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

Just as an FYI.
If my post had been all caps then yes that would have been a "yelling" post.
But when just one word is in caps it signifies a highlight of that one word ( or more than one in this instance) within said post.

Just wanted to clear that up as I was most definitely not yelling at you George, life is too short.

However I am interested in the Gryphon story as I do not think I have read that from you before and it is actually very relevant and thank you for that.

As I have clearly stated many times, if people have tried something and found no difference or change or even worse it made matters worse then that is what it is.
A result that they perceived they heard or not heard whichever the case may be.

So both yourself and Wolf have tried or been party to trying of aftermarket fuses and did not consider them a worthwhile sonic benefit.
That is perfectly fine and a report of what you discerned.

It does not of course mean they are a waste of money and do not work period, just they did not work for you guys at that time in those systems.
And you cannot say any more than that.

Note to self: the plan of appeasement doesn’t appear to be very successful. 
I did talk directly to Pass Labs and they suggest to keep my amp on 24/7.   Paul McGowan ( CEO of PS Audio) also recommends to keep the PS Audio amps on 24/7. Some reasons to keep always on are less stress on the system (from the initial current inrush) and thermal stabilization.

David Pritchard

@davidpritchard, the folks at Reno HiFi suggest turning off the Pass class A amplifiers when not in use due to the fact that are always conducting full power.  The Pass class A/B amps can be left on 24/7
The difference one can hear with a fuse depends on the amp and the system it’s part of. With my Marantz Reference PM15S2b, the result in a change of fuse was immediate and distinct. Even directionally. With my Kinki EX-M1, it was much subtler, but still there. In fact, after trying out 3 different fuses with the Kinki, I went back to the standard, ceramic fuse as the amp appeared to be designed with  that fuse being used, which gave the best results.

Even Alvin (the exporter for Kinki) said as much when I asked him about it. I don’t have the email anymore but the one he sent me had the brand and a picture of the fuse and it cost a little over $2.

The fuses I tried were of a mid priced nature (none exceeding $60) so I have no idea how an SR fuse would fare in the same situation.

You’ll never know until you try.

All the best,