J Mascis's guitar strings: the Dinosaur Jr. indie-rock rig, sourced
Documented string gauges, brands, and tunings J Mascis uses with Dinosaur Jr. Featured in Ernie Ball's String Theory series. With citations.
Dinosaur Jr. · reviewed by the Change Your Strings editorial team ·
J Mascis uses Ernie Ball Regular Slinky Cobalt (.010–.046) with Dinosaur Jr. His Cobalt use is documented in Ernie Ball's String Theory artist profile and in forum threads where Mascis discussed moving to the Cobalt line from nickel-plated Slinky. Primary guitar is a purple Fender Jazzmaster with his signature Squier and Fender signature models available. Tuning is E standard on most current material.
What J Mascis reaches for
Sourced by the Change Your Strings editorial team · last verified 2026-04-20 · Affiliate links
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At a glance
Role
Active
Affiliations
- Dinosaur Jr. (founder, lead guitarist + vocalist)
- Solo artist as J Mascis
- Squier J Mascis Jazzmaster signature
- Fender Custom Shop signature partner
- Featured artist, Ernie Ball String Theory
Notable credits
- Dinosaur Jr., You're Living All Over Me (1987)
- Dinosaur Jr., Bug (1988)
- Dinosaur Jr., Where You Been (1993)
- Dinosaur Jr., Beyond (2007)
- J Mascis, Several Shades of Why (2011)
- Dinosaur Jr., Sweep It Into Space (2021)
Official media
What's on the guitar
J Mascis's rig is one of the most recognizable in indie rock:
- Guitars: Fender Jazzmaster (primary), signature Squier and Fender Jazzmaster models available.
- Strings: Ernie Ball Regular Slinky Cobalt (.010–.046).
- Tuning: E standard (current), Eb standard (some earlier catalog).
- Amps: Three full Marshall stacks, all on simultaneously, for the Dinosaur Jr. wall-of-guitar sound.
- Pedals: A very long signal chain, including multiple Big Muff variants and a Tube Screamer for solos.
Mascis is one of the few Cobalt users whose sound depends on the strings not sounding tight or hyper-articulate. His style is volume, sustain, feedback, and long sustained notes bent through Marshall stacks, the opposite of a prog-metal clarity argument. The Cobalt choice here is about compensating for the Jazzmaster's lower-output pickups, not about tightening a rhythm attack.
Endorsed vs. verified use
Mascis is a documented Ernie Ball Cobalt user via String Theory and the Ernie Ball forum. His String Theory profile page treats him as a featured artist, and the Ernie Ball forum thread "J Mascis of Dinosaur Jr. likes Cobalts" documents his move to the line from nickel-plated Slinky.
Why Cobalts for a Jazzmaster
Jazzmaster pickups are wide, flat, and lower-output than Strat or Tele single coils. Many Jazzmaster players swap pickups for higher-output options (Curtis Novak, Lollar High-Wind) to get more saturation and articulation out of the guitar. Mascis went a different direction, he kept the vintage-voiced stock Jazzmaster pickups and added Cobalt strings to get the output bump at the string level instead of the pickup level.
This is the same engineering case as Steve Vai's .009 Cobalts through passive humbuckers: when the guitar's own output is lower than a high-gain style demands, the Cobalt wrap closes the gap without requiring a pickup swap.
Sources
- "Ernie Ball String Theory: J Mascis." https://www.ernieball.com/stringtheory/j-mascis
- "J Mascis of Dinosaur Jr. likes Cobalts." Ernie Ball Forum. https://forums.ernieball.com/threads/j-mascis-of-dinosaur-jr-likes-cobalts.55273/
- "Ernie Ball Cobalt Slinky." Product page. https://www.ernieball.com/guitar-strings/electric-guitar-strings/cobalt-slinky
- "Equipboard, J Mascis gear." https://equipboard.com/pros/j-mascis
Re-verified on each Dinosaur Jr. tour cycle or Ernie Ball String Theory update.
If you want this rig
Regular Slinky Cobalt (.010–.046)
Why this one: J Mascis's exact set. Cobalt wrap compensates for the Jazzmaster's lower-output single coils by adding magnetic read at the string, not the pickup.