2x12 cabinet schematics y?kleme,build your own toyota innova,coffee tables cheap online 2014 - Review

05.08.2013
The JTM45 panels were changed to the JTM50 panels with the switch to the EL34 output tubes. The hand bent aluminium chassis was replaced by the steel machined chassis, making the amps much more robust and road proof.
The sixties (1962 - 1967) which is the "Jurassic" period of Marshall and is the time of the JTM's. Although this division is not entirely accurate, it does give a good impression of the different era's. These amps had 2 channels with each a volume control and two inputs (making a total of four inputs). Very few of the 1972 2x12" (horizontal) extension cabinets were built and these cabinets are very rare.
In the first half of 1967 the JTM panels were dropped all together and the JMP panels were introduced. In 1965 the first (prototype and production) 100W amps (model 1959) were constructed using two 50W output transformers.
The Tremolo version was an idea of Pete Townsend but it wasn't very popular and not many were produced. This set consisted of a 20W head amp and two speaker cabinets each with fitted two 13"x8" eliptical speakers. The US distributor at that time (Unicord Inc.) decided to switch to 6550 output tubes in favor of the EL34's. The 2002 and 2003 Master PA amps (introduced in 1966) were the first 19" rack mount Marshall amps. This amp was produced using the last tremolo chassis in Artiste head cabinets, so sometimes these a heads are referred to as Artiste's which they are not! Although these aren't tube amps, these amps are still (a small) part of the Marshall story. The 2000 Lead and 2001 Bass heads are probably the loudest and most powerfull Marshall tube amps ever built. Having been finally freed from the 15 year exclusive Rose Morris distribution contract, Marshall launched the new JCM800 serie early in 1981. The JCM800 range is split into the Lead amps (this section) the Bass amps and the solid state amps. The JCM800 amps had a larger logo than before, and the heads also featured grille cloth on the upper two thirds of the front instead of being completely covered with the usual black vinyl. In 1982, the 20th anniversary of Marshall Amps, some of the JCM800 amps were issued in neat white vinyl. See Mark Huss's Marshall JCM800 2204 page for more information and some pictures on this amp.
With the JCM800 Bass range of amps Marshall specifically wanted to get a foot into the Bass amp market.


The design of the JCM800 1986 and JCM800 1992 amps departed from the "classic" Marshall Bass amp design and incorporated a better tone stack with a mid sweep and a slope control not found on the older JMP 1986 and JMP 1992 amps. The following three schematics are generic schematics for the 1959 & 1987 Super Lead heads, the 1986 & 1992 Super Bass heads, the 2203 & 2204 Master Volume heads and the 2103 & 2104 Master Volume combo's. The (Super) Leads (1959 & 1987) were issued as heads only, while the Master Volumes (2203 & 2204) and the new Split Channels (2205 & 2210) were also issued as combo's (4103, 4104, 4210, 4211 & 4212). User manual for Master Volume and Lead models: 1959, 1987, 2203, 2204, 4001, 4010, 4103, 4104, 5002, 5005 & 5010 (483kB). JCM800 pre amp schematic with 3x ECC83 for models: 1959, 1987, 2203, 2204, 2103 & 2104 (Marshall, 1981). JCM800 power amp and PSU schematic with 2x EL34 (50W) or 4x EL34 (100W) for models: 1959, 1987, 2203, 2204, 2103 & 2104 (Marshall, 1981).
User manual for Split Channel models: 2205, 2210, 3203, 3210, 4203, 4210, 4211, 4212, 5210, 5212, 5213, 5215 & 5275 (947kB).
Allthough these amps do not contain any tubes, I feel that the Marshall amps story is incomplete without mentioning these amps.
Desperate to build a factory large enough to meet demand, Jim Marshall made a deal with the Rose Morris company. It is said that the first prototype and early production amps were fitted with two 5881 beam power tetrodes, three ECC83's and a GZ34 rectifier tube, but soon KT66 tubes were used instead of the 5881's.
The mix resistors (which mix together both channels after the first triode sections) were originally 270k? on the early models.
Later (probably in 1963) aluminium panels were used having JTM 45 and MK II printed on them (implying the first serie of amps were the MK I's). This was the amp Eric Clapton used on the legendary John Mayall's Bluesbreakers "Beano" album early in 1966.
This increased power handling was probably due to the four Celestion ceramic speakers fitted in these cabinets. In July 1969 Marshall dropped the Plexi face plates and switched to the gold colored brushed aluminium metal face plates as we know them still today.
This is a two channel amp, one channel is that of a 1987 Lead amp and the other channel is that of a 1986 Bass amp, making it quite a versatile amp. The heads retained their original model numbers, but the combo's were given model numbers in the 4000 range.
They were fitted at first with 4 Celestion G12-65 T3101 16? speakers and later (1983 onwards) with 4 "Marshall-Celestion" 12" 16? speakers.
It isn't quite clear to me whether or not these amps were actually part of the JCM800 range, as these amps don't have the JCM800 logo's, but they were included in the JCM800 catalog and they were manufactured in the same period and had the same looks and style. In exchange for the necessary funding (to build this new factory) Rose Morris acquired the exclusive worldwide rights to distribute Marshall amps for the next 15 years. They were angled front cabinets and were fitted with four 12" Celestion G12-15 speakers, instead of the four 10" Jensen speakers in an open cabinet like Fender did.


The GZ34 rectifiers were phased during this time, allthough there are even JMP 50 models with GZ34 rectifiers. The first 100W Lead and Bass models used left over JTM45 panels (until some time in 1966) but the 100W PA models did use JTM100 panels, as these amps sported 8 inputs instead of 4, requiring different panels anyway. These amps used two EL84 tubes in the power amp, two ECC83's in the pre amp and a solid state rectifier in the power supply.
Apparently the EL34's didn't like to be knocked about while being shipped from Europe to the US of A. This is a two channel amp, one channel is that of an 1987 Lead amp and the other channel is that of an 1986 Bass amp.
Early 2104's were fitted with two Celestion G12-65 15? T3054 speakers, later 2104's were fitted with two Celestion G12-65 15? T3120 speakers.
The whole JCM800 serie was discontinued in 1989 just prior to the introduction of the JCM900 serie amps.
The solid state and hybrid heads were given model numbers in the 3000 range and the solid state combo's were given model numbers in the 5000 range.
These 12" Alnico speakers were essentially the same speaker as the Celestion VOX Blue speakers.
These are not the small magnet G12-20s, but are actually 25W Greenbacks with a different cone, sounding different than a typical 25W Greenback from a 1960's 4x12 cab. In the course of 1968 the Low-High tone control circuitry was changed to a Low-Mid-High tone control and these amps were now called the Marshall Majors. Instead of fitting new EL34's, Unicord decided to fit 6550's, thinking that these "heavier" tubes would last beyond the warranty period.
These cabinets had smaller dimensions than the usual 4x12's, and they were part of the "Mini-Stack" range.
In some older schematics the 4103 & 4104 combo's are still referenced to as models 2103 & 2104. Due to a design mistake of Drake (the transformer supplier at that time) the US primary tap wasn't correct, giving a dangerous B+ of around 640V! These amps used two EL84 tubes in the power amp, three ECC83's in the pre amp and an EZ81 rectifier in the power supply. This in itself was true, but many American guitar players were wandering why their Marshall amps sounded so different from their European brothers.
Some people actually like the bright sound of the 6550's in their Marshall amps but most guitar players prefer the original sound of the EL34's.




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