The output of the third prototype is supposed to have exceeded 100 watt (Doyle, History of Marshalla big Hammertone Radiospares power transformer (with taps for both 350VAC and 425VAC).
According to tech reports, these early amps have around 470VDC on the plates of the KT66s (indicating that the 350VAC tap was used).
Dating a Marshall amplifier can be a daunting task for even the most savvy of suitors — Amp Archives is here to help.
The earliest Marshall amplifiers were made in 1962 and had no model or serial numbers.
Sadly, Jim Marshall, the Guv'nor, passed away on april 5th 2012. These amps were built as heads (or tops) separated from the speaker cabinets. These amps were introduced in april 1981, around the same time as the JCM800 series.
These amps were more or less a copy of the Fender 1959 Tweed Bassman. This was the combo version of the 2098 Master Lead head. The 2000 Lead and 2001 Bass heads are probably the loudest and most powerfull Marshall tube amps ever built.
The Marshall Bluesbreaker is the popular name given to the Models 19 guitar amplifiers made by Marshall from 1964/1965 to 1972.
For all of its differences when compared with the Bassman, the sound of the JTM 45 is still described as "like a tweed Fender"; it has more sag and less crunch than the later Marshalls, and is favored for blues and rock rather than for hard rock and metal.
According to Robb Lawrence's The Early Years of the Les Paul Legacy, Jim Marshall initially gave Clapton a Model 1961 with 4×10" speakers, which was soon replaced with a 2×12" Model 1962.
Due to its iconic status amongst collectors, the Bluesbreaker has become one of the most collectible and valuable vintage guitar amplifiers.
Model 1961 was essentially the lead version of the Model 1987 JTM 45, fitted with tremolo and installed into an open backed speaker cabinet, while Model 1962 was the bass version of the JTM 45 (Model 1986), also fitted with tremolo and open backed cabinet.
The output of a typical Bluesbreaker was only about 35 watts, and thus the sound would break up at more moderate volumes as compared to larger amplifiers.