Valve Power Amps
EL84 20/20,
EL34 50/50
& EL34 100/100
Handbook
1
Marshall Amplification plc
Denbigh Road, Bletchley, Milton Keynes, MK1 1DQ, England
Tel: (01908) 375411
Fax: (01908) 376118
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.
Jan ‘99
Introduction
Models EL84 20/20, EL34 50/50 and EL34 100/100 stereo valve power amplifiers are the latest step forward in valve
rack technology from Marshall. Built as dedicated guitar system based units, they incorporate many features that are
both revolutionary and evolutionary. From stunning styling, through to the radical circuit design, these power amps are
in a sonic class of their own.
EL84 20/20
The EL84 20/20 is the latest all valve power amp from Marshall and utilises EL84 power valves to obtain that classic
british tone, famous since the birth of British rock guitar in the early sixties. Despite its compact size and modest power
rating, the 20/20 packs a big punch, both sonically and in terms of features. Carefully designed to maximise clean
headroom and also endowed with superb overload capability, the 20/20 is ideal for compact rack rigs, for both sessions
and club gigs alike. When miked up on larger concert stages it will provide pure valve tone with the minimum of stage
spill.
The remotely switchable deep switch can be used to alter the sonic character of your pre-amp patches to great effect.
Also the innovative valve line stage, at the input of each channel, helps to give true valve warmth to even the most sterile
sounding pre-amp. The EL84 20/20 is a compact powerhouse which can greatly enhance the tonal palette of any rack rig.
EL34 50/50 & EL34 100/100
With the EL34 50/50 and EL34 100/100 the specially designed Marshall ‘Gold’ front panel provides a deep recess in
which the controls are sited giving a smooth uncluttered finish, whilst allowing the controls to be set, with little fear of
accidental re-adjustment. The two power amp halves of your EL34 50/50 or EL34 100/100 are totally separate
‘MonoBlocs’, a feature that is normally only found on expensive valve hi-fi power amps. This means that the only
common electrical item (apart from when specifically cross linking inputs) is the mains supply and that nothing that
occurs to one power amp can sonically react with the other half. Also in the unlikely event of one side breaking down,
the other side will carry on working regardless.
Our constant research into valve amplifier technology has resulted in further circuit design improvements which
dramatically affect the overall feel and playing response of your Marshall valve power amp. These improvements
include Marshalls latest True Differential Inverter technology, which expands the capability of the phase splitter
(inverter). Put simply, the phase splitter takes the incoming signal and inverts half of it. This inverted half of the signal
forms the bottom half of the sound envelope and the non-inverted half forms the top half. The effect of T.D.I. technology
is to give a more defined spectrum of sound over a broader band width, without compromising the overdrive and
compression effects for which valve amplifiers are famed. This also allows more radical uses of feedback networks and
the incorporation of the ‘voicing’ switching found on each channel. These incredible ‘voicing’ options, which can be
remotely activated, can be used to greatly expand your pre-amps tone forming at the flick of a switch.
Mounting the Power Amp in a Rack
To allow the secure fastening of 19 inch rack units in a rack enclosure, a series of mounting holes are provided on the
front of the EL84 20/20 and on both the front and rear of the EL34 50/50 and EL34 100/100. As with all rack mount
products of substantial weight, such as the EL34 50/50 & 100/100, the rear of the unit must be supported as well as the
front, therefore suitable brackets should be obtained and fitted between the provided rear mountings and the rack case. It
should always be remembered that valve amplifiers generate a certain amount of heat, therefore they should never be
mounted, or used, in any situation without adequate airflow.
2
WARNING!
PLEASE READ THE FOLLOWING LIST CAREFULLY
A. ALWAYS fit a good quality mains plug conforming to the latest B.S.I. standards where necessary (UK only).
B. NEVER attempt to by-pass 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. WARNING: When fitted into a standard rack or flight case, ALWAYS ensure that the front and back of the
case are completely removed. For stand alone use, a clearance of 30cm is required at the top, back and sides.
J. PLEASE read this instruction manual carefully before switching on.
WARNING : This apparatus must be earthed.
1. Mains Input
Connects the amplifier to the mains
power supply.
Left Outputs
2. 16 Ohm Jack
Speaker jack for 16 Ohm speaker
cabinet for left side of power amp.
3. 8 Ohm Jack
Speaker jack for 8 Ohm speaker
cabinet for left side of power amp.
4. Line
Attenuated version of speaker signal giving
whole tone of power stage. For connection to subsequent
effects processor and larger power amp.
Note:
When 20/20 is in use, speakers must be connected
to both sides at all times. See Loading points later.
Right Outputs
5. 16 Ohm Jack
Speaker jack for 16 Ohm speaker
cabinet for right side of power amp.
6. 8 Ohm Jack
Speaker jack for 8 Ohm speaker cabinet
for right side of power amp.
7. Line
Attenuated version of speaker signal giving
whole tone of power stage. For connection to subsequent
effects processor and larger power amp.
Note:
When the 20/20 is in use, speakers must be
connected to both sides at all times. See Loading points
Loading Points
-The 20/20 delivers 2x20 Watts into 8 or 16 Ohms.
-The 20/20 must have either an 8 Ohm or 16 Ohm
speaker connected to either side. Under no circumstances
should both the 8 and 16 Ohm sockets of the same side be
used together.
-The 20/20 must have speakers connected to both sides
when in use.
Remote Switching
8. Deep
In addition to the front panel, the Deep facility
can be switched remotely by a footswitch or
programmable device, such as an effects processor.
It should be noted that this will override the front panel
switch position.
Inputs
9. Left
Takes the left input from a stereo pre-amp.
10. Right (Mono)
Takes the right input from a stereo
pre-amp, or the mono input from a mono pre-amp.
A mono input will drive both channels.
1. Level
Controls Level or volume of the EL84 20/20.
2. Presence
Adds brightness and top end bite to your
sound.
3. Deep
The Deep switch on the 20/20 affects the
speaker damping. By depressing the Deep switch you will
add more bottom end thud to your guitar sound. Similar to
the difference between open and closed back cabinets.
4. Standby LED
Indicates operating status of standby
(see 6).
5. Power LED
Indicates operating status of amp
(see 7).
6. Standby
Controls the H.T. supply to the valves and
allows the valves to remain heated when not in use.
7. Power
On/Off Switch for mains power to the
amplifier.
Note:
To prolong the life of the valves it is always
advisable to switch on the Mains Power Switch (item 7)
about 1 minute before switching on the Standby (item 6).
This allows the valves to heat up to full working
temperature before use.
On switching off, the Standby should always be
switched before the Power Switch.
The standby facility is particularly useful live, where
before playing and between sets, it allows you to keep the
valves operating at a slightly reduced temperature but
without any sound being produced.
3
STANDBY
POWER
OFF
ON
OFF
DEEP
010
010
STANDBY
POWER
EL84 20/20
STEREO VALVE POWER AMPLIFIER
ON
LEVEL
PRESENCE
INPUTS
RIGHT OUTPUTS
LEFT OUTPUTS
16Ω SPEAKER 8Ω
16Ω SPEAKER 8Ω
LEFT RIGHT(MONO)
LINE
120V ~ 60Hz
220 WATTS
MAINS INPUT
REMOTE SWITCHING
LINE
DEEP
2x20 Watts RMS
POWER OUTPUT
INTO 8/16
Ω
1 2 3 4 5 6 7
EL84 20/20 Front Panel Features
EL84 20/20 Rear Panel Features
1 2 3 4 5 6 7 8 9
10
1. Channel A mains power rocker switch
Connects channel A to incoming mains supply.
LED 3 indicates red when activated.
2. Channel A standby switch
Connects channel A's
high voltage circuit to the power supply.
LED 4 indicates green when activated.
Note!
To conserve valve life, standby switch 2 should
remain off for at least 1 minute after powering up the
amplifier.
3/4. Mains & standby LED's.
5. Voice B LED
Indicates red when channel A's voicing
option B is activated.
6. Channel A voice toggle switch
Selects voice
option A or B, this function is repeated on a remote
switching jack on the rear panel (see rear panel
functions). The switch should be in the B position for the
remote switch to be operative.
7. Channel A presence control
Rotary control to
boost the upper mid to high frequency content of sound.
8. Channel A gain control
Rotary control to set and
balance the incoming signal level.
9. Channel B gain control
10. Channel B presence control
11. Channel B voice switch
12. Channel B voice LED
13. Channel B standby LED
14. Channel B mains LED
15. Channel B standby switch
16. Channel B mains switch
Note!
Channel A's notes also apply.
17. Front rack mount fixing holes.
4
A
B
EL34 50/50
Dual MonoBloc Amplifier
1. Mains input socket
Connects amplifier to
incoming mains supply.
2. Channel B mains fuse
Please see specifications for
correct ratings.
3. Channel A mains fuse
Please see specifications for
correct ratings.
4. Channel B H.T. fuse
Please see specifications for
correct ratings.
5. Channel A H.T. fuse
Please see specifications for
correct ratings.
6. Channel B loudspeaker jacks
Connects channel B
to loudspeaker load - model EL34 50/50 - 50 watts RMS,
model EL34 100/100 - 100 watts RMS.
EL34 50/50 & EL34 100/100 Front Panel Features
1 2
3 5 6 7 8 9
10 11
4
12 14 15 16
17
13
Rear Panel Features
MAINS INPUT
120V ~ 60Hz
350 VA
HT FUSE
T315mA
CH B CH A
CH B
LOUDSPEAKER
OUTPUT
CH A
LOUDSPEAKER
OUTPUT
REMOTE VOICE
SWITCHING
(SHORT TO GROUND) USE 'A'
ONLY TO SWITCH BOTH
CHANNELS
CH B CH A
SIGNAL INPUT
USING INPUT 'A' ONLY GIVES DUAL MONO OPERATION (A+B)
WARNING OUTPUT A & B MUST HAVE INDIVIDUAL LOADS IN THIS MODE
CH B CH A
LINK INPUT INPUT LINK
OUTPUT
SELECT Ω
16 8
OUTPUT
SELECT Ω
16 8
WARNING! No user serviceable parts
inside; refer servicing to qualified
personnel only.
AVIS! Risque de choc. Ne pas ouvrir.
WARNING! Fire & Shock Hazard: Do not
expose this unit to rain or moisture. This
Apparatus Must Be Earthed. Do not open
Made in England by:
Marshall Amplification plc, Bletchley, Milton Keynes.
DO NOT USE WITHOUT CONNECTING SPEAKER LOAD SEE MANUAL FOR CORRECT OPERATION AND RATING
EL3450/50
MAINS FUSE
115 V- T3. 15A
230V -T1.6A
CH B CH A
1 2 3 4 5 6 7 8 9
10 11 12 13 14 15
7. Channel B output impedance select 16 Ohm or
8 Ohm - it is important that your amplifier and loudspeaker
load are correctly matched.
Note!
If 4 Ohm output is desired please consult your
authorised Marshall agent.
8. Channel A output impedance select
(See 7 for notes).
9. Channel A loudspeaker jacks
(See 6 for notes).
10,11. Remote voicing switching jacks
10 operates on channel B, 11 operates on channel A.
Short to ground function. Using jack 11 only links
channel A & B switching functions for simultaneous use.
12. Channel B link out jack
Connects channel B
input signal to further power amp inputs.
13. Channel B input jack
Accepts input from pre-
amp.
14. Channel A input jack
Accepts input from pre-
amp.
Note!
Using 14 only connects input signal to both
channels A & B for parallel mono operation.
15. Channel A link out jack
Connects channel A
input signal to further power amp inputs.
Valve Location Guide
5
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Rear Mounting Fixing Hole
FRONT
OUTPUT
TRANSFORMER
OUTPUT
TRANSFORMER
EL34
EL34
EL34 EL34
EL34EL34EL34EL34
Rear Mounting Fixing Hole
ECC81
12AT7
ECC83
12AX7
ECC83
12AX7
ECC81
12AT7
Not Fitted To EL34 50/50
MAINS
TRANSFORMER
MAINS
TRANSFORMER
Parameter EL34 50/50 EL34 100/100 Notes
Size 19" 3U x 331mm deep 19" 3U x 331mm deep The unit must be supported at
the rear when mounted in a rack
Weight 29.5 kg 34.5 kg
Power input 350 watts 700 watts
Voltage Input 115V or 230V 115V or 230V Consult amp rating plate or dealer
Frequency 50 or 60 Hz 50 or 60 Hz Consult amp rating plate or dealer
Mains fuses T3.15A/115V T4A/115V Per channel
T1.6A/230V T2A/230V Per channel
H.T. Fuses T315 mA T1A Per channel
Output Power 50W RMS 100W RMS At clipping (per channel)
Output Impedance 8 or 16 Ohm* 8 or 16 Ohm* Consult dealer for 4 Ohm
Input sensitivity OdB OdB
Input impedance 20KΩ 20KΩ
Output valve 2 x EL34 4 x EL34 Per channel
Phase inverter 1 x ECC81/12 AT7 1 x ECC81/12 AT7 Per channel
Pre Driver 1 x ECC83/12 AX7 1 x ECC83/12 AX7 Per channel
Specification Chart
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