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

Fuses simply do not have a "sound" as they're not designed doesn't matter how many hyperbole festooned claims of their sonic influence are written...they just can't and don't and will never do anything except wait patiently for something to cause them to blow. If spending 150 bucks to massage an expectation bias makes somebody feel better, it doesn't change the fact that fuses are simply fuses, a fact that yeah, designers like Nelson Pass (who seems to be into every single little tonal aspect of his designs and is actively involved with the audio geek community...not likely to miss out on the Magic of Special Fuses if they were an actual thing) know all about.
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.

It’s a cry in’ shame 😭 those two guys don’t believe in fuses or wire directionality 🔛  Too bad those two guys are so stubborn. They’re probably not good listeners. 😁

That’s why they are "Nelson Pass" and "Roger Modjeski", and you are __(pause)__well, Geoff Kait??, snake oil peddler

I do appreciate all input about Pass Labs amplifiers and possible changes that might or might not affect their sound. I also found it very interesting that reversing the direction of an ordinary brand new Bussman fuse several times did consistently affect the sound I heard.

I own three Pass Lab amplifiers and like many audiophiles I respect what Nelson and his main co-designer Wayne do.
David Pritchard
@davidpritchard I have used a Blue Fuse in my Pass XP-20 preamp. It was easy to choose direction and, when in the correct direction, contributed to superior performance versus the stock fuse (which was also checked for direction and removed and reinserted as a check).
I do hope many who read this thread will go to " You Tube " and type in "Nelson Pass". Watch several of those videos and I think you will get a fabulous insight as to what most interests him, what he tries to achieve in a design, the trade offs he has to make, the parts he uses, etc.

I am not aware of a designer - manufacturer who is more open about his approach to audio amplifiers.
David Pritchard