Many of the places we play in – music venues, practice rooms, or home studios – suffer from “dirty” AC power, where the mains power coming from the wall outlets contains a lot of unwanted interference which can work its way into our audio signals as noise, affecting the quality of our sound. This interference is usually caused by other devices connected to the power. Common culprits are: fluorescent lighting, dimmer switches; fridges, freezers and other appliances; electric fences; pool pumps; and even nearby radio stations.
Surges and Spikes
Occasionally the voltage of the power supply will be uneven, rising above the rated voltage (220V – 230V here in South Africa). Short increases are called “spikes” and longer increases are called “surges”. This can affect the operation of, or in extreme cases even damage or destroy your valuable equipment.
Tackling Dirty Power
Firstly, when possible, make sure all your equipment is plugged into the same outlet and try make sure that nothing else is sharing the same outlet. If you seem to be getting a lot of noise on your sound system, try a different outlet to see if it makes a difference. Ideally stage or studio power should be on a dedicated circuit breaker at the power distribution box (but rarely is), so the best thing is be prepared and use a power conditioner.
Tools of the Trade
A plug-in mains socket tester is a simple and inexpensive tool that is an essential part of any gigging toolkit. You simply plug into any power outlet and it immediately shows you if there are any major problems with the power such as missing earth lines or reversed polarity power. While reverse polarity is not necessarily a big issue (particularly if all your equipment is plugged into the same outlet), a power outlet with a bad earth connection can be lethal, so is serious enough to cancel a gig over if there is no alternative. Make sure to test the outlets in any new venue you play and if you find any problems report them to the venue owner.
A simple surge protector protects against damage due to surges or spikes by absorbing or draining off the excess power safely. In extreme cases (such as lightning strike, they will usually try to self-sacrifice, blowing before your equipment can. These are relatively simple and cheap and can be in the form of single outlet or a multi-plug adaptor.
A power conditioner is a device that “cleans” AC power, filtering out noise and smoothing the wave. A typical power conditioner has up to 10 power outlets and commonly provides surge protection as well as noise filtering. The noise filtering will usually be rated in decibels (dB), with higher numbers being better (you want at least 40dB reduction, ideally 60dB or better). The better quality power conditioners for audio will have isolated power outlets, which eliminate ground loops and help with interference and “cross-talk” between components in a system. The less expensive models will be in the form of a multi-plug adaptor, while the better units are mostly 1U or 2U rack devices, usually include rack lighting and sometimes even a voltage meter.
Often confused with power conditioners, line conditioners not only condition the power but also regulate voltage, boosting it when it drops or acting as a surge protector when it peaks, maintaining a steady flow of electricity at the set voltage. Mostly used more in the bigger studios, as they are usually much more expensive, larger rack mount or free-standing units.