Carver PM 1400 Owners Manual

Page 2

Safety Information

RISK OF ELECTRIC SHOCK
DO NOT OPEN

if CAUTION

CAUTION: TO REDUCE THE RISK OF ELECTRIC SHOCK
DO NOT REMOVE COVER (OR BACK)
NO USER-SERVICEABLE PARTS INSIDE
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL

The lightning flash with arrowhead symbol
within an equilateral triangle is intended to alert
the user to the presence of uninsulated
"dangerous voltage within the product's
enclosure, that may be of sufficient magnitude
to constitute a risk of electric shock to persons.

The exclamation point within an equilateral
triangle is intended to alert the user of the
presence of important operating and main-
tenance (servicing) instructions in the literature
accompanying the appliance.

Page 6

3. Unpacking and
Paperwork

Carefully unpack the amplifier and keep the
original carton and packing materials for future
moving, shipment or long-term storage.

Atter opening the box, please check for any
visible signs of damage that were not apparent
from the outside of the box. If you do encounter
what appears to be concealed damage, please
consult your Carver Dealer before proceeding to
further unpack or install the unit.

Important Paperwork

Make sure to save your sales receipt. Your
receipt is extremely important to establish the
duration of your Limited Warranty, andfor insur-
ance purposes. Next, make a note of the serial
number which is located on the back of the ampli-
fier. Record it in the space provided below for
convenient reference

Model: pm1400

Serial Number:
Purchased at:

Date:

I-inally, take a moment to fill out and return the
Warranty Registration Card packed with the
amplifier and return it to Carver, This will allow
us to keep you informed about new products as
they become available

4. Operation

Front Panel Features

1. POWER switch

When this switch is pressed, the power turns
ON and the READY indicators illuminate. lie suit
all connections are made and double-checked
before switching the power amplifier ON.

2. STANDBY LED

This indicator illuminates when the power
switch is turned OFF. It also lets you know when
the amplifier is connected to AC power, When 1hr
power switch is OFF and the amplifier is pluggml
into an AC outlet, the LED illuminates to inclh all
that AC power is available and the amplifier t an in
powered up, When the power switch is ON, llu
LED turns off.

3. AC Power Fuse

This protects the amplifier from catastrnphu
failures that could damage internal circuiln
Repealed fuse blowing is a sign of internal that ii
Refer to an authorized Carver Service (Zentm lnn
evaluation.

CAUTION: REPLACE WITH THE SAlVll-I '| \ ll
lSAJZSV FUSE.

ATTENTION: UTILISER UN FUSIBLl-Z l)l'
RECHANGE DE MEME TYPE DE 15A lZS\

4. MediaLink indicator

This is an LED that lets you know when llh
PowerLink Circuit (it installed) is comrnunu hat
with a MediaLink control and monitoring m l r
This LED will illuminate green when the h um i
Link circuit is active. It can be changed in rm
MediaLink to flag the amplifier should ll I. ~
attention.

5. CH 1 and CH 2 Level Controls

These controls are used to adjust llu' input it -
of each channel. When the controls an» lnih
clockwise the amplifier operates at ma\innnn ~ n»
Turning the controls counter-clock iw .n it uh n
the input signal.

The Level controls can be byptusttl lill\ in in
to lock the amplifier at its full gain «ulna n
page 20 for information about the 1 (ml in it n
Switch,

Page 15

6. Technical information

CIRCUIT DESCRIPTION
pm1400

This section discusses the theory of operation of the
pml400. Fora better understanding of the circuitry
involved, refer to the schematic diagrams presented later
in this mantra]. Op-amps described in the circuitry use
the following notation: U1(7) means U1 at pin 7.
Unless otherwise noted, this discussion centers around
the CH 1 circuitry. The CH 2 circuitry is essentially
identical.

Low Level Circuitry

Input signals enter the circuit via the rear-panel XLR
connectors or 1/4vinch phone jacks, which are in
parallel with each other, located on the input Board. JP3
and JP4 allow the polarity of the XLR connector to be
configured for pin 2 hot or pin 3 hot. The pm1400 is
supplied from the factory configured for pin 2 hot. Note
that changing the jumpers does not affect the polarity of
the TRS 1/4" phone jacks.

The signal passes through 51 which directs the signal
according to the mode of operation selected (Dual
Mono, Normal Stereo, Bridged Mono).

The amplifier may be configured to operate as a
conventional 2-channel stereo amplifier, as a Z»channel
stereo amplifier with a common mono input (Dual
Mono), or as a single-channel mono amplifier with high-
voltage output (Bridged Mono). It can also be configured
to operate as a single channel mono amplifier with high-
current output (Parallel Mono). For now, assume that St
is set for 2~channel, stereo operation (NORMAL).

P7 through P10 are provided as insert points for
accessories.

U1A(6) is a high common-mode rejection differential
amplifier configured for unity gain operation. D12-D15
provide protection to U1 from ESD (electrostatic dis
charge). The signal then passes to the 1/0 Board via
J1~16. Switch 811% allows the signal to bypass the Level
Control R102. R8 and U3 form an attenuator whose loss
is dependent on the resistance of U3, an LhD-LDR
module. The drive for the LED portion of U3 comes
from the clipping eliminator circuitry, which will be
discussed later on

C3, R8 and R10 form a subsonic filter (-3dB @ 5H1),
and UlB, C4, C8 and R12 provide low-pass filtering
(-3dB @ 45kHz), The signal then passes to the Amplifier
Board via 7120(1-6/1201-6.

Power Amplifier Circuitry

'tlie pm1400 uses a conventional class AB puslrpull
power amplifier circuit, with a commutated "stage
lduaierail, class H) power supply. UlGOr-ltli is the input
stage, oroviding differential inputs for input and

feedback connections as well as most of the open-loop
voltage gain of the circuit. Local and global negative
feedback from the output stage via R109, R113, R111/
R112 and R129 sets the closed-loop gain at 36.7 dB.
Removing jumperjl100 disconnects Rlll from the
circuit and sets the closed-loop gain at 30.7 dB. The
Output of U100A(l) drives Q100 and Q1 01, operating as
common emitters that level-shift the drive signal and
couple it to the pre-driver amplifiers Q10Z and Q103.
(2102 and (2105 provide additional voltage gain, and
when combined with the voltage gain of the input op-
amp is sufficient to swing the input signal between the
i106V power supply rails. (1104 and Q122 are connectv
ed as an NlN-lNl) conjugate pair and used as a V,
multiplier for bias control. Q104 is thermally connected
to the output transistors and together with Q122
provides bias stabilization over a wide temperature
range. R124 allows the bias current to be adjusted to its
optimum value.

The predrivers (Q102 and Q103) provide the base
current to the drivers Q1025 and Q109. These drive the
output transistors; Q110, Q112, Q114, Q116, Q118 and
Q120 for the positive half-cycle, and Q111, Q113, Q115,
Q117, Q119 and Q121 for the negative half-cycle.

Q105 operates as a V-1 limiter, sensing the voltage
drop across emitter resistor R150 (Q106 across R151 for
the negative side), and reducing the drive signal to the
output stage under overload conditions (see section on
Over-Current Protection further on).

From the Amplifier Board, the signal passes to the
Output Board via E100. R100, L100, R1 10 and C100
comprise the output pole circuit for amplifier stabiliza-
tion. Relay K100 is used to connect the output signal to
the Speaker Output Binding Posts.

Magnetic Field Power Supply

The main power supply for the pm1400 is a dual-
voltage design which provides no-load voltages of +/-106
and +/-53 volts DC. The triac drives the primary of the
magnetic field power transformer by operating as a
phase controlled switch; its gate signal depends on the
signal supplied to opto-isolator U3 located on the
regulator board. U48 provides steering for the photo,
diac in U3, allowing the triac to fire on both alternations
of the power line.

112 on the Regulator Board provides AC to DC
conversion, with the AC line voltage providing the input
to the converter through limit resistors R3/R4, and the
lZfiVDC output determined by feedback resistor R6.
This voltage provides the positive supply for U4, DC
reference for comparators U4C and U41), and the
current through optoeisolator U1 which sets the voltage
for the \oltageetoecurrent converter Until. Note that U4
(MC3405) is a dual 'imp and dual voltage comparator
in a single package 1 'U-tB are opeamps and U4C/
U41) are open collecttt miparators).