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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This is the second of three planned posts evaluating the effect of different fuses on three different Pass Labs amplifiers.

This evaluation is using the Pass Labs HP-1 amp. I enjoy this amp especially for night time listening. My favorite headphones were used, the Focal Utopias and the Sennheiser 800.. The source is a Marantz SACD player.

The amplifier and SACD player were kept on 24/7.

 The fuses evaluated were the stock fuse - wire around a ceramic rod enclosed in a glass case, a Synergistic Research Blue fuse, and a Synergistic Orange fuse. Listening was done at night,  room temperature was a constant 73 degrees, humidity 35-41 percent and all other electrical devices except refrigerator and heating system were off.

Listening was done with four cd's. Male vocals- Willie Nelson - "Stardust" (SACD disc), female vocals- jazz singer Nnenna Freelon- "Live", acoustic instrumentals featuring multiple instruments and complex percussion - "Sera Una Noche" and solo piano- "Mozart -Works From His Golden Age".

The last two Cd's are on the MA record label. MA owner Todd Garfinkle records using only two microphones in buildings that have wonderful ambient spacious sound qualities.


The Orange fuse's effect on the sound clearly gave the biggest improvement. Especially with the MA recordings, the ability to hear micro details during the decay portion of a played note made me forget I was listening to headphones. Many times I felt as though I was a solitary guest who was allowed to sit in during a performance.

 On the Nnena Freelon album ( Concord Records) , the live crowd ambience was not a distraction but added to the enjoyment of listening to the performance.

Willie Nelson's nylon guitar sounded more detailed and richer when the Orange fuse was in the system.

I found the Orange fuse to give a significant improvement to my Pass Labs powered headphone system. I think the cost benefit ratio is most excellent.

Both the Cable Company and VH Audio did announce a buy two and get one free Synergistic Research fuse special. This according to the Cable Company (E-mail which arrived today) is only for the next two weeks. 

David Pritchard
Great review David.
And if I am not mistaken SR did a similar deal last year whereby you received a free Blue fuse upon purchasing a Blue duplex.
Pretty sure it was just before Xmas as now.
Intrigued as my Ayre EX 8 uses..... Three fuses....
🤔🤔
uberwaltz:

I do hope you audition the Orange fuses in the Ayre EX 8. What a special amplifier. Put the fuses in and do a final evaluation after 14 days. If you like the sonic change - Merry Christmas !  Send them back if you do not think the are worth it. Please report what you hear. I am a big fan of Ayre products as well as Pass Labs products.

The last few days I have been watching "You Tube" videos after telling the search microphone on my TV - " Audiophile fuses".
Multiple interesting videos both pro and against.

    Magneplan Fuse Upgrade
    Audiophile Fuses
    Audio Magic Beeswax Fuse vs. Furutech Blue
    Fuse AMR
    Fitting More Internal Audiophile Fuses
    Upgrading to Audiophile Fuses
    Audiophile and Ceramic Fuses Tests and Thoughts
    Audiophile Snake Oil !
    Synergistic Research Orange Fuse

I hope readers of this thread will take time to watch some of these interesting videos. I continue to be impressed with the improvement the Synergistic Research Orange fuse has on the performance of the Pass Labs HP-1 amplifier.

 The HP-1 which is a   wonderful amp that was specifically designed for both low impedance and high impedance headphones is now performing at an even higher level of sonic enjoyment.

David Pritchard
Way back I was very skeptical of power cables.  I have not tried fuses myself.  I suppose the reason of improvement by fuses more or less the same along the line of power cables.  

The first time I've ever heard of "fuses", was when reading an article about YBA designer, a rather eccentric French man who believed fuses have a detrimental affect on the sound.  The best fuses is no fuses at all.  With all the beefy power cables, water hose size speaker cables, it is rather comical that the electrical current has to pass through such tiny wire in the fuses.  

I know a lot of very capable electrical engineers who don't believe in power cables, fuses and so on ... and think of them as crack pot science.  


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