Marshall JTM-45 Amp

Marshall JTM 45 MK II Head and 1960A  4x12” Slant Cabinet, 1966/1968, SN: 7200

This is a 1960’s era Marshall Half Stack with a JTM-45 MK II head, Cezar Diaz modified and a Marshall slant front 1960A 4x12” cabinet. The head is an early “Plexi” version, so named for the reverse-painted clear plexiglass gold control panel. The panel itself is painted with “MK II” next to the On/Off switch, Standby switch and round On/Off indicator light. Knobs for Presence, Bass, Middle, Treble and two Loudness knobs, one marked High Treble and the other marked Normal. Four inputs follow, two marked Input One and two marked Input Two. Finally, the model designation, JTM 45, is painted to the right of the inputs. The black Tolex covering is segmented with gold piping, a feature unique to this era of Marshall products from the middle 1960’s. The original white plastic Marshall logo is intact, though the gold overlay has faded over time. The original handle with gold hardware remains intact as well. 

The back panel is made of opaque white plastic. This is a holdover from earlier JTM 45’s, though later examples with these white plastic panels are known, like this one,  as Marshall ran down their stocks of earlier parts. Two outputs are followed by a speaker impedance selector, a voltage selector, the Serial Number: 7200, a Bulgin plug for the Mains (power cord) and a 2 Amp Fuse. All of the lettering, with the exception of the embossed serial number, are cast into the plastic and painted a now faded black. The panel is bracketed by a Tolex plate, removable with six screws, with two cutouts for a gold mesh ventilation panel and the white plastic panel. Originally, the back Tolex panel would have a printed badge held in place with four brass pins. This badge is no longer present. 

The tubes consist of a pair of matched vintage KT66 power output tubes, one clear glass GEC and a smoked glass Marconi. Three vintage 12AX7 tubes and a British-made GZ34 round out the tube complement. The power transformer, output transformer and choke are all made by Drake and they are all original to the amplifier. The output transformer is marked 784103. They are mounted to an aluminum chassis. The end caps of the chassis are cast aluminum, a feature of the 1966-67 time period. One cap was signed by Cezar Diaz 10-11-95, at the time he completed his modifications to the circuit. At the time, he replaced a couple of out of spec components, most notably the multi-section capacitor mounted, on the interior, to one of the aluminum end caps. The top mounted multi-section cap was recently replaced and the original part is included with the sale. 

Diaz also added a few light modifications to the otherwise untouched circuit. Mostly, he added a few resistors and capacitors, here and there, to modify the tone of the second Input Channel. A footswitch, also included in the sale, has one input and two outputs. One output plugs into Input One and the second plugs into Input Two. The switch allows the player to choose between channels. The first has been left as a “clean” channel, while the second is louder and more distorted, two great tones at the flip of a switch! 

The cabinet is a 1960A Slant Cabinet. Like the head, this cabinet was built in the era of gold piping, which remains in the top panel. The Tolex was removed long ago and the cabinet was refinished. Originally, castors were mounted on the bottom. They are no longer in place, but the routes and mounting holes can still be seen on the bottom panel. The grill cloth is the traditional heavy woven paper, though it, the white edge piping and the white plastic Marshall logo all have been replaced. The steel side handles are original and in excellent condition. The back panel includes the mount for the input jack. 

The interior bottom panel is signed by Jim Marshall. There are four Celestion Greenback speakers mounted inside. The two upper speakers are the G 12 M variety in the 25 watt configuration. These have the earlier-style speaker lead tab. One has the model and serial number on the inside flange of the speaker and the other has that information on one leg of the speaker basket, both variations are common for 1968, when these were made. The two lower speakers are G 12 M 30 Watt Celestion Greenbacks, though these are slightly later with 1971 date codes and the later speaker lead mountings. All four speakers have their correct original Pulsonic speaker cones. The 25 Watt speakers have the correct manufacturer codes printed in white, ending in 102 003 and the 30 Watt cones are identical in appearance, but with illegible pencil marks instead. Again, these were common variations during the original production.

How does it all sound? Brilliant! The clean channel is thick with tons of midrange detail, warm bass notes and clear highs. The overdrive channel does just that, more distortion, but very articulate. The Cezar Diaz modifications take this already rare high performer to another level.