Fuses for Audio Components: Determining What Your Component Has

 Common Types of fuses used in Audio Components

Size

Fortunately for mainstream audio components, there are (usually) only 2 sizes of fuses, and even among those two sizes, most newer components are opting for the smaller 5mm x 20 mm size. 

5mm x 20 mm - Known as the "Small" fuse in our industry. Most common in all newer components
6mm x 30 mm - Known as the "Large" fuse in our industry. More common in older components

Slow Blow, Fast Blow and Time Delay

What many of us consider to be slow blow fuses are often time delay fuses. The writing on the fuse band indicating the type usually starts with a "T". Like T2A, that would indicate a 2 amp time delay fuse. Technically time delay fuses are slower to blow than fast blow fuses, but they do differ slightly from a traditional slow blow fuse. A traditional slow blow fuse can handle a larger inrush of current for a longer period of time. For example, a tube component might need a traditional slow blow fuse because the current draw to heat up the filaments of the tubes might be more intense and last longer than a solid state component. I said might, as there are no hard and fast rules here. Fuses are the designer's choice based on measurements and circuitry. The innuos Statement is a solid state component, but it's massive power supply has a 3.15 amp true slow blow fuse inside. a T-type may work, but why risk it? Especially if you are investing in a QSA Red or Red/Black fuse. 

Also, a time delay fuse filament generally looks different from a slow blow fuse filament. Take a look at the photos below.

A T type fuse filament looks more like a thin wire.

A true slow blow fuse filament looks like a coiled spring

So grab a magnifying glass, or your smart phone, and take a close look at the writing on the metal bands, as well as the filament. 

Amperage

Amperage is the amount of current, in amps, that a fuse will withstand before failing. It is marked on one of the metal fuse caps, usually right before the voltage rating. So a 2 amp fuse might read on one of the caps: T2A 250V. That tells you that it is a 2 amp fuse, rated up to 250 volts.

Confused? Contact us!

As always, we are just an email away from helping. We will do everything we can to help you determine the exact replacement fuse you need. But we are only human and our resources are limited, so as I tell my children, don't be lazy. Investigate on your own first. :)