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1. Power Switch
On / Off Switch for mains power to the amplifier.
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. Indicator
The Indicator will be lit when your amplifier is on
and will not be lit when the amplifier is switched off.
4. Presence Control
Adds higher frequencies to the guitar tone, creating
crispness and bite. Turning this up will make the
sound more cutting and ‘present’.
5. Bass Control
Controls the amount of low frequencies or bottom
end in your tone.
6. Middle Control
Dictates the middle register of the amplifier.
Turning this up will make your guitar sound fatter.
Conversely reducing the amount of middle in your
tone will result in a sharper and thinner guitar sound
for a more ‘scooped’ tone.
7. Treble Control
Controls the high frequencies of the guitar tone,
making your guitar sound brighter when increased.
(Note: The tone network is highly interactive and
altering one control can change the shape of the
sound in relation to the other tone controls.
Experimentation is the best way to achieve your
desired sounds.)
8. High Treble Loudness 1
Controls the overall output level of Channel 1.
Note: This channel is voiced for a higher treble
response than Channel 2.
9. Normal Loudness 2
Controls the overall output level of Channel 2.
Note: Channel 2 is voiced for normal response.
10. Input Jack
Connects the guitar to Channel 1.
Note: Though the first input of the first channel is
the input that most guitarists use, don’t be afraid to
experiment. Some guitar players prefer to mix the
two channels together by connecting a short,
screened patch lead between the second input of
Channel 1 and the first input of Channel 2. If you
then plug your guitar into the
first input of Channel 1 (item 10),
you can mix the different tonal
characters of each channel for
greater flexibility. (See diagram).
11. Input Jack
Connects the guitar to the lower sensitivity input on
Channel 1.
12. Input Jack
Connects the guitar to Channel 2.
13. Input Jack
Connects the guitar to the lower sensitivity input on
Channel 2.
1/2. Loudspeaker Outputs
These are for connection to an external load, i.e.
speaker cabinet(s). (See item 3).
Please refer to Important Safety Instructions, page 2.
3. 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.
4. 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.
5. 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.
6. 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.
2245 (JTM45) Rear Panel
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