Updated from 7:29 a.m. EDT

Among hi-fi enthusiasts, they're called "tweaks." These are little items and things you can do to improve the sound of your home music-reproduction system.

For instance, some people believe wires that carry music signals should never run parallel to wires that carry AC electricity (have them cross at right angles). Or that using a black Magic Marker around the edges of a CD improves the sound (it does). Or that certain small pieces of wood or even stone pebbles -- placed judiciously on hi-fi components -- can change the sound (you could spend thousands of dollars trying this).

Actually, for a price, I'd be willing to come over to your house and wave a magic wand to make things sound better!

But I've found something that makes an incredible difference -- not only for your hi-fi, but also for your high-priced video-playback system.

All it means is replacing a fuse.

Home electronics (audio and video) were fitted with user-replaceable fuses for decades. These fuses consist of a piece of wire inside a tiny glass tube with metal caps at each end. To this day, they're usually sold in small, slide-open metal containers -- three to five fuses per pack. Each fuse now costs 50 cents or so. (I remember when a package of five fuses cost 50 cents, but that was back when gasoline was 30 cents a gallon.)

Ultra Systems

These fuses were (and still are) made to blow if there was something wrong with the AC power supply -- or the equipment. If a fuse is accessible from the outside, replacing it takes no tools and about 30 seconds. Internal fuses could take a few minutes longer to get to.

Over the years, little had changed when it came to fuses. They blew. You went to an electronics store (or the local RadioShack ( RSH) to buy replacements, and that was that.

Until recently.

That's when electrical engineers and hi-fi addicts started thinking about the fuse itself. Engineers were spending hundreds of hours -- and dollars -- to find the best-sounding components for their gear. But they soon realized that the AC fuse was the lowest common denominator. The inexpensive, throwaway part acts like an hour-glass for electricity. What would happen if they could re-engineer the fuse?

Enter the HiFi-Tuning fuse imported by Ultra Systems of New Hope, Pa. Made in Germany, this is a super-premium, drop-in replacement for short (0.75 inch) and long (1.25 inches) glass fuses.

Instead of cheap, throwaway items, these are hand-made and tested, the wire inside is pure silver, the casing is ceramic rather than glass (for better resonance characteristics) and the end caps are made of silver but they're also coated in gold. When finished, they're cryogenically treated (super-cooled) for maximum clarity.

The result is a rugged-looking little fuse. But forget about how it looks (you'll never see it once it's installed). It's how it sounds.

The fuse makes the largest change I've ever heard in my home stereo equipment. Currently, I'm testing a great-sounding system from Resolution Audio (I'll tell you more soon). The system sounded very good with the cheapo fuse. With the HiFi-Tuning device, the system is world-class. The difference is anything but subtle.

I've heard similar differences with older Quad hi-fi gear. Changing to the HiFi-Tuning fuse changed the sound of my system -- all for the better.

And, I've gotten similar results when changing the fuse in my Sharp flat-screen TV. Colors and sound were both improved -- all by changing one small fuse.

This magic doesn't come cheap, though.

These fuses cost $30 each (for the shorter version) and $40 for longer ones. They're available in a slew of amperages -- in both regular and slow-blow versions.

I know that sounds expensive -- but not when you hear the difference they can make.

Know What You Own: RadioShack operates in the electronic services retail industry, and some of the other stocks that it competes with include Best Buy ( BBY), Circuit City ( CC)CC and even Wal-Mart ( WMT). These stocks were recently trading at $41.21, $3.84 and $49.89, respectively. For more on the value of knowing what you own, visit TheStreet.com's Investing A-to-Z section.

Gary Krakow is TheStreet.com's senior technology correspondent.

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