Keith Merrow's guitar strings: the 7-string solo rig, sourced

What's on the guitar

Keith Merrow's rig sits on the technical side of modern metal:

Guitars: Schecter KM-7 MKIII (current signature), Schecter KM-7 MKII (previous generation), 7-string neck-through construction.
Strings: Ernie Ball 7-string Cobalt Slinky, custom .009–.062.
Tuning: 7-string Drop A (A-E-A-D-G-B-E) as the primary tuning for Conquering Dystopia and solo material.
Pickups: Seymour Duncan Nazgûl (bridge) + Sentient (neck).
Amps: Fractal Audio Axe-Fx III, Kemper Profiler, and a long history of Peavey 6505 / 5150 profiles.

Merrow is one of the original "YouTube-first" metal guitarists, his public gear documentation has been unusually detailed across a decade of videos, rig rundowns, and Sevenstring.org forum activity. That's part of why his string spec is easy to source.

Endorsed vs. verified use

The relationship is signature guitar endorsement with factory Ernie Ball Cobalt. Schecter's KM-7 MKIII product page and Sweetwater's listing both document the factory string set as Ernie Ball Cobalt Slinky 7-string .009–.062. Merrow's own Sevenstring.org forum activity confirms the same spec as his personal preference.

Why .009–.062 on a 7-string

Most 7-string sets run .010 or heavier on the plain high E. Merrow's .009 is a deliberate choice for lead playability, faster runs, wider bends, lighter picking attack on the top strings. The heavier .062 low A anchors the low end on a standard 25.5-inch scale (Merrow does not play a fan-fret or baritone, the KM-7 is a conventional 25.5 neck).

The Cobalt wrap choice matters most on the .062 low string. In Drop A on a 25.5-inch scale, the low note is near the bottom of a comfortable tension range. Cobalt's higher magnetic read translates that low note into a more defined rhythm attack than nickel would at the same gauge, which is the entire engineering case for the 7-string Cobalt line.

Sources

Schecter KM-7 MKIII Legacy 7-String product spec. https://www.sweetwater.com/store/detail/KM7M3TBB--schecter-keith-merrow-km-7-mk-iii-legacy-7-string-electric-guitar-transparent-black-burst
Sevenstring.org "Keith Merrow EB string gauge" thread. https://sevenstring.org/threads/keith-merrow-eb-string-gauge.311770/
Conquering Dystopia rig documentation and Merrow's own YouTube rig-walkthrough videos.

Re-verified on Schecter spec updates.

If you want this rig

Ernie Ball

Cobalt Slinky 7-String (.010–.062)

Price tier: $$

Why this one: Closest off-the-shelf match to Merrow's custom .009–.062. The .010 plain high E is slightly heavier than his custom; the rest of the set is the 2730 stock spec.

View on Amazon

Next steps

Full Cobalt line breakdown: Cobalt Slinky review.
Adjacent 7-string prog rigs: Mark Holcomb, Jason Richardson, Wes Hauch.
Drop C tuning guide for 6-string equivalents.

Frequently asked questions

What strings does Keith Merrow use?

Ernie Ball 7-string Cobalt Slinky in .009–.062, a custom gauge specifically called out on his Schecter KM-7 MKIII signature guitar spec. The .009 plain high E is lighter than most 7-string sets.

Why does Merrow use .009 on the high string?

His solo material leans heavily on fast picking and wide-interval melodic phrasing, which reads more easily on a lighter plain string. The Cobalt wrap compensates for the lower output .009 would produce on a nickel set through a passive pickup.

What tuning does he play in?

7-string Drop A (A-E-A-D-G-B-E) is the Conquering Dystopia and solo default. Some material extends lower. His 6-string work sits in Drop C or E standard.

Is Merrow endorsed by Ernie Ball?

He's endorsed by Schecter Guitar Research (his signature KM-7 MKIII), which ships with Ernie Ball Cobalt Slinky as the factory set. The string endorsement is brand-to-signature-guitar rather than a direct EB signature artist contract.

What pickups are on the KM-7 MKIII?

Seymour Duncan Nazgûl (bridge) and Sentient (neck), a common pairing for high-gain 7-string rhythm work, voiced for tight low-end articulation.

Is the Schecter KM-7 MKIII the same guitar as earlier KM-7 models?

No, the MKIII is the third-generation signature. Earlier KM-7 and KM-7 MKII models shipped with different factory string gauges. The MKIII Legacy is the current-production model that ships with the .009–.062 Cobalt set.