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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That this site is the only place where so much time and effort is put into discussing how fuses sound (mostly by the same handful of people) says a lot. 
It’s a wonder the rest of the world is able to function in lieu of expensive fuses. 
There are places in the world where people do not even consider having a pet because of poverty. 
There is also this place where people are encouraged to drop $100s of dollars on fuses based on a handful of opinions and total hearsay. 
Just saying....
"That this site is the only place where so much time and effort is put into discussing how fuses sound (mostly by the same handful of people) says a lot...."

I wonder how many are associated/affiliated with SR?   
As the original poster I do think it is important to remember I few points that I wrote about the topic.

 This was an experiment to see if there were sonic differences using three different fuses - each installed and removed multiple times and in both directions. A well know respected amplifier brand ( Pass Labs) was used that has a reputation for having a excellent power supply. This was done on purpose to discount the experiment being devalued due to a "poor power supply being a factor in the observed results".

No other changes were made to the system for the past five months. So there are no other known major  variables going on. The humidity (measured), and room temperature (measured) were kept constant. The time of day for listening was kept constant - 8:00 to 10;00 at night. The Pass Labs amplifier was also chosen as it can and was left on 24/7 (except when it was turned off to change fuses). Since this amplifier has a screw in fuse holder, fuses can be easily and safely changed.

This was a serious attempt on my part to do a meaningful evaluation of three fuses and their sonic effect on a well respected amplifier. It is the first of several experiments I have planned pertaining to this subject.

It was earlier pointed out earlier  that testing - evaluating fuses is " by necessity a time consuming affair". That is absolutely correct and one reason I chose to  report this experiment. It is a lot of work. It takes a lot of time.

My observations indicating a change in sound have not and will not ever have a percentage number assigned to them. 

I have found it very helpful to watch all the You Tube videos posted featuring interviews with Nelson Pass and his co-designer Wayne Colburn of Pass Labs Inc. I will not attempt to condense what their approach to perfecting a design is but it involves both measurements and a lot of listening. Nelson also discusses the  subjective and objective  and their place in developing audio products.

Wayne Colburn of Pass Labs has been most gracious in his time and expertise to directly answer questions I had about Pass Labs's use of fuses and circuit breakers.  

David Pritchard
I certainly welcome off line discussion about audio observations I have made and posted. My areas of interest are especially in fuses, wall outlet sonic changes, and Pass Labs amplifiers.

David Pritchard
575-644-1462
Imagine a world with no poverty so everyone can own a pet, no snide remarks about participants in a thread, and where audio is dirt cheap.

Now, back to the real world.

All the best,
Nonoise