SOUNDMASTER VF 250 User manual

SOUNDMASTER TM
VF 250
MOS-FET POWER AMPLIFIER
OWNERS MANUAL
U.K. 220-240v
Before you use this equipment
please read the instructions
The SOUNDMASTER name and logo
are the registered trade marks of M-Jay Electronics Limited

1
Table of Contents
INTRODUCTION ..........................................................2
Introduction .........................................................2
Technical Specification ................................................2
Protection Details .....................................................2
Declaration of Conformity ....................................................3
FRONT PANEL FEATURES .................................................4
A. C. Power Switch ...................................................4
Input Attenuators .....................................................4
Bridge Mode ........................................................4
Signal Inputs ........................................................4
Amplifier Outputs ....................................................5
AC Power Input ......................................................5
DC Fuses ...........................................................5
INTERNAL FACILITIES ....................................................5
Bridge Link .........................................................5
GENERAL DETAILS .......................................................5
Ventilation ..........................................................5
Service .............................................................5
Rack Fitting Details ...................................................5
CONNECTOR WIRING .....................................................6

2
INTRODUCTION
Please read this manual before connecting the amplifier.
Introduction
Your new SOUNDMASTER amplifier has been manufactured from the highest quality
components and materials. Please read these instructions carefully and your amplifier will
provide many years of service. This amplifier is designed for use in professional high power
sound systems and it should be installed bya competenttechnician as described in the following
instructions.
Beforeswitching the amplifier on pleasecheck that the mains leadis correctlywired and that the
mainsvoltage selectorisset to thecorrectsupplyvoltage.Themains voltage selectorisset in the
factory to 240v AC
Technical Specification
Output power per channel 130 watts into 4SRMS
90 watts into 8SRMS
Bandwidth 5Hz to 60KHz
Input sensitivity 0dB (0.775v)
Input impedance 10Kohms Unbalanced
Hum and Noise Less than -96dB
Output rise time 7uS
A. C. Power input 220-240v AC 50Hz 300VA max
Dimensions 19" x 3.5" x 9.5"
Shipping weight 5 kilos
Protection Details
A. C. Power supply fuse
D. C. Power supply fuse (2 per channel)

3
Declaration of Conformity
Equipment Soundmaster VF 250 power amplifier
Manufacturer M Jay Electronics Limited
Address Albion Mills
Church Street
Morley
Leeds
LS27 8LY
European Standards 1) EN 50 081-1 Emission
2) EN 50 082-2 Immunity
3) EN 60 555 Conducted Emissions
4) EN 60065
Conformity Criteria 1) Radiated emissions are less than 30 dB:V/m @
10m from the equipment.
Conducted emissions are less than 56dB:V/m.
2) The performance of the equipment will not be
impaired by a radiated signal in the band 27MHz
to 500MHz with a signal strength of 3v/m and
with 80% modulation
3) The AC power input currentharmonics are within
the limits set by EN 60 555-3,-3. The conducted
RF emissions are below the limits described in
EN55 022 class b.
Description of Equipment 250 watt Audio Power Amplifier
Icertify that the apparatus identified above conforms to the requirements of Council Directives
89/336/EEC and 73/23/EEC and therefore complies with the requirements of Council Directive
73/23/EEC, (The Low Voltage Directive) on the harmonisation of the laws of Member States
relating to electrical equipment designed for use within certain voltage limits as amended by
Article 13 of Council Directive 93/68/EEC
Signed ..................................
John Varley B.Eng(Hons) C.Eng MIEE
Date 19 August 1997
Position Managing Director
Company M Jay Electronics Limited

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FRONT PANEL FEATURES
A. C. Power Switch
The power switch is a double pole type to
ensure that both the live and neutral mains
supply is disconnected from the amplifier
when it is not in use. When the mains power
supply is on, the switch will be illuminated.
Input Attenuators
Both the input channels have an input
attenuator to adjust the incoming signal and
theseare usually set to the same position for
stereo or monoapplications.If the amplifier
isusedinsystemswhenthe twochannelsare
supplyingdifferentsignalsordifferentloads
they can be set separately e.g. Bi-amplified
speaker systems or for sound distribution to
two different rooms in a building.
Theamplifier is designed for an input signal
level of 0dB to provide full drive to the
output (which is the output level of most
soundmixers)sothatthecontrolsmaybeset
to maximum (10) to obtain full output.
Caution The use of a graphic equalizer
between the mixer and the amplifier can
result in the signal to the amplifier being
higher than 0dB. The use of VU type meters
on some mixers can cause under reading on
certaintypesofsignal,in thiscasetheoutput
level should be set to ensure that the output
of the amplifier does not go into distortion.
When the amplifier is used with music or
speechit is possibletoexceed thefull power
rating of the amplifier, this is due to the
power stored in the reservoir capacitors
being discharged onlyby peaksin the music
and recharging in quiet passages. In these
circumstances up to double the rated output
power may be available for short periods.
Bridge Mode
The amplifier can be used in the bridged
mode by changing the internal link to the
bridge position. The link is located on the
main PCB near to the right hand output
connectors. The signal is connected to the
left hand input jack socket. The right input
socket should not be used and the right
channel input attenuator shouldbe turned to
O. The speaker load should now be
connected between the positive outputs of
the left and right channels. (The tip of the
jack plug). NB the minimumload should be
8S.Shouldasignalbeconnectedtotheright
input the output will be the difference
between the left and right inputs and will
sound distorted.
Signal Inputs
Each channel can be connected by either of
the ¼" Jack connectors. Both the jack
sockets for each channel are wired in
parallel to enable amplifier inputs to be
linkedtogetherforlargesound systems.The
inputs which are unbalanced have a 3 pole
jack socket for compatibility with balanced
systems. They should be wired as follows:
Tip Positive phase
Ring Negative phase
Sleeve Screen
For balanced inputs the screen and negative
phase will be connected together if a 3 pole
jack plug is used or theinput canbe wired to
a2 pole jack plug with the positive phase to
the tip and the negativephaseand the screen
connected to the sleeve. DO NOT leave
either of the negative or positive phase
inputs unconnected as this will result in a
reduced output level and increased noise.

5
Amplifier Outputs
Two Standard ¼" 2 pole jack sockets are
provided for each channel. The minimum
load impedance is 4S. The connectors are
wired:
Tip Signal
Sleeve Ground
In the bridge mode the output should be
taken between the tip of the jack socket of
each channel.
AC Power Input
The AC power is supplied via a 3 pin IEC
Euro-Connector moulded plug and cable
which is supplied with the amplifier. The
free end of the cable is not suppliedwith a 3
pin plug so that the cable can be wired into
the equipment rack power distribution
system.
The lead should be wired using the
following code:
Green/Yellow Earth
Brown Live
Blue Neutral
CAUTION- THIS AMPLIFIER MUSTBE
CONNECTED TO EARTH, FAILURE TO
DO SO COULD BE FATAL.
DONOTdisconnectthegreen/yellowmains
safety earth. This amplifier has a special
electronic circuit to eliminate hum loops.
DC Fuses
There are two 20mm DC fuses for each
amplifier, one for the positive and one for
thenegative powersupplyand theyarerated
at 5@0A quick blow. Before changing a fuse
turn the amplifier mains switch off and
disconnect the mains supply from the
amplifier.
INTERNAL FACILITIES
Bridge Link
The bridge Link is located inside the
amplifier in front of the right hand output
sockets so that it is not inadvertently
connected and therefore requires the
removalof the lid to operate it.CautionYou
should disconnect the mains supply before
removing the amplifier lid.
GENERAL DETAILS
Ventilation
Tokeepthe amplifiercool a goodflow ofair
is required. If the amplifier is housed in a
rack or other enclosed space it is essential
that adequate ventilation is provided, with
holes in the bottom of the rack for cool air to
enter and holes in the top for hot air to
escape. In large systems involving many
amplifiers in the same rack, forced air
ventilation may be required.
Service
This amplifier is a precision piece of
equipment, should it require servicing it
should be returned in it's original packing to
the dealer or agent it was purchased from.
Service work should only be carried out by
qualified and experienced engineers. Please
note that any workon or modification to the
amplifier by unauthorised persons may
invalidate the guarantee.
Rack Fitting Details
The amplifier will fit in a standard 19" rack
and is 2 units high.

6
CONNECTOR WIRING
M-Jay Electronics have a policy of continuing development and we reserve the right to alter
models and/or specifications at any time. E&OE
Copyright M-Jay Electronics Limited 1997