Marshall
25/50 CUSTOM SERIES
HANDBOOK
Marshall
Jim Marshall (Products) Limited, Denbigh Road, Bletchley, Milton Keynes MK1 1DQ.
Telephone; Milton Keynes (0908) 75411. Telex; 826483 MARAMP-G.
Introduction
Iwould like to thank you personally for selecting onc of our
amplifiers.
50 years ago in 1937, [first began my career in the music
business as a singer and then # drummer with dance bards.
Since that time 1 have been involved with many professional
and semi-professional musicians worldwide, Indeed, the first
Marshall amps were produced 25 vears ago in 1962, to cater
directly for the demands of the leading musicians of that time. ]
have continued looking after the guitarists’ needs ever since.
The roots und development of the “Custom Series” can be
traced back to the very beginning of Marshall providing the
quality and reliability always associated with the name,
However, these units have been uprated in some very special
ways to make them a truly outstanding scrics, incorporating
the versatility and sound quality expected by even the most
demanding modern guitarists.
Thanks are due to the veritable army of musicians who, by
their appreciation of, and skill in using Marshall Amplitiers
over the years, have helped us to create the Custom Series
amplifiers.
Please be sure to return your registration card so that we may
enter your name in our roster of Marshall users.
Again, thank you sincerely.
Marshall 25/50 Custom Series Handbook
Custom Series models avallabic are:—
2555 iaa 50/100 watt valve head
2550 Lo... LL. 25/50 watt valve head
2553 LL... LL. 25/50 watt mini-stack size valve head
2554 e. 25/50 watt 1 x 12 valve combo
2558 ee. 25/50 watt 2 x 12 valve combo
Front Panel Functions for Models 2555, 2550, 2553, 2554, 2558
| 00С ТОТ
12 11110 9 8 7 6 543 2 1
2554, 2558
TITS _ 5
on 1
|. Input Jack: Connects instrument to amplifier.
2. Input Gain Adjusts the overall sensitivity of the input circuit. Controls the amount of drive
Control required for different types of distortion, {plus the level of the clean rhythm sound).
(+ Pull The pull switch activates the rhythm clip made, providing more heavily distorted
Rhythm Clip) rhythm sounds. N.B. The apparent drop in volume when the rhythm clip mode is
selected may be overcome by increasing the output master level (No. 5) accordingly.
Cu
3. Lead Master
4. Lead Channel
L.E.D::
5. Output
Master
Control:
(+ Lead
Channel
Pull-Switch)
6. Treble
Control:
7. Middle
Control:
Adjusts the output level of the
supercharged lead channel
against the rhythm channel
when selected via the
footswitch. M.B. The lead
channel may also be activated
by the “pultswitch” on output
master control (No. 5). (This
selection would then override
the normal channel.)
Indicates red when lead
channel is selected.
Adjusts the output of the pre-
amp section to the power
amplifier and hence controls
the overall volume of the
whole amplifier. The pull
switch activates the lead
master section, allowing full
use of channel swilching
facilities without connecting the
footswitch. N.B. It must be
remembered that both pull
switches are not independent
and that one will override the
other depending on switch
position.
Adjusts the amount of upper
harmonics in the sound
content.
Adjusts the mid-range
frequencies in the sound
content. High settings will
provide a fatter sound by
boosting the middle. Lower
settings cut the lower mid,
range providing a hollow sound
and giving more sound
spectrum for the treble and
bass controls to work on.
8. Bass Control:
9, Presence
Control;
10. Output Power
Switch:
11. Standby
Switch:
12. Power Switch:
Adjusts the low frequency
content of the sound. N.B.
Too much bass can make the
guitar sound muddy at high
volume levels.
Adjusts the amount of upper
mid range boost and sets the
‘brightness’ of the whole
amplifier in conjunction with
the treble control, (No. 6).
switches the amp from high to
low power output. The low
setting configures the output
stage in ‘triode connection, to
give half the rated amplifier
output, i.c. 30 watts from 100
watt model and 25 watts from
50 watt models. The high
power position is connected in
the normal “pentode”
configuration and gives the ful]
rated output.
Allows the amplifier to be
turned off whilst the tube
filaments remain warm thus
keeping the amp constantly
ready for use. (It is
recommended that the standby
switch 1s left off for a few
seconds when the amplifier is
initially switched on).
Connects mains power to the
amplifier indicating red when
on, N,B. Output and mains
should he checked before
switching on the amp. On no
account must the unit be
turned on without the output
properly connected to a
suitable loudspeaker system, as
serious damage may ensue.
Rear Panel Functions for Models 2555, 2550, 2553, 2554, 2558
2555
9996699 OO [100
3 14 15 16 17 В 19 20 2] 2 2
13. Footswitch Comnects remote footswitch to 19. Output Matches amplifier output to
Jack Socket: channel switching circuits. Impedance loudspeaker load impedance.
Selector: (Speaker impedance is usually
14. Effects Send Connects amplifier circuit to marked on cabinet, if in doubt,
Jack: input of external effects check with supplier).
system. (Approximately
—10dBM level). 20. Mams Matches amplifier power
Voltage supply to correct incoming
15, Effects Return Connects amplifier to output of Selector: mains voltage.
Jack: external effects.
21. Mains Input: Connects amplifier to power
16. D.I Jack: Frequency compensated line supply.
level for feeding directly into
slave amplifiers or mixing 22. Mains Fuse: — For 110v/120v. supply, 1se
desks. 4A slow blow fuse only,
| For 220v/240v. supply, use
17/ Loudspeaker Parallel connected loudspeaker 2A slow blow fuse only.
18. Output Jacks: output jacks, (total loudspeaker
load must be matched to 23. HT. Fuse: Replace with a 1A slow blow
amplifier). 250v. fuse only.
2550, 2553
099099 00 90
13 148 15 16 17 18 19 20 1 2 2
[09700909900
13. Footswitch Connects remote footswitch to
Jack Socket: — channel switching circuit,
14. Effects Connects amplifier circuit to
Send Jack: input of external effects system
{approximately —10dBM Jevel).
15. Effects Connects amplifier to output of
Return Jack: external effects.
A frequency compensated line
t6. D.L Jack:
into slave amplificrs or mixing
desks.
17/ Loudspeaker
load must be matched to
amplifier).
Operational Functions
Connect the amplifier to the power supply using
the mains lead provided. Before switching on
check that speakers are connected (sockets 17 &
18), that impedance is correctly set (item 19), and
that mains supply is correctly selected (item 20}.
Switch on mains switch (item 12) first, followed
by standby switch (number 11) a few seconds
later, after allowing the valves to warm up, Turn
all front panel controls to zero and plug the guitar
into input (number 1).
The rhythm sound should be selected using the
input gain control (number 2} in conjunction with
output master control (number 5). For clean
sounds the output master (number 5) should be
set high and the input gain (number 2) set low.
For distorted sound the reverse applies, i.e. input
gain set high and output master set low. Extra
distortion may be introduced using the ‘rhythm
clip’ pull switch incorporated in control number 2.
N.B. The selection of the rhythm clip mode
appears to reduce the volume slightly, therefore
some adjustment to the output master may be
necessary.
level output for feeding directly
Parallel connected loudspeaker
18. Output Jacks: output jacks, (total loudspeaker
с,
19. Output Matches amplificr output to
Impedance loudspeaker load. {Speaker
Selector: impedance is usually marked
on cabinet, if in doubt check
with supplier).
20. Mains Matches amplificr power
Voltage supply to correct Incoming
Selector: mains voltage,
21. H.T. Fuse; Replace with S00mA slow
blow 250v. fuse only.
22. Mains Fuse: — For 110v/120v, supply use
3A slow blow fuse only.
For 220v/240v. supply use
2A slow blow fuse only,
23. Mains Input:
power supply,
The lead sound may be introduced either by
footswitch or by pulling the output master control
(number 3). Selection of the lead section overrides
the rhythm channel, therefore it is advisable to sel
the balance between the twa sections before
playing.
The level of lead distortion can be adjusted using
the lead master control (number 3) in conjunction
with the output master control (number 5) —
The tone and presence controls should be used to
create the type of sound required, experimentation
being the best process.
Finally, the output switch (number 10) may be
utilized to increase or decrease the output power
level as required.
Connects amplificr to incoming
\ VARNING PLEASE READ TH E FOLLOWING LIST CARE FULLY
С.
ALWAYS fit a good quality mains plug, G. ALWAYS have this equipment serviced or
conforming to the latest B.S.IL standards.
repaired by competent qualified personnel.
ALWAYS wire the plug according to the H. NEVER use an amplifier in damp or wet
colour code attached to the mains lead.
NEVER, under any circumstances, operate 1.
the amplifier without an earth.
NEVER attempt to bypass the fuses or fit
ones of the incorrect value.
NEVER attempt to replace fuses or valves
conditions.
DO NOT switch the amplifier on without the
loudspeaker connected, and ensure that the
impedance selector 15 correctly matched to
the speaker or speakers.
J. PLEASE READ this instruction manual
carefully before switching on.
with the amplifier connected to the mains.
DO NOT attempt to remove the amplifier
chassis, there are no user serviceable parts.
ALWAYS ENSURE THAT MARSHALL APPROVED COMPONENTS ARE USED AS REPLACEMENTS
Amplifier Cabinet Set-Ups
Amphifier Impedance
Amplifier Cabinet Settings
1x1960A 16 ohms
2250,2555 1x 1960A & 1 x 1960B 8 ohms
1х 1960 АУ 8 ohms
1 x 1960AV & 1 x 1960BV 4 ohms
1х 1966 А 8 ohms
2553 1x 1966A & 1x 1966B 4 ohms
1x 1966AV $ ohms
1x1966AV & 1 x 1966BV + ohms
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