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JCM900
SL-X 2100 & SL-X 2500
Master Volume Models
&
4100, 4500, 4101, 4102, 4501 & 4502
Dual Reverb Models
Denbigh Road, Bletchley, Milton Keynes, MK1 1DQ, England
Web Site - http://www.marshallamps.com
Whilst the information contained herein is correct at the time of publication,
due to our policy of constant improvement and development, Marshall
Amplification plc reserve the right to alter specifications without prior notice.
Marshall Amplification plc
Tel: (01908) 375411
Fax: (01908) 376118
Nov ‘98
Handbook
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VALVE
SERIES
INTRODUCTION
WARNING!
PLEASE READ THE FOLLOWING LIST CAREFULLY
A. ALWAYS fit a good quality mains plug conforming to the latest B.S.I.
standards (UK only).
B. ALWAYS wire the plug in accordance with the colour code attached to
the mains lead (UK only).
C. DO NOT attempt to remove the amplifier chassis. There are no user
serviceable parts inside.
D. ALWAYS have this equipment serviced or repaired by competent,
qualified personnel.
E. NEVER under any circumstances, operate the amplifier without an earth.
F. NEVER use any amplifier in damp or wet conditions.
G. ALWAYS ensure that the impedance of the amplifiers speaker or
speakers connected does not fall below the minimum impedance rating.
I. PLEASE READ this instruction manual carefully before switching on.
Marshall have specialised in the production of valve amplification
since 1962.
The unique tone and playing response of the valve has formed the
cornerstone of the Marshall “Sound of Rock”, which we have
modified over the years to cope with the changing demands of the
evolving guitar player.
The JCM 900 models split into two distinct product ranges, the
Master Volume SL-X and the Dual Reverb. Though they share
common ancestry and have similar rear panel functions their
applications are quite different.
JCM 900
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HI GAIN MASTER VOLUME SL-X
The latest innovation from our valve designers involves the use of an extra ECC83 pre-amp valve in the gain
stage of the Master Volume SL-X models.
This gives a gain soaked front end that is the most extreme yet produced by Marshall and is controlled by twin
gain controls, the first (item 2), from 0-10, the second (item 3), from 10-20! Combinations of these two
controls can take you from classic Marshall crunch in lower positions, to pure overdriven outrage on
maximum. It is well worth experimenting with these twin gains in conjunction with the tone network (items
6-9) to really get to know the full capability of your new SL-X head.
The twin Master Volumes (items 4 & 5) are another unique feature of the SL-X amp giving you two
footswitchable output volume levels, ideal for rhythm to solo switching.
Although a clean sound is available, this amp was designed for the uncompromising high gain player who
demands a no compromise sound.
HI GAIN DUAL REVERB
The Dual Reverb range was designed for versatility with two independently controlled footswitchable
channels, each voiced totally differently.
Channel A is voiced for brilliant clean tones with the gain control (item 2) on lower settings and crunch to
lower gain lead as you turn it up.
Channel B is boosted with enough gain (item 3), for fearsome lead tones, ranging from classic on lower
settings to contemporary screaming solos on maximum.
Channel master volumes (items 9 & 11) and individual channel reverb controls (items 8 & 10) give you
incredible control and all round versatility in either, head or combo form.
VALVE OUTPUT POWER
The JCM 900 range use high quality 5881 output valves (x2 in 50 Watt models, x4 in 100 Watt models) for
their unique distortion properties and fluid tone.
With most valve amplifiers, particularly Marshalls', the best sounds are achieved when the Master Volumes
are set high enough to be utilising the driving power of the output valves to the full.
This delicate working balance between the pre-amp and power amp levels can only be achieved by
experimentation.
You will find that all the JCM 900 models like to work hard and are designed to withstand prolonged use at
full power quite readily. The PB100 Power attenuator is ideal for this use (connects between amp and
cabinets) as it will allow you to run your amp at full power but keep the overall volume low.
The important thing to remember here is that it is the interaction between all the controls that plays a part in
achieving your sound.
HI GAIN MASTER VOLUME 900 SL-X
FRONT PANEL FUNCTIONS
Models 2100 & 2500
1. Input Jack
Connects the instrument to the amplifier. (A high quality screened lead must be used).
2. Pre-Amp Volume Control
Sets the initial gain level of the pre-amp section (0-10). Lower settings for clean sounds - higher settings for
crunch and overdrive.
3. Gain Sensitivity Control
Sets the secondary gain level of the pre-amp section (10-20).
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NOTE:
Combinations of the two gain controls (items 2 and 3) provide a wide range of clean, crunch and overdrive
possibilities. Experimentation will reveal the optimum settings for each.
4 & 5. Master Volume “A” Master Volume “B”
Twin footswitchable Master Volume Controls. Master “B” controls the overall volume exclusively when a
footswitch is not connected. The connection of footswitch P801 allows switching between Master “A” or “B”
giving independent volume levels for rhythm and solo playing.
6,7,8 & 9. Treble, Middle, Bass & Presence
Passive equalisation circuit. These controls are interactive to provide the maximum range of tonal variation.
10. Master Volume B “ON” LED Indicator
Indicates red when Master Volume “B” is selected.
11. Footswitch Jack Socket
Input for the connection of remote footswitch (model P801).
12. Standby Switch
Controls the H.T. supply to the amplifier valves. Allows the filaments to remain heated during breaks.
13. Power Switch
On/Off switch for total mains power to the amplifier.
HI GAIN DUAL REVERB
FRONT PANEL FUNCTIONS
Models 4100, 4101, 4102, 4500, 4501 & 4502
1. Input Jack
Connects the instrument to the amplifier. (A high quality screened lead must be used).
2. Channel “A” Pre-Amp Gain Control
Sets the gain level for channel “A”. Lower settings give clean sounds - higher settings for medium drive and
crunch rhythm.
3. Channel “B” Lead Gain Control
Sets the gain level for boosted Channel B. Lower settings give slight overdrive - higher settings for maximum
drive and sustain.
4,5,6 & 7. Treble, Middle, Bass & Presence
Passive rotary equalisation circuit. These interactive controls provide a wide range of tonal possibilities for
both channels.
8. Reverb Control Channel A
Controls the amount of reverb on Channel “A”.
9. Master Volume Channel A
Controls the overall volume level of Channel “A”.
10. Reverb Control Channel B
Controls the amount of reverb on Channel “B”.
11. Master Volume Channel B
Controls the overall volume level of Channel “B”.
12. Channel B ‘ON’ Push Switch/LED
Indicates red when Channel “B” is selected either manually or by remote footswitch (models P802).
13. Footswitch Jack Socket
Connects the remote dual footswitch (models P802) for reverb ON/OFF and Channel A/B switching.
14. Standby Switch
Allows the amplifier to remain at “standby” (i.e. the valve heaters remain on, ready for instant use, but
without the signal circuit being active).
15. Power Switch
On/Off switch for total mains power to the amplifier.
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REAR PANEL FUNCTIONS
The Hi Gain Master Volume SL-X and Dual
Reverb models feature comprehensive connection
and control facilities on the rear panel which are
common to both ranges.
50 Watt Models 2500, 4500,
4501 & 4502
1. Effects Loop Level Control
Adjusts the level of the effects loop from -10dBV
to + 4dBm. Higher settings match modern effects
processors and lower settings match floor pedals.
NOTE:
Some effects such as distortion and compression
are best suited to connection via the front panel
input as opposed to the loop.
2. Effects Send Socket
Jack socket for connection to the input of external
effects processor.
3. Effects Return Socket
Jack socket for the connection from the output of
external effects processor.
4. Recording Compensated Line-Out
Socket
Jack socket for direct connection to recording
equipment or PA system. The signal is specially
filtered for optimum recording performance.
5. Direct Line-Out Socket
Unfiltered pre-amp signal for connection to
external power amplifiers.
6. Impedance Selector Switch
Two-way switch for matching the amplifier to
speaker impedance. Amp heads feature 8 or 16
Ohm operation. Combo versions feature 4 or 8
Ohm options.
7. Loudspeaker Output Jack Sockets
Parallel wired jacks for linking speaker cabinets.
Ensure that the speaker system is easily capable of
handling the full amplifier power and that the
impedance (item 6) is correctly selected. If in doubt
consult your dealer.
8. Output Mode Switch
Switches the amplifier from high to low power
output. The “low” setting configures the output
stage to “triode” operation, which gives half the
rated output (i.e. 25 Watts on 50 Watts models - or
50 Watts on 100 Watt models). The “high” power
position gives “pentode” operation for the full
rated output.
9. Valve Failure L.E.D.
Indicates red when output valve fails and causes
valve fuse (item 10) to operate.
10. Valve Failure Fuse
Operates in the event of an output valve failure and
prevents any internal damage to the amplifier.
NOTE:
On 50 Watt models items 11 & 12 DO NOT
appear.
13. Mains Power Input
Connects the amplifier to the mains power supply.
NOTE:
Always ensure that the incoming mains voltage
matches that of the amplifier. If in doubt consult
your Marshall dealer.
14. Mains Power Fuse
Protects the amplifier and mains supply in the
event of a fault.
NOTE:
Always ensure that the fuse value matches the
labelling on the amplifier rear panel. If in doubt
consult your dealer.
REAR PANEL FUNCTIONS
100 Watt models 2100, 4100,
4101 & 4102
Items 1 to 8 follow the same format as the 50 Watt
models.
9 & 10. Valve Failure LED (OPV1-OPV4)
Valve Fuse (OPV1-OPV4)
In the case of output valve failure (OPV1-OPV4),
the fuse (item 10) will operate and illuminate LED
(item 9). The amplifier will continue to function on
reduced power (Using OPV2-OPV3 Only). Service
should be obtained as soon as possible to prevent
the premature ageing of (OPV2-OPV3).
11 & 12. Valve Failure LED (OPV2-OPV3)
Valve Fuse (OPV2-OPV3)
Similar functions to items (10) and (11) but
operating on OPV2 and OPV3.
13. Mains Power Input
Connects the amplifier to the mains power supply.
NOTE:
Always ensure that the incoming mains voltage
matches that of the amplifier. If in doubt consult
your Marshall dealer.
14. Mains Power Fuse
Protects the amplifier and mains supply in the
event of a fault.
NOTE:
Always ensure that the fuse value matches the
labelling on the amplifier rear panel. If in doubt
consult your dealer.
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0
1
POWER STANDBY
JCM900
SL-X
100W Hi Gain Master Volume
MASTER (B)
FOOTSWITCH
JCM 900 SL-X HI GAIN MASTER VOLUME
MASTER GAIN PREAMP
4 6
2
0 10
PRESENCE BASS MIDDLE TREBLE VOLUME (B) VOLUME (A) SENSITIVITY VOLUME
4 6
8 2
2
0 10
8
4 6
0 10
8 2
4 6
0 10
8 2
4 6
0 10
8 2
4 6
0 10
8 12
14 16
10 20
4 6
18 2
0 10
FRONT PANEL
8
INPUT
Model 2100 SL-X
13 12
Manufactured in Great Britain by:
Marshall Amplification plc,
Bletchley, Milton Keynes.
POWER STANDBY
11 10
9 8
7
6
5
4
3
2 1
JCM 900 SL-X HI GAIN MASTER VOLUME
& DUAL REVERB REAR PANEL
NOTE: On Combo models the rear panel is reversed
HIGH LOW
LOOP
LEVEL
1
EFFECTS
SEND RETURN RECORDING
COMPENSATED
LINE OUTPUT
DIRECT
POWER LEVEL OUTPUT
LOUDSPEAKERS
IMPEDANCE
SELECT
(4) 16 8 HIGH LOW
DO NOT USE WITHOUT CONNECTING SPEAKER LOAD
SEE MANUAL FOR CORRECT OPERATION AND RATING
100W R. M. S.
765432
MODE
8
T500mA T500mA
FAIL
OPV-1-4 OPV-2-3
9 10 11 12
OUTPUT
VALVE
FUSE
MAINS INPUT
240V~50/60-Hz
375 Watts
13
FUSE
220/240V-T2A
110/120V-T4A
14
Where applicable, This Apparatus Must Be Earthed
WARNING! No user serviceable parts inside; refer servicing to qualified
personnel only.
WARNING! Risk of shock. Do not open
AVIS! Risque de choc. Ne pas ouvrir.
Fire & Shock Hazard: Do not expose this unit to rain or moisture.
HI GAIN DUAL REVERB
FRONT PANEL
NOTE: On Combo models the front panel is reversed
MASTER
PUSH ON
FOOT
SWITCH
(CH. B)
0
1
JCM900
100W Hi Gain Dual Reverb
(CH. B)
4 6
2
0 10
VOLUME REVERB VOLUME REVERB PRESENCE BASS MIDDLE TREBLE LEAD GAIN GAIN
8
4 6
2
0 10
8 2
4 6
0 10
MASTER
(CH. A)
8 2
4 6
0 10
8 2
4 6
0 10
8 2
4 6
0 10
8 2
4 6
0 10
8 2
4 6
0 10
8 4
PREAMP
(CH. B)
8 12
0 20
16 2
PREAMP
(CH. A)
4 6
0 10
8
INPUT
Model 4100
15
14
13 12 11
10
9
8
7
654321
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