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September 2014
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45 Degrees of Tone: The JTM45 Roundup




MetroAmp JTM 45 Kit and GPM 45 Custom Build

George Metropoulos is no stranger to the world of Marshall amps or to the online ampbuilding community. Having run MetroAmp for some time now, George offers everything from fully built replicas of many classic Marshalls to ready-to-build kits and hard-tofind replacement parts for vintage Marshalls. A player, George honed his amp-tech skills by adopting a DIY approach, taking care of his own amp repairs on the road. This extended into repair work at home, and then really took off when amps began coming in for restoration rather than simple re-tubing. After his ’73 Super Lead was stolen from a gig, he realized it might be best to leave the valuable amps at home, and so he embarked on a never-ending quest to replicate the tone of the old Marshalls.

Like all the builders in the roundup, George is passionate about vintage Marshalls and obsessive over the details that make these amps so coveted. We received two amps from Metro: the JTM45 kit (which can be purchased already assembled for an additional $400) and the GPM45, George’s custom-built JTM45 using NOS vintage parts. When we fired up the MetroAmp 45s, it was clear that they both came from the same camp. Both amps were meticulously built and incredibly precise in their layouts. The main physical differences between the amps came down to the caps, resistors and tubes. Both amps shared the same iron and layout, so they also shared a lot of the inherent tone in their circuits. As George is a fan of the mid-sixties JTM45s, Metro’s transformers are based on the Drakes, rather than the earlier Radio Spares iron. Still, there was no question that the GPM45, which included NOS Phillips mustard caps, Allen Bradley carbon comp resistors and a gorgeous set of Genelex KT66s, was sweeter sounding.

While those differences accounted for a tonal upgrade, what made the differences even more compelling was the way they affected the touch factor of the amp. Much like our ’65, the custom-built Metro had an ease about it that felt like a broken-in vintage head, making it a breeze to dig in, or to lay back on the strings and feel the amp act as an instrument. It was truly inspiring. Of all the amps in the roundup, this amp sounded most like our ’65—frighteningly close! I should mention that the Metro kit version was actually plugged in first, and before comparing it to the GPM45, we all agreed we’d be thrilled to have one in our collection. We may be splitting hairs here to some degree, but knowing that anyone can buy a complete kit for under a grand, and have that kind of quality and tone—that says a lot.

metroamp.com

JTM45 Kit:



GPM 45 Custom Build: