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the 'low sensitivity' input was recommended for higher
output pickups (e.g.: humbuckers).This said, the majority
of guitarists - then and now - ignore these
recommendations and plug high output guitars into the
'high sensitivity' input because it further boosts the
strength of their signal.
Performance Note: 'Jumping' the two
channels
Because both Channels of the JTM45/100 have the
same number of gain stages and are in phase with each
other, it is possible to 'jump' (a.k.a.'link' or 'bridge') them
together and use them both at the same time. Doing
this enables you to expand upon the amp's tonal
capabilities.
The most common way of doing this is to plug your
guitar into the top (high sensitivity) input of Channel I
and then run a short 'jumper' guitar cable (i.e. a
screened cable) from Channel I's bottom (low
sensitivity) input to the top (high sensitivity) input of
Channel 2.Adjust both channel volumes (Loudness I & 2
controls) until the desired mix of tone is achieved.
The reverse is also possible, i.e. plugging your guitar into
Channel II's top input and then running the 'jumper'
cable from Channel 2's bottom input to Channel I's top
input.
whether the channels are linked or not is
entirely the choice of the individual players taste in tone.
NOTE:
As always, experimentation is the key.
Technical Specification
JTM45/100 Head
Power Output
100W RMS
Weight
22 kg
Size
740mm x 270mm x 210mm
- Note: This equipment has been tested and found to comply with the requirements of
the EMC Directive (Environments E1, E2 and E3 EN 55103-1/2) and the Low Voltage Directive in the E.U.
EUROPE ONLY
EUROPE ONLY - Note: The Peak Inrush current for the JTM45/100 is 39 amps.
812T40 & 812B40 Cabinets
Power Handling (per cabinet)
100W RMS
Weight - 812T40
Weight - 812B40
Size
754mm x 741mm x 355.5mm
6
Rear panel features
2 2 5
There are two loudspeaker output jacks provided for
1. LOUDSPEAKER OUTPUTS
connection to speaker extension cabinet(s). However,
due to the unique power amplifier output configuration,
they are not in parallel, as are standard models. Please
always ensure that the amplifier's output impedance
selector is set correctly (see item 2) and ALWAYS
ensure you use good quality speaker (non-screened)
cables. NEVER use guitar (screened) cables.
Always use a non-screened Marshall approved speaker
lead when connecting an extension cabinet to these
units.
Never use the amplifier without a load
attached!
WARNING!
Matches the amplifier's output to the load (speaker)
2. OUTPUT IMPEDANCE SELECTORS
impedance.
Originally, the output selectors were situated on the
shrouds of the transformers themselves, however, this is
not allowed by current safety requirements.We have
therefore logically put them on the rear panel.
Your JTM45/100 should be completely powered down
before either Output Impedance Selector is turned.
It is imperative that: a) at least one of the speaker
outputs of the amplifier is connected to a load whilst in
operation and b) the impedances on the output
selectors matches the impedance of the extension
speaker cabinet(s) being used.The following
combinations are our recommendations:
- Selectors on 16 Ohm.
Use either speaker output.
1x16 Ohm cabinet
- Both selectors on 16 Ohm.
Use both outputs.
2x16 Ohm cabinets
- Selectors on 8 Ohm.
36 kg
Use either output.
1x8 Ohm cabinet
39 kg
- Both selectors on 8 Ohm.
Use both outputs.
2x8 Ohm cabinets
- Selectors on 4 Ohm.
Use either output.
1x4 Ohm cabinet
- Both selectors on 4 Ohm.
Use both outputs.
2x4 Ohm cabinet
2
1
2
Stereo cabs can be used provided attention is given to
impedance and power handling i.e. at least 50 watts per
side.
Use of any other combination of cabinets
and/or impedances may result in sub standard sound
WARNING!
and possible damage to the amplifier!
Failure to comply with any of the points raised in this
section may result in damage to the amplifier.
Your amp is provided with a detachable mains (power)
3. MAINS INPUT
lead, which is connected here. The specific mains input
voltage rating that your amplifier has been built for is
indicated 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 technician.Your
Marshall dealer will help you in this respect.
The correct value of mains fuse is specified on the rear
4. MAINS FUSE
panel of the amplifier.
fuse or fit one of incorrect value.
The correct value of this H.T. fuse is specified on the
5. H.T. FUSE
rear panel of the amplifier.
the fuse or fit one of incorrect value.
Originally this fuse was mounted internally; however, it is
logical to provide access on the rear panel.
Follow all instructions and heed all warnings
KEEP THESE INSTRUCTIONS !
7
3
4
5
attempt to bypass the
NEVER
attempt to bypass
NEVER
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