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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

davidpritchard
almarg's avatar
almarg
9,670 posts
 
Regarding directionality, I would remind everyone that in past fuse-related threads there are two members who have cited actual experience rotating the position of a fuse in its holder without changing its direction. Namely Atmasphere and SGordon1. Both gentlemen reported that doing so resulted in audibly significant sonic consequences. Based on his experiments Ralph (Atmasphere) also stated that ...
Reversal is improving the contact area because fuse and holder are not dimensionally perfect and the fuse might sit better in the holder in one direction. By rotating the fuse in the holder without reversing it gets the same effect only more profoundly.
If so, it would seem to say that many and probably most of the reports of sonic differences occurring as a result of changing the direction of a fuse are accurate, while assertions that it is impossible for a fuse to be intrinsically directional in an AC circuit (which I believe to be true) are also accurate.

In any event, it seems to me that dismissing the findings of these two gentlemen and/or Atmasphere's explanation of those findings on the basis of conjecture, rather than actual experience, is no less objectionable than dismissing reported findings of directionality on the basis of conjecture rather than actual experience.

Regards,
-- Al

geoffkait's avatar
geoffkait
23,365 posts
 
Yeah, sure, Al. You guys keep bringing this issue with the fuse holder up and I keep shooting it down. The fuse holder theory, assuming It’s true, which I seriously doubt, is that it would be random, whereas directionality of the fuse itself is not. It’s always the same direction that is superior, for ANY given fuse.

The “correct direction” for any fuse is in the direction of the lowest outage drop. For anyone with ears the correct direction of the fuse exhibits much less noise and distortion than the incorrect way. Differences in the fuse holder end, if any, would not (rpt not) exhibit these rather dramatic differences. This is all just another example of you can’t teach an old dog new tricks. But thanks for reminding us of this silly theory, anyway.
mijostyn's avatar
mijostyn
8,570 posts
 
bdp24, thanx for making sense. Both Nelson and Roger have access to serious test equipment. I think over the years they have established which measurable anomalies sound bad (IM distortion) and which are euphoric (harmonic distortion). Nelson admits to adding small amounts of harmonic distortion to make his amps sound like tube amps. I suspect John Curl does the same thing. Having played with and measured hundreds if not thousands of circuits I am sure they are quite aware of what alterations do absolutely nothing like fancy fuses. 
I do not know what it takes for people to understand the power of our central nervous systems to modify perception. All our senses, hearing included are adjusted by our central nervous systems to perform well under various circumstances. Emotion can also make changes which are measurable. This is how lie detectors work. The fact is, if you think something will sound better or worse it will and it does. But the next time you are in a bad mood it will sound awful. 
mijostyn's avatar
mijostyn
8,570 posts
 
And Uberwaltz, I am not criticizing your hearing or the CNS behind it. I am just giving you the real reason behind what you think yo are hearing. The operative word here is, "think."
nonoise's avatar
nonoise
11,088 posts
 
I wonder what the measured difference would be by just rotating a fuse in it's holder. Two well respected amp builders have heard for themselves a difference in sound from a part of the amplifier that they say has no effect on the sound, just by rotating a fuse in it's holder.

Well, which is it?

Members here, cite these gentlemen as being above reproach and line up behind them in their arguments, other than to claim a form of neurosis on the part of those who hear a difference.

It's been said that the HiFi Tuning reports findings of a difference in directionality aren't enough to justify the difference in sound but what if the differences were in the same, or similar, amounts, to rotating the fuse in it's holder? Better yet, what if the measured differences in directionality are larger than just rotating a fuse? How would the argument go from there?

My bet would be that they'd double down on the insanity claim and still, never try it for themselves. 

All the best,
Nonoise
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