The introduction to Thoughts On Audio featured a letter to the editor Roger wrote to John Atkinson of Stereophile, so we thought it would be fitting to conclude with another letter to the editor from Roger to John Atkinson, this one on the topic of fuses. Roger was opinionated about a lot of things when it came to audio but his strongest and perhaps harshest opinions were reserved for what he called “boutique fuses”. In a nutshell he hated them. As a little taste of Roger’s rancor, check out this link to the topic on Roger’s Music Reference forum on Audio Circle: https://www.audiocircle.com/index.php?topic=105425.0
By the way, I would be neglectful if I didn’t point those of you interested back to Audio Circle where Roger’s archived Music Reference forum exists, albeit buried with the other archived manufacturers circles. There are more discussions about fuses in the Music Reference forum, as well as many other discussions on audio. So, while you are there you might want to peruse some of the other threads as well, there is a lot of good information, and not just from Roger: https://www.audiocircle.com/index.php?board=124.0
Dear John,
I feel it is important for the public to know that many of the premium fuses will afford no protection in certain applications. In particular, tube fuses must be of the high breaking construction to do their job. A high breaking fuse is filled with sand in a ceramic body. The sand is most important as it fills the space when the fuse element vaporizes in a high breaking application.
When a tube fuse blows in a DC circuit of high voltage it does not melt, it violently vaporizes forming a conductive plasma that continues until the entire energy of the power supply is dumped into the circuit destroying the tube it was meant to protect and possibly damaging the output transformer, and other components associated with the tube. I have seen these fuses cause extensive damage in several amplifiers. I have seen melted fuse holders (plasma is hot stuff).
Music Reference is not the only company using high breaking fuses. Audio Research has used them, Conrad Johnson uses high breaking KTK type fuses which one reviewer has recommended replacing with Tuning Fuses. He goes so far as to say one must have several on hand because blowing tube fuses is going to happen. This advice puts your amplifier at great risk.
The claims made for these types of fuses are egregious. To think that a fuse is microphonic is a stretch. To think that in the AC line this little microphone (if it indeed exists) can make any sound in an audio system stretches my imagination to the breaking point. One such claim is “resonance control”. Perhaps this valuable information can be used to make a new electronic musical instrument where fuses of different construction become tone generators. We would have to amplify their resonance by an extraordinary degree to hear them at all.
The reduction of series resistance is minimal. One manufacturer warns that their fuses are more precise in their current rating so a slightly larger value might be needed. I suspect they have had many blow with inrush current demands of power amps as their time vs. current curves are non-standard. If one goes much over the original rating to keep the fuse from blowing at turn-on one will lose the protection that the amplifier maker designed into their equipment.
This is a serious matter from both an editorial and technical point of view. It is my professional opinion and the opinion of many others that these kinds of products undermine our faith in the reviewers who state in print that these fuses elevate the product they are reviewing to a new level of performance.
Although Stereophile has had minimal mention of premium fuses other publications are touting their perceived virtues and listing them in many of the reviewer’s systems. One reviewer has “peppered his system” with them.
I encourage other manufacturers to comment on their findings, concerns, and any thoughts about these products.
Sincerely,
Roger A. Modjeski