Quantum Science Audio
QSA 5 x 20mm Slow Blow Fuse
Who knew something so physically insignificant could so completely transform the performance of an audio component.
"Many high-end audio tweaks I've heard sound great, but none have matched QSA's remarkable performance. I repeat, none." — Clement Perry, StereoTimes
"Same." — Mike Garner, Tweek Geek
Please Note: All QSA Fuses are special order and non-returnable. They can be exchanged for store credit and are upgradeable via our QSA Trade-Up Program.
It's Not the Fuse. It's What's Been Done to It.
A standard fuse is a $1 part — a tiny filament of wire that every watt of power feeding your component must pass through before it reaches the circuit. Your expensive power cord gets the signal to the component. Your power conditioner cleans it up. And then all of it runs through that little filament.
QSA's position, backed by over 22 years of research and development, is that this is the single biggest bottleneck in audio component performance. They call it "bottle neck distortion" — the sonic degradation introduced at this chokepoint in the power chain. Their proprietary treatment process is designed to eliminate it entirely, allowing your components to perform at their true potential rather than a filtered-down version of it.
The result is music that sounds more alive, more dynamic, and set against an ultra-dark background that lets every detail breathe.
The Value Proposition — and the Challenge
QSA will tell you directly that their fuses will outperform the sonic benefits of power cords and cables costing many times more. That's not marketing language. That's a challenge.
We've taken them up on it ourselves. Our listening tests of the Red fuse convinced us within seconds. It is not an overstatement to say that QSA fuses represent a paradigm shift in how we think about what actually matters in an audio system. They are the single most significant upgrade in sound quality we have ever heard from any accessory, cable, or tweak. It's not close. They redefine what value means in high-end audio, and we guarantee that.
How the Levels Work
Like QSA's receptacles and other products, the fuses are available in ascending levels: Yellow, Violet, Red, Black/Red, Black/Red Ultra, and Gold. Each level represents a more intensive application of QSA's proprietary treatment — deeper conditioning, more cycles, and in higher tiers, additional treatment protocols.
The jump between levels is not subtle. Customers who move from Yellow to Red don't describe a refinement — they describe a transformation. The Gold fuse, at the top of the range, is analogous to the Gold AC receptacle. Having both working together on a state-of-the-art system is, in our experience, something that has to be heard to be fully appreciated.
Start where your budget is comfortable. The Trade-Up Program means no dollar you spend today is wasted.
What to Expect When You Install One
The emotional and musical engagement these fuses unlock is unlike anything else we've encountered at any price point. Listeners consistently report:
- A dramatically darker, quieter background
- Increased dynamics and authority
- Finer detail retrieval without any added hardness or brightness
- A sense of ease and naturalness that draws you deeper into the music
Most of the break-in happens in the first 24 hours, though the fuse will continue to settle and improve for up to a month. Don't form your final opinion on day one.
Installation Notes
Directionality QSA fuses are directional — the arrow on the fuse indicates the correct orientation. If after installation the sound seems thin, harsh, or brittle, simply reverse the fuse and listen again. One of the two directions will be immediately and obviously better.
Which Fuse to Upgrade First If your component houses multiple fuses, focus on the mains fuse — the one accessible from the outside of the component, or the first fuse the power encounters on the inside. That is where the bottleneck is most significant. Replacing secondary fuses yields minimal additional benefit.
Warranty & Policies
- QSA fuses carry a 1-year warranty against manufacturing defects.
- All fuses are special order and non-returnable — please confirm your fuse size and type before ordering. We're happy to help if you're unsure. Contact us here.
- If you accidentally blow the fuse during the warranty period, we'll replace it once, no questions asked.
- Not sure where to start or which level is right for your system? Send us a message — this is exactly the kind of question we enjoy.
Customer Comments
- "This thing is amazing! Only 24 hours in but it sounds exactly as you and others have described. I'm thrilled!"- Evan S., Red fuse
- "After about 3.5 hrs listening, first 1-2 hrs Meh..2-3.5hrs these are SERIOUS fuses, Freakin Amazing at times!"Tom J., Violet and Black fuses
- "Just to let you know the fuse already arrived today!! I immediately installed it.The effect is fucking bonkers!!!I installed it in my Lampizator Pacific Dac with 300B's Molybdenum tubes from Elrog ... This Dac has turned into a sonic beast! It was already super fast, but this is now a stereoid version of what it used to be... It's insane, and completely what I hoped it would be. The money is heavy, but the sonic result makes it `almost' cheap."- Nico K., Red/Black Fuses
- "The clarity and quietness of these fuses is uncanny." - Chip F., Yellow fuse
-"Thanks for the amazingly quick ship on the new QSA fuse! If this is the 2nd from the bottom of their lineup, I can't imagine what some of the higher priced versions do. Installing this in my Decware Torii MK III was a revelation, and I had already tried several other after-market fuses!"- Chris P. Blue Fuse
I have 4 components - Power Conditioner, Transport, DAC and Amplifier. All four have the Red/Black fuse installed. I installed the first three fuses six weeks ago and just installed the Amplifier fuse three days ago. My experience with burn in is interesting. After five weeks, the first three fuses were still improving the sound - still getting better every day (although it is decreasing). This is fun because the stereo sounds better every day even though I have done nothing. Of course the sound changes the most in the beginning; the first few hours it changes a lot. The same is true for the first few days - big improvement every day! Some highs (like a triangle or bell) didn't sound right for the first 2 days, but then they were better than ever.
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The Sound
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General Impressions
- Everything sounds more beautiful
- There is more emotion in the music
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Specific Impressions
- Much lower noise floor
- More micro-detail is revealed
- There is less glare (I didn't even know I had glare!)
- Individual voices and instruments are more apparent
- They don't blur together when massed together
- I think it is called individuation
- The soundstage is deeper, wider and higher
- The sounds are more solid in the soundstage
- There are no gaps in the soundstage
- Everything sounds natural
- Frequency Response is linear at all volumes
- Understanding lyrics is much easier
- Bass goes deeper than before
- Bass is better defined and easier to follow
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General Impressions
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The Sound
The music just "pulls you in." You don't want to stop listening - very addictive. - Chris S., Black/Red Fuses
Our Impressions
What Reviewers Are Saying
Not one, but THREE Stereotimes reviewers have given QSA fuses their endorsement for 2020 Most Wanted Components. Read below to see what each reviewer had to say. Full Article
"...Upon placing two of the QSA Red/Black fuses in each Behold amplifier (I have two amps which require two fuses each - plus an extra fuse for my preamp), I turned up some music and just sat there slackjawed. The room filled with sounds from the studio I never detected before. When cymbals hit, the rivets sounded like rainfall. WTF is going on??? The music developed a renewed sense of PRaT that it never had prior. The music began flowing out of my loudspeakers in a way that closely resembled the Audio Note gear in my downstairs rig. That's an 8-watt 300B SET setup and sounds ever so sweet and delicate. The upstairs rig is more like a 600 lbs gorilla - with wings: bigger and bolder, but with the same earmarks that relay the music in the purest sense of the word. These are sonic enhancements said to be impossible to achieve from solid-state components and digitally-based systems. Not True."
"... Once installed I could not believe the effect that took place in my system after a 24-36 hour break-in period. My system was currently functioning at an exceptionally outstanding high level. I thought any improvement in the sound, going forward, would be a small one. Boy, was I wrong! These tiny miracles allowed my system's current significant attributes to expand beyond what I thought possible. Every characteristic we lovers of music hold important in sound reproduction became so much more pronounced. I'm delighted to say that at least four Stereo Times colleagues who now have these fuses in our systems have all experienced a similar dramatic result...this is one time where all of us who took the plunge feel it was well worth the cost. This is why I have chosen this QSA fuse as my 2020 Stereo Times Most Wanted Component. - Dan Secula
