MARSHALL BLUESBREAKER MODEL 1961 Description
- 30-35W (1964-mid-1966) or 50W (late 1966-1972), 4-10 in. Ceramic magnet speakers, guitar combo, seven-tube chassis (1964-mid-1966) including preamp: 4 X ECC83/12AX7, power: 2 X KT66, rectifier: GZ34 or six-tube chassis (late 1966-1972) including preamp: 4 X ECC83/12AX7, power: 2 X EL34, solid-state rectifier, two channels, tremolo, top gold control panel, four inputs (two per channel), eight knobs (p, b, m, t, v1, v2, s i), black covering, white or gray Bluesbreaker/Pinstripe (1964-early 1965), Marshall Bluesbreaker/Pinstripe (mid-1965-1968), or full-face Basketweave (1968-1972) grille cloth, mfg. late 1964-1972.
The Bluesbreaker was originally equipped with Radiospares transformers, and in circa 1965 Drake transformers began being phased in and the Marshall Bluesbreaker/Pinstripe grille cloth was used exclusively. During the second half of 1966 the upgraded JTM50 chassis was offered with a full 50 watt power rating, which utilized the EL34 power tubes, Drake transformers, and solid-state rectifier. In 1967, the JTM designation was changed to JMP for Jim Marshall Products. The control panel designations remained the same as above. By 1968, the Bluesbreaker was known as the JMP50, although it kept the same cabinet dimensions and control panel layout as the circa mid 1965/1966 Series II, but included the new Basketweave full-face grille cloth, introduced in 1968 and the revised electronics stated above.