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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

128x128davidpritchard
davidpritchard's avatar
davidpritchard OP
866 posts
 
rbyington:
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

testpilot
895 posts
 
@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
nonoise's avatar
nonoise
10,547 posts
 
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,
Nonoise
davidpritchard's avatar
davidpritchard OP
866 posts
 
Wonderful post. You do not know for sure until you try. But if you are not interested in the possibility, do not try.

Concerning leaving amplifiers on, you will have a lower electric bill if you turn them off. Class A amps  use a lot of  electricity whether they have a signal or no signal. Mark at Reno Hi Fi certainly knows Pass Labs products. I would follow his advice. Indeed the Pass Labs SIT-3 amplifier (being delivered today) was purchased from him. It will use much less electricity than some of the other amps and so will always be left on.

Except when turned off to evaluate different fuses and their direction.
David Pritchard
georgehifi's avatar
georgehifi
10,312 posts
 
So both yourself and Wolf have tried or been party to trying of aftermarket fuses and did not consider them a worthwhile sonic benefit.
Not just in sonics, but as a tweak with absolutely no Electronic Engineering foundation. And where even the manufacturers won't come on these forums and back the claims here.

Like I said before, there is not ONE manufacturer that would not hesitate in backing his product in debates like this with the claims made here, that's because AC mains fuses that have these claims are all just snake oil voodoo. 
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