Fuse Direction for Pass Labs Amp and Preamp

I am going to re fuse my Pass X250.8 and XP-32 with Synergistic Research purple fuses in a couple of days. I was hoping to get advice on a rule of thumb for direction of the fuses. My instinct tells me to start by installing the fuse by the direction of the lettering on the fuses. I am thinking that the direction should be the lettering left to right with the beginning of the lettering facing out of the amp and the end of the lettering facing into the amp. Does this sound right?


Hi @nonoise 

Thank you, that is exactly (and succinctly!) what I was looking for.  I will get an itch to give fusses a go at some point.  I have bigger fish to fry at the moment, as in interconnects.  As you might imagine I have a bunch due to the four amps and external electronic x-over.  



Clearly the orange fuses combine the best qualities of the red fuses and the yellow fuses, while the purple fuses combine those of the red and the blue.

I have been in this obsession (euphemistically, a "hobby") for some 50 years and I can still hear the better part of the human range. The SR Purple Fuses are major --  repeat major -- audible improvements, both in my VTL 7.5 iii preamp and more latterly, my Sansui TU-X1 tuner (ca. 1979), often regarded as the finest tuner ever made.  I am beyond audio "snake oil" and can hear --  or not hear -- the difference.

I don't know the physics, but with my simple but experienced ears, I do know you have to tell which fuse's end is in and which points out, to hear which way is better. Neal


Thanks for bringing to my attention that there's a fuse in the tuner, which I've overlooked all these years. Now I have something to look into..

All the best,

"It’s funny that us audiophiles sometimes believe we understand electronics better than electrical engineers do. If DCS, Pass, and other good brands ship their products with standard cables and fuses - shouldn’t we be able to reject the urge to upgrade those?"

If you leave the "US" and "WE" out of the post you might be close. I’ve worked around a lot of different engineers. Every sound engineer was working on sound walls and every EE was working on CANN Buss/OBD2 equipment. They normally were working out a way to add another computer to the mix.

Sound is as subjective as anything on earth and very prone to BIAS. I understand that. The difference with people that are PAID to listen vs people that PAY to listen is pretty simple. Music SQ vs a strange noise in the engine compartment is just a little different skill set.

It took many mechanics decades of learning to hear and then feel a potential issue.

I bow to only a few when it comes to better hearing and with better skills.

I suggest many people and the way they learn to listen is the greater issue. It’s only a problem if "WE" can’t learn to change and learn a BETTER way to listen.
I understand just like fine wine, eventually it all turns to vinegar (hearing).


With that said, what can I say about this:

"Our customer that brought them in exclaimed how they were so transformative. We ran a comparison, just for fun, between them and our shop cables, which we made up from 10ga oxygen free copper wire. Everyone in the shop was challenged to hear a difference. Our speakers though are 16 Ohms and speaker cables are far less critical when driving 16 Ohms as opposed to 8 or 4 Ohms."

OK you got me, you win, 10ga OFC spools cable is just as good as SRs speaker cabling. I suppose you hooked it all up and did a side by side on two identical systems too? GIVE ME A BREAK, you did NOT. Second if you can’t hear the difference in a UP-OCC/teflon weave from your 10ga OFC spool wire. QUIT trying your hearing is SHOT. Stick with the old scope.

The thing about any mechanic worth his salt is to question his/herself abilities before others do.. I’m not the one that couldn’t hear the difference. I suggest a little training is in order. Start with the easier ones first. 2-4ohm 90-92% efficient speakers. The more efficient the speaker, the easier it is to learn about cables, not WIRE.

It’s not hard to understand that a mechanic is usually a pretty skilled engineer with dirt under his fingernails. Certainly had to go to school a LOT longer. I still attend 3-6 classes per year, 40 years after my Master Certs (7 years). I taught hydraulics with OHM for over 20 years.

We both worked with James Bongiorno and a few of his crew. He would chew anyone out for not paying attention to single wire or cabling. 35 years ago? He did some amp board work for a series of cranes we has issues with in the heat..

Carver use to teach a winding class for 2nd year guys. Cheapest guy I ever new, but not with other people’s money.. :-)

Can’t hear a difference? "just for fun" try to learn a new skill set.

My best to you all.

PS Ralph, I think you're one of the finest contributors to the forums with a wealth of knowledge and as always a gentleman all the way.. We've met in passing many years ago..