Marshall Amplification JTM45 User Manual

WARNING!  
Please read the following list carefully.  
A. ALWAYS use the correct power cord  
B. NEVER attempt to by-pass the fuses or fit ones of the incorrect value.  
C. NEVER attempt to replace fuses or valves with the amplifier connected to the mains.  
D. DO NOT attempt to remove the amplifier chassis, there are no user serviceable parts.  
E. ALWAYS have this equipment serviced or repaired by competent qualified personnel.  
F. NEVER use an amplifier in damp or wet conditions.  
G. DO NOT switch the amplifier on without the loudspeaker connected.  
H. ENSURE that any extension cabinets used are of the correct impedance.  
I. PLEASE read this instruction manual carefully before switching on.  
WARNING : This apparatus must be earthed!  
WARNING : Do not obstruct ventilation grille and always ensure free movement of air around the amplifier !  
KEEP THESE INSTRUCTIONS  
Introduction  
As Jim has already stated, our goal, when building this limited edition, offset reissue, was simple. To make it as  
close to the original as humanly possible! To this end we have gone to great lengths to recreate every single aspect  
and specification of this visually and aurally striking item-from sourcing an exact replica of the original coffin logo (so  
called because it was first made for us by a coffin manufacturer!), to ensuring that the output and power transformers  
boast the same exact core lamination materials as they did back in 1962. Likewise, the amplifier circuit itself is hand-  
wired on a hand-built tagboard, the chassis is constructed from aluminium and the valve complement is 3 x ECC83s  
in the preamp, a GZ34 rectifier and a pair of KT66s in the power amp - just like the original.  
We are delighted to report that many of our suppliers went to the same exacting lengths as we did when providing  
us with parts for this reissue, and none-more-so than Celestion. Thanks to their commitment to this project they  
successfully recreated the Alnico magnet, silver G12, model T0652 loudspeakers found in our museum piece-right  
the way down to matching the same exact colours and lettering fonts used on the original label!  
As is the case with all our amplifiers, the best way for you to truly appreciate this remarkable reissue is to grab  
your favourite guitar, plug it in and play. Enjoy!  
JTM45 O/S Front and Rear Panel Features  
Front Panel Functions  
The JTM45 O/S features four inputs, two per channel. The first channel is voiced for a high treble response with the  
second channel voiced for normal response. The first input of each channel has more gain than the second input of  
each channel and hence is louder. Though the first input of the first channel is the input that most guitarists use,  
don’t hesitate to experiment. Some guitar players prefer to mix  
the two channels by putting a patch lead between the second  
input of channel 1 and the first input of channel 2 and then plug  
their guitar into the first input of channel 1. Doing this allows  
you to mix the different tonal characters of each channel for  
greater flexibility.  
See Diagram right.  
JTM45 O/S Front and Rear Panel Features (continued)  
10.Input Jack  
Front Panel Functions  
Connects the guitar to channel 1.  
Note - this input has less gain than item 9.  
1. Power Switch  
On / Off Switch for mains power to the amplifier.  
11. Input Jack  
2. Standby Switch  
Connects the guitar to channel 2.  
Controls H.T. or high voltage to the valves to allow  
them to attain correct working temperature before  
playing. To prolong the life of the valves it is  
always advisable to switch on the Mains Power  
Switch (item 1) about 2 minutes before switching  
on the Standby (item 2).  
12. Input Jack  
Connects the guitar to channel 2.  
Note - this input has less gain than item 11.  
Rear Panel Functions  
On switching off, the Standby should always be  
switched before the Power Switch.  
1/2. Loudspeaker Jacks  
The standby facility is particularly useful live  
between sets and before playing, as it allows you to  
keep the valves operating at a functional  
temperature but without any sound being  
produced.  
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.  
3. Presence Control  
Adds higher frequencies to the guitar tone, creating  
crispness and bite. Turning this up will make the  
sound more cutting and further forward.  
Note - The matching cabinet supplied with this  
amp is wired for 16 Ohms.  
4. Bass Control  
Controls the amount of low frequencies or bottom  
end in your tone.  
Failure to comply with these points will result in  
damage to the amplifier.  
5. Middle Control  
3. Output Selector  
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 the classic ‘scooped’ tone.  
Matches amplifier output transformer impedance  
to loudspeaker load impedance.  
4. H.T. Fuse  
See label for correct value.  
6. Treble Control  
5. Mains Input  
Controls the high frequencies of the guitar tone,  
making your guitar sound brighter when increased.  
Connects unit to power supply.  
6. Mains fuse  
7. Volume I  
See label for correct value.  
Controls the overall output level of channel 1.  
Note - this channel is voiced for a higher treble  
response than channel 2.  
8. Volume II  
Controls the overall output level of channel 2.  
Note - channel 2 is voiced for normal response.  
9. Input Jack  
Connects the guitar to channel 1.  
9
11  
JTM45 O/S Front Panel  
1
2
3
4
5
6
7
8
10  
12  
JTM45 O/S Rear Panel  
1
2
3
4
5
6
Marshall Amplification plc  
Marshall Amplification plc  
Denbigh Road, Bletchley,  
Denbigh Road, Bletchley,  
Milton Keynes, MK1 1DQ  
Milton Keynes, MK1 1DQ  
England  
England  
Tel: (01908) 375411  
Tel: (01908) 375411  
Fax: (01908) 376118  
Fax: (01908) 376118  
Whilst the information contained herein is correct at the time of publication; due to our constant improvement and development, Marshall  
Whilst the information contained herein is correct at the time of publication; due to our constant improvement and development, Marshall  
Amplification plc reserve the right to alter specifications without prior notice.  
Amplification plc reserve the right to alter specifications without prior notice.  

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