Musicians have been killed through faulty equipment or dodgy club wiring.

Voltages above 50 DC or 30V AC can kill. It only needs 50mA, which is one-twentieth of an amp. Given the right conditions the speaker voltage from a 500 watt amp could kill. Hence the current requirement for sealed speaker connectors like Neutrik.

The best way to stay safe is to use a Residual Current Device or RCD. These devices detect any difference between the current in the live and neutral wires; these should be equal. If they are not, current is either going to earth through your faulty equipment or through you! The RCD senses that current difference and switches off the power.

An RCD plug adaptor that you can plug into any socket to protect you can be brought at a cost of between £10 and £20. If you plug your extension cord into this, all devices on that board will be protected.

All exposed metal parts of amplifiers are earthed, so that if by fault the exposed metal becomes live, current flows to earth and the fuse blows. For this to happen the equipment earth must be connected to electrical earth and the correct fuse fitted. So check your mains plug and your earth.

(Some equipment is known as double insulated and does not require an earth)

Double Insulation SymbolIndicated by this symbol

A worthwhile device is the neon screwdriver which glows when it contacts a high voltage. Check your kit by touching the exposed metal with the tip of the screw driver, if it glows then you have a problem. It is either live or has an induced voltage in the earth wire. This can happen if there is a faulty earth on either the equipment or the club's wiring. To stop induced voltages in your sound system, make sure that ancillary equipment like mixer desks or record decks are earthed via their supplied earth connection.

The fuse

The fuse is vital to your safety and your equipment safety. The fuse must be replaced by exactly the same type as fitted which should also be the same value as seen on the equipment. Never fit a higher value fuse than the maker's specification. If the fuse keeps blowing there is something wrong. Do not fit a higher value ever. The fuse current rating is not the value that the fuse will blow at, it is instead the current the fuse will take.

The mains plug fuse

These fuses are of the same type but different values: 3 amps, 5 amps and 13 amps. The current rating is not the value that the fuse will blow at it is instead the current the fuse will take. Equipment that runs on 4 amps will only need a 5 amp fuse fitted to the mains plug. Only large power amplifiers will need a 13 amp fuse.

The equipment fuses

These are of different values and come in a wide range of values, sizes, casings and types.

Fuse values

Fuses come measured in amps and milliamps. A milliamp is 1/1000 amps or 0.001 amps.

Fuse casings

Fuse casings are ceramic for mains plug fuses, equipment fuses can be either glass or ceramic. The ceramic casings are fireproof and must be replaced with the same type as removed. Casings come in various sizes; once again, replace like with like.

Fuse types normal fuse and slow blow fuse

The slow blow fuse or delayed fuse is marked by the T symbol on the fuse, this is printed next to the fuse value. This means that the fuse allows equipment to draw an extra-large current for a very short time before blowing. This is for big amplifiers with large power supplies as the power supply capacitors will draw a high current on switch on as they charge up. The time delay can be created by adding a little blob of extra metal to the fuse and this extra metal absorbs the heat from the fuse allowing it to survive small overloads without burning out.

Thermal fuses

Thermal fuses blow at a specific temperature dependent on the fuse. These come in two types: use once and resetting fuses. Use once fuses are normally built into transformers by the manufacturer. Resetting fuses consist of a bi-metal strip which breaks contacts when hot and connects contacts when cooled down. These types of fuses are fitted by the equipment maker and are normally fitted to heat sinks or other surfaces liable to overheat.

Other fuse types

There are also many specialised fuses such as fast blow or very fast blow. Some of these can be hard to identify and even harder for the general public to source. Fusible resistors are also fitted to many circuit boards, these are difficult to identify on the board and also not easy to buy. Do not try changing these yourself. They are safety critical components, and require you to be skilled in de-soldering and soldering.