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

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
David, you hit it right on the head,”less emotionally involving.”
Although I do not own one at this time, Mr Pass makes some of the best sounding amps. I think Beethoven proved that you don’t have to be able to hear, you just have to know what you are doing.
Some days my system sounds killer, other days not as good even with the same recording. The only things that have changed are the humidity and the barometric pressure. The real culprit is my state of mind, happy vs pissed off. If there is just one neuron in your brain that thinks something is going to sound better, it will. This does not mean that there are not meaningful changes you can make, there are. In my experience there is always a sound reason why something sounds better. In the case of the fuses there is not one. I use to bypass all the fuses in my system including speaker fuses. Then I started doing AB experiments with fuses, wire and switches. There was a slight improvement in bass bypassing speaker fuses. Otherwise the differences were hard to appreciate. I also always have a second set of ears participating. It would be better to have 100 sets but it would be hard to arrange for obvious reasons.
In most cases you are better off buying more music. 
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).
How is it that one way it sounds better than the other-way??
When the AC (clue here "alternating current") is changing it direction 60 x a second?? You would have to be changing the fuse direction also 60 x a second to prove what you said that it "it sounds better one way than the other".