Monday, May 11, 2009

FFW14: Safe, clean power

This was written as a practical follow-up to the previous First Word, ‘Acts of God, and other dirty deeds…’ (FFW13). As much as I enjoyed littering ‘Acts of God…’ with pathetic and regrettable puns, my primary goal was to offer useful advice for protecting audio equipment from lightning and similar electrical events. So in this follow-up I described the numerous devices I used to ensure my equipment was connected to clean and safe power. I’ve always taken electrical powering seriously, not just because of the damage it can do when things go wrong, but because of the effect it has on the end result. Dirty power means dirty signals, plain and simple; but more about that later. The information contained below is still valid and relevant (you can’t change physics!), but I doubt the specific product makes and models are still available. Some of the products mentioned were at least six years old when I wrote this in 2000, which means they were on sale 15 years ago. The chances of finding the same products and manufacturers are remote, at best…

Safe, clean power
In the last issue I discussed the damage caused when lightning strikes a power line, telephone line, or television antenna. This issue I’m going to look at products that protect your equipment from such damage, along with some other helpful power-related devices.

According to the IEEE (Institute of Electronic and Electrical Engineers), a lightning strike on the power lines can deliver up to 20,000 volts and 10,000 amps into a building’s electrical power wiring. Such a sudden and dramatic increase in voltage and current is known as a ‘surge’. The bad news is that surges don’t only come from lightning strikes.

The average home electrical system experiences hundreds of surges every year. The vast majority of these are not from lightning, fortunately, and are therefore not so harmful. They’re created by appliances that contain powerful electric motors and/or heating elements, such as electric heaters, washing machines, dishwashers, air conditioners, refrigerators, and power tools. Whenever such an appliance switches on there is the possibility of a power surge. If your audio system makes a thump or click when an appliance switches on, you’re hearing a surge that has managed to get into the signal path. Although these surges aren’t big enough to cause serious damage (beyond perhaps blowing a fuse), they’re big enough to confuse personal computers and other digital devices, causing them to freeze or crash. They can also make their way into your recorded sound, and may even damage your monitors.

So what can you do about surges? The IEEE recommends two levels of protection. The first is a heavy-duty protector located in your fuse box – where the mains voltage enters the building – for frontline protection against lightning strikes and other externally generated surges. This should be supported by the use of surge protecting power boards that, apart from offering a second level of protection against externally generated surges, also protect your equipment against surges from household appliances.

You will need a qualified electrician to install the surge protection that goes into your fuse box. If that level of protection is too expensive, at least invest in one or two surge protecting power boards. There are a number of these on the market, priced from about $30 upwards. They’re readily available from electronics and electrical retailers, home appliance centres, and hardware stores. If you’ve got a modem connected to your system, be sure to get a board that also includes protection for your telephone line.

It is worth bearing in mind that most of the affordable protection devices use an electronic component called a Metal Oxide Varistor (MOV) to provide the protection. These components are sacrificial: the more surges they encounter, the more they degrade. So before investing in such protection, check that it has a status light to indicate the health of the MOV.

While there are many low cost surge protecting power boards on the market, one that caught my attention is the Panamax series available from Dick Smith Electronics. It’s based on a six-way power board with a ‘Protection OK’ light to show the health of the MOV(s). Modules can be added to include protection for phone lines, antenna and cable TV wiring, RS232 computer interfaces, and more. For a couple of hundred dollars you can put together exactly the system you need.

One step beyond surge protectors are mains filters. The mains power supplied to our buildings contains a lot of electrical noise that, like surges, plays havoc with digital equipment. At the affordable end are passive filters that are usually built into power boards. For a bit more money you can choose from a small number of active designs that provide superior performance. If you’re going to invest in a mains filter, be sure that it also includes surge protection. I have a KCC ‘Squeeky Clean’ LF-3 high-speed power and data filter with active monitoring, which I bought from David Reid Electronics six years ago. It offers protection against surges (including lightning strikes), filters out noise and other interference, protects the phone line, and has some very useful status indicators. A worthwhile investment.

There are two electrical problems that surge protectors and filters can’t protect you from: black-outs and brown-outs. A black-out is a total power failure: the lights go out and everything turns off. A brown-out is when the mains voltage drops, or ‘sags’, significantly. When your lights dim for no apparent reason, that’s a brown-out. Both of these can interrupt your workflow, and may even damage your equipment.

For protection against black-outs and brown-outs, you need an Uninterruptible Power Supply (UPS). This monitors the incoming power and, when it detects a black-out or brown-out, sounds an alarm and instantly generates 240V AC from a built-in rechargeable battery system, allowing your equipment to continue functioning. Most affordable UPS’s can’t generate this replacement power for very long, but it’s enough time to save your work and power down properly. The Sola 305 range, available from Dick Smith Electronics, also includes surge protection, mains filtering, and phone line protection. Priced from $299 to $499, the more expensive models offer longer back-up time. If you’re considering a UPS, be sure to get one with sufficient power rating for your equipment; otherwise, it might only provide a few seconds of backup power.

Apart from the obvious benefits of these products, providing clean power to your system may also improve the sound quality. The KCC filter I use improves the sound of my location recording rig in certain electrically noisy environments. But the biggest sonic improvement I’ve heard from any power device comes from balanced power. I’ve been using the locally-made Peach Audio balanced power supply and filter for the last four years, and it never ceases to amaze me – especially when taking analogue signals from digital sources. Improvements range from subtle to blatantly obvious. Balanced power is also good for minimising the humming and buzzing associated with tube guitar amplifiers, and avoiding certain earth problems. When all else fails, balanced power to the rescue!

So, how can dirty mains power affect the cleanliness of your audio signal? To explain that properly requires a lesson in electricity, which I’m not prepared to give here. Instead, let’s use a simple analogy…

Imagine a mountain with a number of villages on its slopes. Snow falls on the top of the mountain, melts and causes a stream to flow down its side. Each village takes water from the stream for drinking, cooking, washing, sewerage and so on, and tips the dirty water onto the ground, where some finds its way back into the stream. The village at the top gets pure fresh water, directly off the melting snow. The village at the bottom gets a cocktail of freshly melted snow mixed with dirty water from each of the villages upstream. The inhabitants of the top village can safely drink from the stream, but those at the bottom wouldn’t dare! They’ll need to filter and sterilise the water before it is safe for drinking.

The power wiring that runs through our cities, buildings and homes is very much like that mountain stream, beginning at the electricity generator and making its way through our streets. Each house and building draws power from the mains wiring, and some of its unwanted ‘dirty’ power ends up back on the power line. The further downstream you are from the generator, the dirtier your power gets. To make it worse, the people operating the generators are adding ‘dirt’ to the electricity before it even hits the power lines; for example, special signals to control off-peak hot water systems and so on. This is like adding fluoride to the mountain stream to improve the dental health of the villagers – the intentions may be good, but if you don’t want it then you need to filter it out.

Many audio products don’t have sufficient filtering in their internal power supplies to remove these unwanted signals; such filtering adds to the cost of the product but offers no measured differences in laboratory conditions (where the powering is inherently clean), and therefore has no marketing value. Without such filtering, the unwanted signals pass through the internal power supply and manifest as part of the audio signal. In some cases they are clearly audible as clicks, hums and buzzes, in others they form a layer of grit in the background that makes your recordings sound dirtier and cheaper than intended. Your best bet for clean and safe power is a combination of: 1) protection against surges, 2) filtering to remove most of the unwanted dirt, and 3) balanced power to neutralise the effects of any remaining dirt.

Alternatively, do as I’ve done and wean your audio system off the dirty communal mains power altogether. Switch to battery power and say goodbye to hums, buzzes, clicks, pops and all that other grit.

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