Marshall Plexi
The Marshall Plexi , officially initially (1962-1966) JTM-45 (/ 100) , later (from 1967) JMP Super Lead called, was an early tubes - guitar amplifier the British company Marshall Amplification from the 1960s. Jim Marshall developed the prototype in England in 1962 based on the Fender Bassman . The name suffix Plexi is explained by the Plexiglas front panel of the amplifier, which was replaced by brushed, anodized aluminum between 1967 and 1968. In the first models, English type KT66 tubes were used in the output stage, and in 1966 they were replaced by the European type EL34 . In addition, the amplifiers in the pre-stage were equipped with ECC83 tubes and a GZ34 rectifier tube. The plexi has been used by numerous rock and pop musicians, including Eric Clapton while at Cream , Jimi Hendrix and Pete Townshend . It was the latter who pushed the further development of this amplifier by asking Jim Marshall for more and more powerful amps.
The fascination with Plexi has never lost its importance: Hundreds of thousands of guitarists worldwide swear by these old tops to this day, such as Angus Young from AC / DC or Jimmy Page from Led Zeppelin . The prices for the originals from the 1960s are correspondingly high. Marshall now offers numerous new editions as cheaper alternatives. Hundreds of other manufacturers are also trying to capture and reproduce the sound of an old Marshall Plexis with their products.
For many people, the sound of a cranked Marshall Plexis is the epitome of the rock sound of the 1960s and 1970s, as it could be seen and heard on almost every major stage from this time.
Sound properties
The Plexi is characterized by its high dynamics: With a light touch (for example when fingerpicking) you can play quietly and almost undistorted, with an increasingly strong attack (for example when striking chords) the distortion increases so that the sound can be varied easily between undistorted and distorted using the velocity.
In addition, it was and is popular because of its overtone-rich, warm (popularly erroneously called power amplifier distortion) distortion of the phase inversion stage. A big problem with these amplifiers is the volume: only when the volume control is turned up very far does the phase inversion stage begin to saturate. This problem was only resolved in 1975 with the introduction of a "master controller", which allowed independent volume control of the preamp and power amplifier. However, the distorted sound of the amplifier equipped with a master controller does not correspond to that of a saturated phase inverter stage, so that many guitarists prefer soaks for power reduction (these are resistor circuits inserted between the amplifier and the box that provide part of the output power convert into heat). Alternatively, the installation of a master controller behind the phase reversal stage (PPIMV, Post-Phase-Inverter-Master-Volume) is also possible. So-called power scaling systems are also being experimented with. These reduce the grid voltage of the power amplifier tubes: The amplifier loses power and thus also volume.
Web links
- Marshall Company website (English)
- Marshall website (German)