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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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davidpritchard's avatar
davidpritchard OP
866 posts
 
As the original poster I chose to perform an experiment that I considered fun and thought it was worth while to report the results.

 I chose the Pass Labs amplifier as their products do have the reputation of having a good power supply and being well built . I did not want to waste my time evaluating fuses in a product that has a questionable build quality. On all the Pass Labs amps that have fuses, the fuse is easily removed using a  screw in fuse holder which is next to the on -off power supply switch. I also considered this an important reason to chose a Pass Labs amp. I do consider safety to be important.

The experiment was not designed to be sales pitch for a new product but to examine if fuses in an amplifier might affect the sound. The test results I obtained revealed that three different fuses had three different effects on the sound, and that in each case simply removing the fuse and changing the direction of the fuse also changed the sound.

 I did not expect to hear a change in sound with the Bussman brand fuse. This alone made the experiment worthwhile to me. So for some audiophiles, simply changing the direction of the fuse may change the sound for the better. Fun to try if you have a fuse installed as the Pass products do.

 Since changes of fuse type and direction were made multiple times  an amplifier who's fuse  was easy and safely removable was a conscious decision that I made.
 
After spending many hours doing this, I thought it would be informative to the audiophile community to publish my results. I hope others will repeat similar experiments and report their results.

David Pritchard

uberwaltz's avatar
uberwaltz
13,381 posts
 
And we thank you for the thread and the information contained within David.
Confirms my findings but on a much more organized scale.
geoffkait's avatar
geoffkait
23,365 posts
 
At some risk of being flamed 🔥 can I point out that because of the rather long burn-in times required for fuses generally and the vagaries of fuse directionality, as well as possible fuse holder issues interfering, that any comparison or evaluation of fuses is by necessity a time-consuming affair fraught with all sorts of possible interfering conditions that might impose themselves on such a test and make conclusions questionable. Also, I think that it would be of value to select an amplifier with a reputation for a crappy power supply on which to experiment with fuses.
wolf_garcia
6,737 posts
 
A couple of years ago I tested a pile of SR fuses just to give my ranting some credibility (!) and found they were useless and somewhat dangerous as their ratings were suspect. You can look it up...also, note that nobody responded to my previous post regarding internal wire direction chaos which, to my thinking anyway, negates fuse influence as described by the Athletic Supporters of fancy fuses. 
marqmike
847 posts
 
Wolf
Useless in what way. If you do not have measurements and triple bypass blind testing on everything with a reputable company I can’t believe what you are saying is true. You know the bias factor also comes into play.. The first thing I would want to know is how big a pile is that you mentioned. You see something else could of been in that pile that you used for a fuse. So come back with extensive documentation and I just might start to listen.
I am being sarcastic. I do hope you are enjoying your system even without those terrific fuses.
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