Marshall Amplification JCM800 - Manual (Page 4)

Effects Loop Send & Return Jacks
To increase the flexibility of your 2203 even further, you
may choose to add external effects in its Series Effects
Loop, which allows direct connection of either floor pedals
or rack processors, with the Level switch (1) providing the
correct operating level.
1. Effects Loop Level Switch
This switch offers two different loop levels to enable you
to match the type of effect(s) connected to the Series
Effects Loop. The higher level (+4dBV: switch ‘out’) suits
rack processors and the lower level (-10dBV: switch ‘in’)
suits floor pedals (stomp boxes).
2. Effects Loop Bypass
When ‘out’ this switch completely bypasses the circuitry
involved in the effects loop to maintain the amp’s absolute
tonal integrity.
3. Effects Loop Return Jack
Connect the (mono) output of an external effects
processor here.
4. Effects Loop Send Jack
Connect the (mono) input of an external effects
processor here.
NOTE: As a rule, time based effects such as Chorus, Delay
and Reverb are best suited for use in an effects loop. Effects
involving distortion or Wah Wah aren’t usually put in an
effects loop because they sound best when they’re ‘before’
the amp (i.e. placed between the guitar and the amp’s
input). This said, when it comes to tone there are no rules!
5/6. Loudspeaker Output Jacks
These are for connection to an external load, i.e. speaker
cabinet(s). (See item 7). Please refer to Important Safety
Instructions, page 2.
7. Output Selector
Matches the amplifier’s output to the load impedance.
With all-valve amplifiers it is imperative that the amp is
connected to a load whilst in operation and that the
impedance selected on the amp matches the total
impedance of the speaker cabinet(s) being used. For
example, if the amp is running into a single 16 Ohm cab,
the amp should accordingly be set to 16 Ohms. If running
into two 16 Ohm cabs, the amp should be set to 8 Ohms. If
running into two 8 Ohm cabs, the amp should be set to 4
Ohms. Failure to comply with these points will result in
damage to the amplifier.
Your amp should be completely powered down before
the selector is turned.
8. Mains Selector
Matches the amplifier mains transformer voltage to the
incoming mains voltage. Ensure that the rotary Mains
Selector is set to the correct mains voltage applicable to the
country where used. If you do not know the mains input
voltage contact your authorised Marshall dealer.
Your amp should be completely powered down before
the selector is turned. Adjustment from 230/220V to
110V or vice versa will require the mains fuse to be
changed to the corresponding value as detailed on the
rear panel.
9. Mains Input
Your amp is provided with a detachable mains (power)
lead which is connected here. The specific mains input
voltage rating that your amplifier has been built for is
shown on the back panel. Before connecting for the first
time, please ensure that your amplifier is compatible with
your electricity supply. If you have any doubt, please get
advice from a qualified person. Your Marshall dealer will
help in this respect.
10. Mains Fuse
The correct value of mains fuse is specified on the rear
panel of the amplifier. Please refer to Important Safety
Instructions, page 2.
11. H.T. Fuse
The correct value of H.T. fuse is specified on the rear
panel of the amplifier. Please refer to Important Safety
Instructions, page 2.
6
1. Power Switch
This is the On/Off switch for the mains power to the
amplifier. Whenever it is switched ‘On’, the switch will
light. Please ensure the amplifier is switched off and
unplugged from the mains electricity supply before being
moved.
2. Standby Switch
The Standby Switch is used in conjunction with the
Power Switch (item 1) to ‘warm up’ the amplifier
before use and to prolong the life of the output valves.
When powering up the amplifier always engage the
Power Switch (item 1) first. This allows the
application of the voltage required to heat the valves
to their correct operating temperature. After about 2
minutes, when the valves are up to the correct
temperature, the Standby Switch can be engaged.
Upon doing this the H.T. (High Tension) which is the
high voltage required by the output valves to pass
signal (and hence produce sound) is applied.
To prolong valve life, the Standby Switch alone
should be used to turn the amplifier on and off during
breaks in a performance. Also, upon full power down,
always disengage the Standby Switch prior to the
main Power Switch (item 1).
3. Presence Control
This control operates in the power amp section of your
amp and adds high frequencies to your tone, creating
crispness and bite. As you turn this control up
(clockwise), your sound will become more cutting.
4. Bass Control
This controls the amount of low frequencies (bottom
end) in your tone.
5. Middle Control
This controls the all-important mid-range of your
sound. Turning this up (clockwise) will make your guitar
sound fatter and fuller. Conversely, turning it down
(anticlockwise) will reduce the mids in your sound, giving
you that aggressive ‘scooped’ tone that is a staple of
thrash and nu-metal guitar playing.
6. Treble Control
This control determines the amount of treble and makes
your guitar’s tone brighter as it is turned up.
IMPORTANT NOTE: The 2203’s tone network is highly
interactive and, because of this, altering the setting of one
control can change the way the other controls behave.
So, don’t be afraid to experiment!
7. Master Volume
Controls the output volume of the amplifier. This allows
the user to turn up the Pre-Amp Volume control (8) for
maximum gain whilst keeping the amp’s overall loudness
at a desired level.
8. Pre-Amp Volume
This controls how hard you drive the pre-amp valves.
Turning this control up overdrives the pre-amp and
creates a desirable, harmonically rich distortion.
9. High Sensitivity Input
This is the High Sensitivity input of the amp – in theory,
such an input is supposed to be used for low-output
pickups. This said, 99.9% of all 2203 users ignore this
and plug guitars loaded with high-output pickups into this
input, because it enables them to drive the pre-amp even
harder.
10. Low Sensitivity Input
This is the Low Sensitivity input of the amp, which was
designed for hot (high-output) pickups; we would
suggest you try both inputs and then decide which one is
best for you.
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Front Panel
Rear Panel
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Front Panel Features Rear Panel Features
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