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RE: Voltage drop

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In Reply to: RE: Voltage drop posted by 1973shovel on January 16, 2023 at 04:20:35

Ralph is generally pretty good with his comments, but that one was nonsensical.
Of course there is a minute drop in voltage across a fuse. But that voltage drop will not increase (or decrease) if the fuse is switched in orientation.....all other things being equal. You could measure voltage across a fuse, switch its direction and measure again. Do that 100 times and compare the results and there'd be no consistency at all regards direction.
This requires no subjective evaluation, no voltage measurements, no anything. It's implicitly obvious based on the conditions the fuse is operating in.
What we have here is schlock marketeers creating a belief in the audiophile brain and then selling a product to that belief. :)
Dave.

Edits: 01/16/23

Follow Ups:

RE: Voltage drop, but there's something you're not getting - Ralph 11:42:55 01/20/23 (2)
Is that a lot also depends on in what the fuse is being used.

In the case I measured, the amp was a zero feedback tube amp with a rather large filament circuit (about 19 Amps). Because there's no correction, yes, changes in line voltage most definitely affect it (not only does the plate voltage go down but the tubes cool off a little as well)! To measure the effect on such an amp, measure output power, distortion and output impedance. With greater voltage drop, the output power decreases and the other two metrics increase.

WRT fuse direction, that is so much poppycock. What is happening is the fuse isn't perfectly symmetrical and can get a better connection in the fuse holder one way or the other, so less voltage drop. For this reason people wind up thinking they are directional, which obviously is impossible.

You can get the same effect by rotating the fuse in its holder without reversing it; measure for the least voltage drop.

We make a class D amp that employs quite a lot of feedback and as a result of the rejection offered by that feedback, does not seem to respond to fuses at all.

The takeaway is the current draw, the kind of load and what feedback is present all play a role.
- RE: Voltage drop, but there's something you're not getting - Davey 18:17:07 01/20/23 (1)
  There's nothing I'm not getting Ralph. I well understand there are different applications where fuse voltage drop might have a significant, maybe even audible, effect.
  What this thread is about, and what my comments have been about, is only in regards to fuse 'directionality'.
  Cheers,
  Dave.
  
  Edits: 01/20/23
  - You're right; my apologies nt - Ralph 10:22:08 01/23/23 (0)
    -
"Ralph is generally pretty good" - 1973shovel 04:56:28 01/17/23 (3)
I suppose Ralph's sensibilities are why I've hung onto his voltage drop explanation as at least some form of an explanation for my otherwise skeptic nature.

One other thing which hasn't been touched on in this thread, and the primary reason I haven't tried a boutique fuse for myself, is that I don't know if I can trust their ratings. I'm not willing to sacrifice an expensive amplifier because the 4 amp boutique fuse I'd spend $150 on, actually wouldn't open until current reached 8 amps.
- RE: "Ralph is generally pretty good" - Davey 06:52:08 01/17/23 (2)
  I think if that's the reason you're not trying boutique fuses you're missing the whole point.
  
  Dave.
  - "you're missing the whole point" - 1973shovel 06:35:19 01/18/23 (1)
    I don't think that I'm missing the point. I'm a born skeptic, but I don't consider myself such a pedantic theorist that I wouldn't at least try a boutique fuse if I had one, to prove to myself that these guys are imagining things.
    
    Note that the key word is "try" though. I have no desire to actually buy a non-UL rated, non-returnable, disposable item like a fuse. But if someone handed me one, I wouldn't not try it.
    - RE: "you're missing the whole point" - Davey 07:37:51 01/18/23 (0)
      This is not pedantic theory we're talking about here.
      If you hold open the possibility of trying fuse orientation to prove to yourself something then......? (This is the point I'm referring to.)
      Some things are factually obvious without experimentation to prove it. If I have a wheel of known circumference and desire to know how many revolutions it takes to travel 100 yards, I don't need the wheel and a football field to determine that.
      Dave.
      
      Edits: 01/18/23

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