Fuses that matter.

Audiofeil, That's uncalled for. This is an audio forum, where sharing experiences is the primary objective and desire. I notice you have a pronounced tendency not to participate in meaningful discussions, choosing instead to fire off your usual snarky, sophomoric comments.

Poor cockroaches. Not sure if they noticed which direction the fuse was pointing either, but I (not a cockroach) have noticed a slight smearing when a fuse has been used one way then flipped around. I have noticed a similar sound when using a speaker cable the "wrong way" around too.

I think this difference in sound with the direction of a fuse depends on a few things:-

1 the equipment fuse used in. I haven't noticed fuse direction issues in DACs or transports. But i believe i have in preamps & tube amps.

2 the system. How transparent etc?

3 how well you know the system/gear being used?

4 whether you are experience in listening for such small changes in presentation/tone, which is obviously linked to point 3.

Personally I think a fuse can be a nice tweak, and an important one for those of us audiophools.

Bryoncunningham, sorry I am not going to post further on this aspect of fuses. If you want to further discuss your experiences or where you had success, I am interested.

Chadeffect, my first experience with fuses and their direction was when Lloyd Walker of Walker Audio concerning his power supply for his turntable. He said that I might want to reverse it and see if I heard a difference which was better. Lloyd is very sincere, so I took him seriously and tried it. He was right. I did frequently check this on components thereafter. Like you some showed little difference and others a great difference. Mainly, I just tried the fuse both ways and chose the best. But some times I learned which side of the fuse was the wall plug side. Later when I got the IsoClean fuses there was an arrow to indicate this direction. This was also when I first experienced shall I call them "designer" fuses.

Has anyone considered what portion of the total resistance the fuse contributes to the whole of the circuit in which it is inserted?

From the Tuning Fuse data sheet their 2 amp slow blow 5x20 fuse has a resistance of 24.077 milliohms in one direction and 24.115 in the other direction and 26.257 in the holder. If a butterfly flew by while the measurements were taking place we might see a bigger difference than the 0.038 milliohm difference in direction. Of course it might depend on which direction the butterfly was flying. But nevermind, the direction measurements were made with DC and we are using these fuses in AC circuits. Perhaps if the butterfly flies clockwise vs counterclockwise there will be a difference.

Sorry I just had to put that in to keep up with all the humor that has been presented here.

Back to the numbers: A common fuse of the same rating from Littlefuse has 37 milliohms (note that they don't take the numbers to 5 places being real scientists). So lets look at the total resistance of the circuit. A device that uses a 2 amp fuse will typically have a transformer whose primary resistance is 5 ohms or so and it's wound with around 200 feet of ordinary copper magnet wire of about 24 gauge.

The wiring from your high grade hospital outlet back to Hoover Dam is about 0.5 ohms, which is really quite amazing. It could be as high as 1 ohm. And lets not even think of what that's made of.

So to add it up the tuning fuse has a total of 5.525 ohms in the primary circuit and the Littlefuse has 5.537 for a difference of 0.012 ohms or one part in 458. In decibles that difference is 53 dB down. Now a power supply takes in 120 volts and when by the time it gets rectified and filtered the hum at the main filter is about a volt so now we have reduced the AC to 1 part in 120 thats another 41 db.

Your unit likely has a 50 cent three terminal regulator that reduces the hum by another 60 db or the amplifier itself does that. So now we are down 53+41+60 dB for a grand total of 154 dB. I am really impressed with listeners who can hear a difference that's 154 dB down.

Shall we do the numbers on the microphonics next?

Thank you, Roger, for bringing the expertise of a distinguished designer to this issue. As I said in my post dated 4-29-12, the explanations that tend to be offered for the supposed benefits of expensive fuses seem plausible until they are looked at quantitatively.

Best regards,
-- Al