Ernie Ball Super Slinky Cobalt 5-String Bass (.040–.125) review: the lightest 5-string Cobalt gauge

Ernie Ball's Super Slinky Cobalt 5-String Bass takes the lightest gauge in the brand's 5-string Cobalt lineup, .040 to .125, 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 the easiest-playing option in Ernie Ball's 5-string Cobalt family, not a stripped-down afterthought. Ernie Ball ships three 5-string Cobalt gauges: Super Slinky (.040–.125, this set), Regular Slinky (.045–.130), and Power Slinky (.050–.135). Super Slinky is the pick when you want a 5-string's range without a 5-string's extra tension, useful on basses with a lower-tension neck or for players moving from a lighter 4-string Cobalt gauge who don't want the low B to feel like a different instrument.

No bassist is independently confirmed on this exact Cobalt gauge as of this review, so treat the tone claims below as Ernie Ball's own manufacturer positioning rather than a documented rig fact. That distinction matters: CYS doesn't guess at endorsements.

For the fully measured Cobalt vs nickel breakdown (output dB, brightness curve, longevity, bend feel), see Cobalt vs nickel Slinky: the voicing difference, measured. That comparison is built on Ernie Ball's guitar Cobalt line: the wrap-wire alloy and Ernie Ball's marketing claims carry over to bass, but CYS hasn't independently measured bass-specific numbers.

Regular Slinky Cobalt 5-String is the set Pantera's Rex Brown documents on his Spector USA NS-5, and the working-pro default for B-standard 5-string metal. Power Slinky Cobalt 5-String (.050–.135) is Ernie Ball's heaviest tier, built for down-tuned 5-string metal. If Regular feels stiff under your hand, or you're moving up from a 4-string Cobalt gauge and don't want the low B to dominate the feel of the neck, this Super Slinky tier is the easier-playing step down.

Ernie Ball's Cobalt bass catalog also ships a 6-string gauge (.032–.130) for extended-range players, outside this page's scope.

Full picture of how the Cobalt name works across Ernie Ball's whole catalog: Cobalt Slinky gauges explained.

Ernie Ball's standard nickel Slinky bass line ships the identical three-tier 5-string structure, Super, Regular, and Power Slinky, and two of those three tiers match their Cobalt counterparts exactly. Not this one. Cross-checking Ernie Ball's own nickel and Cobalt catalog pages against each other this run turned up a real, easy-to-miss difference: the nickel Super Slinky Nickel Wound 5-String (SKU P02824) runs .040, .060, .075, .095, .125, a half-thousandth heavier A string than this Cobalt set's .040, .060, .070, .095, .125. Every other string in the set is identical.

That quirk is specific to the Super Slinky tier. Ernie Ball's Regular Slinky Cobalt 5-String (.045–.130) and Power Slinky Cobalt 5-String (.050–.135) both match their nickel equivalents string-for-string. If you're swapping a bass between the nickel and Cobalt versions of this exact tier, expect a very slightly lighter A string on the Cobalt set rather than a true drop-in match. The practical difference at pitch is small enough that most players won't feel it during a string change, but it's worth knowing before you assume "same gauge, different alloy" applies uniformly across Ernie Ball's whole catalog. It doesn't, not on this specific tier.

• 5-string players who want easier tension. The lightest of Ernie Ball's three 5-string Cobalt gauges, useful on basses with a lower-tension neck or for anyone who finds Regular Slinky Cobalt 5-String too stiff.
• Players stepping up from a lighter 4-string Cobalt gauge who want a 5-string's range without the low B dominating the feel of the neck.
• Passive-pickup 5-strings especially, though the magnetic-response claim still applies through an active preamp.

• Aggressive down-tuning below B standard. The .125 low B is built for standard 5-string B tuning. For heavier down-tuned 5-string metal, Regular Slinky Cobalt 5-String or the heavier Power Slinky Cobalt 5-String hold pitch with more authority.
• 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.
• Budget-conscious players. At $44.99 versus the nickel Super Slinky 5-String's $27.99, Cobalt costs significantly more per set for a nearly identical gauge.

Because this is a lighter 5-string gauge than Ernie Ball's Regular or Power Cobalt tiers, a bass coming off a heavier set may need a light truss rod relief check, lower tension means less forward pull on the neck. Give a 5-string bass a proper setup check when moving to this gauge for the first time: nut slot width for the B string, saddle spacing, and intonation. 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.

Super Slinky Cobalt 5-String Bass is the easiest-playing entry point into Ernie Ball's 5-string Cobalt line: a lighter .040 to .125 gauge wound in the same cobalt alloy that Regular and Power Slinky Cobalt use, for players who want extended range without extended tension. It's a real catalog SKU with wide retail distribution, not a filler gauge, but no bassist is independently documented on this exact tier yet.

If you want the working-pro B-standard default instead, Regular Slinky Cobalt 5-String (.045–.130) is Rex Brown's documented Spector gauge. If price matters more than the Cobalt alloy bump, the nickel Super Slinky 5-String runs nearly the same gauge for $27.99 versus this set's $44.99.