Formula Sound Manual FSM-400

Formula Sound Manual FSM-400
FSM-400
PRODUCTION MIXER
USERS MANUAL
FSM-400 INTRODUCTION
The FSM-400 is a compact fixed format stereo production mixer. The design allows the unit
to accept one microphone input and seven stereo music inputs.
The FSM-400 is essentially a four channel mixer with each channel switchable to two inputs.
Channel 1 is switchable between low impedance microphone and a stereo line input.
Phantom power is available for microphones (internal selection). Channels 2 to 4 are
switchable between A and B stereo line inputs. The A input may be internally selected to
RIAA or normal line. These channels are fully assignable to the crossfader. Three band
equalisation is fitted to all channels with a range of +5dB to -20dB. The large amount of cut
eliminates the need for frequency cut switches. A gain control is also fitted to all channels.
Channels 2 to 4 have internal jumpers to provide 2 gain settings per input, the gain range is:normal +/- 15dB or low setting +2dB to -19dB. Illuminated push button switches are used for
input selection, PFL (pre fade listen), routing, etc. A smooth 60mm fader, which is arranged
to eliminate the ingress of dirt, complete the channel controls.
The output section provides plenty of facilities to cope with most applications. It includes a
new design of crossfade circuitry that places less demand on the fader to ensure exemplary
attenuation and extended life. A punch button facility is also included.
Unlike the majority of fixed format mixers on the market all connectors are fitted to the back
face which allows unrestricted access when the mixer is fitted through a work top or console.
Although the FSM-400 is a fixed format design the use of individual circuit cards per channel
improve reliability and aid servicing should the need arise. Construction and audio quality
are to Formula Sound’s usual highest standards.
Power
The mixer features a fully regulated internal power supply that is designed to operate on 220240Vac or 110-120Vac. The selection is by an internal switch mounted on the power supply
circuit board and is accessed by removing the front cover.
DAMAGE MAY RESULT IF THE UNIT IS CONNECTED TO THE WRONG SUPPLY
VOLTAGE
Fuses
Mains fuse sizes are 315mA anti surge for 220-240V operation and 800mA anti surge for
110-120V operation. It is important for safety reasons that the correct fuse sizes are
always used.
N.B. Internal settings should only be undertaken by skilled personnel
Always remove the power cord before removing any covers.
Page 1
1M
INPUT CHANNEL 1
1L
Input selector switch selects input used. M = microphone
(XLR connector). L = stereo line (phono connectors). 2
parallel pairs of phono sockets allow easy parallel of
source to a second input if required.
GAIN
L.e.d.s and label area clearly show which input is in use.
Gain control sets input gain level. Check by selecting
PFL and adjusting so that V.U. meter just peaks into red.
TREBLE
3 band equalisation provides +5dB -20dB control.
MID
BASS
MUTE
E.Q. OUT
Mute push button cuts the channel signal when
depressed (switch illuminated).
E.Q. OUT
This push button bypasses the equaliser section.
This is a useful function to either switch e.q. in or out for
effect or for bypassing mic e.q. when using the line input.
PFL
PFL (pre-fade listen) routes the channel signal to the
monitoring system (V.U. meter and phones). If more than
1 PFL is selected the sum is routed to the monitoring
system. If no PFL is selected the monitoring system
reads main output.
60mm channel fader.
Note
For normal microphone operation the fader should not
be holding much gain. Set the fader to No. 7 and adjust
the gain for normal volume. If the fader is below No. 7
during normal operation turn down the gain control and
turn up the fader. This gives the best performance.
Page 2
2A
2B
GAIN
INPUT CHANNELS 2 TO 4
Input selector switch selects input used. A = input A
B = input B. Input B is always a stereo line input
(internal jumpers selects input A to be either RIAA
magnetic cartridge or a standard line input. (phono
connectors)).
L.e.d.s and label area clearly show which input is in
use.
TREBLE
Gain control sets the input gain level. Check by
selecting PFL and adjusting so that V.U. meter just
peaks into the red.
MID
3 band equalisation provides +5dB -20dB control.
BASS
XF A
XF B
PFL
XF A and XF B (Illuminated push buttons) assign the
channel to the crossfader. If neither button is pressed
the channel is fed via the stereo buss to the output and
the crossfader will have no effect on this channel. If
both buttons are pressed the channel will be assigned
to A only
PFL (pre-fade listen) routes the channel signal to the
monitoring system (V.U. meter and phones). If more
than 1 PFL is selected the sum is routed to the
monitoring system. If no PFL is selected the monitoring
system reads main output.
60mm channel fader.
Note
For normal operation the fader would normally be used
at maximum and the gain control adjusted for normal
volume. If the fader is set below No. 7 during normal
operation turn down the gain control and turn up the
fader. This gives the best performance.
Page 3
Output Section
POWER
MAIN OUTPUT / PFL
-20
-10
-7
-5
-3
MUSIC MUTE
ZONE
-1
0
+1
+2
+3
+6
PFL SELECTED
Power switch switches the
mains feed to the mixer
power supply. N.B. to
avoid switch on thrumps
audio systems need
powering up in sequence.
A good rule to remember is
- power amps on last and
off first.
BOOTH
ATTENUATION
PHONES
TALK OVER
SPLIT
MASTER
STEREO
JACK
FSM-400
PUNCH
FORMULA SOUND
MONITORING
Twin l.e.d. bargraph V.U.
meters show the main
output signal or PFL
signals. The changeover is
by selecting PFL on any
channel. Any number of
PFL sources may be
selected and the sum of
these will be monitored.
This provides a very
versatile monitoring facility.
Depressing the SPLIT
button allows both main
output and PFL signals to
be monitored
simultaneously. This
function is often preferred
when mixing tracks in
synchronisation. The two
signals are summed to
mono and presented to the
monitor section with the
main output fed to left and
PFL fed to right sections.
The phones output always
follows the metering so
what you see is what you
hear.
As an extra aid an adjacent
l.e.d. illuminates to indicate
when any PFL source is
selected.
Page 4
BOOTH - controls the booth output level. This output may be used to provide a local monitor
output. To eliminate any possibility of feedback no microphones are fed to this output.
Stereo or mono outputs are available via the 0.25” jacks on the rear panel.
PHONES - the master volume control for the headphone monitoring system. Two stereo
jacks are provided, one on the front panel and one on the rear. STEREO jacks must be used
- a mono two circuit jack will present a short to one half of the phones amplifier and although
current limiting protection is included, prolonged use should be avoided. The phones
amplifier is very powerful and capable of delivering over 1 Watt per channel into the optimum
load of 30 ohms.
MASTER - controls the level of the main output and features balanced outputs on XLR
connectors as well as a separate mono output on a 0.25” jack.
CROSSFADE - A 45mm fader is featured that can be used to smoothly fade between the
XF-A buss and XF-B buss. To improve crossfader life and also ensure good attenuation at
the ends of travel, studio quality VCA circuits have been used. The use of VCA’s over
conventional faders give superior crossfade performance.
PUNCH - A momentary action push button is fitted, which when pressed, switches both XF-A
and XF-B signals on. Wherever the crossfader is set pressing the punch button will always
add the opposite side. The Punch circuit action is click free, and provides the creative
operator with a useful facility.
ZONE - controls a further output similar to the master output but without the balanced output
driver. Stereo or mono outputs are available via the 0.25” jacks on the rear panel.
TALK OVER - circuitry is included that is selected via an illuminated push button. The action
of this circuit is to attenuate the music when the switch is pressed. The attenuation level of
the music is variable - turning the pot clockwise turns up the music.
RECORD OUTPUTS - Two sets of stereo record outputs are available via phono connectors.
One is a complete programme mix, the other is music sources only (similar to the booth
output). All record outputs are unaffected by the master controls.
SUB BASS OUTPUT - a mono output via 0.25” jack is provided for driving a sub bass
loudspeaker system to enhance low frequency performance. The filter allows frequencies
below 70Hz to pass through. An internal jumper allows higher bass output if required.
SOUND TO LIGHT (TRIG) - a fully floating transformer isolated trigger output is available on a
0.25” jack to provide safe connection to lighting equipment.
REMOTE MUSIC MUTE - To cater for the increasing requirement to mute music signals in
entertainment venues when the fire alarm is activated the FSM-400 has provision to remotely
mute all music sources by linking two pins on the connector provided. The fire alarm panel
needs to provide a fully floating pair of contacts which close when the alarm is activated. An
l.e.d. positioned below the V.U. meter clearly shows if the music mute is activated
Page 5
Service and Configuration
Several internal options are available on the FSM-400. These should only be undertaken by
qualified personnel.
Always remove the power cord before removing covers.
To gain access to the internal parts of the FSM-400 remove 4 screws from each of the two
side covers which surround the FSM-400. This will give access to the internal jumpers and
adjustments.
Channel options (remove top cover).
Channel 1. One jumper fitted towards the top of the channel pcb provides microphone
phantom power selection. Pcb notation shows positions.
Channels 2-4 - N.B 2 jumpers per channel must be moved
4 jumpers located behind the input selector switch provide selection for input A and B to be
set to low gain. They are labelled AR (chan A right) BR (chan B right) AL & BL etc. The low
gain setting is with the jumper positioned away from the switch.
Ensure that the correct jumpers are moved and they are correctly located on the pins.
Removing all the jumpers will set inputs A and B to the low gain settings.
2 jumpers provide selection for the A input to be a flat line input or an RIAA magnetic
cartridge input. Pcb notation shows the position for the jumpers. Ensure that both
jumpers are moved to the correct positions and located correctly on the pins.
MAINS VOLTAGE SELECTION - The FSM-400 can be switched to operate on
220-240Vac or 110-120Vac. The selection is by a slide switch mounted on the power supply
pcb at the mains transformer end. Notation on the pcb and switch clearly show the switch
position. If you need to change the mains operating voltage you will also need to change the
main fuse. The fuse is located in a slide out drawer which is part of the mains connector. The
connector is mounted on the mixer rear panel.
Fuse sizes 220-240v operation = 315mA anti surge 5 X 20mm fuse
110-120V operation = 800mA anti surge 5 X 20mm fuse
Removing the top cover also exposes the right end output pcb. The sub bass adjustment is
located on this board - and is controlled by 1 jumper located above the sub bass jack socket.
Adjacent notation shows the positions.
Fader Replacement
Should fader replacement become necessary any of the faders can be replaced by removing
the bottom side cover. Remove the 2 screws securing the fader and disconnect the
connector. Replace with a new fader assembly.
Page 6
Mixer Dimensions
Width
Height
Depth
382mm (15”)
283mm (11.125” )
110mm (4.33”)
Installation cut out for mounting the FSM-400 through a work surface.
330mm wide X 270mm height
Formula Sound Ltd
Ashton Road
Bredbury
Stockport
Cheshire
England
SK6 2SR Tel +44 (0)161 494 5650 Fax +44 (0)161 494 5651
Page 7
INSTALLATION, CONNECTIONS AND GOOD WIRING PRACTICE
The installation of professional audio systems should be left to experienced engineers
wherever possible. The interconnection of audio systems can be fairly complex depending
on the type and size of system and obviously well outside the scope of this handbook. We
have included a few basic points for information for anyone who is new to audio systems.
Good wiring practice should be observed when connecting any audio equipment. Good
quality connectors and screened cable should be used for all audio connections .
Twin screened cable should be used for all balanced lines particularly microphone
connections.
Always ensure cable clamps in connectors are fully tightened and gripping the outer sheath.
Good strain relief and mechanically sound connections will increase reliability at virtually no
extra cost.
GROUND LOOPS
In our experience this is the most common problem encountered when connecting together
different items of audio equipment. It is the most common cause of hum (50Hz noise) on a
system and is caused by incorrect system grounding.
When several items of audio equipment are connected together with unbalanced connections
(i.e. 2 connections, single screened cable, etc.) the signal common connection is the screen
and this will be connected to mains earth at some point. If several items of equipment have
their signal common connected to mains earth this will form a loop (hence ground loop).
Current will flow in this loop and appear in the form of hum (50Hz mains frequency) added to
the audio signal. The problem is aggravated if the equipment is located a distance apart as
the loop is larger. It is possible to have several ground loops within a system. The solution is
to connect the system to mains ground only once. This is usually done at the mixer. You will
need to investigate the various items of equipment you are using and isolate their signal
common from mains earth. Many manufacturers fit a ground lift switch for this purpose. On
some equipment this is in the form of a removable link. Unfortunately with some equipment
you have to get inside to identify where the connection is and remove it.
YOU MUST NOT DISCONNECT THE MAINS EARTH WIRE FROM
THE MAINS PLUG OF ANY EQUIPMENT. THIS IS FITTED FOR
SAFETY REASONS AND MUST BE CONNECTED TO ENSURE THE
CASE IS EARTHED.
Page 8
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