Manley Jumbo Shrimp upgrade

Fuses are not part of the active, tone producing circuits in any amp, and are simply designed to allow current to pass through them and fail immediately if necessary to save the circuits from frying. Although SR fuses have a cult following with astonishing claims of transforming the tone quality of amps, I've tested these (SR Black) and found these claims to be nonsense, even while providing the weeks of break-in (!). In fact, after my little comparison to the Littlefuse (and other generally stock fuses) products I've used for years, I discovered an SR Black had been left in my amp for months, which I replaced with the original  Littlefuse with zero change in tone. Try asking anybody how these little graphene enhanced seriously overpriced tiny wire devices actually work (magically coat the electrons with Special Sauce?) and prepare for scorn. The SR business model seems to be "money paid equals results experienced" even when the products are laughably unnecessary.

It should probably be mentioned that for the fuse skeptic and/or audio cheapskate it's worth reversing the current stock fuse(s) in one’s system you know, to see if perhaps one way actually is better than the other. What are the odds? Gotta be 50%.

celtic66, you might check with Manley, providing your serial number, to see if there are any factory upgrades.

Otherwise, if you'd like to experiment I'd agree with trying a few different tubes.  I don't have experience with expensive fuses so cannot comment on those.

Of course one might ask what sort of improvements you hope to achieve before thinking about changing anything.

celtic66
I believe in your question you were requesting suggestions of who in the industry modifies the Manley Shrimp, or maybe both regarding technicians and types of mods. If you haven't already, I would contact Manley. I would think they would be able to refer you to repair and/or modification services/providers. Why not pose the question to the AG community of those owning the Manley Shrimp; what internal component modification they may have benefited from.
Also I found both repair and mod services for Manley products by an individual named Ben Jacoby. I have included the company address below.
http://www.highendaudiorepair.com/manley.html

Fuse directionality in AC circuits is technically irrelevant, and perceived changes in sound from reversing a fuse are likely imagined. Some think changing the direction meant you cleaned the fuse contacts and are hearing the results of that, but if the fuse worked before being reversed that's also very unlikely, although cleaning any contacts is generally a good idea. Like washing your hands after meeting a politician.