I first tried some Isoclean audio grade fuses in January of 2008 (Isoclean Review). I replaced the 12 amp power line fuses in my Parasound Halo JC 1 monoblock amplifiers. I am far more impressed with these fuses now than then. The AC power infrastructure and vibration abatement improvements implemented in the fall of 2008 provided new levels of resolution that made the benefits of these fuses more apparent.
Isoclean fuse at top left and HiFi Tuning fuse at right. Their stock counterparts are below them.
Although the power amp fuses are the same, my audio power infrastructure is vastly different. In January of 2008, I did not have multiple dedicated AC circuits, multiple passive AC conditioners, an AC regenerator, and low noise power cords. I did not start AC infrastructure upgrades until August of 2008.
Now, switching back to the stock power amp fuses was the visual equivalent to going from a well lit room to dimming the lights a quarter way down. Tactile sensation and sound stage width and depth was also significantly reduced.
Oscilloscope measurements revealed that these fuses are actually noise filtering/power conditioning devices in addition to protection devices. I speculate that the manufacturers of audio grade fuses do not describe them as power conditioning devices because:
1. They would have to describe the proprietary filtering mechanism in more detail than they care to.
2. Classifying the fuses as power conditioning devices would add another layer of regulatory approval (and more costs to the manufacturer).
Both the HiFi Tuning and Isoclean fuses have arrows on their cases which indicate that they should be oriented in the direction of current (energy) flow. Some people have scoffed and ridiculed the idea of "directional" AC fuses. Rather than something to ridicule, I saw the arrows as indications that there was something going on inside the "fuses" that required a specific orientation. Initially, my ears told me that the fuses sounded better in the direction of the arrows than against it. Noise spectrum measurements with an oscilloscope verified that the line noise was lower in the direction of the arrows than against it.
I sent the following email to HiFi Tuning's offices in Germany:
I tried a 0.5 Amp Hifi Tuning fuse in my Pass Labs Xono phono preamp and Pass Labs X0.2 line level preamp. The results were spectacular.
Listening tests confirmed that the best, most detailed, most open sound was achieved when the fuses were installed with the logo pointing in the direction of current flow.
I also took some noise spectrum measurements with an oscilloscope and I definitely saw more power line noise after the fuse when it was installed with the logo pointing against the current flow.
The resistance of the fuse measured the same in both directions.
What is it about the Hifi fuse's construction that makes it directional?
I received this response the same day:
Thanks for the Feedback,
Please understand that a magician never tell anybody his tricks....;.-)
But be sure that we made the best fuses on the planet, nobody can make it better!!!
I sent the following email to Isoclean's offices in Hong Kong:
"What is the electrical theory behind the reason why the IsoClean fuses need to be installed in one direction for best sound quality?"
I received this reply:
The meaning is same as arrow direction in signal cables. Always want to keep same direction as indicated. Hope you understand.
The only thing I understood from Isoclean's response was that they just wanted me to go away.
Fortunately, as a result of my power line noise reduction research, I had become aware of physicist Jack Bybee's pioneering research in materials-based noise reduction using special metal oxides and ceramics. His research was focused primarily on "quantum purifiers" which reduced noise at the quantum level rather than the gross level (RF, EMI). Bybee filters are used in every aspect of high end audio gear, from speakers, to amps, to source components to turntable motors. My Teres Reference II turntable motor uses Bybee noise filters. It is apparent that these audio grade fuses employ Bybee or a similar materials-based noise reduction technology. The interested reader can find further information on this fascinating technology at the Bybee Technologies Website and numerous other online resources. Just do a search on "Jack Bybee", "Bybee purifier", or "quantum purifier".
A lot of HiFi Tuning's website is in German, but I was able to glean enough information to tell that they are heavy into materials-based noise reduction products.
At the time of my initial purchase of Isoclean audio grade fuses in January of 2008, I did not have a good understanding of what they were doing. I clearly heard improvements and I also heard the fuse's better performance in one direction than the other. It was only after I took noise spectrum measurements that I came to realize that these devices, rather than being mere "fuses", are actually noise gates and resolution enhancement devices. Accordingly, in an audio system with appropriate resolution capability, they provide benefits well in excess of their cost. I was initially stung by what I considered to be high prices for these "fuses" ($25 to $45). Now, in light of what they actually do, and my better understanding of noise reduction science, I realize they are one of the most effective low cost resolution enhancement tweaks you can buy. Please be aware that, as with any electrical noise reduction device, your results will vary according to your associated equipment and power line quality.
The improvements that the Isoclean fuses brought to my power amps were very obvious. The improvements that the HiFi Tuning fuses brought to my line level and phono preamps were transformational, with respect to sound stage width and depth, dynamics, overall detail and tactile sensation, with the phono preamp benefiting more so than the line level preamp. The phono preamp has a much lower noise characteristic than the line level preamp. This makes noise reductions, even small ones, easier to discern.
Replacing the stock 1A wire wound fuse in my Pass Labs X0.2 preamp with a HiFi Tuning fuse resulted in a dramatic improvement in sound stage dimensions and quality as shown in figure 1.
Figure 1. Sound stage dimension changes after preamp fuse upgrade.
Figure 1 shows the changes in instrument and vocal locations before and after the HiFi Tuning fuse installation for the CD version of the song "Funkin' For Jamaica (NY)" by trumpeter Tom Browne (released in 1980).
"Funkin' For Jamaica (NY)" comprises a layered mix of well recorded and spatially stable audio images. The band members engage in dialog talking about events from their everyday lives in Jamaica, New York as well as comments about the physical attributes of the female vocalist and comments about trumpeter Tom Browne's personality and his dedication to music. The band member's voices are scattered across the sound stage.
Under everything is a constant, heavy, growling electric bass beat. On the left and right of the sound stage are identical constant "popping" effects which sound like they are made by a guitar, but it might have been a synthesizer since a synth is listed in the song's instrumentation list. There is an electric lead guitar to the far right which only plays accent notes at the end of the vocalist's phrases.
Before installation of the HiFi Tuning fuses in the Pass Labs X0.2 preamp, Tom's Browne's trumpet and the lead male vocalist shared the same space. The "popping" guitars, female vocalist and the lead electric guitar were 3 feet ahead of the speaker plane. There was a band member's voice coming from the space directly in front of each speaker.
Everything is apparently louder, certainly clearer and definitely more dynamic.
The female vocalist, popping guitars and lead guitar came forward 2 feet for a total of five feet ahead of the speaker plane.
The lead male vocalist now had his own clearly defined space between the female vocalist and the trumpet.
The band member's voice that was on the left edge of the left speaker was pushed to the left by 1 foot.
The band member's voices in front of each speaker were repositioned a foot further forward.
The vocal/popping guitar/lead guitar grouping on the right were repositioned 2 feet further to the right.
The electric bass growl was faster, more detailed, and much heavier...it was now more reminiscent of an animal's growl than that of an electric instrument...and had more textures. Individual bass notes had more clearly defined trailing edges and decay.
The popping guitar's pops were heavier, more sharply defined and more percussive.