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On or Off?

One of the most frequent questions I get asked as a pro audio technical engineer is: “are you dating anyone yet?” Well, such is the life! But, when I’m not talking to family, another question I hear a lot is, “should I leave my equipment on all the time, or is it better to switch it off when I’m not using it?” The correct answer is “it depends”. In some situations it is better to leave it on, and in other situations it is better to switch it off. Let’s take a look at why it matters and see what works best for you.

A lot of techs that I have worked with over the years were convinced that the best thing to do was to leave the equipment on all the time. Why? Because, just like the engine in your car, the most wear and tear occurs right when you start it up. The oil has settled down in the pan and it takes a minute to get pumping through the engine. Or, think about all the burnt out light bulbs you’ve had to replace. Have you ever noticed that most of the time a bulb burns out just as you flip on the power? You hit the switch, there’s a flash of light and then “plink”, out goes the light. It’s not very often that a light will be on for hours and then burn out.

What’s going on? In light bulbs and in electronics you have something called “negative temperature coefficients”. There are also “positive temperature coefficients” but just like “positive feedback” is something you want to avoid in your monitor system, positive temperature coefficients are usually avoided in electronics. Here’s how it works. When you turn on your gear, electric current starts flowing though the circuits and resistance (like friction) causes things to heat up. If the electronic parts have a positive temperature coefficient, that would mean the hotter it gets, the more current flows, and the more current flows, the hotter it gets – and so on. It’s called thermal runaway and in extreme cases something might burn up. On the other hand, a negative temperature coefficient means that the hotter it gets, the less current flows, and when less current flows, things cool off, and the gear settles in at a comfortable quiescent temperature. However, a negative temperature coefficient also means that electronics use a little more current when they are first switched on because they are still cold. This puts more stress on the power supply and the circuits delivering power throughout the equipment.

On top of this higher current draw, there is another, much greater demand for current known as in-rush surge. All equipment uses capacitors. They are like “reservoirs” for electricity, and they are empty until the power is turned on. A large audio console, for example, might have several hundred capacitors, and within the first few seconds of flipping on the switch, a surge of current rushes in to fill all those reservoirs.

That causes a lot of electronic stress, and it explains why most failures occur just as you turn on the power. But there’s more to the story.

Physical stress occurs as well. Changing temperatures caused by turning equipment on or off also means expanding and contracting parts. Over time; screws and nuts can work themselves loose, connectors and I.C. chips can work their way out of sockets. Even good soldering can migrate and become thin and cracked over time.

So far, it’s starting to sound like turning gear on and off all the time is a recipe for disaster. Now, before you run out and proclaim “thou shall not switch off the equipment!” we’d better take a look at the other side of the fence.

True, most equipment failures happen as a result of stress caused by cycling the power, but leaving the equipment on all the time has its perils too. Some are obvious and may have already popped into your mind.

For example, “What if there’s a power surge, or an electrical storm, and no one is around?” Power surges happen all the time, and you should have a good power conditioner, even if you aren’t planning to leave the equipment on all the time. Power surges are a legitimate concern. However, most surges are arrested by the power supply and at worst may blow out a fuse or a diode. Usually, it is an inexpensive repair, but there have been times where a nasty surge has meant buying new equipment, or in extreme cases, calling the fire department.

Now, how many times have you been hit by lightning? If you’re like I was, you might be skeptical and think, “The chances of getting hit by lightning are like, a million to one – it’ll never happen!” That’s what I used to think before I went to work in the service department of a U.S. console distributor. Then, I began seeing at least a dozen consoles a year that had been struck by lightning. It seems that choir microphones hanging from the ceiling and connected to ground through a console make a wonderful attractor for lightning bolts. Now, if you experience a direct hit, I don’t think it will matter if your console is on or off. On the other hand, I have heard that a well placed static shock from shuffling across a carpet can take-out a mic pre or even an entire automation system.

There’s also the other obvious expense of wasted electricity when you leave equipment on all the time. A large audio console may idle at seven or eight amps – that’s like having a 1000 watt light bulb on all the time. Not only are you paying for that 1000 watts of electricity, it’s creating an extra 1000 watts of heat in the room, and you would presumably be using another 1000 watts of electricity to run the air handler to keep the room cool. If you want to pick at nits, the air handler is not going to be 100% efficient so it’s really using more than 1000 watts – well, you get the point – it’s a waste.

All that extra heat has another detrimental effect. Remember, all equipment uses capacitors? Well, capacitors age and dry-out over time, and eventually, may need to be replaced. Heat accelerates the aging of capacitors. A capacitor that normally may have lasted 15 or 20 years might only last seven to ten years in equipment that’s left on 24/7.

In the end, what I tell people is that it really depends on how they use their equipment. If you are talking about equipment that is going to work several days consecutively, it would be best left on. If you are only using the equipment one or two days a week, it would be best to turn it off during the interim. On the one hand, you might “eventually” pay extra for more maintenance, and on the other hand, you would pay more for electricity “now” and be at a higher risk for electrical surges.

Generally, a working studio or broadcast facility would be advised to leave their equipment on all the time. However, a church for example, would only need to power up for rehearsals and services, and might leave the equipment on occasionally for consecutive days during multi-day events.

Now that you have a better understanding of the trade-offs, you can decide the best way to manage your particular system. If you have any questions, comments or criticisms; or if there’s a topic you’d like me to research for a future article, feel free to contact me through our website at:

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