OF EARLY MARSHALL AMPLIFIERS
1963-1973 MARSHALL HANDWIRED AMPLIFIERS
This article focuses on
the early generation Marshall amplifiers, which were offered during 1963 to 1973. For the purpose of this article, the
1963-1973 handwired amplifiers are categorized into
1963 to 1964 Metal Paneled
1965 to mid-1969 Plexiglass
mid-1969 to mid-1973 Metal Paneled
from this period were known for their simplicity in design and awesome
tone. Many of the pre-plexi and plexi Marshall amplifiers
have become collector items and are quite valuable now.
Marshall amplifiers during this period had
similar uncluttered control layouts. They were simple straight forward
amplifiers. Features such as an effect
loop or a master volume control was not offered. A few models would later be offered with
Tremolo as an option. Reverb was even a
rarer option. The early generation Marshall
amplifiers consisted of a simple circuit design that
allowed the amp to provide a raw natural tone.
The smooth distortion, generated mostly from the power amp tube section,
had plenty of overtones and harmonics.
Many modern amplifiers generate a good portion of their distortion from
multiple preamp gain stages, which can sound “buzzy”
and reduces the “touch” response of the amplifier. The extra “bells and whistles” found on some
amplifiers, requires extra circuitry and wiring (or additional circuit board
trace lengths) that increases signal loss, which often has a negative effect on
the overall tone.
Marshall amplifiers referred to in
this article are the original vintage handwired
1963-1973 Marshall amplifiers and
with highlights of Marshall’s more recent reissue handwired products.
YEARS OF MARSHALL AMPLIFIERS
1963-1964 METAL PANELED (Pre-Plexi)
1962, Jim Marshall along with Ken Bran began their work on the first Marshall amplifier. The
prototype units became known as the MK I,
with subsequent production models labeled as MK II along with the JTM 45 markings. The JTM
acronym represents Jim & Terry Marshall. The JTM 45 amplifier circuitry was a close
copy to the popular 1959 Fender Tweed Bassman 5F6A circuit, and today, both the JTM 45 and the 1959 Fender Bassman are legendary amplifiers,
each providing their own unique tone. The
JTM amplifier was Marshall’s
response to the Fender Bassman. At that
time, the Bassman
was quite expensive in England, since the Bassman was imported from the US
to the UK. Back in those days, Jim Marshall wouldn’t have known the JTM would become an all time favorite
blues and classic rock amplifier.
In 1964 Marshall began production of the amplifiers in the back of his shop.
Prior to that in 1963, only a few amplifiers were produced and these few were not made in a formal workshop.
The initial amplifiers had the chassis offset to one side and the entire front panel was covered with an off white grill cloth (Vynair).
This was followed by a center mounted chassis, with
a front panel that was covered completely with the off white grill cloth.
Then a cabinet, also with the center mounted chassis, but the
front panel had a smooth black material (Rexene) on the upper portion and the off white grill cloth on the bottom portion, which is known as the "Sandwich Paneled" cabinet.
The 1963-64 Marshall amplifiers had
aluminum metal front and back face panels, along with a Marshall "coffin" logo.
The panels were finished in natural aluminum with silk screened lettering or white engraved (Traffolyte) ply-panel. While these amplifiers were referred to as JTM, the prototypes and early product
models did not have any model designations or markings on their front
panels. Later production units would
have the MKII and JTM 45 markings on the front aluminum
The earlier amplifiers were equiped with a pair of 6L6 power tubes, followed by 5881 and KT66 power tubes.
Initially, the amplifiers were
sold only as head cabinets, with optional matching speaker cabinets sold
separately. By late 1964, Marshall
offered their first combo amplifiers.
the first generation Marshall
Amplifiers evolved, component and cosmetic changes often took place; therefore
there are a few different variations of these early amplifiers. Additionally, the component and/or design
changes did not necessarily take place at the end or beginning of the calendar
Marshall Amplifiers in original condition
are considered highly prized collector items in today’s market.
(PLEXIGLAS PANELED) ERA
with the JTM 45 circuit design, in 1965, Jim Marshall changed the front and back
panels from metal to Plexiglas - hence the name "Plexi". For a short period between mid-1964 and
1965, the JTM was provided with
cream colored front and back Plexiglas panels, followed by a gold plexiglas front panel that
included a cream plexiglas rear panel. Marshall
then settled on gold front and back plexiglas
panels, as the majority of the JTM
amplifiers were equipped in this fashion.
during the Plexi Era:
JTM 45 with a pair of either 6L6, 5881 or KT66 output tubes and a GZ34
JTM 50 with a pair of EL34 output tubes; a few
amplifiers were offered with the GZ34
tube and the majority equipped with a solid state rectifier;
JMP 50 with a pair of EL34 output tubes and with a solid state rectifier.
JTM 45-100, a 100 watt amp,
equipped with four KT66 output
tubes and solid state rectifier
JTM 100/JMP 100
, a 100 watt amp,
tubes and solid state rectifier.
18 Watt with a pair of EL84 output tubes and a EZ81 tube rectifier
20 Watt with a pair of EL84 output tubes and solid state rectifier.
versions of these amplifiers were sold as head cabinet, with a smaller quantity
sold configured as combos. The most
famous combo was the JTM 45 Tremolo 2x12
played by Eric Clapton when he was with John Mayall's
Blues Breaker group; hence, this amplifier is referred to as the "Blues Breaker". During this period, the JTM 45 and JTM 50 were
offered with and without tremolo, in both head and combo versions. The 18w
was available with Tremolo and as a combo version only.
models offered during the 1965-1968 Plexi Era
included the Lead, Bass, Organ, PA (JTM 45 and 50), the Super 100 Amplifier, Superlead, Superbass, Super PA (100
watt), the Marshall Major (200
watt). The electronic component difference between
Lead, Bass and P.A. versions within each series was not major. Often only a few components within the tone
circuitry had different values. Additionally, each model designation was not
limited to one specific use. For
example, Bass and PA models were often also used by guitarists. These models can also be easily converted
from one model type to another, simply by altering a few tone circuit
1965, Marshall introduced the 18 watt combo. The 18
watt was equipped with a pair of EL84
output tubes. While the 18 watt does
not offer the same amount of clean headroom of larger wattage amplifiers, this
particular amplifier was very popular for those wanting the "cranked up
tone" at a lower overall volume level.
The 20 watt head was
introduced in 1967, but has proven to be less popular than the other Marshall
amplifiers built during this era.
1963 until 1967 the Marshall
chassis were built using aluminum. Around the end of 1967 or beginning of
1968, Marshall began using a steel chassis for most models.
JTM45 amplifiers from 1963 up to 1966
were equipped with a GZ34 rectifier
tube. Tube rectified amplifiers will
"sag" when fully cranked up.
This was the result of the rectifier’s internal resistance and the tube
"trying" to quickly provide enough current as required by the
amplifier. Many guitarists like the
"feel" and compression of tube rectified amplifiers, while others
like the faster reacting solid state rectified tube amps.
1965-1968 Plexi Era – Year of Introduction:
1965 JTM 45
Plexiglas paneled - 1962-1964 with metal panels.
Rated between 30 - 45 watts.
GZ34 tube rectifier, (2) 6L6 (KT66/5881) output tubes.
Tube driven Tremolo effect optional.
Offered in both Head and Combo cabinets.
1965 JTM 45-100 (KT66), JTM 100 (EL34)
100 watt rating, solid state rectified, initially (4) KT66 Power tubes,
then in 1966 changed to EL34s.
The 100 watt was available in the new "Large" box head, in order
to provide enough air circulation for the 4 power amplifier tubes.
18 Watt Series
EZ81 tube rectified with (2) EL84 output tubes.
Tube driven Tremolo standard with tube driven Spring Reverb optional.
First Marshall amplifier to have the Reverb option, although it is rare to
find one so equipped. Combo cabinets
offered: 1x12, 2x12 and 2x10. Head
cabinet was not available.
The 18 Watt amplifier was
available only for a short period between mid 1965 until 1967.
Basically a JTM 45 equipped with
EL34 output tubes.
During this period, the GZ34 rectifier tube was being phased out in favor
of the solid state rectifier that provided a different "feel" to the
JTM 50 can be found with either
tube or solid state rectifiers.
Tube driven Tremolo effect optional.
Offered in both Head and Combo cabinets.
1967 Marshall Major (200
Solid state rectified with (4) KT88 output tubes.
1967 20 Watt Series
Solid state rectifier with (2) EL84 output tubes.
Offered as head cabinet only.
Solid state driven Tremolo option; no Reverb option.
1968 JMP (50 and 100)
Marshall changed the model
designations from JTM to JMP.
JMP 50 and JMP 100 were equipped with EL34 output tubes and a solid state
rectifier, and were basically the same amplifiers that would become the JMP metal panel amp which was later
released in 1969.
The 1968 JMP amplifiers had plexiglas panels.
Production of metal panel JMP
amplifiers began mid-1969.*
JMP 50 amplifiers were offered
in both Head and Combo cabinets; tube driven Tremolo effect was optional.
The JMP 100
was only offered in the head cabinet version.
In mid 1971 Marshall began migrating their JMP50 amplifiers from the small box head cabinet to the
larger 100 watt style head cabinets. Marshall deleted the vent screen on the top of the cabinet for the
JMP50 amplifiers. Small box JMP50 amplifiers can be found into 1972, however, the majority
of the late 1971-73 JMP50 amplifiers are the large box versions.
box JMP 50 heads are rarer and
typically more valuable than the large box versions.
this period, Marshall also manufactured
the JTM/JMP style amplifiers under
the Park and Kitchen-Marshall brand names.
In late 1966 through early 1967, the JTM logo on the front plexi panel of the 50 and 100 watt amplifiers had a reverse logo, also known as the Black Flag logo or Black Flag amp.
1965 - mid-1969 Plexi
amplifiers are quite a collector’s item these days and continue to appreciate
THE METAL PANEL, HANDWIRED ERA mid-1969 - 1973 (JMP Models)
mid-year 1969, the gold Plexiglas front and back panels were dropped in favor
of brushed gold aluminum panels; hence the term "Metal Panel" JMP. The electronic circuit design remained close
to the original "Plexi"
circuitry, and the amplifiers continued to be handwired
through the middle of 1973.
offered included the Lead (50 watt),
the Super Lead (100 watt), a Bass Model and PA Model. JMP 50 amplifiers were offered in both
head and combo configurations, with and without Tremolo effect. The JMP
100 amplifiers were available only in the head configuration.
All of the handwired metal panel JMP 100 amplifiers and the majority of
the JMP 50 amplifiers were of the
"large" box variety. In
general, the Marshall amplifiers became "brighter"
sounding through the years. While the JMP 50 watt electronic circuitry was
similar to the JTM 45, the tone was
quite different due; to the tuning of the circuit "brightness", the
use of EL34 power amplifier tubes,
solid state rectifier instead of a tube rectifier, and different electrical
specifications for the both power and output transformers. Another key difference was the JMP 50 and JMP 100 amplifiers had a split biased preamp section for each
channel, whereas the JTM 45 and JTM 100 had a common biased preamp section. This resulted in the JMP amplifiers having slightly different gain in the first preamp
stage for each channel, whereas the JTM amplifiers
had the same gain in the first preamp stage for each channel. Both the JTM and JMP amplifiers
had one “bright” and one “dark” channel for added bass response.
metal paneled JMP amplifiers were
equipped with EL34 power tubes that
provided the famous cranked up "Marshall
Crunch". EL34 tubes are known for their compressed, tight, and mid-focused
distortion, in comparison to the JTM
amplifiers that were equipped with 6L6
(5881/KT66) tubes that provided a more open and less heavy distortion. The JMP
set the standards for hard rock tone.
1972, the Marshall Amplifiers that
were sold in the US were equipped with the US made 6550 power tubes. The 6550 tubes offered their own unique tone
which is often favored by metal style guitarists. However, most guitarists prefer the tone of
the EL34 tubes over the 6550 tubes. Marshall
amplifiers that were originally equipped with the 6550 tubes can be converted back for EL34 use.
Marshall handwired metal paneled
Rated at 50 watts, solid state rectified and equipped with a pair of EL34 or 6550 (KT88) output tubes;
Tremolo effect optional;
Head and combo cabinet options.
Rated at 100 watts, solid state rectified and equipped with quad EL34 or
6550 (KT88) output
Head cabinet only.
handwired metal panel amplifiers include; the 20 Watt Series and the 200 Watt Series. Both of these amplifiers were only offered
in the head cabinet configuration.
production of Marshall’s early
generation handwired amplifiers lasted from their
conception in 1963 through the middle of 1973.
Marshall then began phasing
in printed circuit board (PCB) designs and phasing out their handwired amplifiers by the middle of 1973. By 1974, most models, but not all, were of the printed
circuit board (PCB) design, ending the early handwired
era. The PCB versions of the JMP amps were offered through
1981. The 1969-73 Marshall handwired
JMP is an all time favorite hard rock amplifier.
Marshall Model Numbers (1962-1973 handwired era)
Model No. Product
1958 2x10 Combo: 18watt, 20 watt
1959 Super Lead, JTM 100, JMP 100
1959T Tremolo Super Lead: JTM 100, JMP
1968 Super P.A.: JTM 100, JMP 100
1974 1x12 or 2x12 Combo: 18watt, 20
1985 P.A.: JTM 45, JMP 50
1986 Bass: JTM 45, JMP 50
1987 Lead: JTM 45, JMP 50
1987T Lead, Tremolo: JTM 45, JMP 50
1989 Organ: JTM 45, JMP 50
1961 4x10 Combo:
JTM 45, JMP 50
1962 2x12 Combo:
JTM 45, JMP 50 “Blues Breaker”
1992 Super Bass: JTM 100, JMP 100
1992T Tremolo Super Bass: JTM 100, JMP
2061 20 watt Lead/Bass Head
1960 4x12 Cabinet
1972 2x12 Cabinet
1982 4x12 Cabinet
For those new to the Marshall model numbers, the year of production can be easily mistaken
for the model number, since the model numbers all begin with 19xx.
Cabinet and Speakers
cabinets and speakers contributed as much to the "Marshall" tone as the amplifier itself. While the JTM's electronic circuitry was
modeled after the Fender Bassman circuitry, the JTM produced its own unique tone.
Differences in tone between the US made Bassman and the British made JTM can be attributed to the components
available in the U.K. such as - brand and type of British & European tubes,
British manufactured transformers, and the various electronic components
sourced in England. The Fender Bassman
was mostly composed of US manufactured parts,
therefore these amps would naturally sound different. Also playing a significant part in overall
tone was the use of the Marshall 4x12
enclosed cabinets. The large fully closed
back cabinet, equipped with Celestion 12 inch speakers, provided a thunderous low end
response. The 4x12 speaker enclosures
were available as a straight front bottom cabinet and a
angled front top cabinet. The two
cabinets, along with the Marshall head, became known as the "Marshall Stack".
Marshall being a British company
speakers manufactured in England. Most
famous were the Celestion 12" speakers that were used in
the Marshall speaker
cabinets. The vintage Marshall/Celestion
speakers are known as Pre-Rola and Rola.
refers to the pre 1970 Celstion speakers labeled as:
CELESTION LTD, THAMES
to the post 1970 Celestion speakers were labeled as:
ROLA CELESTION LTD.,
difference being manufactured in either the Thames Ditton,
Surrey, England factory and labeled as CELESTION LTD. (pre -Rola)
prior to 1970 or the Ispwich, Suffolk, England
factory labeled as ROLA CELESTION LTD. (Rola) from
1970 onwards. Celestion
speakers manufactured from either factory during this period were all under the
same company, Rola Celestion
are typically more expensive following “the
older the better” motto.
Marshall initially used the 12
speakers equipped with lightweight ALNICO magnets. During the mid-60s, Marshall switched to the Celestion speakers equipped with ceramic magnets. These 12 inch ceramic speakers were
available with medium and heavy magnets and with cone material designated as 75
Hertz (Hz) or 55Hz. The 75Hz designed
more for lead guitar use and the 55Hz designed more for, but not limited to
bass guitar applications. The ceramic
speakers were available during the Celestion pre-Rola and Rola eras.
models offered in Marshall cabinets during the JTM/JMP
G12M – a medium weight
G12H – a heavier weight
Ceramic G12M and G12H speakers are referred to as Greenbacks, this
is due to their plastic Green colored magnet covers. The G12M and G12H speakers were also
available with plastic Black and Grey colored magnet covers and are known as Blackbacks and Greybacks.
current line of Celestion
reissue Greenback speakers, as well
as the majority of Celestion’s
guitar speakers, are now made in China.
A few of Celestion’s high end speakers such as
the G12 Blue (ALINICO), G12 Gold (ALNICO)
and Heritage Line (Ceramic) are
still manufactured in England (UK).
Tubes (Valves) Used in the Handwired Marshall
12AX7 (7025, ECC83) - The 12AX7
(US Designation) is a very popular 9 pin twin triode preamp tube. This tube was used nearly exclusively
throughout the preamp circuit in the early Marshall
amps. The 12AX7 was used in the early gain stage(s), tone control stage and
in the phase inverter circuit. The 7025 is a high grade version of the 12AX7. The European
Designation for the 12AX7 is ECC83.
Power Amp Tubes
6L6 (KT66/5881) - The 6L6, KT66 and 5881 are
from the same family of tubes. The
majority of the JTM amplifiers were
supplied with power amp tubes of this group.
The 6L6 (US Designation) is a
very popular power amp tube and is also found in many of the larger Fender
amps. As used in the JTM 45 applications, a pair of 6L6GC tubes can deliver around 45 watts
or slightly more.
5881 (US Designation) is an upgraded
(Military version) of the 6L6 tube.
KT66 (European Designation) falls in
the same family as the 6L6. The KT66
was manufactured by GEC of England;
however these tubes have not been in production by the original manufacturer
for more than a couple of decades. The KT66 is technically known as a Beam Tetrode Tube. Many guitarist and audiophiles consider the
original GEC KT66 tubes as the "holy grail" of power
amp tubes. Today NOS GEC KT66 tubes command very high prices. Marshall
rated the JTM with a pair of KT66s
at 30 watts,
however a fully cranked Marshall
with a pair of GEC KT66s can put out
closer to 40 watts. There are several
current tube manufactures offering their version of the KT66 tube.
the 6L6, 5881 and KT66 tubes are from the same family,
each type provides its own unique tone.
These tubes as used in the JTM amplifiers are known for their warm blues tones and
excellent classic rock overdriven tone.
EL34 (KT77) – The EL34 (European Designation) was used in
the JTM 50 amplifiers and throughout
the JMP amplifiers series. The EL34 has been the primary power amp
tube from the late 60s through today for the Marshall amplifiers. One
major difference in tone between the JTM
and the JMP amplifiers is the use of
the EL34 tubes. These tubes provide a very tight distortion
and the famous Marshall
"crunch". A pair of EL34 tubes is typically rated at 50
watts; however 60 watts or more can be achieved. The EL34
is a popular choice for hard rock and heavy metal applications.
6550 (KT88) - Earlier JMP amplifiers
delivered to the US were equipped with EL34
tubes, however later versions to the US were provided with the 6550 (US Designation) tubes. The 6550
provides a loud clean tone and is also popular in Bass amplifiers. When cranked up, the 6550 provides a very tight
crunch tone, which is popular with heavy metal players.
EL84 (6BQ5) – The EL84 (European Designation) tube was
used in the Marshall 18 and Marshall 20 watt amplifiers as well as
the VOX AC15 and AC30.
These tubes are very popular today in mid sized amplifiers. The EL84
provides a warm blues break up
and very nice overdriven tone, with
plenty of harmonics.
5AR4 (GZ34) – The 5AR4 (US Designation) is a very widely
used rectifier tube and is found in the Marshall
JTM amps, large wattage Fender
amps, VOX amps, as well as many
other tube amplifiers.
EZ81 - The EZ81
(European Designation) was used in the Marshall
18 watt amps and can also be found in the VOX AC15 and other amplifiers in the 20 watt range.
Marshall used Radiospares, Drake and Dagnall brand transformers and chokes.
earlier Marshall amplifiers used the Radiospares transformers. In 1965, Marshall began migrating to the Drake transformers. In general, the 1966 and onwards the Marshall 45 and 50 watt handwired amplifiers were equipped Drake
transformers. Also, the earliest Marshall 100 watt handwired amplifiers were equipped Radiospares transformers, then with Drake transformers, and finally around 1968 they were fitted with the Dagnall transformers.
output transformer contributes to the overall tone of the amplifier. The primary impedance of the output
transformer is typically selected to be within "ball park" of the
vacuum tube manufacturer's recommendation.
The power amplifier tubes transfer power most efficiently to the
speakers when the primary impedance of the transformer matches the combined
output tube’s impedance. Like speakers,
vacuum tubes also have reactive output impedances. The vacuum tube’s impedance will vary
according to the operating point of the tube; therefore, there is no exact
"correct" primary impedance value.
The tube manufacture specifies their recommended impedance based on the
typical operating range of the tube.
primary impedance value, type of wire used, core material type, bobbin material, winding design
and wiring technique affect the overall tone of the amplifier.
JTM 45 – The JTM 45 was equipped with either a Radiospares or Drake brand transformers. The 1962-1965 Marshall amplifiers had the RS Spares transformers. From 1965-68, the JTM45/50 amplifiers used the Drake transformers.
The Drake output transformer (p/n 784-103) has a
primary impedance of 8,000 ohm. Radiospares offered output transformers
with primary impedances of 6,800, 8,000 and 9,000 ohm. The Radiospares output transformer with a primary impedance of 6,800 and 8,000 ohm were used in the JTM 45 amplifiers.
primary impedances were selected based on the JTM being equipped with the 6L6/KT66/5881 group of tubes. With different primary impedances and the
fact that they were manufactured by two different companies, the Drake and Radiospares have different tonal qualities.
JTM 50 and JMP 50 – the EL34/6550
equipped JTM and JMP 50 watt Marshall amplifiers were fitted with the Drake (p/n 784-139) output transformers
that had a primary impedance 3,400 ohm. In 1968 Marshall began equipping the 100 watt amplifiers with the Dagnall brand transformers, the
JMP 50 amplifiers continued to be eqiupped with the Drake transformers.
JTM 100 and JMP 100 – In 1965 the JTM45/100 prototype and production amplifiers were equipped with two JTM 45 Drake output transformers (four KT66 tubes) and an upright RS Spares power transformer.
In 1966, Marshall then switched to a single Drake (p/n 784-084) output transformer wound for a primary impedance of 4,000 ohm (four KT66 tubes) and a Drake 1203-43 laydown power transformer.
This was followed in 1967, with amps during the middle of 1967 supplied with the Drake 1202-119 output transformer (1.9k ohm primary, with four EL34 tubes) along with the 1203-80 power transformer.
Then in late 1967, the Drake 1202-132 output transformer (2.2k ohm primary, with four EL34 tubes) was used. Also in 1967 Marshall began to label the front plexi panels with the "JMP100" designation.
Around 1968 Marshall switched to Dagnall power (T2562) and output (C1998) transformers (four EL34 tubes). From 1969 - 1973 most 100 watt Marshall amplifiers have the Dagnall transformers, although a few have the Drake 1202-99 output transformer and the Drake 1209-3 power transformer.
100 Watt Power Transformer (PT) and Output Transformer (OT) Chronological Summary:
1965 PT: Radio Spares Upright, OT: a pair of Drake 784-103
1966 Drake PT: 1202-43, OT: 1202-84
mid-67 Drake PT: 1203-80, OT: 1202-119
late-67 Drake PT: 1203-80, OT: 1202-132
1968-73: Dagnall PT: T2562, OT: C1998
1971-73: a few amplifiers have the Drake PT: 1209-3, OT: 1202-99
Common Marshall Amplifier Transformer Part Numbers:
Radiospares P/N not available JTM 45 (Upright style)
Radiospares P/N not available JTM 45/100 (Upright style)
Drake 1202-55 JTM 45 (Laydown style, began late 1964)
Drake 1202-133 JMP 50 (Laydown style, 1967)
Drake 1202-118 JMP 50 (Laydown style, 1967 - 69)
Drake 1202-164 JMP 50 (Upright style, 1969 and after)
Drake 1202-324 JMP 50 (Upright style, replacement transformer)
Drake 1204-43 JTM45/100 (Laydown style, 3" Stack, 560 VDC B+ or higher)
Drake 1203-80 JTM 100 (Black Flag), JMP 100 (Upright & laydown style, 2.5" stack, 490 VDC B+ typical)
Drake 1202-99 JMP 100 (Upright style, used on a few early 70s amps)
Dagnall T2562 JMP 100 (Upright & laydown style, 1.8" stack, 490 VDC B+ typical)
Radiospares P/N not available (Primary: 6.6k, 8k, 9K ohm Secondary: 4, 8, 16 ohm) JTM 45
Drake 784-103 (Primary: 8k ohm, Secondary: 8, 16 ohm, 100V line) JTM 45, JTM 45/100 (dual output transformers)
Drake 784-128 (Primary: 3,5k ohm, Secondary: 4, 8, 16 ohm, buried 100V winding) JMP 50
Drake 784-139 (Primary: 3,5k ohm, Secondary: 4, 8, 16 ohm) JMP 50
Drake 1202-84 (2" Stack, Primary: 4k ohm, Secondary: 8, 16 ohm, 100V line) JTM45/100
Drake 1202-119 (2" Stack, Primary: 1.75k ohm, Secondary: 8, 16 ohm, 100V line) JTM 100 (Black Flag) , JMP 100
Drake 1202-132 (2" Stack, Primary: 2.2k ohm, Secondary: 4, 8, 16 ohm) JTM 100 (Black Flag), JMP 100
Drake 1209-3 JMP 100 (2" stack, used on a few early 70s 100 watt amps)
Dagnall C1998 (1.5" Stack, paper bobbin, Primary: 1.75k ohm, Secondary: 4, 8, 16 ohm) JMP 100
Dagnall C2668 (1.5" Stack, nylon bobbin, Primary: 1.75k ohm, Secondary: 4, 8, 16 ohm) JMP 100
Radiospares P/N not available (20H) JTM 45, JTM 45/100 (dual output transformers)
Drake 352-114 (3H, 100mA) JTM45, JMP 50, JTM45/100 JMP 100
Dagnall C1999 (3H, 100mA) JMP 50, JMP 100
the purpose of this article, the 1963-1973 handwired Marshall amplifiers
were categorized into three eras. They
are grouped according their face plate panel material.
1963 - 1964 Metal Paneled
1965 - mid-1969 Plexiglas
mid-1969 - 1973 Metal Paneled
some people refer to JTM strictly as
the JTM 45 model and plexi covering the JTM 100, JTM 50 and JMP
Marshall JTM 45 amplifier changed
the tone of` Rock and Roll. While being
based on the 1959 Fender Bassman circuit, the JTM's tone was distinctively
different. 1963-64 pre-plexi Marshall amplifiers today, in original
condition, are rare and valuable.
Plexi “Plexiglas” paneled Marshall amplifiers
were available from 1965-1968. During
this period Marshall expanded their
models, which included the JTM 45,
50,100, an 18 watt and a 20 watt. Tremolo versions of the JTM 45, JTM50 and 18 watt
amps were also offered.
JTM 45 is an all-time favorite
vintage amplifier. The type of power
amplifier tubes contributed a lot to the JTM
45's tone. The JTM45 amplifiers were equipped with the 6L6 family of tubes, which
also included the 5881 and KT66 power tubes.
These tubes provided a very nice warm clean or broken up blues tone, and
a "classic rock" distorted tone when pushed full out. The JTM
45 is an all time favorite blues
and rock amp.
guitarists who liked the JTM 45 tone
but wanted more output power, turned to the JTM 100, that had a power
output rating of 100 watts.
the metal paneled, hand wired Marshall amplifiers from 1969-1973 are the
most affordable of the early hand wired Marshall
amplifiers. The JMP 50 and 100 watt
amplifiers are both identified with the "Marshall Crunch". The JMP amplifiers that are equipped with
either the EL34 or 6550 tubes are associated with hard rock and heavy metal
tones. The solid state rectifier
provided the JMP with more punch and
much less sag as compared to the tube rectified JTM amplifiers. The JMP set the standards for hard rock tone.
JTM and JMP are all time favorite guitar amplifiers, each with its own
unique tone. The 6L6/5881/KT66 equipped JTM
is favored for its blues and classic rock tones. The EL34
equipped JMP amplifier is a favorite
for those seeking the heavier "Marshall
Marshall 18 watt combo utilizing a
pair of EL84 power amp tubes, is very popular with the guitarist who want an
excellent blues or rock tone at lower volume levels.
to all of these Marshall handwired amplifiers was the
minimal amount of preamp gain stages.
Minimal preamp stages, allows the clarity of the guitar's signal to pass
less distorted through the preamp circuitry; therefore the distortion is
generated by overdriving the power amp section.
Many high gain amplifiers rely on overdriving multiple preamp sections,
creating a lot of their distortion prior to the power amp section. Thus, power amp distortion vs. pre amp
distortion. The awesome overdriven tone
from these Marshall amplifiers, was generated mostly in the power tube section,
providing a warm overdriven tone as compared to the “buzzy”
tone from overdriven pre-amp tubes.
contributing to the tone in a positive way, was the lack of effects, or minimal
use of effects, such as only a Tremolo circuit. Most effect circuits will alter the original
tone of the amplifier. For example, Effects
Loops requires modification to the
original circuit by adding extra components and wiring,
directly in series or in parallel with preamp path and typically one or two
extra preamp gain stages is also added.
The additional circuitry creates signal loss and alters the amplifier's
original tone. In the case of creating
ultimate tone, less circuitry and “straight forward” design is often better, as
these Marshall amplifiers have
a lot to Marshall's signature tone
was the use of British Celestion speakers and the 4 x 12 Marshall enclosed cabinets. Today some of the Pre-Rola and Rola speakers, as used in the Marshall speaker
cabinets, are collector items. There are
many versions of these speakers available and to understand the different
versions can involve a lot of research.
all models of Marshall amplifiers from the handwired era
have become popular among collectors and players. Each model providing a
unique tone of its own. The
value of these handwired Marshall basically follows the era they are from, the older being
Who comes to mind as
guitarist who favored the early Marshalls?
Jimi Hendrix, Eric Clapton, Duane Allman, Paul Kossoff, Jeff
Beck, Pete Townshend & John Entwistle
, Ritchie Blackmore,
Eddie Van Halen, Randy Rhoads, Slash, Angus Young,
Peter Frampton, Eric Johnson, Yngwie Malmsteen, and Zakk Wylde, to name just a few. Hard to argue with the tone produced by these legendary guitarist!
Marshall Reissue Handwired Amplifiers:
1974X - Reissue of the 18 watt 1x12 combo with tremolo, reissue Dagnall transformers
2061x - Reissue of the 20 watt head with matching slant 2x12 cabinet, reissue Dagnall transformers
JTM45 Offset - Reissue of the earliest production JTM45 amplifier head with matching cabinet, limited run of 600 units
1959HW - Reissue of the classic 100 watt "plexi" head, Dagnall reissue transformers, EL34 power tubes
Super 100JH (Hendrix) - Reissue of the Hendrix JTM45-100 "Monterery" amplifier head with matching slant and tall cabinets (full stack), Drake Laydown Power Transformer, Drake "Fat Stack" Output Transformer, KT66 power tubes, limited run of 600 units
JTM45/100 40th Anniversary - Reissue of the earliest production 100 watt amplifier with matching cabinets (full stack), reissue Radiospares style "upright" power transformer with two JTM45 output transformers, KT66 power tubes, limited run of 250 units
50th Anniversary Bluesbreaker Combo Amp with Gibson Reissue 1957 Les Paul package (released 2012) - Reissue of the JTM45 (2 x KT66 tubes, Tremolo effect) 2x12 combo amplifier. Model: 1962LE. Tom Murphy (hand aged) Gibson 1957 Reissue Les Paul. Limited run of 50 guitar/amp units. MRSP $29,500
The History of Marshall –
Considered one of the best books on Marshall Amplifiers.
The Fender Bassman 5F6-A – Richard Kuehnel
In depth and highly technical review of the 5F6-A
circuit. Includes a
technical section on differences between the JTM45 and 5F6-A circuitry.
Copyright © 2012 ARACOM
Amplifiers (rev. 0312-1)