Hi-Fi Tunig Fuses & Parasound A21

I recently replaced all the fuses in my a 21 with hi-fi tuning supreme fuses. As others have noted, you hear an immediate improvement in speed and resolution when you replace the back panel fuse. When you replace the fuses in the rails, an additional improvement in these characteristics result, along with an improvement in the weight of the sound.

I experimented with Furutech TF audio file fuses. With a hi-fi tuning fuse in the back panel, and four. Tech fuses in the rails, the sound was too forward, warm, and slow for my ears. The best set up was a hi-fi tuning fuse in the back panel, a pair of. Tech fuses in the outside rails, and stock fuses in the inside rails. This gave a uncanny, lifelike presence to vocals. But the resolution of sounds from instruments was less sharp than with the all hi-fi tuning fuse set up. If you really like listening to vocal music and to rock, this might be your set up. Electric guitars are reproduced with a lot of energy and a bright tone.
I also experimented with mixing stock fuses with hi-fi tuning supreme fuses in the rails: two stock fuses in the inside rails and hi-fi tuning supreme fuses in the outside rails. The all hi-fi tuning supreme set up was better by a small margin, greater speed and resolution and more lifelike.
My system: Bluesound Vault 2 --> Parasound Halo JC2BP --> A21 --> Vandersteen Quatro Wood CT.

So, I have a question. How did you establish the correct direction for so many fuses and combinations? Just curious.

@geoffkait 
The HiFi Tuning Fuses are marked with an arrow. When I placed the fuses, I put the arrow in the same direction as the flow of current.The stock and Furtuech fuses are unmarked. I did not test opposite directions.
I also did not test all possible combinations of fuses, so there are other ways in which my test was incomplete.
I place some confidence in my observations because they consistent with characterizations others have made of HiFi Tuning and Furutech fuses.
Cheers.

The HiFi Fuses are marked with diode symbols and, as I understand it, the direction of the diode “arrow” is random. So, you need to try both directions. The diode symbol is useful in knowing which way the fuse was oriented just before you changed directions.

For multiple fuses the only rational way to test for direction is start with one fuse, change direction and listen. Decide which direction sounds better, then move to the next fuse. After completely this test for all fuses repeat, in case you were uncertain about a fuse’s direction the first time around. As you proceed the sound will improve and make it easier to hear fuse directionality.

@geoffkait
Hey.
Flipped a fuse.
Ka-boom!
I flipped the fuse on the left inside rail. Perfection. Sound snapped into place. Before the edge of vocals were just a bit blurry. Very subtle difference. But difference between perfection and not.
Slim evidence on which to conclude changing the direction of the fuse was the cause.  A more convincing demo would have required flipping it back and back again to check if change in sound was specific to change in direction of fuse. And, experimenting with flipping other fuses. It is possible I had other fuses right and just this one wrong. Maybe I got lucky.
Regardless, I owe you thanks.
Very happy with sound. Not touching a thing.

Appreciate your knowledge. Enjoy your mischievious posts.