave with a -3dB córner of
35 Hz (Butterworth response). Ullra-sonics are rolled off wilh a second
order Bessel response and -3dBcórner of SOkHz.
A compression circuil in eachchannel maybe switched off, on slow, or
on fast by swilches on Ihe rearpanel.Thiscompressor is aclivaled by
eilherinputoverloadord¡stort¡on(cl¡pping). Compressionratio is infinite
(operates asa peak limiter).
Thefour-quadrant lopology used inthe grounded oulpul slages is called
Ihe groundedbridge and makes full useof Ihe powersupplies.This
patentad lopology also makes peak-lo-peak voltages available lo the
loadwhich are twice the vollage any output device ¡s everexposed to.
The groundedbridge is covered in detail inthe BASICS seclion of this
texl.
MA-5000VZ - 1

Notes
The two channels maybe usedtogether to double the voltage(bridged-
mono)orthecurrent(parallel-mono)presentedto the load.Thisfeature
gives the User flexibility in maximizing the power available tothe load.
Output power ofthe 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
ParallelMono 2 ohm:4000W
ParallelMono 1 ohm:5000W
Macro-Techamplifiers utilize a wide bandwidth multiloop designwith
state oftheart compensation techniques. Thisproducesidealbehavior
and results ¡n ultra-low distortion valúes.
Aluminum extrusions have beenwidelyused for heatsinks in power
amplifiers dueto their low cost and reasonableperformance.However,
measured ona watts per pound or watts per volume basis, the extrusión
technology doesn't perform nearly as well asthe thermal diffuser
technologydeveloped for Macro-Techpoweramplifiers.
Our thermal diffusers are fabricated from custom cutfin stock that
provides an extremelyhighratio of área to volume, or área to weight. All
power devices are mounteddirectly to massive heat spreadersthat are
electricallyhot.Making the heatspreaderselectrically hot allows
MA-5000VZ:
CHANNEL1
SHOWN
4 (ooep)
MA-5000VZOverall Block
Diagram
D
(ODEP)
2- MA-5000VZ

improvedthermalperformance by eliminating the insulating interface
underneath the powerdevices. The chassis itself is used as part ofthe
thermalcircuit, and this maximizesutilization ofthe availableresources.
Air flow in this amplifier is front to rear, also a departure from other
Macro-Techs. Fan speed isa function of ODEPIevel. AlthoughODEP
was covered in detail inthe BASICSsection of thistext, the specif icsof
the MA-5000VZODEPcircuit are unique and will be coveredhere.
Notes
OUTPUT STAGE CIRCUITRY
The MA-5000VZ, like otherMacro-Techs,uses the groundedbridge. It
does differ, however, in certain aspects. For example,quadrants use
four devices ¡n parallel ratherthan the normalmáximum of three.Output
stages are alsophysically built ina modularway, for ease of field
replacement.
Electrically,there are also a few differences. Biasservonetworks
consist oftwo transistordevices perVbe multiplier(one setfor highside,
one setforlow side).Also,ODEPaffects thelow side as well asthe high
side by stealing low side bias and drive.Takingthat a stepfurther, any
protective action which limits, mutes, or shutsdown the amplifierwill
accomplish the samething by stealingdrive.
Circuitry onthe positive and negativeoutputmodules¡ncludebias
circuitry, current limit circuitry (theMA-5000VZ hastwo speedcurrent
limit), last voltageamplifiers(LVA's),pre-driyers,drivers, and output
devices.Temperature sensors are alsomounted tothe heatsinks vía
the outputmodules.Thesedeliver¡nformation tothe main module
which computesactualcalibratedtemperature for ODEP and
temperature measurement.
H-15V
R571
2.7K
Positive (NPN)Output Stage
Thermal SensorCircuitry
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 voltagetranslatorstage toa positivedrivevoltage fortheNPN
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 isin highvoltage
mode. D522 prevenís the +LVA'sfromproducinga highnegativeoutput
totheHSNPN stage.
MA-5000VZ - 3

NotesQ507,Q508,
and Q509 arethe -LVA's andare arranged ¡n mirror image
to the +LVA's, ¡ncluding D513.
On the positivesideD514,D515, and C506 vía the +LVA's actto limit
slew rate. D514 and D515 also preventdangerouslyexcessivecurrent
through the LVA's. D516, D517, and C507 arethe negative HS mirror
image.
Q534 and Q540 provide two-speedcurrentlimiting ¡nthe outputstage.
Sense lines are arrangedsuchthatexcessivecurrentthrough any single
HS outputdevice will result in currentlimitprotection.Q535 and Q541
are the negativesidemirrorimage.
Q503 onthe positiveoutputmoduleworks in tándemwithQ505 onthe
negativeoutputmodule asaVbe multiplier circuit. Theyproduceand,
withgreat stabilily, control biasforthe HighSide NPN and PNP devices.
PotentiometerR505 is usedprecisely set biasvoltage.Biasvoltage is
easilymeasured from pin2 (hot) topin4 ofATE ports TP1and TP2.
Refer to section 2 for appropriatetestprocedures.
Q504¡stheHSNPNpre-driverandQ511 istheHSNPNdriver. These
devices are biased class ABfor ultra low distortion inthe zero-crossing
región.
Q513,Q515, Q517, and Q536 aretheHSNPN outputdevices.These
devices are biased class B,in soft cut-off, Together with driver and pre-
driver,theyfunction asa three-deepDarlington. The outputdevices
work ¡n parallel asa giantcomposite. The over-all biastopology is
referred toas AB+B, originallyconceived and patented by Crown
engineers in 1966. This ¡s still the most efficient, stable, and distortion
free methodusedtoday.
Positive LVA, Portion ofHS Bias,
& Positive Current Limit Section
VCC1
HighSide +LVA's, Current Limit,
andthe portion ofthe Bias Servo
Network onthe PositiveOutput
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 HSNPN outputquadrant. In the event
that a back EMF (flyback)pulseexceedspowersupplyvoltage, the
flyback diode will shuntthisvoltage tothe supply in order to protect the
outputdevices.
PNP pre-drivers, drivers, outputdevices, and flybackdiodeD508 area
mirror image oftheNPN side.
Overall the High Side of bridgeoperatesmuch like a conventionaloutput
stage, buttheLow Side (LS) is quiteunique.
TheLS sensesoutputvoltage and common (ground)busspotential.
The audiooutput is inverted by U503. Also inthe U503input circuitry
are static and dynamicbalancecontrols. These controlsprovide a fine
balance ofthe groundedbridge.Output ofthe op-amp drives theLS pre-
driver circuits through theLS biasnetwork.
LS bias ¡s controlled ina fashion similar to that oftheHS.Two
transistors,Q529 and Q530, along fixLS biasvoltage as measured from
pin 15(hot)topin13ofapplicableATEportTP1 orTP2.Potentiometer
R556 adjusts bias intheLS.
DiodesD504 and D505control polarity of applied LS drivesignal. Via
the biastransistorssignal ¡s delivered tothe bases ofthe pre-drivers
Q527 (NPN) and Q528(PNP). Pre-drivers, drivers, and outputdevices
in theLS opérate class AB+B, exactly like theHS.The major difference
¡s that rather thandriving a load, theNPNandPNP stagescontrol the
groundreference forthe high voltage rails. AstheHS NPN'sconduct,
LS PNP'sconduct, and viceversa (as explained in section 4.2.1).
When the ODEPcircuitsensesthatlimitingdrive is necessary to prevent
a dangerousthermal condition, ¡t provides an outputwhichlimitsdrive
Notes
+VCC1
OUTPUTPOSITIVESECTION
+VCC BUSS BAR
+ LVA
H-VCC1
Q513 Q515Q517 Q536 '
C5O6
220pF _L C510
' O.O1
D5O6
HighSidePredrivers,
Drivers, Output Devices,
and FlybackDiodes.
Notice the varioussense
lines. These are used
for variousfunctions
such asVZ switching
senseand protection
features.
MA-5000VZ - 5

-I-VCC1
o
I-15V I-15V
C524
2OOpF
R552
1OO
R553
1OO
To NPNLS
Predriver
D518
D5
J
D4
y
H
I
C52
10p
D521
N
d
RS56
500
4 1
LOWS
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:sensingamplifieroutput and ¡nverting the signal,
Low SideBias (portion on positiveoutputmodule), and differential
circuitwhichclamps Low Sidesignal ¡nthe event of ODER or other
protectivefunction.
+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
S5W
• i
BU rj
S R538 /
> 0.33 >
S 5W S
i
Q523
R54O
0.33
5W
-*S
V"
R542
4.
0.
3
50W
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,OutputDevices, and Fl^
Diode ontheNPN side.
LLL
6- MA-5000VZ

to the output stages. FortheHS, this limiting ¡s accomplished onthe
mainmodule and isexplained ¡nsect¡on4.4. Forthe LS, ODEPprovides
(viawires labeled ±LL) a signal which limitsbiasfeed totheLS output
devices.This is accomplishedthroughcurrentmirrorsQ532 and Q531
(LS NPN quadrant), and Q542 and Q543 (LSPNP quadrant).
Notes
POWER
TRANSISTOR
SPEAKER
LOAD
POWER
TRANSISTOR
VZ POWER SUPPLY
POWER
TRANSISTOR
SPEAKER
LOAD
POWER
TRANSISTOR
VZ
STAGE
VZ
STAGE
Low Voltage,HighCurrentMode
VZ POWERSUPPLY
POWER
TRANSISTOR
SPEAKER
LOAD
POWER
TRANSISTOR
VZ
STAGE
VZ
STAGE
HighVoltage, Low CurrentMode
VZ POWER SUPPLY
TheVZsupplyintheMA-
SOOOVZworks, inconcept, very
much like the MA-3600VZ. For
the sake of completeness,
some conceptualthings will be
duplicated here.
VZ means VariableImpedance
andisthe ñame of Crown's
patented articulated power
supplytechnology. It enables
Crown to packtremendous
power intojust5.25inches of
vertical rack space.
A powersupplymust be large
enough to handle the máximum
voltage and current necessary
for the amplifier to drive its
máximumratedpowerinto a
specifiedload. Inthe process
of fulfillingthisrequirement
cónventionalpowersupply
designsproduce lots of heat,
are heavy, and take up precious
real estáte. And it's no secret
thatheat isoneofa power
amplifiersworstenemies.
According to Ohm'sLaw, the
bigger the powersupply, the
more heai the power transistors
must dissipate. Also, the lower
the resistance ofthe power
transistors, the morevoltage
you can deliverto the load. But
at the sametimethat you lower
the resistance of the transistors,
you increase the current
passingthrough them, and
again¡ncrease the amount of
heat theymustdissipate.
An articulatedpower supply,
like VZ,can circumventmuch
of thisproblem 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,
youcan safelypackmorepowerinto the chassis.
TheVZ supply is divided¡ntosegments to bettermatch the voltage and
current requirements ofthe powertransistors.Rememberthataudio
signáis like music are complexwaveforms.
For music the average level is always much less than the peak level.
This means a powersupplydoes not need to producefullvoltage all the
time.
The VZ supply is divided into two parís. When the voltagerequirements
are not high, it opérales ina parallelmode to producelessvollage and
morecurrent.
The powertransistors slay cooler andare 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 toa seriesmode
to producehigher vollage and less currenl. The amplified oulpul signal
never misses a beal and gels fullvollagewhen it needs il—not when il
doesn'tneed ¡t.
Sensing circuilry walches Ihe vollage of Ihe signal lo delerminewhen
GROUNDEDBRIDGE
OUTPUTSTAGE
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 highestdynamictransfer
function—you hear only the musió andnotthe amplifier. Yougetnot
only the máximumpowerwith the máximumsafety, you also get the best
power matching to yourload.
Actual current flow withpowersupply and groundedbridgeoperating
together is shown onthe previouspage.
The individual components are shown below. Upstream ofthe toroid
transformer, though not shown, is whereshutdownprotection and soft-
start circuitrytaps into control AC mains¡nput tothe power supply. The
VZ Controlcircuitrysenses audio level and switches the articulating VZ
supplies to eitherparallel(highcurrent)mode for lower levelaudio, or
series (highvoltage)mode for highprogrampeaks.
Notes
Toroid Bridge 1
In bothexamples itcanbe seenthat when the MOSFETswitch is off,
the dual supplies are torced to opérate ¡na parallelmode.Audiolevel
is sensed viaa line tapping offthe NFb loop. Whenaudiolevel ¡s rising
andat about 80%ofthe parallel modesupplyvoltage, the MOSFETs
(the switch is actually a three-device compositeswitch) are turned on.
No current will flowthrougheither ofthe controldiodes (D810 and D811,
as shown for channel 1) becausereversepolarity is appliedthrough the
MOSFETswitch.Since this happens to bothrectifiersources atthe
sametime, andthe negativeside of Bridge 1 ¡s then shorted tothe
positiveside of Bridge 2,the supplies are forced to opérate in series
mode. Like two batteries, the supplieswillprovidedoublevoltage in
seriesmode,doublecurrent ¡n parallelmode.
Although shipped from the factory ¡n normal VZ mode, the user may
switch modes to lock low voltage(highcurrent), lock highvoltage, or
opérate the supply in Bi-ODEPmode.Bi-ODEP is similar to normal VZ
MA-5000VZ - 9

Notes
mode, exceptthat ¡n the eventODEP ¡s activated to protect the
amplifier, theVZ will automatically lockinto low voltage(highcurrent)
mode. While thismode of operationwill cool the amplifiermorequickly
inthe eventthat the thermalreserve ¡s exhausted, itmay causevoltage
clippingratherthanODEP limiting, this maybea worsecondition for
speakers.Seldomwill the amplifier be operatedlocked in high current
mode unless a very low impedance is beingdriven. Bythe same token,
it ¡s also unlikelythat a userwillopérate the amplifierlocked in high
voltage mode forthe thermalreasonsmentioned.
To BottomRectifier
Positivo Sense
/N
VCC BUSS BAR
-VCC BUSS BAR
N/
To Top Rectifier
Negative Sense
From 555for
Switch Control
-VCC BUSS BAR
VZ SwitchControl Circuitry
10-MA-5000VZ