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Pass Labs and Fuses

I continue to enjoy my Pass Labs Int-60 amplifier with my horn based system. My listening area has been intensively treated for acoustic - speaker interaction and it is always a joy for me to listen to a Dialed In system.

For my latest listening experiment I decided to evaluate the sonic differences using three fuses in the Pass amplifier. A brand new Bussman fuse, a Synergistic Research Blue fuse and a Synergistic Research Orange fuse. I keep this amp on 24/7 as suggested by the manufacturer. The Blue fuse has over a 1000 hours on it and the Orange had a 160 hours (continuous playing time) on it before any listening evaluations. The Bussman was listened to for the first time immediately out of the box.

The Bussman fuse did a fine job. But going from the Blue fuse which I had been using to the Bussman, there was a definite change. With the Bussman the sound was now more two dimensional. Instruments were not as full bodied. The depth of the soundstage was compressed front to back. I was more aware that I was listening to a recording versus being in the room with the musicians. The music was less emotionally involving. I did for completeness sake reverse the direction of the new Bussman fuse several times. It did consistently sound better installed in one direction, not huge but it is there.

Comparing the Synergistic Blue Fuse to Orange Fuse was similar to my past tube rolling experiences with my 300B tubed amplifier (but cheaper to carry out). Different tubes change the sound and these different fuses change the sound. Both of these fuses brought out more of the music that the Pass Labs amp was playing when compared to the Bussman fuse. Before any serious listening was undertaken, the fuses were evaluated for best sounding direction - and they both were directional.

The Orange fuse really is exceptional in it’s ability to let me enjoy the music and who is playing what. The detail of Willie Nelson’s nylon strings on his guitar had much better dynamics and richer texture than I have previously heard using the Blue fuse. His Stardust album continues to impress me.

When listening to music that has more musicians playing, such as on Sierra Una Noche, I can more easily distinguish each instrument and it’s contribution to the musical whole. Also in this live recording that uses only two mics, I get a better feel of each musician’s distance from the microphones and that they move toward and away from the microphones while playing. These factors allow me to forget I am listening to a recording of an event. With the Orange fuse, I feel I am at the event as it is playing.

This fuse experiment was fun to do and educational.
Feel free to call.

David Pritchard
575-644-1462

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Showing 3 responses by bdp24

bdp24's avatar
bdp24
9,510 posts
 


@uberwaltz,I brought up the opinions of Pass and Modjeski regarding fuses only as an intellectual exercise, for the sake of discussion. I like to hear opposing opinions on subjects, and don’t necessarily have to agree with one I cite (some consider that a cop-out. I don’t.).

I find it interesting when a designer who doesn’t "believe" in the audible superiority of certain boutique parts in all applications produces a product found to provide higher sound quality than those of a designer who does. Is that superior sq the result of design knowledge and wisdom, or merely a happy accident? I mean, if, say, Roger (or Nelson, or anyone else you care to name) can’t hear the difference between garden-variety and "audiophile" fuses, is the superior sound quality of his products achieved because he knows what good sound is---and what design choices lead to that superiority, or in spite of not knowing what doesn’t?

I myself have no opinion on the audibility of fuses (the used ARC PH3 I bought came with both a stock fuse and a Tuning Fuse, but I never A/B’ed them---I didn’t have the PH3 for very long), but do heed Modjeski’s warning about using the Tuning Fuse in a tube power amp. By the way, when I had Ric Schultz (of Electronic Visionary Systems, or EVS) modify my Audible Illusions Modulus 2 pre-amp into a phono-only RIAA amp, I took him up on his offer to bypass the fuse, a thought that now horrifies me!

Here is something I found interesting (hope you do too ;-): In a discussion on his Music Reference AudioCircle Forum on the subject of bass traps, Modjeski stated he was perplexed as to why anyone would spend money on subs, then spend more on bass traps to get rid of the bass they produce. In a flash, I realized that in spite of his vast knowledge of amplifier design, vacuum tubes, and many other hi-fi matters, Roger was not well-versed in matters concerning room acoustics. Bass traps are used not to suck up the bass produced by subs (or woofers in general), but rather the standing waves created by listening room dimensions (modes).

I do admit that when it is said a fuse changed the perceived tonal balance or other timbre-related issue, I find that claim extremely unlikely, if not impossible. How could a fuse possibly be frequency-related (other than 60Hz, etc.)? That just completely defies common sense and rationality. I also consider a fuse in an AC signal to obviously be bi-directional. How could it not be?!


bdp24's avatar
bdp24
9,510 posts
 

Modjeski actually did find the Tuning Fuse he tested measured differently than the Little Fuse brand he routinely uses. The difference was on the order of 120dB down ;-) . If your system can reveal that, and your ears can hear it, congratulations, you do indeed have a mighty fine system and golden ears.

Yeah, I know not everything that can he heard can be measured. But for a fuse to effect the tonality of a system? C'mon, man, you know that's not possible. A fuse doesn't know about tone, any more than an acoustical instrument knows about electricity.

As for fuse directionality in an AC application, that defies what used to be called common sense. Yeah I know, what about all the people who insist to hear a difference when the fuse is reversed? I have no idea (mechanical issues perhaps), but people also claim to hear God talking to them. Do you?

bdp24's avatar
bdp24
9,510 posts
 
Nelson Pass and Roger Modjeski (Music Reference) are two designers responsible for some of the best sounding amplification available today, and neither "believes" in fuses having a sound. What a coincidence. I guess that their designs sound good is just a happy accident ;-) . Pretty good for two deaf guys.
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