Back in the dark ages, when large analog consoles occupied much of the space in a studio control room, there was fairly standard policy of leaving the console turned on day and night. And there was good reason for it. The huge collection of metal, circuit boards, and active components took a long time to warm up to a point of thermal stability, and an even longer time to cool down. Being that all functions were analog, and especially the EQ, the temperature variation could easily change the carefully derived settings from the day before if the console was in the process of changing temperature. And that practice became de rigueur. As a side effect, most studio engineers would leave everything else in the control room on as well; amplifiers, compressors, gates, limiters, reverbs, and other outboard equipment.
Many churches have adopted this approach, especially if the chief engineer came from a studio background. But with today's modern equipment, it's literally a waste of time. Let's look at what we mean by that and why.
All electronic components and assemblies have an MTBF, which means Mean Time Before Failure. Fans, potentiometers, and other moving parts are usually the first to go, but transistors, op-amps, rectifiers, integrated circuit chips of all flavors, and even the lowly resistor will eventually fail or change value appreciably, at some point or another. Capacitors fail too, but they have a tendency to sink gradually, rather than die outright. The progressive march towards failure is literally useful operation time wasted for nothing. And that's because...
Today's consoles, even the analog types, heat up and cool down quickly, especially the smaller ones used in most churches. Digital consoles have almost no warm up or cool down period that makes any difference to the sound quality or settings, except for some minor changes in their analog front ends and analog output stages. For the most part, the temperature change from a cold start to a few hours in the sun are relatively meaningless. It therefore makes good sense to reduce the “power on” time to as little as possible, to extend the life of the components.
There was a huge thunderstorm during the night in which the thunder clap caused the mic to feedback. The feedback loop never stopped, but grew in intensity. Not long after, some of the woofer cones heated to the point where they caught fire.
And there's a second very good reason for your equipment to be off-line whenever it's not actively being used. Why you ask? Well, in a typical church setting, actual usage, including rehearsals, is likely to be about 3% to 5% of the hours in a normal week if no special events are scheduled.
Power Surges
And that's the answer to the riddle. Power is very, very stable in the United States, but not 100%. There are low voltage periods called brownouts, especially in very hot areas at the high point of the day when air conditioners are running at full tilt. There are short-term surges that you can't even see on a meter unless it has a recording graph (these exist for trouble-shooting difficult AC problems). Surges can occur when a large factory shuts down large machinery for the night. They can occur when the nearby stadium fires up its million-plus watts of lighting for a nighttime baseball game. They can occur when a water treatment plant takes a generator off line for repair. There are even waveform variations when the big generators are being serviced way back at the hydro or nuclear power plant. So why expose your equipment, especially sensitive computers and digital consoles, to such potential problems when there's no reason for it, and good reason not to?
A power strip surge protector may help a bit, but it probably isn't fast enough to handle very short-term spikes. Nor can most cheap power strips handle much fault current. If a large pump (or other) motor on the grid near your church suddenly has a locked rotor, the fault current on the neutral and ground can be extremely high. It's not common, but it's also not a rarity to see high-voltage switch gear literally explode in water treatment plants and food or chemical processing plants. I've seen holes in concrete ceilings that were the result of a 1000-Amp circuit interrupter not interrupting fast enough. The back EMF (Electro Motive Force) that heads rearward down the power line to the grid can be of astounding value, even if it's only for a split second.
It's Not Just Power
And there's more to think about than power. I once tuned a system in a gymnasium, in which the owners elected to keep the amplifiers on 24/7. They inadvertently left a mic and mixer on as well, at least one time I know of. There was a huge thunderstorm during the night in which the thunder clap caused the mic to feedback. The feedback loop never stopped, but grew in intensity. Not long after, some of the woofer cones heated to the point where they caught fire. The smoke triggered the fire alarm and sprinklers, causing a very sizeable and expensive mess. This is yet one more reason to shut it all down when you leave the building. It's far too easy to leave that one mic on accidentally, especially in a big system that might have more than one console. It could be the monitor console, it could be the house console, it might even be a talkback mic that wasn't switched off.
And lastly, there's the issue of lightning strikes. While rare, they do occur. If they hit the power line anywhere upstream of the feed to the church, the short-term voltage spike could kill every electrical device in the church in a few milliseconds. Even turning everything off may not suffice. If you live or work in an area that is prone to regular thunder and lightning, I recommend that you have an electrician install a large contactor (that's the electrician's term for a big relay) that completely breaks the AC circuit to all the AV and IT equipment. Moreover, a second contactor, normally closed, should be put in place that brings the output terminals of the main power contactor to ground, to keep the power surge from jumping across the contacts (of the main contactor). Most electricians will not have heard of this before and might even be amused that you asked for it. Let them smile. There will need to be a timer relay that opens the NC (Normally Closed) contactor before the main contactor is engaged and in reverse, opens the main contactor before the NC contactor to ground is allowed to de-energize. Given a big storage capacitor in the switch box, and the use of DC coil contactors, the operation can even occur properly when there is a full power outage. That extra three or four hundred dollars in installation fees could save thousands in repair bills.
If you are still using a large analog console, say a PM-5000 or Midas XL4 for example, and you are worried about the warm up time, it's a legitimate concern. Your EQ may be all over the place until the circuitry reaches thermal stability (this is why my Apogee CRQ-12 parametric equalizer is probably the only one in the world that has a two-speed fan in it. I've seen the drift on an analyzer...and it ain't pretty). So if that is the case, simply put a timer on the console and have it switch on a few hours before each service or rehearsal. If the console draws a lot of current – and the large analog consoles usually do – use an industrial timer, not one of those plug-and-play types that are made for turning lights on and off in the home. It might cost a few hundred dollars to have an electrician install it, but it could save many thousands of dollars of repair or replacement, if a power problem occurs.
This article was originally published in June 2015.
