Custom Shop Build Overview

Martin Custom Shop GJ-28 Ambertone Grand Jumbo #3037731

The Martin Custom Shop GJ-28 Ambertone Grand Jumbo is a bold, full-range acoustic guitar that brings the rich harmonic complexity of a Style 28 into an expansive Grand Jumbo body.

This Custom Shop build pairs a premium spruce top with East Indian rosewood back and sides, delivering deep bass, shimmering overtones, and a wide dynamic range. The larger Grand Jumbo body increases internal air volume, producing enhanced projection, greater sustain, and a powerful, room-filling voice.

Finished in a striking Ambertone burst, this guitar blends traditional Martin tone with a visually rich, vintage-inspired aesthetic that stands out both on stage and in the studio.

Why the Grand Jumbo Body Matters

The Grand Jumbo body expands on the dreadnought concept by increasing surface area and internal air volume, creating a broader tonal footprint.

Deep, piano-like bass response
Greater overall volume and projection
Wide dynamic range for expressive playing
Full, immersive sound ideal for live performance

Combined with rosewood back and sides, the result is a powerful, harmonically rich voice with exceptional sustain and clarity.

Custom Shop Craftsmanship

Handcrafted in Nazareth, Pennsylvania, this Custom Shop instrument features Martin’s traditional dovetail neck joint and solid tonewood construction to maximize resonance and long-term stability.

The guitar is built to deliver both strength and responsiveness, allowing the top to move freely while maintaining structural integrity under dynamic playing styles.

The classic Style 28 aesthetic, combined with the Ambertone finish, gives the instrument a timeless look that complements its powerful tonal character.

Tone & Performance

The GJ-28 delivers a rich, expansive voice with the depth and overtone content that players expect from a rosewood-bodied Martin. The Grand Jumbo body enhances projection and sustain, creating a commanding acoustic presence.