Mix Interview: Arthur Kelm

Jun 1, 2009 12:00 PM, By George Petersen

A WELL-GROUNDED APPROACH TO AC POWER PROBLEMS

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If you have the money, go for a chemrod — they're expensive but last 28 years. The alternative is driven-steel rods, but they lose their effectiveness after about 10 years as they rust away. For all intents and purposes, they're just pieces of copper-plated rebar, and that copper coating wears away as the rod is pounded into the ground. Once the copper's gone, the bar starts rusting.

Ground maintenance is also important. You need to check your ground every few years with a clamp-on meter. Only about 10 percent of the ground systems I've checked even met the code — which is 25 ohms — and most measure somewhere between 35 to 600 ohms.

Oddly enough, if electrical inspectors see a water pipe ground and a driven ground rod, they won't even bother to measure it, saying, “That's good enough.” It can change with time and soil conditions. Moisture can help, but the quality of the ground is based on the soil's mineral content.

Once you have a good grounding system established, it's amazing how much better things are. It really works and it's not rocket science.

So if humans can fly to the moon, why can't I get the buzzing out of my Strat?

Blame it on the Earth's magnetism. [Laughs] Actually, it's not the Earth's magnetism, but unless you get way out in the country — like out at Neil Young's ranch — you're constantly being inundated with magnetic fields. And single-coil pickups are the most sensitive device we have in the audio business. If there's a hum or magnetic field out there, they'll find it. Concrete/steel rod-reinforced buildings are huge Faraday cages — they actually radiate, bringing hum into a system. They're giant 60Hz antennas.

In some outboard devices like AMS units and Harmonizers, their power supplies throw off a huge [EMF] field, which you can prove by putting your guitar close to them. I have a single-coil pickup and Danelectro HoneyTone battery-powered amp I can turn on and move around inside buildings and track down hums. When I design a room, I try to place all electrical within steel conduit and twist the hot and neutral wires together to cut down on EMF fields.

Lighting dimmers can be culprits, and APC UPS [Uninterruptible Power Supply] units can back-feed noise into the electrical system.

What advice do you have for the budget home studio?

Always have a single source for your audio power. In most bedroom/home studio conversions, one of the biggest issues is having two separate circuits that are daisy-chained back to the panel through some other rooms. Here, you're destined to have a hum or buzz if you wind up having two paths back to the panel board of varying length, with different things plugged in along the way. Most small rooms will have a single 20-amp circuit, so go from that to power strips and avoid plugging audio gear into different outlets around the room.

If you need to go beyond a 20-amp capacity, you should call an electrician in to pull in a separate circuit — or two dedicated circuits in that room. Going slightly more upscale, have an electrician run a 240-volt circuit to the room and go from that to my rackmount isolation transformer, which splits it to six 20-amp breakers. Here, the isolation transformer separates you from the house, creating your own small service.

You can designate certain circuits in a room as “dirty” and use those for lighting and non-audio gear.

Exactly. If you have three 20-amp breakers feeding a room and put all your audio gear on one breaker and everything else on another, you're already miles ahead of where you were.

Any surprises you've learned along the way?

Just because you've hired a good chief electrician doesn't mean the workers on the job pulling wire and putting in plugs are as good. I had this situation doing Don Henley's studio installing an old API console, which was quiet. After putting in three pieces of outboard gear, the noise floor started moving up. I turned off the power, went to the main panel board, pulled all the green wires off the IG ground bus and started testing them back to the utility and found four shorts. On the neutral bus I found the same thing — five more shorts, shorted to utility. I called the electricians and told them there were shorts on the IG outlets. They begrudgingly came out and fixed the shorts, and everything was dead-quiet. Oddly enough, these faulted outlets were in other parts of the studio I wasn't using. Never assume anything with electricians.


George Petersen is the executive editor of Mix and runs a small record label at www.jenpet.com.






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