registered trademarks of Crown International, Inc. Other trademarks are the property
of their respective owners.
®
130366-1
11-00
Rev. A
MA-3600VZ Service Manual
The information furnished in this manual does not include all of the details of design, production, or
variations of the equipment. Nor does it cover every possible situation which may arise during installation,
operation or maintenance. If you need special assistance beyond the scope of this manual, please contact
the Crown Technical Support Group.
Mail: P.O. Box 1000 Elkhart IN 46515-1000
Shipping: Plant 2 SW 1718 W. Mishawaka Road Elkhart IN 46517
Phone: (800) 342-6939 / (219) 294-8200
FAX: (219) 294-8301
130366-1 Rev. A
CAUTION
TO PREVENT ELECTRIC SHOCK DO
NOT REMOVE TOP OR BOTTOM
COVERS. NO USER SERVICEABLE
PARTS INSIDE. REFER SERVICING
TO QUALIFIED SERVICE PERSON-
NEL. DISCONNECT POWER CORD
BEFORE REMOVING REAR INPUT
MODULE TO ACCESS GAIN SWITCH.
WARNING
TO REDUCE THE RISK OF ELECTRIC
SHOCK, DO NOT EXPOSE THIS
EQUIPMENT TO RAIN OR MOISTURE!
AVIS
À PRÉVENIR LE CHOC
ÉLECTRIQUE N’ENLEVEZ
PAS LES COUVERTURES.
RIEN DES PARTIES UTILES
À L’INTÉRIEUR.
DÉBRANCHER LA BORNE
AVANT D’OUVRIR LA
MODULE EN ARRIÈRE.
II
The lightning bolt triangle is used to alert
the user to the risk of
electric shock.
The exclamation point triangle is used to alert the user to
important operating or maintenance instructions.
This manual contains complete service information on
the Crown® MA-3600VZ power amplifi er. It is designed
to be used in conjunction with the Reference Manual;
however, some important information is duplicated
in this Service Manual in case the Reference Manual
is not readily available.
MA-3600VZ Service Manual
feature balanced inputs with bridged and parallel
monophonic capability. Specific features vary
depending on model.
1.3 Scope
This Service Manual in intended to apply to all
versions of the MA-3600VZ amplifier. The Parts
Listings include parts specifi c for the US version and
the European version (E17CE). For parts specifi c only
to other versions contact the Crown Technical Support
Group for help in fi nding part numbers.
NOTE: THE INFORMATION IN THIS MANUAL
IS INTENDED FOR USE BY AN EXPERIENCED
TECHNICIAN ONLY!
1.2 The Macro-Tech Series Amplifi ers
The Macro-Tech® series is a complete family of
amplifiers designed for pro sound reinforcement.
Macro-Tech amplifiers are designed to provide
enormous levels of pure, undistorted power in
a rugged low-profile package, utilizing Crown's
patented Grounded Bridge™ output topology. They
also employ Crown's patented ODEP® protection
circuitry, which keeps the amplifi er working under
extreme conditions that would shut down a lesser
amplifi er. The MA-3600VZ features Crown's PIP™
(Programmable Input Processor) expansion system.
The PIP expansion system makes it easy to tailor
the amplifier to a specific application. Providing
high power amplifi cation from 20 Hz to 20 kHz with
minimum distortion, Macro-Tech series amplifiers
Crown Customer Service
Technical Support Group
Factory Service
Parts Department
1.4 Warranty
Each Reference Manual contains basic policies as
related to the customer. In addition, it should be
stated that this service documentation is meant to be
used only by properly trained personnel. Because
most Crown products carry a 3-Year Full Warranty
(including round trip shipping within the United
States), all warranty service should be referred to
the Crown Factory or Authorized Warranty Service
Center. See the applicable Reference Manual for
warranty details. To fi nd the location of the nearest
Authorized Warranty Service Center or to obtain
instructions for receiving Crown Factory Service,
please contact the Crown Technical Support Group
(within North America), or your Crown/Amcron
Importer (outside North America). If you are an
Authorized Warranty Service Center and have questions regarding the warranty of a product, please
contact the Field Service Manager or the Technical
Support Group.
These specifi cations apply to 120 VAC units in stereo mode with 8 ohm loads and an input
sensitivity of 26 dB unless otherwise specifi ed.
120 VAC, 60 Hz Units: These units are equipped with transformers rated for 120 VAC,
60 Hz power.
International Units: These units are equipped with transformers for either 100 VAC, 50/60
Hz, or 230 VAC, 50/60 Hz power.
2.1 Performance
Frequency Response: ±0.1 dB from 20 Hz to 20 kHz at 1
watt.
Phase Response: ±10° from 10 Hz to 20 kHz at 1 watt.
Signal-to-Noise Ratio: Greater than 105 dB below rated
output (20 Hz to 20 kHz, A-weighted); 100 dB below rated
output (20 Hz to 20 kHz, no weighting).
Harmonic Distortion (THD): At rated output, less than 0.05%
from 20 Hz to 1 kHz increasing linearly to less than 0.1% at
20 kHz.
IM Distortion (IMD): Less than 0.05% from 368 milliwatts to
full rated output.
Damping Factor: Greater than 1,000 from 10 Hz to 400 Hz.
Crosstalk: See Figure 2.1.
Slew Rate: Greater than 30 volts per microsecond.
Voltage Gain: (At maximum output) 20:1 ±3% or 26 dB ±0.25
dB at +26 dB sensitivity, and 124.6:1 ±12% or 41.9 dB ±1.0
dB at 0.775 volt sensitivity.
2.2 Power
Output Power:
Note: Maximum average watts per channel (unless in Mono
mode) at 1 kHz with 0.1% or less THD.
120 VAC, 60 Hz Units:
Stereo mode with both channels driven:
1800 watts into 2 ohms.
1565 watts into 4 ohms.
1120 watts into 8 ohms.
Bridge-Mono mode:
3505 watts into 4 ohms.
3140 watts into 8 ohms.
Parallel-Mono mode:
3555 watts into 1 ohm.
3190 watts into 2 ohms.
100 VAC International Units:
Stereo mode with both channels driven:
1460 watts into 2 ohms.
1300 watts into 4 ohms.
980 watts into 8 ohms.
Bridge-Mono mode:
2835 watts into 4 ohms.
2625 watts into 8 ohms.
Parallel-Mono Mode
2820 watts into 1 ohm.
2585 watts into 2 ohms.
MA-3600VZ Service Manual
120 VAC International Units:
Stereo mode with both channels driven:
1490 watts into 2 ohms.
1300 watts into 4 ohms.
985 watts into 8 ohms.
Bridge-Mono mode:
2980 watts into 4 ohms.
2600 watts into 8 ohms.
Parallel-Mono Mode
2980 watts into 1 ohm.
2600 watts into 2 ohms.
230 VAC International Units:
Stereo mode with both channels driven:
1520 watts into 2 ohms.
1325 watts into 4 ohms.
965 watts into 8 ohms.
Bridge-Mono mode:
2800 watts into 4 ohms.
2515 watts into 8 ohms.
Parallel-Mono Mode
2910 watts into 1 ohm.
2565 watts into 2 ohms.
Load Impedance: Rated for 16, 8, 4, and 2 ohm use only.
Safe with all types of loads, even reactive ones.
AC Power Requirements: 100 VAC, 50/60 Hz; 120 VAC,
50/60 Hz; and 230 VAC, 50/60 Hz units are available. 230
VAC, 50/60 Hz units can be used with 220 and 240 VAC.
All versions draw 90 watts or less at idle. 100 and 120 VAC
units can draw up to 30 amps of current; 230 VAC units can
draw up to 15 amps. Refer to the back panel for your unit’s
specifi cations.
2.3 Controls
Enable: A front panel push button used to turn the amplifi er
on and off.
Level: A 31-position detented rotary attenuator for each
channel located on the front panel used to control the output
level.
Stereo/Mono: A three-position back panel switch used to
select Stereo, Bridge-Mono or Parallel-Mono operation.
Sensitivity: A three-position switch located inside the PIP
compartment used to select one of three input sensitivities
for both channels: 0.775 volts or 1.4 volts for standard 1 kHz
power or a voltage gain of 26 dB.
Input Ground Lift: A two position back panel switch used to
isolate the phone jack signal grounds from the chassis (AC)
ground.
Reset: A back panel button for each channel used to reset
the corresponding power supply. 100 and 120 VAC units
have 15 amp circuit breakers. 230 VAC units have 7.5 amp
circuit breakers.
2.4 Indicators
Enable: This amber indicator is on when the amplifi er is
switched on to show that the low voltage power supply is
operating.
Signal / IOC: Two green indicators fl ash with medium inten-
sity in sync with the amplifi er’s outputs to show signal pres-
ence. In the unlikely event the output waveform differs from
that of the input by 0.05% or more, they fl ash brightly to indi-
cate distortion. As sensitive distortion indicators they provide
proof of performance. Note: It is normal for the Channel 2 IOC
indicator to remain on in Parallel-Mono mode.
ODEP: Each channel has a multifunction LED (light emitting
diode) indicator that shows the channel’s energy reserve
status. Normally, the LEDs are brightly lit to show that reserve
energy is available. An indicator will dim proportionally as the
energy reserve for its channel decreases. In the rare event
that a channel has no reserve energy, the indicator turns
off and ODEP proportionally limits the channel’s output drive
level so the amplifi er can continue safe operation even when
conditions are severe.
2.5 Input/Output
Input Connector: Balanced ¼-inch phone jacks on chassis
and internal PIP connector. (Balanced 3-pin XLR connectors
are provided on the P.I.P.-FX which is a standard feature.)
Input Impedance: Nominally 20 k ohms, balanced. Nominally
10 K ohms, unbalanced.
Input Sensitivity: Switchable between 0.775 V (unbalanced)
for rated output or a fi xed voltage gain of 26 dB.
controls are active; Channel 2 controls are inactive but
notremoved from operation.
2.7 Construction
Durable black powder coated steel chassis and aluminum
front panel with Lexan overlay; specially designed “fl ow-
through” ventilation from front to side panels.
Cooling: Forced-air with custom heat diffusers and patented
circuitry to promote uniform dissipation.
Dimensions: 19 inch (48.3 cm) standard rack mount (EIA
Std. RS-310-B), 3.5 inch (8.9 cm) height, 16 inch (40.6 cm)
depth behind mounting surface and 2.5 inches (6.4 cm) in
front of mounting surface (see Figure 2.2).
Approximate Weight: Center of gravity is 6 inches (15.2 cm)
behind the front mounting surface.
Macro-Tech amplifi ers are protected against shorted, open
or mismatched loads; overloaded power supplies; excessive
temperature, chain destruction phenomena, input overload
damage and high-frequency blow-ups. They also protect
loudspeakers from input/output DC and turn-on/turn-off transients.
If unreasonable operating conditions occur, the patented
ODEP circuitry proportionally limits the drive level to protect
the output devices, particularly in the case of elevated temperature. Transformer overheating results in a temporary
shutdown of the offending channel. When it has cooled to a
safe temperature, the transformer automatically resets itself.
Controlled slew rate voltage amplifi ers protect against RF
burnouts, and input overload protection is provided by current-limiting resistance at the input.
Turn On: The four second turn-on delay prevents dangerous
turn-on transients. Turn-on occurs at zero crossing of the
AC waveform, so power sequencers are rarely needed with
multiple units. Note: The turn-on delay time may be changed.
Contact Crown’s Technical Support Group for details.
Circuit Breaker: Circuit breaker current ratings vary based
on the AC operating power.
It should be noted that over time Crown makes
improvements and changes to their products for
various reasons. This manual is up to date as of the
time of writing. For additional information regarding
these amplifi ers, refer to the applicable Technical
Notes provided by Crown for this product.
MA-3600VZ Service Manual
front panel and are of the rotary type. Front panel
indicators let the user know the status of the low
voltage power supply (enable), an ODEP indicator for
each channel which shows the reserve energy status,
and a SPI/IOC indicator for each channel which
indicates signal output and distortion. In general, the
packaging of this model is designed for maximum
watt/price/weight/size value with user friendly
features.
For additional details refer to the specifi cation section,
or to the applicable Owner’s Manual.
This section of the manual explains the general
operation of a Macro-Tech 3600VZ power amplifi er.
Topics covered include Front End, Grounded Bridge,
ODEP, and VZ supply. Due to variations in design
from vintage to vintage (and similarities with other
Crown products) the theory of operation remains
simplifi ed.
3.2 Features
Macro Tech amplifiers utilize numerous Crown
innovations including grounded bridge and ODEP
technologies. Cooling techniques make use of the
what is essentially air conditioner technology. Air
fl ows bottom to top, and front to side. Air fl ows a
short distance across a wide heatsink. This type of
air flow provides significantly better cooling than
the “wind tunnel” technology used by many other
manufacturers. Output transistors are of the metal
can type rather than plastic case. This allows for
a signifi cantly higher thermal margin for the given
voltage and current ratings. All devices used are
tested and graded to ensure maximum reliability.
Another electronic technique used is negative
feedback. Almost all power amplifi ers utilize negative
feedback to control gain and provide stability, but
Crown uses multiple nested feedback loops for
maximum stability and greatly improved damping.
Most Crown amplifi ers have damping in excess of
1000 in the bass frequency range. This feedback,
along with our compensation and ultra-low distortion
output topology, makes Crown amplifi ers superior.
Features specifi c to the Macro Tech Series’ include
two seperate power transformers (one for each
channel), a full time full speed fan which also serves
as the low voltage transformer, slew rate limiting,
and audio muting for delay or protective action. This
amplifi er can operate in either a Bridged or Parallel
Mono mode as well as dual (stereo). A sensitivity
switch allows selection of input voltage required
for rated output. Level controls are mounted on the
3.3 Front End Operation
The front end is comprised of three stages: Balanced
Gain Stage (BGS), Variable Gain Stage (VGS), and
the Error Amp. Figure 3.1 shows a simplifi ed diagram
of a typical front end with voltage amplification
stages.
3.3.1 Balanced Gain Stage (BGS)
Input to the amplifi er is balanced. The shield may
be isolated from chassis ground by an RC network
to interrupt ground loops via the Ground Lift Switch.
The non-inverting (hot) side of the balanced input
is fed to the non-inverting input of the fi rst op-amp
stage. The inverting (negative) side of the balanced
input is fed to the inverting input of the fi rst op-amp
stage. A potentiometer is provided for common mode
rejection adjustment. Electrically, the BGS is at unity
gain. (From an audio perspective, however, this stage
actually provides +6dB gain if a fully balanced signal
is placed on its input.) The BGS is a non-inverting
stage. It’s output is delivered to the Variable Gain
Stage.
3.3.2 Variable Gain Stage (VGS)
From the output of the BGS, the signal goes to the
VGS where gain is determined by the position of the
Sensitivity Switch, and level is determined by the
level control. VGS is an inverting stage with the input
being fed to its op-amp stage. Because gain after
this stage is fi xed at 26dB (factor of 20), greater
amplifi er sensitivity is achieved by controlling the
ratio of feedback to input resistance. The Sensitivity
Switch sets the input impedance to this stage and
varies the gain such that the overall amplifi er gain is
26 dB, or is adjusted appropriately for 0.775V or 1.4V
input to attain rated output.
3.3.3 Error Amp
The inverted output from the VGS is fed to the noninverting input of the Error Amp op-amp stage through
an AC coupling capacitor and input resistor. Amplifi er
output is fed back via the negative feedback (NFb)
loop resistor. The ratio of feedback resistor to input
resistor fi xes gain from the Error Amp input to the
output of the amplifier at 26 dB. Diodes prevent
overdriving the Error Amp. Because the Error Amp
amplifi es the difference between input and output
signals, any difference in the two waveforms will
produce a near open loop gain condition which in
turn results in high peak output voltage. The output
of the Error Amp, called the Error Signal (ES) drives
the Voltage Translators.
3.4 Voltage Amplifi cation
The Voltage Translator stage separates the output of
the Error Amp into balanced positive and negative
drive voltages for the Last Voltage Amplifi ers (LVAs),
translating the signal from ground referenced ±15V
to ±Vcc reference. LVAs provide the main voltage
amplifi cation and drive the High Side output stages.
Gain from Voltage Translator input to amplifi er output
is a factor of 25.2.
3.4.1 Voltage Translators
A voltage divider network splits the Error Signal
(ES) into positive and negative drive signals for
the balanced voltage translator stage. These offset
reference voltages drive the input to the Voltage
Translator transistors. A nested NFb loop from
the output of the amplifi er mixes with the inverted
signal riding on the offset references. This negative
feedback fi xes gain at the offset reference points (and
the output of the Error Amp) at a factor of -25.2 with
respect to the amplifi er output. The Voltage Translators
are arranged in a common base confi guration for
non-inverting voltage gain with equal gain. They shift
the audio from the ±15V reference to VCC reference.
Their outputs drive their respective LVA.
Also tied into the Voltage Translator inputs are
ODEP limiting transistors and control/protection
transistors. The ODEP transistors steal drive as
dictated by the ODEP circuitry (discussed later). The
control/protection transistors act as switches to totally
shunt audio to ground during the turn-on delay, or
during a DC/LF or Fault protective action.
3.4.2 Last Voltage Amplifi ers (LVAs)
The Voltage Translator stage channels the signal
to the Last Voltage Amplifi ers (LVA’s) in a balanced
confi guration. The +LVA and -LVA, with their push-
pull effect through the Bias Servo, drive the fully
complementary output stage. The LVAs are confi gured
as common emitter amplifiers. This configuration
provides suffi cient voltage gain and inverts the audio.
The polarity inversion is necessary to avoid an overall
polarity inversion from input jack to output jack, and
it allows the NFb loop to control Error Amp gain by
feeding back to its non-inverting input (with its polarity
opposite to the output of the VGS). With the added
voltage swing provided by the LVAs, the signal then
gains current amplifi cation through the Darlington
emitter-follower output stage.
3.5 Grounded Bridge Topology
Figure 3.2 is a simplifi ed example of the grounded
bridge output topology. It consists of four quadrants
of three deep Darlington (composite) emitter-follower
stages per channel: one NPN and one PNP on the
High Side of the bridge (driving the load), and one
NPN and one PNP on the Low Side of the bridge
(controlling the ground reference for the rails). The
output stages are biased to operate class AB+B for
ultra low distortion in the signal zero-crossing region
and high effi ciency.
BGSVGSError
Audio
Inputs
+
-
Figure 3.1 Typical Amplifi er Front End and Voltage Amplifi cation Stages.
The High Side (HS) of the bridge operates much like
a conventional bipolar push-pull output confi guration.
As the input drive voltage becomes more positive,
the HS NPN conducts and delivers positive voltage
to the load. Eventually the NPN devices reach full
conduction and +Vcc is across the load. At this time
the HS PNP is biased off. When the drive signal is
negative going, the HS PNP conducts to deliver -Vcc
to the load and the HS NPN stage is off.
The output of the +LVA drives the base of predriver
device. Together, the predriver and driver form the
fi rst two parts of the three-deep Darlington and are
biased class AB. They provide output drive through
the bias resistor, bypassing the output devices,
at levels below about 100mW. An RLC network
between the predriver and driver provide phase shift
compensation and limit driver base current to safe
levels. Output devices are biased class B, just below
cutoff. At about 100mW output they switch on to
conduct high current to the load. Together with
predriver and driver, the output device provide an
overall class AB+B output.
The negative half of the HS is almost identical to the
positive half, except that the devices are PNP. One
difference is that the PNP bias resistor is slightly
greater in value so that PNP output devices run
closer to the cutoff level under static (no signal)
conditions. This is because PNP devices require
greater drive current.
HS bias is regulated by Q18, the Bias Servo. Q18
is a Vbe multiplier which maintains approximately
3.3V Vce under static conditions. The positive and
negative halves of the HS output are in parallel with
this 3.3V. With a full base-emitter on voltage drop
across predrivers and drivers, the balance of voltage
results in approximately .35V drop across the bias
resistors in the positive half, and about .5V across
the bias resistor in the negative half. Q18 conduction
(and thus bias) is adjustable.
A diode string prevents excessive charge build up
within the high conduction output devices when off.
Flyback diodes shunt back-EMF pulses from reactive
loads to the power supply to protect output devices
from dangerous reverse voltage levels. An output
terminating circuit blocks RF on output lines from
entering the amplifi er through its output connectors.
3.5.2 Low Side (LS)
The Low Side (LS) operates quite differently. The
power supply bridge rectifi er is not ground referenced,
nor is the secondary of the main transformer. In other
words, the high voltage power supply floats with
respect to ground, but ±Vcc remain constant with
respect to each other. This allows the power supply to
deliver +Vcc and -Vcc from the same bridge rectifi er
and fi lter as a total difference in potential, regardless
of their voltages with respect to ground. The LS uses
inverted feedback from the HS output to control
the ground reference for the rails (±Vcc). Both LS
quadrants are arranged in a three-deep Darlington
When the amplifi er output swings positive, the audio
is fed to an op-amp stage where it is inverted. This
inverted signal is delivered directly to the bases of
the positive (NPN) and negative (PNP) LS predrivers.
The negative drive forces the LS PNP devices on
(NPN off). As the PNP devices conduct, Vce of the
PNP Darlington drops. With LS device emitters tied
to ground, -Vcc is pulled toward ground reference.
Since the power supply is not ground referenced
(and the total voltage from +Vcc to -Vcc is constant)
+Vcc is forced higher above ground potential. This
continues until, at the positive amplifi er output peak,
-Vcc = 0V and +Vcc equals the total power supply
potential with a positive polarity. If, for example, the
power supply produced a total of 70V from rail to
rail (±35VDC measured from ground with no signal),
the amplifier output would reach a positive peak
of +70V.
Conversely, during a negative swing of the HS output
where HS PNP devices conduct, the op-amp would
output a positive voltage forcing LS NPN devices
to conduct. This would result in +Vcc swinging
toward ground potential and -Vcc further from ground
potential. At the negative amplifi er output peak, +Vcc
= 0V and -Vcc equals the total power supply potential
with a negative polarity. Using the same example as
above, a 70V supply would allow a negative output
peak of -70V. In summary, a power supply which
produces a total of 70VDC rail to rail (or ±35VDC
statically) is capable of producing 140V peak-topeak at the amplifier output when the grounded
bridge topology is used. The voltage used in this
example are relatively close to the voltages of the
PB-1/460CSL.
3.6 Output Device Emulation Protection
(ODEP)
To further protect the output stages, a specially
developed ODEP circuit is used. It produces
a complex analog output signal. This signal is
proportional to the always changing safe-operatingarea margin of the output transistors. The ODEP signal
controls the Voltage Translator stage by removing
drive that may exceed the safe-operating-area of
the output stage.
ODEP senses output current by measuring the
voltage dropped across LS emitter resistors. LS NPN
current (negative amplifier output) and +Vcc are
sensed, then multiplied to obtain a signal proportional
to output power. Positive and negative ODEP voltages
are adjustable via two potentiometers. Across ±ODEP
are a PTC and a thermal sense (current source). The
PTC is essentially a cutoff switch that causes hard
ODEP limiting if heatsink temperature exceeds
a safe maximum, regardless of signal level. The
thermal sense causes the differential between +ODEP
and –ODEP to decrease as heatsink temperature
increases. An increase in positive output signal output
into a load will result in –ODEP voltage dropping;
an increase in negative output voltage and current
will cause +ODEP voltage to drop. A complex RC
network between the ±ODEP circuitry is used to
simulate the thermal barriers between the interior
of the output device die (immeasurable by normal
means) and the time delay from heat generation at
the die until heat dissipates to the thermal sensor. The
combined effects of thermal history and instantaneous
dynamic power level result in an accurate simulation
of the actual thermal condition of the output transistors.
The total effect is to deliver a peak to peak voltage to
the speaker load which is twice the voltage produced
by the power supply. Benefi ts include full utilization
of the power supply (it conducts current during both
halves of the output signal; conventional designs
require two power supplies per channel, one positive
and one negative), and never exposing any output
device to more than half of the peak to peak output
voltage (which does occur in conventional designs).
Low side bias is established by a diode string which
also shunts built up charges on the output devices.
Bias is adjustable via potentiometer. Flyback diodes
perform the same function as the HS fl ybacks. The
output of the LS is tied directly to chassis ground
via ground strap.
Theory of Operation 3-4
3.7 VZ Power
VZ means Variable Impedance and is the name of
Crown’s patented articulated power supply technol-
ogy. It enables Crown to pack tremendous power into
just 3½ inches of vertical rack space.
3.7.1 Background
A power supply must be large enough to handle
the maximum voltage and current necessary for
the amplifi er to drive its maximum rated power into
a specified load. In the process of fulfilling this
requirement conventional power supply designs
produce excessive heat, are heavy, and take up
precious real estate. It’s no secret that heat is one of
a power amplifi ers worst enemies.
According to Ohm’s Law, the bigger the power
supply, the more heat the power transistors must
dissipate. Also, the lower the resistance of the power
transistors, the more voltage you can deliver to
the load. But at the same time that you lower the
resistance of the transistors, you increase the current
passing through them, and again increase the amount
of heat they must dissipate.
3.7.2 The VZ supply
An articulated power supply, like VZ, can circumvent
much of this problem by reducing the voltage applied
to the transistors when less voltage is required.
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 into segments to better
match the voltage and current requirements of the
power transistors. Remember that audio signals 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 parts. When the
voltage requirements are not high, it operates in
a parallel mode to produce less voltage and more
current (Figure 3.3). In this mode the power transistors
stay cooler and are not forced to needlessly dissipate
heat. This is the normal operating mode of the VZ
power supply.
VZ POWER SUPPLY
POWER
TRANSISTOR
+
VZ
STAGE
SPEAKER
LOAD
POWER
TRANSISTOR
+
VZ
STAGE
Figure 3.3 VZ Supply in Parallel Mode
When the voltage requirements are high the VZ supply
switches to a series mode to produce the higher
voltage and less current (Figure 3.4). The amplifi ed
output signal never misses a beat and gets full voltage
when it needs it—not when it doesn’t need it.
VZ POWER SUPPLY
+
POWER
TRANSISTOR
SPEAKER
LOAD
POWER
TRANSISTOR
VZ
STAGE
+
VZ
STAGE
Figure 3.4 VZ Supply in Series Mode
Sensing circuitry watches the voltage of the signal
to determine when to switch modes. The switching
circuitry is designed to prevent audible switching
distortion to yield the highest dynamic transfer
function—you hear only the music and not the
amplifi er. You get not only the maximum power with
the maximum safety, you also get the best power
matching to your load.
3.7.3 VZ Switch Control
The two halves of U03 form identical comparators
that monitor the available voltage of DC supply V2
and compare it to the output voltage of the amplifi er.
When a positive going output voltage exceeds a
predetermined ratio of the available supply voltage,
U03 pin 1 produces a low voltage triggering U04.
When triggered, the “Q” output of U04 changes from
low to high driving the gates of FET’s Q00, Q01, and
Q02. The other half of U03 (pin 7) reacts to negative
going output voltage. Both halves of U03 receive V2
and amplifi er output voltage differentially.
The time constant set by C18 and R16 on the input
of U04 sets the maximum switch frequency of the
supply. This time constant forces the supply to stay in
the series mode regardless of amplifi er condition for
200 ms. The reset pin of U04 (pin 4) forces the output
of U04 low when FET damage conditions exist.
C16 and C17 provide hysteresis around the comparators of U03 to insure stable operation.
VZ Protection Circuit
Protecting high current transistors can be troublesome
in circuits that do not provide convenient current
sample points. FETs Q00-Q02 fall into this class of
problems, but protection has been designed based
on the following two conditions being present at
the same time:
• Higher than normal on-state drain to source
voltage
• Gate drive present.
When both of these conditions exist, a reasonable
assumption can be made that the FETs are operating
in an area that if sustained will cause damage to
the FETs. These two conditions are detected by U05
pins 5 and 7.
U05 detects gate drive to the FETs at pin 7. Pin 6 is
a reference input with the reference voltage set by
R22 in series with R19.
U05 detects excessive source to drain voltage on the
DISPLAY
BALANCED
INPUTS
XLR
1/4" PHONE
P.I.P.
FX
BALANCE
GAIN STAGE
VARIABLE
GAIN STAGE
PANEL
ERROR AMP
VOLTAGE
TRANSLATOR
ODEP
VOLTAGE
TRANSLATOR
FETs at pin 5. R17 in series with R18 forms a voltage
divider to pin 5 of U05. The reference is set by a
voltage divider formed by R29, R20, and R22.
When both conditions are detected the outputs of U05
(pins 1 and 2) allow C20 to start charging through
R23. After 20µS, C20 will be suffi ciently charged to
turn on the section of U05 whose output is pin 14,
discharging C21. As C21 discharges, it turns on Q03
which pulls the non-inverting input low (pin 9). U05
pin 13 drives the reset pin of U04 low which removes
gate drive from the FETs. This hysteresis makes the
circuit auto-resetting. Every 10ms (set by C21 and
R26) it will make another 20µs try at driving the FETs.
R25 prevents Q03 from pulling the input of U05 below
its negative supply.
DANGER: The outputs of this amplifi er can produce
LETHAL energy levels! Be very careful when making
connections. Do not attempt to change output wiring
until the amplifi er has been off at least 10 seconds.WARNING: This unit is capable of producing high
sound pressure levels. Continued exposure to high
sound pressure levels can cause permanent hearing
impairment or loss. User caution is advised and
ear protection is recommended when using at high
levels.
WARNING: Do not expose this unit to rain or moisture.
WARNING: Only properly trained and qualified
technicians should attempt to service this unit. There
are no user serviceable parts inside.
WARNING: When performing service checks with
the power off, discharge the main power supply fi lter
capacitors fully before taking any measurements
or touching any electrical components. A 300-ohm
10-W resistor is recommended for this. Hold the
resistor with pliers, as the resistor may become
extremely hot.
WARNING: Under load, with a sine wave signal
at full power into both channels, the amplifi er may
draw in excess of 30 amperes from the AC service
mains.
WARNING: Do not change the position of the Mode
Switch when the amplifi er is turned on. If the position
of this switch is changed while the amplifier is
powered, transients may damage your speakers.
WARNING: Heatsinks are not at ground potential.
Simultaneously touching either heatsink and ground,
or both heatsinks will cause electrical shock.
CAUTION: Eye protection should be worn at all
times when protective covers are removed and the
amplifi er is plugged in.CAUTION: Disconnect the power cord before installing or removing any cover or panel.
4.2 General Information
The following test procedures are to be used to verify
operation of this amplifi er. DO NOT connect a load
or inject a signal unless directed to do so by the
procedure. These tests, though meant for verifi cation
and alignment of the amplifier, may also be very
helpful in troubleshooting. For best results, tests
should be performed in order.
MA-3600VZ Service Manual
All tests assume that AC power is from a regulated
AC source appropriate for the unit under test.. Test
equipment includes an oscilloscope, a DMM, a signal
generator, loads, and I.M.D. and T.H.D. noise test
equipment.
4.3 Test Procedures
4.3.1 Standard Initial Conditions
Level controls fully clockwise.
Stereo/Mono switch in Stereo.
Sensitivity switch in 26 dB fi xed gain position.
Ambient Temperature: 20 to 30 degrees C.
It is assumed, in each step, that conditions of the
amplifier are per these initial conditions unless
otherwise specifi ed.
shorted.
Procedure: Measure DC voltage at the output
connectors (rear panel). There is no adjustment for
output offset. If spec is not met, there is an electrical
malfunction. Slightly out of spec measurement is
usually due to U104/U204 out of tolorance.
4.3.3 Test 2: Output Bias Adjustment
Spec: 310 ±10 mVDC.
Initial Conditions: Controls per standard, heatsink
temperature less than 40°C.
Procedure: Measure DC voltages on the output PWA
across R02, adjust R26 if necessary. Measure DC
voltages on the output PWA across R21, adjust R23 if
necessary. Repeat for second channel.
4.3.4 Test 3: ODEP Voltage Adjustment
Spec: Bias Per Chart, ±0.1V DC.
Initial Conditions: Controls per standard, heatsink
at room temperature 20 to 30°C (68 to 86°F). Note:
This adjustment should normally be performed
within 2 minutes of turn on from ambient (cold)
conditions. If possible measure heatsink temperature,
if not measure ambient room temperature. Use
this information when referencing the chart on the
following page.
–ODEP Procedure: Measure pin 6 of U100 and, if
necessary, adjust R121 to obtain V–ODEP as specifi ed above. Measure pin 6 of U200 and, if necessary,
adjust R221 to obtain V–ODEP as specifi ed above.
+ODEP Procedure: Measure pin 6 of U103 and, if
necessary, adjust R132 to obtain V+ODEP as specifi ed above. Measure pin 6 of U203 and, if necessary,
adjust R232 to obtain V+ODEP as specifi ed above.
4.3.5 Test 4: AC Power Draw
Spec: 100 Watts maximum quiescent.
Initial Conditions: Controls per standard.
Procedure: With no input signal and no load,
measure AC line wattage draw. If current draw is
excessive, check for high AC line voltage or high
bias voltage.
4.3.6 Test 5: Common Mode Rejection
Spec at 1KHz: –70 dB.
Initial Conditions: Sensitivity switch in 0.775V
Procedure: No load. Inject a 0 dBu (.775VRMS) 1K
Hz sine wave into each channel, one channel at a
time, with inverting and non-inverting inputs shorted
together (common mode). Adjust R512 for minimum
A.C output of Channel 1, R612 for Channel 2. At the
output measure less than –28 dBu (30.5mVRMS).
4.3.7 Test 6: Voltage Gain
Spec 26dB Gain: Gain of 20.0 ±3%.
Spec 0.775V Sensitivity: ±12%.
Spec 1.4V Sensitivity: ±12%.
Initial Conditions: Controls per standard.
Procedure: 8 ohm load connected. Inject a single
ended 0.775 VAC 1 kHz sine wave with the Sensitivity
Switch in the 26 dB position. Measure 15.5 VAC, ±0.3
VAC, at the amplifi er output. Switch the Sensitivity
Switch to the 0.775V position. Adjust the level of
the input signal so that the output is at rated power.
Measure 0.775 VAC ±12% at the amplifier input.
Switch the sensitivity switch to the 1.4V position
Measure 1.4 VAC, ±12%, at the amplifi er input.
4.3.8 Test 7: Phase Response
Spec: ±10° from 10 Hz to 20 kHz at 1 Watt.
Initial Conditions: Controls per standard, 8 ohm
load on each channel.
Procedure: Inject a 1 kHz sine wave and adjust for
1 Watt output (2.8 VAC). Check input and output
signals against each other, input and output signals
must be within 10° of each other.
INOUT
Figure 4.1 Differentiator Circuit
Mantenance 4-2
.047µf
1k ohm
Figure 4.2 Differentiated wave form at current limit
Spec: Level controlled by level controls.
Initial Conditions: Controls per standard.
Procedure: No Load. Inject a 1 kHz sine wave.
With level controls fully clockwise you should see
full gain. As controls are rotated counterclockwise,
observe similar gain reduction in each channel. When
complete, return level controls to fully clockwise
position.
4.3.10 Test 9: Current Limit
Spec: Current Limit at 43 - 48 Amps
Initial Conditions: Controls per standard.
Procedure: Load each channel to 1 Ohm. Inject a 1
kHz differentiated (or 10% duty cycle) square wave.
See fi gure 4.1. Increase output level until current limit
occurs. Current limit should occur at 43 - 48 Amps
(43-48 Vpk). Disregard waveform overshoot. Observe
clean (no oscillations) current clipping. See Figure 4.2
for differentiated wave form at current limit.
4.3.11 Test 10: Slew Rate & 10 kHz Square Wave
Spec: 30 - 40 V/µS.
Initial Conditions: Controls per standard.
Procedure: Load each channel to 8 ohms. Inject a
10 kHz square wave to obtain 90 volts zero-to-peak at
each output. Observe the slope of the square wave.
It should typically measure 30 to 40 V/µS. Also, the
square wave must not include overshoot, ringing, or
any type of oscillation. See Figure 4.3 for typical 10
kHz square wave response.
4.3.12 Test 11: Crosstalk
Spec: -60dB at 20 kHz.
Initial Conditions: Controls per standard. Terminate
input of channel not driven with 600 ohms.
Procedure: 8 ohm load on each channel. Inject a 20
kHz sine wave into the Channel 1 input and increase
output level to 80 VAC. Measure less than 80 mVAC
at the output of Channel 2. Inject a 20 kHz sine wave
into the Channel 2 input and increase output level to
80 VAC. Measure less than 80 mVAC at the output
of Channel 1.
4.3.13 Test 12: Output Power
Spec at 8 Ohm Stereo: ≥ 1125W at 0.1% THD.
Spec at 4 Ohm Stereo: ≥ 1625W at 0.1% THD.
Spec at 2 Ohm Stereo: ≥ 1800W at 0.1% THD.
International 8 Ohm Stereo: ≥ 945W at 0.1% THD.
International 4 Ohm Stereo: ≥ 1255W at 0.1% THD.
International 2 Ohm Stereo: ≥ 1490W at 0.1% THD.
Initial Conditions: Controls per standard.
Procedure: Load each channel to 8 ohms. Inject a
1 kHz sine wave and measure at least 94.67 VAC at
the output of each channel. Load each channel to 4
ohms. Inject a 1 kHz sine wave and measure at least
80.62 VAC. Load each channel to 2 ohms. Inject a
1 kHz sine wave and measure at least 60.00 VAC.
All power measurements must be at less than 0.1%
THD. For international units, calculate output voltage
with above power specifi cations.
4.3.14 Test 13: Reactive Loads
Spec: No oscillations. Safe with all types of loads.
Initial Conditions: Controls per standard.
Procedure Capacitive: Load each channel to 8
ohms in parallel with 2 µF. Inject a 20 kHz sine wave
with 48 VAC output for 10 seconds.
Procedure Inductive: Load each channel to 8 ohms
in parallel with 159 µHenries. Inject a 1 kHz sine wave
with 36 VAC output for 10 seconds.
Procedure Torture: Load each channel with the
primary (red and black leads) of a PSU transformer
(D 7040-5). Inject a 35 Hz sine wave for an output
level of 89.5 Vrms, for 10 seconds.
Procedure Short: Inject a 60 Hz sine wave with 30.0
VAC at the amplilfi er output. After establishing signal,
short the output for 10 seconds.
4.3.15 Test 14: ODEP Limiting
Spec: ODEP Limiting occurs per the procedure.
Either channel controls limiting in Parallel Mono
Mode.
Initial Conditions: Controls per standard; rag or
other obstruction blocking fan so that it does not
turn.
Procedure: Load the amplifi er to 2 ohms on each
channel. Inject a 60 Hz sine wave and adjust for
30 Vrms at the output. After a few minutes observe
a wave form similar to Figure 4.4. Both positive
and negative alternations must show the distinctive
waveform. There is no requirement of symmetry
between positive and negative alternations. There is
no requirement of uniformity from channel to channel.
Remove the input signal from both channels and
allow the amplifi er to cool for a few minutes. Switch
the amplifi er to Parallel Mono and remove the load
from Channel 1. Inject the signal into Channel 1 and
observe that ODEP limiting occurs at the output of
both channels. Remove the load from Channel 2, and
install the load on Channel 1. Again, observe that both
channels limit. Return all amplifi er controls to standard
initial conditions. Remove the fan obstruction.
4.3.16 Test 15: LF Protection
Spec: Amplifi er mutes for low frequency.
Initial Conditions: Controls per standard.
Procedure: No load. Inject a 0.5 Hz, 10 volt peak-topeak, square wave, or a 1Hz, 17 volt peak-to-peak,
sine wave into each channel and verify that each
channel cycles into mute.
4.3.17 Test 16: Signal to Noise Ratio
Spec: 100 dB below rated 8 ohm power 20 Hz to 20
kHz. 105 dB A-Weighted.
Initial Conditions: 26dB Sensitivity. Short inputs.
Procedure: Load each channel to 8 ohms. Measure
less than 950 µV at the output of each channel (20
Hz-20 kHz bandpass fi lter).
4.3.18 Test 17: Turn On Transients
Spec: No dangerous transients.
Initial Conditions: Controls per standard.
Procedure: From an off condition, turn on the amplifi er
and monitor the output noise at the time of turn on.
Note: Turn on noise may increase signifi cantly if the
amplifi er is cycled off and on.
4.3.19 Test 18: Turn Off Transients
Spec: No dangerous transients.
Initial Conditions: Controls per standard.
Procedure: From an on condition, turn off the amplifi er
and monitor the output noise at the time of turn off.
Note: Turn off noise may increase signifi cantly if the
amplifi er is cycled off and on.
4.3.20 Test 19: Intermodulation Distortion
Spec at 0 dB Output: 0.02%.
Spec at –35 dB Output: 0.05%.
Initial Conditions: Controls per standard.
Procedure: Load each channel to 8 ohms. Inject a
SMPTE standard IM signal (60 Hz and 7 kHz sine
wave mixed at 4:1 ratio). Set the 60 Hz portion of the
sine wave to 72 Volt RMS. Set the 7 kHz portion to
25%. With an IM analyzer measure less than 0.02%
IMD. Repeat test at –35 dB (reference 72 Volt RMS, 60
Hz portion) and measure less than 0.05% IMD.
4.3.21 Test 20: High Line Cutout
Spec: 10% - 12% above nominal.
Initial Conditions: Controls per standard.
Procedure: Using an AC line variac, increase the
line voltage until the unit goes into standby. The
unit should fo into standby at 10% - 12% above the
nominal (120V U.S. units).
4.3.22 Post Testing
After completion of testing, if all tests are satisfactory,
the amplifier controls should be returned to the
positions required by customer. If conditions are
unknown or unspecified, factory settings are as
follows:
Level Controls: 9 to 11 O’Clock.
Sensitivity Switch: 0.775V U.S., 1.4V International.
Stereo/Mono Switch: Stereo.
Ground Lift: Lift.
Power: Off.
Replacement parts for this Crown amplifi er can be
ordered from the Crown Parts Department.
PART PRICES AND AVAILABILITY ARE SUBJECT
TO CHANGE WITHOUT NOTICE.
5.2 Ordering and Receiving Parts
When ordering parts, be sure to give the product
model, and include a description and part number
from the parts listing. Price quotes are available
on request.
5.2.1 Terms
Normal terms are prepaid. Net-30 Days applies to
only those having pre-established accounts with
Crown. The Crown Parts Department does accept
Visa or Master Card. If prepaying, the order must
be packed and weighed before a total bill can be
MA-3600VZ Service Manual
established, after which an amount due will be issued
and shipment made upon receipt of payment. New
parts returned for credit are subject to a restocking
fee, and authorization from the Crown Parts Department must be obtained before returning parts for
credit.
5.2.2 Shipment
Shipment will normally be made via UPS, or best
other method unless you specify otherwise. Shipments are made to and from Elkhart, Indiana USA,
only. Established accounts with Crown will receive
shipment freight prepaid and will be billed. All others
will receive shipment on a C.O.D. or prepayment
(check or credit card) basis.
5.3 Mechanical Parts
This section includes a mechanical part list for
this product. All serviceable parts and assemblies
will have a Crown Part Number (CPN) listed in this
chapter. The parts listed are current as of the date
printed. Crown reserves the right to modify and
improve its products for the benefi t of its customers.
Note: Old style grilles with the one-piece
fi lter behind the grille are no longer available.
If an older amplifi er needs a new grille, the
only option is to convert it to the new style
by ordering CPN #M46504-3, which includes
the bottom cover, grille extrusion, fi lters and
necessary hardware. New grilles will not fi t
onto old bottom covers.