Synergistic Red Fuse ...

I had written last week that despite the many positive posts on this thread regarding the Black fuses, the number would continue to grow. This has happily been the case unsurprisingly. To the point of being redundant these fuses represent one of the great  tweak opportunities available.  There are very few upgrades that will yield this level of sound quality improvement for so little cost. I'm just very glad that more people are discovering these fantastic products. Keep in mind that the better the quality of an audio system, the more impactful their effect in my opinioon. It is wonderful to realize that  you can noticeably improve your system's performance without having to spend thousands of dollars. 
Charles, 

Here's my data point, which is not at all meant to be a downer or to question the premise of upgraded fuses.   It's a silly and delightful hobby that we cherish here, and this thread is a great example of the power of the web to bring us audio nerds together. That said, this is the deepest down a rabbit hole I've ever felt!  Definitely feel like I had the best sound in my system's life before the Blacks, and now the magic's gone.  (And I didn't note the direction of the stock fuses before I pulled them out, should I want to go back!)  

At ~100 hours on the Blacks I got home and sat down for a listen last night.  What I heard was definitely short of the musical engagement and detail retrieval I enjoyed with stock fuses on my PWDII.  I did hear a slightly lower noise floor, but the highs in particular were rolled off.  Cymbals, for example, just weren't as there as before.  Imaging was flatter.  My mind wandered.

Great to learn that Audiolover notes big difference with direction.  Popping open PWD is trouble enough that I'll probably wait several more days of burn in before I flip them.  

@audiolabyrinth, Keith, although of course I have no specific knowledge of the internal design of your Krell amp, and although you mentioned earlier that Krell's service manager strongly recommended against changing the value of the 1 amp fast blow fuses, IMO changing them to 1.6 amp fast blow SR Blacks is a sensible thing to do. For the following reasons:

1)The failures that were reported earlier, as well as the conversation you mentioned you had with Ted Denney some time ago, suggest that the 1.6 amp SR Black is likely to have a melting point (current squared x time) that is significantly less than the melting point of a 1.6 amp fast blow fuse from one of the major manufacturers of non-audiophile fuses.

2)I agree with your statement of 2-18-16 that:

 ... most anomalies that could happen will be far greater than these slightly higher fuse values, so, in general,  your equipment investment's will be fully protected in my opinion.

(although you were referring just to ratings of up to 0.25 amps over stock).

3)I would never expect a component manufacturer to approve changing a fuse value, no matter how reasonable doing so might in fact be.

IMO. Regards,
-- Al
 

Cymbop, what you are describing very much sounds like the fuse is in the wrong direction. I wouldn't wait. I would change direction now, and decide tje right polarity, then reinstall and let it continue to break in and settle back down.  The differences in direction are very apparent.  I agree with the system being less bright, and it may initially feel less resolving, but ultimately I feel that was artificial brightness from the stock fuses. I am more interested now in listening than before. My imaging has not gone flat. IT WILL NOT SOUND RIGHT IF ITS IN THE WRONG DIRECTION FOR A GIVEN COMPONENT.

Even  my factory fresh ARC  amplifier, which came with a factory ceramic fuse was pencil marked from the factory indicating proper orientation of the fuse. Obviously done during its factory sound check. So, it is obviously a real,variable.

let us know when you change direction if your feelings change. I think they will. 

Just to confuse matters a bit, I saw some conflicting specifications for fuse size on a Pass Aleph P preamp, so I asked Pass, who provided the correct value, but added, "If you are using after market or fast blow fuses, you will have to go up in value."  Seems the answer is the onerous blurry "depends" since the SR Blacks at manufacturers rated fuse values worked fine in a DAC and tube amp. SR should be generous in trade if you played by the rules and they blew.