March 2013 \ And Don’t Miss… \ Gear of the Month \ 1968 Marshall 50-Watt JMP and 4x12

1968 Marshall 50-Watt JMP and 4x12

Chris Kies
 Premier Guitar March 2013

It all started when a drum shop owner couldn’t get rid of three pesky guitarists. If it weren’t for those meddling kids and their gosh-darned guitars, Jim Marshall might have made a name for himself selling drums. The pesky guitarists in question—Ritchie Blackmore, Big Jim Sullivan [the subject of PG’s February 2013 Forgotten Heroes feature], and Pete Townshend—were dissatisfied with their rigs. They yearned for more volume, more distortion, and the right sound. Marshall’s success in addressing those needs sealed the Lord of Loud’s legacy and forever changed the world of guitars and music.

In the early 1960s, after deciding to build handwired amps that rivaled Fender’s current stock, Marshall and his two closest cohorts—Ken Bran, a shop repairman, and Dudley Craven, an 18-year-old apprentice—began building Fender amp clones that used 5881 power tubes. Other small changes included Celestion 15-watt speakers compared to Fender’s preference for Jensen 15-watt models. After working with higher-gain preamp tubes—like the ECC83—and learning how different filters and capacitors had a transformative impact on the tone, Marshall heard a sound he knew guitarists would crave. Thus was born the iconic JTM45—which got its initials from Marshall’s son Jim Terry Marshall. A few years later, Marshall switched to KT66 tubes to create the even louder 100-watt Super Lead 1959. In 1968, the company dialed back the decibels with the unveiling of a 50-watt, small-box head that would be called the JMP—an acronym for “Jim Marshall Products.”

“What really makes this ’68 JMP unique among its brethren is that it was built in early 1968 and was one of two early prototypes that the company used to tweak things making the amp more efficient to build and still keeping it handwired,” says Gene Sinigalliano, owner of Ultra Sound Studios and Amp Sales. “Since the amplifier was a prototype, it is very likely that Jim Marshall or one of his top guys actually labored and constructed this specific plexi.” According to Sinigalliano, this particular Marshall model was an original design—a departure from the company’s first Fender Bassman-based amplifiers. Some of the long-lasting design shifts away from Marshall’s original recipe were the use of EL34 power tubes, a solid-state rectifier tube for more gain, and two separate channels— bright and normal. Guitarists such as Jimmy Page, Jimi Hendrix, and countless others would eventually blend the two channels to get some of the most iconic guitar tones of all time.

“This particular plexi has Mullard EL34s, Mullard 12AX7s in the input, Amperex Bugle Boy and Mini Watt ECC83s,” says Sinigalliano. “All these tubes are similar to what was originally installed in this amp.” The 1968 straight-front 4x12 has Celestion pre-Rola G12-30 speakers with 041 cones, as well as its original basket-weave grille.

Aesthetically, 1968 marked the first year Marshall switched to using white-script logos instead of gold lettering. That year also marked the first time front panels bore the JMP (rather than JTM) designation. Further, ’68 saw one more Marshall evolution— the complete switchover from fret cloth to the basket-weave cab covering that had been partially instituted in late 1967.

A special thanks to Gene Sinigalliano and Ultra Sound Studios and Amp Sales for the opportunity to feature these fine pieces of gear and the story.

Watch the amp in action:


     

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Comments

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UsernameComment
FuzzFace
on 03/09/2013 		Cool. Like to have it.
Cgifford
on 02/12/2013 		I rember the biggest disappointment in my life as a kid was plugging into a Marshall stack, around 1972. ( lore aside regarding this particular amp Btw whose tones are not particularly stellar in this demo I know youtube headgear etc ) using a Les Paul standard pounding out a power chord. My immediate impression was where the grunt. My personal rig at the time was a 1968 Traynor yba1 bass master with 4 jbl k120's . (essentially the same amp but with a higher plate voltage and more substantial transformers )I had a modified low range circuit using one coil out of a Gibson 355 tone circuit ( can't reminder what Gibson called it) and a les Paul standard. Plugged into the bright channel on about 9 and the normal channel dialled around 6-7 as everybody that knows the plexies and the bassmasters gain is effected by the volume of the unused channel . This was and still is to this day a killer amp combination. My personal opinion is that the plexies sounded better using the bright channel and dial in the the normal channel via the volume control. Irregardless what the folk lore claims. I think this demo underscores this. Just sayin Carl
lixamps
on 02/11/2013 		All good tube amps need some finesse when looking for your tone. To me the '59 tweed Bassman and the 50 watt Plexi define the rock & roll sound. But the crucial thing is that you need to coax it out of your guitar coupled with a great amp. The beauty of the old Plexi is that it sounds great with a single coil or humbucker just like the old tweed Bassman's that I used to play. I never had a Plexi but had the same vintage HiWatts and I wish I did have a Plexi. Luckily, I build amps so now I can have what I want!
Randy Aszman
on 02/11/2013 		I had a 100watt Plexi in the mid to late 70's that sounded very similar to this. But I sold it for a Hi-Watt, then sold that for an Orange, then sold that for a Fender Super Twin with a Bassman cab, and finally traded that for a Music Man 150HD. I always looking for a cleaner sound with with just the right edge, and after two or three sets the Marshall just sounded so dirty. But I wish I still had that Plexi.
Marshall50w
on 02/09/2013 		I have a 1970 50W Marshall Tremolo Head & a JTM 45 RI - My favourite sound is volume 6 which maintains a great clean sound just starting to break up. The pre amp valves in both are vintage Mullards ECC83. Can more distortion be had at volume 6 say with a change of valve/s ? rather than using a pedal.
tdclns
on 02/08/2013 		I agree w/ those who stated the tones needed to be dialed in better. Especially with an old amp like this. I have a Marshall JCM2000/DSL100, & it took some time learning where the sweet spots were, dialing in the tone knobs w/ the volumes, gains, etc. etc. Or else, you just get huffy, blah. That's why I get a kick out of guys that plug right in, touch a couple knobs, & shake their heads & say, 'crap.' Spend some time learning about the amp before you go & dismiss it.
Mike
on 02/08/2013 		I have to agree with Jon for the most part. Lots of this demo sounded really good, but the AC/DC and Page licks, etc, were played with way too much gain.
Peter Yianilos
on 02/08/2013 		I have a 68 plexi, which I bought new in 1969 with an 8x10 cabinet. I have sold the speaker cab but recently restored the head to its original glory using NOS parts. As I have owned it all its life, it is now practically a museum piece, in near flawless condition. The restoration process taught me a lot about the dozens of preamp - eq configurations which were issued by the factory over the years. If you have one and don't like the sound, it CAN be corrected very cheaply.
hlestringman
on 02/08/2013 		I remember that sound back from 1968. That is the classic rock and roll sound of the late 60s for sure. I am lucky to have heard it from the players before they became big stars, they were just guys playing in bands trying to make it in the Bay Area. Lots of fun and memories. Thanks for the demo, great stuff.
Dave
on 02/08/2013 		I've got a 68 50 watt plexi that i paid a grand for in 91 at Bay State Vintage guitars ,it was sitting on top of a mint 8 -10 cab and the test guitar was a 56 Les Paul Custom which was the lightest les paul i've ever played and the sound was glorious, Craig the owner wanted $500 for the cab and $6000 for the black beauty , wish i could go back in time with some cash . A few years later i won a USA Ibanez shred guitar that was supposedly worth $2000 at E.U Wurlitzer in a drawing and me being me i asked if i could trade it for a Purple Jeff Beck Strat and the kicked me out of the store. So there i am with this crazy looking Ibanez that had a girl on a motorcycle airbrushed on it . I kept for a few days but i'm a Fender/Gibson guy so i went to Daddy's Junky Music to see what i could trade it for on Christmas Eve and low and behold they had a mint 68 marshall top cab with pre rola celestions and i got it for an even trade , still have em both !!!



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