marshall jcm 2000 dsl 50 schematic drawing

This new amplifier, tentatively called the 'Mark II', was eventually named the ', after Jim and his son Terry Marshall and the maximum wattage of the amplifier. These circuit changes gave the amp more gain so that it broke into sooner on the volume control than the Bassman, and boosted the treble frequencies. Other crucial differences included the use of higher-gain valves throughout the preamp, and the introduction of a capacitor/resistor filter after the volume control. For their Bassman, Fender used four in the same cabinet as the amplifier, but Marshall chose to separate the amplifier from the speakers, and placed four 12-inch speakers in a separate closed-back cabinet instead of the four 10-inch Jensens in an open-back combo. Hence, the modified circuit sits in between CON10 on the main tone control/channel selector PCB and the corresponding connector on the rear PCB.įew speakers were then able to handle more than 15 wattswhich meant that an amplifier approaching 50 watts had to use four speakers. CON10 has IC voltage supplies and the FX send signals. Care was taken to minimise the track lengths within the noise susceptible areas and to use low noise metal film components. FX Loop Modification To eliminate this problem, the FX buffer circuit has been re-created on a seperate PCB that can be installed much closer to where it is actually needed, near the channel/fx loop relays and the CON10 FX loop connector. The proximity of the susceptible circuits to the large tone control voltages allows the buffer to pickup the higher frequency audio signals and transmit them into the FX loop. The position of the IC on the board is also close to the tone circuits that use full value pre-amp audio voltages, as they are situated before the volume controls. The other half of the RC4558 op-amp (IC2b) is used in the tone circuits around the presence control and deep switching elements.

Marshall jcm 2000 dsl 50 schematic drawing