Quantum Science Audio 5 x 20mm Slow Blow Fuse

Quantum Science Audio

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QSA 5 x 20mm Slow Blow Fuses

Who Knew Something So Physically Insignificant Could Sonically Transform Your Audio Components.

Tweek Geek Speek: QSA Fuses The New Top Tier Tweek


"...many high-end audio tweaks I've heard sound great, but none have matched the QSA's remarkable performance. I repeat, none." - Clement Perry, StereoTimes

"Same..." Mike Garner, Tweek Geek


  • Black $28
  • Blue $72
  • Yellow $213
  • Violet $711
  • Red $1422
  • Red/Black $2844
  • Silver $4995

Quantum Sciences & Their Philosophy

Quantum Sciences has been working on research and development of their fuses for over 22 years. Their proprietary technology removes what they call "bottle neck distortion" making the sound reproduced by your components more alive, unbelievably dynamic with an ultra dark sonic background.

The Fuse: One Of The Biggest Bottlenecks in Audio Component Performance

Their belief is that the biggest bottleneck in an audio components' performance is the fuse. all of the power feeding your component (probably from a very expensive power cord) ultimately runs through this tiny filament of wire, a $1 part, before it enters your system. Power cords can an do help, as does power conditioning, but ultimately it is the fuse that is the weak link in the power chain. QSA has spent 22 years working to eliminate this bottleneck. Their line of fuses spans a wide range of performance levels and price points. All are designed to eliminate the distortions created by a typical fuse. The end result are fuses that allow your components to perform their best. Drawing you into the music on an emotional level you might not have thought possible. 
QSA's value proposition and challenge to the customer it that these fuses will outperform the sonic benefits power cords, and cables costing many times more.

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

Our Impressions

Our listening tests of the Red Fuse ($1400) convinced in seconds of their value. It is no understatement to say that they are a paradigm shift in our concept of what matters in the audio system. These tiny devices bring out the emotional/musical potential of any component like no other tweaks or accessory we have EVER listened to has. The amount of performance that these fuses allow your component to perform at is well worth the asking price. We guarantee it.
Bottom Line: These fuses offer the most significant upgrade in sound quality compared to any other accessory, cable, or tweak we have ever tried. It's not even close, they redefine value for high end audio. We encourage you to try them and we stand behind them with our 30-Day money back guarantee.

"...$1422 each! That's crazy? I lamented, "This is just way too much to ask for a fuse, sir." Tsang's only response again was, "this fuse will outperform any tweak in your system. Looking at my components, I started taking an inventory. I've some serious tweaks in my space, namely the Novum Resonators, various Entreq ground boxes, Jack Bybee's iQSE Fatboys, alongside Kemp's AC conditioner and Frank Acoustics Ultra Bank products. All are excellent. None are cheap...

...Knowing the sonic improvements heard between the standard $28.50 Black series to the $711.00 Purple model, I admit, I wasn't sure what to expect. Insuring directionality, I just popped them in and just let the music play for the next 24 hours. Upon my return, I immediately noticed how much of a deafening silence had crept over the system. Weirder was this quiet did not affect the high frequencies negatively whatsoever. In fact, the opposite occurred. The top-end opened up with a sense of relaxation and ease, which aided a remarkable sense of brilliance. Bass was quicker afoot and possessed details that made me sit up and pay closer attention. Voices appeared more transparent but with more harmonic realism, flesh tone, and focus. Out of all these obvious improvements, the absolute lack of noise stood out the most. The top-end sparkle improved with more excellent sparkle, weight, and shimmer (yes, cymbals carry weight).  All in all, the QSA Red series fuses introduced an altogether different sonic fabric that is rarely associated with digital sources and its playback - regardless of format or resolution. This, dear reader, is the magic of analog!..."Clement Perry, StereoTimes

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

publisherschoice2020.jpgQuantum Science Audio Ultra High-End Fuse ($2,844 ea): "...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.

...The QSA doesn't sound like a significantly impressive-sounding fuse as much as it sounds like a hidden technologhoused inside of a significantly impressive-sounding fuse. The QSA Red/Black fuses somehow freed up what I can only describe as bottlenecking occurring inside the amplifier and directly at the fuse-holder. ...Yes, the QSA products are insanely expensive, as are a lot of things in our hobby. But make no mistake, the QSA Red/Black fuses are also about the most impressive after-market tweak to have graced my listening space. Yick Man was right; his fuses do sound as good as any $10,000 AC cords I've owned. (Review in the works Clement Perry)
Quantum Science Audio Ultra High-End Fuse ($2,844 ea):  My first reaction to hearing about the benefits of changing to these fuses was incredulity, to say the least. Then, when learning the price, I actually laughed out loud and said ”no way, I don’t give a s**t  what they do.” I now have to admit that I have to eat those words. The sonic improvements these fuses make are simply astonishing and that is an understatement. In my system (Behold BPA768 amp & pre-amp), there were immediate and DRAMATIC improvements in every aspect of sound that you can think of, (bass, midrange purity, sweet highs, immense soundstage, etc.) with the result that everything becomes more like the real thing and listening pleasure is increased to a level that continues to amaze.  Are they worth the money? Let’s just say I, and others, have spent far more for an improvement in sound that falls far short of what these things do.  (Ron Cook) 


Quantum Science Audio Ultra High-End Fuse  ($2844 ea): "... 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) 

What Customers Are Saying

Chris S. 

The QSA Top of the Line Fuses

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.

  • The Sound

    • General Impressions
      • Everything sounds more beautiful
      • There is more emotion in the music

    • 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

The music just "pulls you in." You don't want to stop listening - very addictive.

These changes have been The single best tweak I have ever made! And I have been tweaking my stereo for 40 years.



These fuses are directional, as indicated by the arrows. If after installing the fuse the music sounds thin, harsh and brittle you may have it facing the wrong direction. Try reversing the direction of the fuse and listening.

Break In

Most of the break in is done in the first 24 hours. But they will continue to improve and change for up to a month in some instances.

More Than One Fuse

If your amp or any component has multiple fuses inside, the most important fuse to upgrade is the mains fuse. The mains fuse is usually the one with the fuse holder on accessible on the outside of the component, or on the inside right where the power is connected initially.  Replacing the other fuses has a very minimal effect.


The QSA fuses are warranted from defects for 1 year. 


If you cause the fuse to accidentally blow during the warranty period, we will replace it one time.

We Stand Behind Our Words and These Fuses

We have been in business since 2003. We made our reputation on offering great advice, knowing  our products, service, service ,service, and our 30-day money back guarantee. We stand behind the QSA fuses with this same 30-day guarantee. If you try one of these fuses and don't think it is worth the investment, simply return it in it's original packaging and condition, and we will refund you the purchase price. You have our word.

1 year warranty. 1 Replacement if fuse is blown by accident. If you blow 2 fuses, there is something wrong within your electrical or audio system you need to address before ordering another fuse.

19 Reviews Hide Reviews Show Reviews

  • 5
    QSA fuses

    Posted by David Conklin on 1st Oct 2022

    I've long realized that fuse upgrades are one of the best improvements you can make in your system. The QSA fuses are wonderful. I started with the red fuses for my integrated amp, DAC, and CD player, and (a bit later) a light violet for my subwoofer. The improvement I heard from my subwoofer was nearly as great as that from my other components, so when the opportunity arose, I got a red/black fuse for the sub. I was not disappointed. Not just better bass, but better tonality throughout the frequency range, and more "solid" overall sound. No negatives.

  • 5

    Posted by Dan Curtis on 8th Jun 2022

    I recently replaced the stock fuses in my Merason Dac1 with a pair of the QSA Yellow fuses the improvement in sound has been amazing ! I also have their Red Receptacle and a Violet fuse in my Qualiton a50i and will soon be adding their Orange fuse to my Innuos Zen MKIII. The qsa products have astounded me in the way they have been able to improve my sound quality in a way I never thought possible!

  • 5
    Quantum Black, Yellow, Red, and Red/Black fuses

    Posted by John on 23rd May 2022

    Starting with three Black fuses (very low risk) I was shocked at the sonic improvement: WAY out of proportion to their cost. I next traded-up to three Yellow's, then to two Red's and a Red/Black, and finally to two more Red/Blacks to complete the three fuses my system needs. 1.) You can't get more improvement/$ than with these fuses, and 2.) The next step up is noticeably bigger than the previous ones. This is NOT snake -oil. If all you do is buy Black's, you'll be thrilled at what you hear ; move up the line (at FULL trade-in value) and you'll be glad you did. The best audio components I've ever bought.

  • 4
    QS Yellow fuses

    Posted by George Hoffmann on 13th Apr 2022

    While not dramatic in my system (lots of tweaks already), the fuses added silkier highs, better center sound stage, and improved timbre (added to a LTA z-10 mk. II amp).

  • 5
    Red fuse

    Posted by Thomas Rhodes on 12th Apr 2022

    The improvement to my system with the red fuse was astonishing. I decided to upgrade to a red/black. I’ve never had any tweak or change in equipment have this profound of a change to my system as the QSA fuse.

  • 5
    QSA fuses

    Posted by Solomon on 24th Mar 2022

    I have installed several violet fuses throughout my system. The effects are profound in every area, especially dynamics, power, separation of voices, clearer upper treble, more impactful bass. I do not understand how fuses can do that, but it is like for each component the tap has been opened more fully, in power, subtlety, and musicality.

  • 5
    Quantum Science Black fuses

    Posted by John T Zermani on 20th Dec 2021

    I started at the bottom with Black's to get an idea of how much difference/improvement they might make. As difficult as it is for some to believe a fuse can accomplish much, I now agree, completely with the manufacturer: Three, $28.50 fuses (Preamp, two monobloc's) have improved the sound of my system more than any IC's, power cords, or speaker cables ever did (at $90 total) and that includes a good number of multi-kilo-buck wires. They may do more than most any component upgrade ever did as well. I am now going up the ladder to Yellow and maybe even Light Violet. Tweek Geek's very generous (and unique, I think) upgrade offer means you lose nothing by the upgrade process and even have insurance against a blown fuse! Just do it; spend $28.50 each. You'll be happy you did.

  • 5
    QSA yellow fuse

    Posted by Tahoe on 23rd Sep 2021

    It's amazing what this fuse does! Don't believe the nay-sayers. I installed this fuse in a 20 year old cheap run-of the-mill CD/DVD player. It was transformed immediately. The noise floor dropped, extra details that I didn't know were there popped out (what was that!) The sound became very transparent, well integrated, with deeper detailed bass, and dynamic, engaging presentation. My old player became very listenable...seriously! It makes more of a difference than a power cord or interconnect upgrade. I plan to upgrade to violet!

  • 5
    QSA Yellow

    Posted by Patrick Mowbray on 1st Sep 2021

    I’ve been an audiophile for 35 years and the yellow fuses are the best upgrade that I’ve ever purchased. Even bigger than adding a $3500 power chord recently. Bigger soundstage, more bass, more texture, more depth, and more musical. Amazing!