Ernie Ball Power Slinky Cobalt 5-String Bass (.050–.135) review: the heaviest 5-string Cobalt gauge

Ernie Ball's Power Slinky Cobalt 5-String Bass takes the heaviest gauge in the brand's 5-string Cobalt lineup, .050 to .135, 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 top of Ernie Ball's 5-string Cobalt family, not a niche outlier. Ernie Ball ships three 5-string Cobalt gauges: Super Slinky (.040–.125), Regular Slinky (.045–.130), and Power Slinky (.050–.135, this set). Power Slinky is the pick when the Regular tier's .130 low B still feels loose, whether that's aggressive down-tuning below B standard or just a player who prefers more mass under the fretting hand.

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. If Regular's .130 low B still feels loose under your attack, or you're deliberately tuning below B standard, this Power Slinky tier is the heavier step up.

Ernie Ball's Cobalt bass catalog also ships a 6-string gauge (.032–.130, SKU P02739) for extended-range players, outside this page's scope and not yet reviewed on CYS.

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. Fetching Ernie Ball's own nickel 5 & 6-String catalog page this run confirmed the Power tier's nickel counterpart, Power Slinky Nickel Wound 5-String (SKU P02821), runs .050, .070, .085, .105, .135, string for string identical to this Cobalt set.

That's a genuinely different result from the Super Slinky tier, where the Cobalt version's A string (.070) runs half a thousandth lighter than the nickel version's (.075). Power and Regular Slinky Cobalt 5-String both match their nickel equivalents exactly; Super Slinky is the one tier where the two alloys diverge. If you're swapping a bass between the nickel and Cobalt versions of this specific Power tier, it's a true drop-in, same tension, same feel, different wrap alloy.

• Down-tuned 5-string metal. The heaviest of Ernie Ball's three 5-string Cobalt gauges, built for players pushing below B standard who need extra mass to keep the low string from flopping.
• Players who find Regular Slinky Cobalt 5-String too loose. Same family, one more full step of tension on every string.
• Passive-pickup 5-strings especially, though the magnetic-response claim still applies through an active preamp.

• Standard B-tuning players who don't need the extra tension. Regular Slinky Cobalt 5-String is the documented working-pro default for straight B standard and will feel less stiff under the fretting hand.
• 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 Power Slinky 5-String's $27.99 for the exact same gauge, Cobalt costs significantly more per set.

Because this is the heaviest gauge in Ernie Ball's 5-string Cobalt line, a bass coming off a lighter set will need a truss rod relief check, more tension means more 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.

Power Slinky Cobalt 5-String Bass is the heaviest entry in Ernie Ball's 5-string Cobalt line: a .050 to .135 gauge wound in the same cobalt alloy that Super and Regular Slinky Cobalt use, for players who want down-tuned range without the low string going slack. 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 Power Slinky 5-String runs the exact same gauge for $27.99 versus this set's $44.99.