Ernie Ball Power Slinky Cobalt Bass (.055–.110) review: the Cobalt line's heaviest 4-string gauge

Ernie Ball's Power Slinky Cobalt Bass takes the heaviest gauge in the brand's 4-string bass range, .055 to .110, and winds it in a cobalt alloy instead of nickel-plated steel. Ernie Ball's own product page describes the Cobalt line as engineered "to maximize output and clarity," giving bassists "an extended dynamic range, incredible harmonic response, increased low end, and crisp, clear highs," with cobalt creating "a stronger magnetic relationship between pickups and strings than any other alloy previously available."

It's a straight alloy swap on a heavy, high-tension gauge. The cobalt wrap is more magnetic than nickel-plated steel, which is why Ernie Ball positions the whole Cobalt family for higher output and a brighter, more articulate voice through a passive pickup. That's a tonal descriptor, not a paid-artist claim: no bassist is independently confirmed on this exact .055 to .110 Cobalt gauge, so treat the voicing claims as Ernie Ball's own positioning.

Power Slinky sits at the heavy end of Ernie Ball's 4-string Cobalt bass family, which runs Extra Slinky (.040–.095), Super Slinky (.045–.100), Hybrid Slinky (.045–.105), Regular Slinky (.050–.105), and Power Slinky (.055–.110, this set). For extended range, Ernie Ball also ships a 5-String Regular Slinky Cobalt Bass with a dedicated low B.

Cobalt is a deliberate upgrade path, not a beginner tier. Ernie Ball prices it above the standard nickel Slinky bass line and aims it at players who already know they want a heavy gauge and want a different pickup response out of it. Power Slinky Cobalt Bass is the pick when you want the tightest, thickest low end in the 4-string Cobalt line, built for down-tuning and heavy attack, with the alloy's extra bite layered on top.

For the broader tradeoff between wrap-wire alloys on bass, see nickel vs steel bass strings. The measured Cobalt-versus-nickel voicing shift is documented on Ernie Ball's guitar Cobalt line; the wrap alloy and Ernie Ball's marketing claims carry over to bass, but CYS hasn't independently measured bass-specific numbers.

Power Slinky is the only 4-string Cobalt bass gauge with a .110 low E, which is what makes it the down-tuning pick: the thicker low string holds tension when you drop to D. If .055 to .110 feels too stiff for standard tuning, step down to the Regular Slinky Cobalt Bass (.050–.105) default. If you need a true low B, the 5-String Regular Slinky Cobalt Bass (.045–.130) is the extended-range answer, not this 4-string set with a string added.

Ernie Ball's standard nickel Slinky bass line runs the same heavy .055 to .110 gauge without the Cobalt wrap-wire upcharge. Everything true about the nickel set's tension and playability carries over here, because Cobalt changes only the wrap wire, cobalt alloy instead of nickel-plated steel, not the tension profile. A bass already set up for the nickel Power Slinky gauge takes this Cobalt set with no adjustment.

What you gain is the alloy's output and articulation bump, which helps a heavy, low-tuned string stay defined rather than muddy. What you pay for it is a higher per-set price and the same uncoated wear curve. No bassist is independently confirmed on the Cobalt version of this specific gauge as of this review, so read the tone claims as Ernie Ball's own manufacturer positioning until a documented player surfaces. For the deeper alloy tradeoff, see nickel vs steel bass strings.

• Down-tuned rock and metal bass. The .110 low string is the heaviest in the 4-string Cobalt line, so it stays tight and clear in Drop D where a lighter set goes slack.
• Heavy-attack players. Pick players and aggressive fingerstyle benefit from the extra tension and the Cobalt output bump, which keeps a hard-driven low string articulate.
• Passive-pickup basses. The magnetic-response claim behind Cobalt's voicing shift matters most on a passive pickup; an active preamp already adds its own gain and EQ, so some of the Cobalt bump gets masked by the preamp's coloring.

• Fast, light-touch players. The .055 to .110 spread is the stiffest in the Cobalt bass line. For quick fingerstyle and light tension, drop to Extra Slinky Cobalt Bass (.040–.095) or Super Slinky Cobalt Bass (.045–.100).
• Five-string players. This is a 4-string set. For a low B, the 5-String Regular Slinky Cobalt Bass (.045–.130) is the purpose-built option.
• Players chasing maximum string life. Cobalt is uncoated, same wear curve as any uncoated roundwound; Ernie Ball's own longevity line is Paradigm (Everlast nano-treatment), not Cobalt.

This is the heaviest 4-string Cobalt bass gauge, so a bass coming off a lighter set may need a setup check: the thicker strings add tension and can pull the neck into more relief, and the .110 low E may need a nut-slot check to seat cleanly. Break-in runs about the same as any fresh roundwound, 15 to 20 minutes of playing before the top end settles. Stretch each string, pull up gently a few times, retune, repeat, before a gig or session. New to restringing a bass, see how to change bass strings.

Power Slinky Cobalt Bass is the heaviest, tightest set in Ernie Ball's 4-string Cobalt bass line, .055 to .110 rewound in cobalt alloy for a defined low end and a brighter, more articulate voice than nickel-plated steel. It's the pick when you want the thickest low string in the Cobalt family, built for Drop D and heavy attack, with the alloy's extra bite layered on top.

If .055 to .110 feels too stiff for standard tuning, the Regular Slinky Cobalt Bass (.050–.105) is the lighter default. If you need a true low B, step over to the 5-String Regular Slinky Cobalt Bass (.045–.130).