Marchand Electronics mb401 User manual

©2001 Marchand Electronics Inc. PO Box 473 Webster NY 14580 [phone] www.marchandelec.com 1
Marchand Electronics Inc.
PO Box 473, Webster, NY 14580
Tel:[phone] Fax:[phone]
[email protected] http://www.marchandelec.com
(c)2002 Marchand Electronics Inc.
MB401 300 Watt MOSFET Power Amplifier
500W into 4 Ohm
300W into 8 Ohm

©2001 Marchand Electronics Inc. PO Box 473 Webster NY 14580 [phone] www.marchandelec.com 2
Features
The MB401 is a mono MOSFET power amplifier for high quality audio reproduction. The construction is all heavy-
duty. The amplifier is housed in an aluminum chassis. Heatsinks on the rear of the unit provide the cooling. Inside
is a toroidal power transformer and power supply with large storage capacitors. The amplifier is designed for use
with a 4 or 8 Ohm load, but it is stable with any output load.
.
XLR Balanced inputs Balanced inputs for high noise immunity
RCA Standard line level inputs
Selector switch Switch between balanced and standard inputs
Binding Posts Connection for the loudspeakers
Fuse Protects the amplifier in case of overload
Thermal cutout Protects the amplifier in case it gets too hot
Power entry connector Standard line cord for 120V AC 1-phase operation.
Specifications.
Frequency response: 20Hz - 20KHz +/- 1 dB
Harmonic Distortion @ 1KHz, 10W0.02% or better
Sensitivity 1.28VRMS
Voltage gain 32dB(40X)
Input impedance (RCA) 500 KOhm
Short circuit output current 20 A peak, 15A Continuous
Output load 8 or 4 Ohm, stable with any load
Max power output 500W into 4 Ohm, 300W into 8 Ohm
Power requirement 120VAC, 6A fuse; 240 VAC available
Construction All metal cabinet, black with white legend
Dimensions: 17” x3.5” x 11” (WxHxD)
Weight: 22 lbs
PR41 Preamplifier
Inputs Left
Right
In in in in in in out
Full Range
MB401 Power Amplifier
In Out
MB401 Power Amplifier
In Out
Figure 1Typical Sound System

©2001 Marchand Electronics Inc. PO Box 473 Webster NY 14580 [phone] www.marchandelec.com 3
PR41 Preamplifier
Inputs
Electronic Crossover
XM6, XM9, XM16 or XM26
In in in in in in out
in out hi out lo
High
Low
Left
Right
MB401 Power Amplifier
In Out
MB401 Power Amplifier
In Out
Left
Right
MB401 Power Amplifier
In Out
MB401 Power Amplifier
In Out
Figure 2Sound System with 2-way Electronic Crossover Network

©2001 Marchand Electronics Inc. PO Box 473 Webster NY 14580 [phone] www.marchandelec.com 4
Figure 3: Inside view. Note the placement of the MB401 power amplifier board (mounted on heatsink on the rear
of the unit) and the PS112 power supply board; (mounted onto the bottom of the chassis) . The toroidal power
transformer is mounted near the left of the unit on the baseplate.

©2001 Marchand Electronics Inc. PO Box 473 Webster NY 14580 [phone] www.marchandelec.com 5
Figure 4Rear view of the amplifier.
Figure 5Inside view of the rear panel

©2001 Marchand Electronics Inc. PO Box 473 Webster NY 14580 [phone] www.marchandelec.com 6
Assembly Instructions for the MB401 Kit.
Parts list.
Qu. Description
1MB401 board assembly
1PS112 board assembly
1chassis base
4rubber feet
4#6 x ½” selftap
1front panel
1front panel spacer
1rear panel
3heatsink
21.0” standoff
50.5” standoff
1500VA xformer + hardware
1RCA connector
1XLR connector
1fuse holder
1fuse, 6A slowblow
1power entry connector
1speaker terminal connector
1DPST power on/off switch
1DPDT slide switch
1thermal cutout
2handles
46/32 x 5/8” sockethead
1resistor 2.4KOhm, 2W
2#6 solder lug
2’ heatshrink 1/8”
1’ heatshrink 1/4”
78/32 x 1/2” socket head
16 8/32 x 1/2” panhead
23 #8 split lockwasher
76/32 x 3/8” flathead
56/32 x 1/2” flathead
16/32 x 1/2” black flathead
16/32 x 1/2” oval head
76/32 x 1/4” panhead
6#6 kepsnut
5#6 split lockwasher
64/40 x 1/2” panhead
24/40 x 1/2” flathead
8#4 kepsnut
2‘ 22 ga wire brown
2‘ 22 ga wire red
2‘ 22 ga wire orange
2‘ 18 ga wire brown
2‘ 18 ga wire red
2‘ 18 ga wire orange
1/2‘ 22 ga wire green/yellow UL
3‘ 22 ga black UL
3‘ 22 ga white UL
1heatsink compound
1line cord
1Hex L-Key 3/32"
1Hex L-Key 7/64"
1Hex L-Key 9/64"
Assembly instructions.
Before assembling the MB401 amplifier complete the
assembly of the MB401 power amplifier board and the
PS111 power supply board.
Rear panel: Remove the rear panel from the cabinet
before starting this assembly. Mount the following
parts to the rear panel:
1 DPDT switch
using 4/40 x 1/2" panhead + kepsnut.
1 XLR connectors
using 4/40 x 1/2" panhead + kepsnut.
1 RCA connectors, .
1 Pair of binding posts
1 Fuse holder
1 Power entry module.
using 4/40 x 1/2" panhead + kepsnut.
1 Thermal cutout
using 4/40 x 1/4" flathead + kepsnut
Now mount the rear panel to the chassis using 5 6/32
x 1/2" flathead screws and kepsnuts. Note that the
chassis bottom has a large hole in the bottom. This
hole is used to mount the transformer. This hole
should be on the left side of the chassis, as seen from
the front.
Now mount the 3 heatsinks to the rear of the chassis.
Make sure all previous steps have been completed
because some screws can not be reached after the
heatsinks have been monted. Use 16 8/32 x 1/2"
screws for this. Do use split lockwashers on all 14
screws.
Front panel: Mount the front panel and front panel
spacer to the chassis using the 4 6/32 x 5/8"

©2001 Marchand Electronics Inc. PO Box 473 Webster NY 14580 [phone] www.marchandelec.com 7
sockethead screws and the handles. Use lockwashers
with these screws. Install the fifth screw in the bottom
of the panel. Use a 6/32 black flathead with kepsnut
for this.
Feet: Install the 4 rubber feet in the bottom of the
cabinet using the #6 selftap screws.
Transformer: Install the transformer. See figure
below.
PS112 Power supply: Install the power supply next
to the power transformer using 5 hex 1/2" standoffs,
as shown in fig x. Use 6/32 x 3/8 flatheads on the
bottom and 6/32 x 1/4" panheads on top.
MB401 power amplifier board: Install the board onto
the heatsink with the 7 8/32 bolts with hex head. Use a
lock washer with each bolt. Access to the mounting
bolts is difficult. Use a long hex-wrench for this.
IMPORTANT: Use heat sink compound to cover the
rear of the MB401 mounting bracket completely
before installing. Locate the board as far to the right
(away from the xformer) as possible. Use the two 1"
hex standoffs to secure the board to the bottom plate.
Wiring: Wire up the rear panel according to the circuit
diagram.
Wiring note: Use the #22 wire with the thick insulation
for the AC wiring to and from the power transformer.
Use the #18 wire for the wire to the loudspeaker
terminals and between the PS111 and the MB401
board. Use #22 wire for all other interconnect.
Chassis grounding. Solder the 2400Ohm, 2W
resistor to a solder lug. Solder a length of black wire
to the other end of the resistor. Install solder lug
under one of the hex standoffs of the MB401 board.
Connect the wire the GROUND connection (terminal
marked G of the three position terminal block) of the
MB401 board. This will connect the chassis of the
amplifier to the DC ground of the power supply.
!!!! Assembly is now complete. !!!!
Initial power up.
The first time power is applied observe any unusual
events, like smoke, etc. Turn the power off
immediately if this happens and check for correct
construction. It is best to power up initially using a
variable power transformer (variac) and observe
operation at about half line voltage.
The bias current of the amplifier board now needs to
be adjusted. Connect a DMM between testpoints TP1
and TP2. With no signal on the input and no
loudspeaker connected use R33 to set the bias of the
MB401 main amplifier board to 50mV.
The heatsinks will become warm during normal
operation. When the amplifier is powered up but no
power is delivered the heatsink should become just
slightly warm to the touch. If they become hot in this
mode check the bias current of the MB401 amplifier
module.
With full AC voltage applied the V+ reading should be
approx. 80V (referred to ground), the V- reading -80V,
the V++ reading +92V and the V-- -92V.
Figure 6: Mounting of power transformer
Metal Plate
Nut
Rubber washer
Chassis bottom
Transformer
Bolt
Rubber washers
Use two of these.

©2001 Marchand Electronics Inc. PO Box 473 Webster NY 14580 [phone] www.marchandelec.com 8
MB401 Power Amplifier
Power wiring
(c)2002 Marchand Electronics Inc.
Thermal
cutout
Circuit
breaker Toroidal
Power
Transformer
PS112
Red (18)
Orange(18)
GND
red
yellow
blue
gray
black
white
DPDT
switch
w.
light
Rear panel
Rear Panel
Power entry
Wire to
Case
N
L
Front
panel
Power
switch
MB401
GND
V+
V-
V+
V-
Brown(18)
AC
CT
TA
AC
Red
Yellow
Blue
Gray
white
black
Green/
yellow
orange
brown
*** primary connections
shown for 120V line
Toroidal
Power
Transformer
black
white
orange
brown
***connect primary like this for
240V line
Toroidal
Power
Transformer
black
black
***use black wires with xformer with
single primary
GND
V++
V--
Red(22)
Orange(22)
Brown(22)
V++
V--
GND
TB
TC
TD

©2001 Marchand Electronics Inc. PO Box 473 Webster NY 14580 [phone] www.marchandelec.com 9
MB301 Power Amplifier
Signal Wiring
(c)2000 Marchand Electronics Inc.
XLR
MB301
inv
GND
non
out
GND
XLR
12
3
RCA
RCA
RED
BLK
Binding
Posts
red
Speaker
red
Orange(22)
orange
Brown(22)
brown
Red(18)
Brown(18)
Use heavy 18
gauge wire for the
speaker wires only
Red(22)
1
2
3
G
IN
brown
Figure 7: Rear panel wiring for signal and speaker.

©2001 Marchand Electronics Inc. PO Box 473 Webster NY 14580 [phone] www.marchandelec.com 10
Assembly instructions for the MB401 main amplifier board.
Parts List
ID Value Description
Resistors
R1 1.00M 1%, 1/4W, Metal Film
R2 1.00M 1%, 1/4W, Metal Film
R3 24.9K1%, 1/4W, Metal Film
R4 24.9K 1%, 1/4W, Metal Film
R5 1.00M 1%, 1/4W, Metal Film
R6 1.00M 1%, 1/4W, Metal Film
R7 1.00M 1%, 1/4W, Metal Film
R8 10.0K 1%, 1/4W, Metal Film
R9 10.0K 1%, 1/4W, Metal Film
R10 100 Ohm Trimmer Potentiometer
R11 not used
R12 100 K 1%, 1/4W, Metal Film
R13 2.00K 1%, 1/4W, Metal Film
R14 2.00K 1%, 1/4W, Metal Film
R15 2.00K 1%, 1/4W, Metal Film
R16 499 Ohm 1%, 1/4W, Metal Film
R17 499 Ohm 1%, 1/4W, Metal Film
R18 499 Ohm 1%, 1/4W, Metal Film
R19 100 Ohm 1%, 1/4W, Metal Film
R20 499 Ohm 1%, 1/4W, Metal Film
R21 100 Ohm 1%, 1/4W, Metal Film
R22 100 Ohm 1%, 1/4W, Metal Film
R23 Jumper
R24 Jumper
R25 not used
R26 100K 1%, 1/4W, Metal Film
R27 not used
R28 100K 1% ,1/4W, Metal Film
R29 not used
R30* 49.9 Ohm 1%, 1/4W, Metal Film
R31*1 Ohm 5W Wirewound
R32*2.00K 1%, 1/4W, Metal Film
R33 10 K Trimmer Potentiometer
R34* 49.9 Ohm 1%, 1/4W, Metal Film
R35*1 Ohm 5W Wirewound
R36*2.00K 1%, 1/4W, Metal Film
R37 not used
*8 places
Capacitors
C1 1.0uF Stacked Film
C2 1.0uF Stacked Film
C3 1pF Ceramic NPO
C4 1pF Ceramic NPO
C5 47uf, 100v Aluminum Electrolytic
C6 47uf, 100v Aluminum Electrolytic
C7 1000 pF Ceramic Disk
C8 4.7uf, 250v Aluminum Electrolytic
C9 4.7uf, 250v Aluminum Electrolytic
C10* 2200uf, 80v Aluminum Electrolytic,SF
C11 6800uf, 6.3v Aluminum Electrolytic
C12 6800uf, 6.3v Aluminum Electrolytic
C13 6800uf, 6.3v Aluminum Electrolytic
C14 0.22uf Stacked Film
C15 6800uf, 6.3v Aluminum Electrolytic
C16* 2200uf, 80v Aluminum Electrolytic,SF
* 4 places
SF Snap Fit
Diodes
D1 1N4735 6.2 Volt Zener Diode
D2 1N4148 Signal Diode
D3 1N4148 Signal Diode
D4 1N4148 Signal Diode
D5 1N4148 Signal Diode
D6 1N4735 6.2 Volt Zener Diode
D7 LED
D8 1N4148 Signal Diode
D9 1N4148 Signal Diode
D10 not used
D11 Jumper
D12 not used
D13 Jumper
D14 1N4735 6.2 Volt Zener Diode
D15 1N4735 6.2 Volt Zener Diode
D16 HER106 1 Amp. Diode
D17 HER106 1 Amp. Diode
Transistors
Q1* ZVNL120A N-Channel SS MOSFET
Q2* ZVNL120A N-Channel SS MOSFET
Q3 ZVNL120A N-Channel SS MOSFET
Q4 ZVP2120A P-Channel SS MOSFET
Q5 ZVP2120A P-Channel SS MOSFET
Q6 ZVNL120A N-Channel SS MOSFET
Q7 ZVNL120A N-Channel SS MOSFET
Q8 MTP2P50E P-Channel MOSFET
Q9 MTP2P50E P-Channel MOSFET
Q10 IRF710 N-Channel MOSFET
Q11 IRF710 N-Channel MOSFET
Q12 not used
Q13 not used
Q14 2N2222 NPN transistor
Q15 2N2907 PNP transistor
Q16 IRFI640 N-Channel Power MOSFET
Q17** IRFI640 N-Channel Power MOSFET