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45 Degrees of Tone: The JTM45 Roundup

Nearly 50 years since its creation, the Marshall JTM45 remains both a relevant and near-perfect example of what a great rock ‘n’ roll tube amp should be.

It was originally built around the design of one of Jim Marshall’s favorites, the Fender Bassman; like the Bassman, the JTM45 was actually a fantastic guitar amp. Because of its consistent popularity, Marshall has offered a reissue version of the head— more than 20 years after production of the original JTM45 ceased. While the reissue is built with modern components and assembly techniques, it retains much of the tone, responsiveness and character of the original, hand-wired versions of the early days. No wonder builders today still carry on the tradition of the JTM45, and guitarists continue to seek out the pure simplicity and touch response of this tone machine. To celebrate the JTM45, I got together with my Sunday afternoon amp group, after contacting a handful of respected amp builders who sent us their versions of the amp. We fired them all up alongside an original and a reissue JTM45 to take a listen—and to enjoy one of the best amps ever designed.

About the Authors
About 5 years ago, while playing a 9/11 benefit show, I had the good fortune to meet two people who would not only profoundly impact my life with tube amps, but would become lifelong friends. John Rossi and Tony Burns were there that day; Tony, a killer player and a regular on the Tempe/Phoenix music scene, and Johnny, his friend and amp tech, making sure Tony’s amps were running well in 115 degree heat at the outdoor amphitheater. When I saw Tony’s wall of Marshalls next to my backline of Marshalls, it was an instant conversation starter.

We spent time between sets that day discussing the various finer points of our amps and gawking at each other’s rigs. The show went great but my ’67 Super P.A. felt a bit stiff, and wasn’t reacting in the most flattering way. This incident proved to be the catalyst, as Johnny was an underground semi-retired tech and ultra-fanatic Marshall enthusiast, and he had some ideas that he wanted to try out. He invited me over the following Sunday to check out the amp, and to experiment with various preamp and power amp tubes while BBQ-ing and having a beer. Tony was there, and it became clear that we all had a deep respect for these amps; rather than modify them, we wanted to bring them back to their former glory. After five years, and dozens of hacked-up Marshalls coming back from the dead, here we are. Over that time we’ve learned more about these amazing amps than any of us ever anticipated, and we’ve have had a blast in the process. I have no doubt in my mind, based on my readings of the various amp forums, that there are plenty of groups just like us all over the world doing the same thing.

The Lineup
The lineup consisted of our own 1965 original and 1990 reissue heads, two MetroAmp JTM45s (a kit version as well as the GPM 45), a Germino Classic 45, a Wallace Amplification BKW45 and Mojave Ampworks’ new Special Edition Plexi 45 head. After searching through our collection of cabinets, we settled on both an eighties Marshall JCM800 4x12 with blackback 25s, and a Mojave 2x12 cab with 1963-era Celestion Alnico Blues. It may sound strange that there were no pinstripe or basketweave cabs used for the roundup, but that wasn’t for lack of trying. Among all the members of the amp group, we actually have a pinstripe, a basketweave and a variety of Marshall 4x12s, but for some reason we always come back to the early-eighties JCM 800 cab with blackback 25s.

That particular cab has more clarity, tone and authority than any other, and it remains our favorite in the bunch—despite the cool factor of the older cabs. The 2x12 with Blues was a natural choice, as that flavor shares similarities with the mid-sixties Marshall cabs and is also a popular speaker configuration for Bluesbreaker combos. The guitars we used were our standard array of Les Pauls from the ‘70s, ‘80s and 2000s, as well as a newer 2008 Fender Strat and two early-seventies Strats. With everything in the room (it was quite a sight!) we were ready to begin.