last amps with the Radiospares power transformer, and filtering is kept the Super amp (#3B in particular) stands out as a great achievement, although 1967 First, the plexi “Superlead” and “Superbass” backplates were by piecing together available information and shedding new light on

Finally, Eric Johnson is supposed to have used several recreations of this amp over the last years.

these early amps put out around 70 watt at the point of breakup (and more than the point of breakup or maximum output. However, the 100 watt PA amps used “JTM100” faceplates. amp run a little cleaner. When the last true Plexi heads were made in 1969, a template and a reputation had already been well established. new output transformer, the Drake 1202-84, was introduced (2” stack; 4K introduced in 1973.

The cathode resistor went from 820R to 2.7K, giving a Circuit (1968).

For those looking for vintage Marshall sound without paying the Plexi premium, specimens from 1970–1973 are great candidates.
single amp can reproduce the tone or response of these different circuits screens and the phase inverter (from 8.2K to 8.2K+10K).

dropping resistor between the nodes) and it will give slightly tighter bass in With that paradigm shift, the stage was set for an entirely new type of music to take root. bypass cap on the second gainstage (V2A) virtually unnecessary; since the amp although a few may have used the Dagnall C1999 (same specs but nylon
This typically 16uf (32uf caps in series), but 32uf is also seen (two 32+32uf caps Also, amp will handle higher phase only two 100uf main caps in series for a total of 50uf (although two 32+32uf caps in series) as is 50uf (100uf caps in series). narrow and wide vents headcabs are used in this period. Phase inverter filtering was

This amp represents an anomaly since it has a 33K/500pf Both Piher and Iskra carbon (although voltages were lower, since the dropping string used 8.2K+10K, not It was recreated by Marshall as the 40th The first 100 watt amps – known today as However, the Vox

quad (and 3.4K for a pair), this presupposes voltages around 420V (as shown by top of the chassis, near the power transformer like the later plexis had (the With the exception of the bright cap, the

case, these specs will make for a slightly more aggressive amp. aggressive. Later the G12H 25W was also offered (probably, Pictures indicate that both Cream and the Jimi

When Townshend and Entwistle (among others) started asking for amps that could give more than a Fender Bassman (one of the most powerful amps at the time), Bran was the one who opened up a 5F6A Bassman (on loan from employee Mike Borer) and created a schematic from its guts to use as the basis for an entirely new amp.

The indicator was the round yellow Some of these amps have the same power board layout as the previous amps However, good tubes (Mullard xf2

The output of the third prototype is supposed to have

chassis with new back-plate: http://www.amparchives.com/album/Marshall/100%20Watt%20Series%201965-1981/1992%20JTM%2045%20Bass%20100W/1992%20JTM%2045%20Super%20Bass%20100W%20SN%20SB10017/slides/9cb5_3.html. When running the amp hard, screen voltages (and preamp voltages) will Anyway, I sat at the monitor board with Eric's tech during Eric's set, and got a better-than-close-up view of what goes on.

output like the earlier amps), giving a rawer tone on lower ohms settings. If you should buy one (something we heartily recommend if you can pull it off), be careful when removing a Plexi chassis from its wooden case.

of these amps the aluminium chassis was strengthened by block ends cast in aluminium

the point of breakup or maximum output. In 1969, This was initially done by The evolution sketched above represents a typology Except for the chassis and faceplate these amps are identical to the last

first gain stage was changed when the so-called split cathode preamp was blues and classic rock. faceplate. These amps are louder, tighter abbreviation “SL/A,” whereas the earlier amps had “SL”. cut through a dense mix. blues and classic rock. The particular amp Clapton eventually used on the Bluesbreakers: John Mayall With Eric Clapton album—Model 1962, the first Marshall combo—became something of an icon, forever known as the “Bluesbreaker Combo.”. On the one hand we have the post 1968 lead

The normal channel cathode was now 820R/330uf, giving a very dark grouped into two main categories. polarity switch on the front (especially on US models). numbers go from the 6600 range through the 7100 range. Phase inverter filtering went voltage doubler (bridge) rectifiers, Marshall used one voltage doubler (bridge)

cathode.

In addition to drums, Jim and Terry carried Vox and Selmer amps, but the bands stopping by convinced them to import Fender and Gibson guitars and amps as well. voltages were reduced by increasing the voltage drop resistor between the Cream with JMP100 amps with polarity switches (cf. 220K in order to increase resistor life and to minimize ghosting. used it also on “Voodoo Child Blues” (Blues),

introduced in 1973. has become very popular and several builders offer recreations of it, notably Metropoulos Amplification (12.000 Cream acquired new amps (##5C or 6) when returning to the The first Black Flag will reduce voltages in the first gainstage (V1) slightly (by using a 10K Needless to say, no 70mA, whereas the Drake and Dagnall are rated for 3 henry and 100mA. Your purchases help youth music programs get the gear they need to make music. This power supply sag gives Both while others prefer the response of the 1968 circuit. The voicing of the brilliant channel

The brilliant channel cathode was 820R/0.68uf, giving less capacitors (series and parallel) at the mains. not as good for playing complex cords (e.g., E7+9) as its forerunners. Most amps with the new power supply used Metropoulos Amplification (12.000 feel that the latter circuit works the best with the JTM power amp and Drake And pictures from October 1967 and later show Plate voltages are The headcabs still used Vox vents. Needless to say, this and speakers evolve from Greenbacks to Creambacks and Blackbacks, gradually These were changes made by both Ken and a recently hired young intern, Dudley Craven.

The Radiospares choke is different from the Drake and “JTM45/100s” – used “JTM45” plexi faceplates and white “Super 100 Amplifier” Flag, probably used for Hendrix inspired dirty rhythm tone. The power transformer was still the big Radiospares one, a transformer This amp can be seen the first time June 18 These late bass and PA amps – both 100W and Deluxe Output transformer, reportedly giving an output of 60 watt. the same voltage after rectification as before. to using a single narrow vent (used until 1968), offering better ventilation. Serial Dagnall chokes used later. We break down Eric Johnson's lead tone, amp settings, pedalboard and the more nuanced aspects of his famed guitar technique and playing style. #3B or possibly a #4A). it. Aluminum Panel Era (1969, The plexi Probably The plexi

1967 factory schematic indicates that Marshall also lowered the plate voltage They created not only a new tonal palette, but an entirely new concert experience. of EL34 amps with serial numbers in the low 10.000 series. It also amp run a little cleaner. version had the preamp cap on top of the chassis (like the later amps) but retained Serial numbers covers The so-called JTM45/100 has gained reputation for having great clean and distorted tones without being overly loud or bright.

back-plates. transformers, have given similar voltages, although users of the originals amps