JM45

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Note: This article has been updated with lastest available information on October 17th, 2021 at 06:02 pm

Positive Grid JM45 Amp is available under the Crunch amp group and is inspired by the Marshall JTM45 Amp.

A special Jimi Hendrix™ version of this amp, J.H. 45/100, is available in the Experience Jimi Hendrix™ add-on for Spark.

JM45 Amp

250px JTM 45 MK II Reissue 1997
Marshall JTM45 MK II Reissue

The Marshall JTM45 amplifier is the first guitar amplifier produced by the British company Marshall. It was initially produced in 1963, and has been ranked among the most desirable of the company's amplifiers.[1]

Notable musicians who have used this amplifier include David Gilmour,[2] The Rolling Stones,[2] and Jimi Hendrix,[3] among others.

History and development

Prototyping of the JTM45 began in 1962, after London musical instrument retailer Jim Marshall decided to create a new amplifier in response to local guitarists' desire for an alternative to imported American Fender amplifiers. Marshall sought the advice of his shop repairman Ken Bran, who recommended electronics "whiz kid" Dudley Craven as the chief circuit designer. Marshall then arranged for Pete Townshend and Ritchie Blackmore demo prototypes to be constructed by Bran and Craven, settling on the sixth prototype as the production model.[4]

This model was dubbed the "JTM45" – for Jim and his son Terry Marshall, and 45 for the RMS-rated wattage[3] – the amplifier mimicked the circuitry of the Fender Bassman but had an all-aluminum chassis, and a 12AX7 valve as the first in the chain (while the Bassman had a 12AY7). In addition, it featured Celestion speakers with a closed cabinet (rather than open-backed Jensen speakers), and a modified negative feedback circuit, which affected the harmonics produced by the amplifier[citation needed].

As Bran later said, "The JTM also had different harmonic content, and this was due to the large amount of feedback that Dudley Craven had given it."[5] Early versions used 6L6 or US 5881 valves (a version of the 6L6[6]) in the output stage; later models used KT66 (from 1964), EL34 (from 1966), or KT88 (from 1967; in the 200W Major), and ECC83 (12AX7) valves in the pre-amplification stage.[1] The amplifier was also available in the bass format (although this model lacked a "bright" capacitor) and an additional PA version (which lacked a "mixer" capacitor).[5] Because of its power, Marshall decided early on to build it as a "head," with a separate 4×12" cabinet with Celestion speakers.

The first-ever use of this JTM 45 model in a live performance was in September 1963, when the amplifier was tested at the Ealing Club, a short distance from the original Marshall shops.[citation needed] By the mid-1960s, the JTM45 had become so popular that it began to supplant the ubiquitous Vox amplifiers, including the Vox AC50, even though the Vox amplifier was equally powerful to the Marshall amplifier.[7]

In late 1965, Marshall introduced its now standard script lettering, in white. By early 1966 it began calling the amplifiers "JTM 50".[5] Some 100 early models had red lettering, and are especially sought after by collectors.[1] Other cosmetic changes included a gradual change to different knobs. The JTM 45 became the basis for many subsequent Marshall amplifiers, most notably the Marshall 1962 combo (later referred to as the "Bluesbreaker" due to its use by Eric Clapton with John Mayall's Bluesbreakers).[8] Production of this model ceased in 1966, but it was reissued in 1989, albeit with a modern printed circuit board and 6L6 output valves.[5] In 2014 Marshall reissued a "handwired" 30 W amplifier based on the JTM45, the 2245THW, whose circuitry is identical to the 1962 combo circuit; it is a "fine high-end piece" according to Vintage Guitar, listed at $4,800.[9]

Name, numbering

The first JTM45s did not have the standard Marshall numbers that later amplifiers had; models that derived from the JTM 45 did not receive serial numbers until 1964–1965 when backplates began to be applied.[5] However, at random some of the early amplifiers had serial numbers stamped into the chassis on their reverse side.

Model number Watts Dates Features Notes
JTM45 35–45[10] 1963–1964 2 channels, 4 inputs Also available in bass and PA versions
1963 50 1965–1966 4 channels, 8 inputs PA version; "JTM50 MK III"
1985 45 1965–1966 2 channels, 4 inputs PA version of JTM50 MK II
1986 45 1965–1966 High treble and normal channels Bass version of JTM50 MK II
1987 45 1965–1966 High treble and normal channels Lead version of JTM50 MK II; also with tremolo as Model T1987
1989 45 1965–1966 For electronic organs Also with tremolo as Model T1989
JTM 45 (2245[11]) 30 1989– 2 channels, 4 inputs Reissue of original JTM45 (1987)
2245THW[9] 30 2014– Handwired head, circuitry identical with Bluesbreaker

Sound

For all of its differences when compared with the Bassman, the sound of the JTM45 is still described as "like a tweed Fender", and is favored for blues and rock rather than for hard rock and metal.[12] The JTM 45 delivers a smooth Marshall sound with a warm bass response due to the EL34/KT66 valves.[citation needed]

Notable users

References

  1. ^ a b c Pittman, Aspen (2003). The Tube Amp Book. Hal Leonard. pp. 66, 68–69. ISBN 978-0-87930-767-7.
  2. ^ a b c d e f g Drozdowski, Ted (29 January 2020). "Peter Green's 1964 Marshall JTM45". premierguitar.com. Premier Guitar. Retrieved 6 December 2021.
  3. ^ a b c d e Motter, Paul; Schu, Peter (7 May 2015). "A History Of Marshall Amps: The Early Years". reverb.com. Reverb. Retrieved 7 December 2021.
  4. ^ Brown, Michael (28 November 2013). "Lust for Power". premierguitar.com. Premier Guitar. Retrieved 6 December 2021.
  5. ^ a b c d e Doyle, Michael (1993). "The JTM Series 1962–1966". The History of Marshall: The Illustrated Story of "The Sound of Rock". Hal Leonard. pp. 17–22. ISBN 978-0-7935-2509-6.
  6. ^ Hunter, Dave (2005). Guitar Rigs: Classic Guitar & Amp Combinations. Hal Leonard. p. 111. ISBN 978-0-87930-851-3.
  7. ^ Hunter, Dave (2005). Guitar Rigs: Classic Guitar & Amp Combinations. Hal Leonard. p. 102. ISBN 978-0-87930-851-3.
  8. ^ Batey, Rick (2003). American Blues Guitar: An Illustrated History. Hal Leonard. p. 106. ISBN 978-0-634-02759-8.
  9. ^ a b Childs, Zac (October 2014). "Bluesbreaker Redux: Marshall Handwired Series 2245THW head and 1960AHW Cabinet". Vintage Guitar. p. 130.
  10. ^ Micheal, Doyle; Nick, Bowcott. The History of Marshall – The First Fifty Years. pp. 44, 48.
  11. ^ "Marshall Amps:: 2245 (JTM45)". Marshall Amplification. Archived from the original on May 2, 2006. Retrieved 1 May 2013.
  12. ^ Hunter, Dave (2005). The Guitar Amp Handbook: Understanding Tube Amplifiers and Getting Great Sounds. Hal Leonard. pp. 75–76. ISBN 978-0-87930-863-6.
  13. ^ Prown, Pete; Lisa Sharken (2003). Gear Secrets of the Guitar Legends: How to Sound Like Your Favorite Players. Hal Leonard. p. 10. ISBN 978-0-87930-751-6.
  14. ^ Prown, Pete; Lisa Sharken (2003). Gear Secrets of the Guitar Legends: How to Sound Like Your Favorite Players. Hal Leonard. p. 2. ISBN 978-0-87930-751-6.
  15. ^ Newquist, H. P.; Rich Maloof (2004). The hard rock masters. Hal Leonard. pp. 23–24. ISBN 978-0-87930-813-1.
source: https://en.wikipedia.org/wiki/Marshall_JTM45

According to Marshall Amps

It’s the amp that started it all, the Jim Terry Marshall 45, more commonly known as the JTM 45. But rewind to 1962 and the amps available in the UK just weren’t cutting it for the grit driven rockers of the time. The most popular amps of the time were imported from overseas and often took a long time to get to the players, which left a gap in the market. Marshall decided to try and fill the gap and along came the first ever JTM 45.

The original amp was based on the Fender Bassman, the favourite amp of Terry Marshall at the time. Like the Bassman early versions of the JTM used 6L6 or US 5881 valves in the output stage, later models were upgraded to the KT66, EL34, or KT88 valves. The Marshall team didn’t just change the valves though, there were some more significant differences including the all-aluminium chassis, a 12AX7 valve as the first in the chain, and a modified negative feedback circuit which affected the harmonics produced by the amplifier. 
 
This meant the JTM had a larger amount of feedback running through it, which not only meant that the harmonic content of the JTM was different to everything else that was around at the time, but also created the distorted, gritty Marshall sound that we’re so famous for today..

Artists using a Marshall JTM45:

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