The Story of the Vitamin Q Capacitor
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Written by CLE Guitar Works
Before it was ever associated with guitars, the Vitamin Q capacitor had a very different mission: survive war.
These oil-filled caps were first developed as part of U.S. military and aerospace equipment, built to meet high-spec reliability standards under the MIL-SPEC 1 series. The “Vitamin Q” label wasn’t a technical designation — it was more of an internal nickname, a nod to its “healthy dose of quality” — a little swagger baked into the cold-war electronics boom.
Born in Defense, Raised in Audio
Manufactured by companies like Sprague and Cornell Dubilier, Vitamin Qs were designed to operate in harsh, high-heat, high-voltage environments: fighter jets, radar systems, cold-war communications gear. But like a lot of military surplus, these parts found a second life when musicians, hi-fi builders, and amp techs began scouring old supply chains for parts with mojo.
And they delivered.
Why? Because these caps had paper-in-oil (PIO) construction, which gave them a unique tonal roll-off — slower, smoother, and more musically “rounded” than the ceramic or plastic film caps that came after. The oil helped reduce microphonic noise and shielded the foil from oxidation, while the paper gave them a warm, gradual taper.
In the ‘70s and ‘80s, boutique amp builders and modders started calling these surplus Vitamin Qs “the holy grail.” You’d see them in vintage Marshalls, Fender tweeds, early Hiwatts, and later, in custom tone circuits where feel mattered as much as function.
The Build That Made Them Famous
Inside each Vitamin Q cap is a stack of aluminum foil and oil-soaked paper tightly rolled and sealed in a glass or metal hermetic casing, often enclosed in an aluminum tube to keep out moisture and interference. They were overbuilt for musical use — rated for up to 600 VDC, with high thermal stability and a low rate of failure.
In other words: bomb-proof, both literally and figuratively.
The Jupiter reissues used in CLE harnesses today are not just copies. They’re built to that same level — with paper-in-oil dielectric, aluminum foil, and a mineral oil fill that mimics the original. The construction may be modernized for consistency, but the tone response remains true to its cold-war DNA.
When They Hit Guitars
While Sprague Bumblebees took center stage in ‘50s Gibsons, Vitamin Qs didn’t show up in production guitars until later — usually through the hands of modders and boutique builders who prized the tone. They were especially popular in telecaster upgrades, PAF-style harnesses, and early boutique rigs in the ‘80s and ‘90s.
Their fans weren’t just hearing things. Compared to modern film caps, a good PIO cap like the Vitamin Q sounds:
- Slightly slower on the taper — the treble rolls off more gradually
- Mids feel rounder
- Top end stays musical, even rolled way back
It’s not “better,” just different. And for certain guitars, certain amps, and certain players — it’s exactly right.
Why Use One Today?
Because some things don’t need fixing.
The Vitamin Q delivers a tone curve that feels familiar, usable, and forgiving. It smooths the top end without dulling it, and behaves consistently at every turn of the knob.
Jupiter’s modern take keeps the soul of the original, while making sure every cap is stable, safe, and sized to fit tight modern control cavities.
Want to try one yourself? Explore harnesses using the Vitamin Q →