5:00 pm.

    Sound check.

    Concert starts at 8:00 pm.  

    Sixteen thousand four hundred tickets have been sold.  More are selling every hour.  

    Radio and television trucks have already claimed parking spots.  Microwave antennas extend yards up in the air.

    Three enormous tractor trailers backed up to the stage.

    An 80' wide, 40' deep stage, five feet high, assembled and leveled by a stage crew of seven.

    Another 40' width for the sound system side wings.  

    Ninety feet away, another, smaller stage, with a state of the art, 56 input mixing console.

    Rack after rack after rack of computerized support electronics.

    200,000 watts of computer controlled stage lighting.

    24 EAW 850 main cabinets with 12 EAW SB850 sub woofers on each side.  

    Over 80,000 watts of audio power for the front-of-house system.

    More power amp racks for the stage monitors with several thousand watts of amplification.

    Altogether, over 2 miles of snakes, cabling, and wiring.

    Approximately 1.75 million dollars worth of stage, sound, and lighting.

    Two drum sets, multiple guitar and bass amps, stage monitors, microphones.

    Everything on stage: the very best names, top of the line equipment - pristine condition, working perfectly.

    A Step Van at the back of the stage, with over a dozen keyboards available.

    A Hammond B3 with 3 Leslies, in stunning condition, stage right.

    Plenty of good food and drink in the dressing rooms, beautiful weather for a concert.  

    Nobody could ask for better show conditions than this.

Until you turn on the Hammond

.... and discover that it's playing flat, compared to the Kurzweil.  20 seconds later, it's in pitch again.  Before the end of sound check, it's gone in and out of tune a dozen times.  The guitar and bass players are looking at you and the Hammond as if you're both on drugs.  Everybody's looking around at everybody else.  It gets real quiet all of a sudden.  This can't be happening.  

But it is.

WE'RE IN TROUBLE

The only instrument on that stage that uses a motor to create its sound is the Hammond.  If the motor is spinning either slow or fast, the organ is out of tune.  Period.

Many large, outdoor concerts must use a generator, because adequate power isn't available any other way.  The generator is a large trailer, or sometimes it's a self contained truck.  It generally has a diesel motor, plus all the connections to hook up power feeds, and send them to the stage area.  It's usually parked pretty close to the stage, and some huge, monster sized cables run from the trailer to the power distribution boxes on the stage, which are actually breaker panels, very similar to the ones in a house.  Somewhere on the trailer, there are typically meters and dials to indicate voltage, current, motor RPM, fuel, temperature, and other details relative to the generator.

As far as our Hammonds are concerned, only one detail has any real importance:

LINE FREQUENCY

Unless the Hammond is getting a true 60 Hz power feed, it's going to play out of tune.  The Hammond run motor maintains its precise speed by synchronizing with the line frequency.  Unfortunately, this situation is virtually unknown to many of the generator operators.  A large percentage of their generator rentals are for construction sites, where the focus is on voltage and current supplied, rather than on precise frequency of the voltage.  Very few guys on the stage crews know about this, either.

This situation has no noticeable effect on anyone except the Hammond player.  That may be why so few people know about it.  The generator companies supply power to anybody that needs it, not just musicians or Hammond players.  The amplifiers, sound system, instruments, lighting, and all the other devices that use electricity on or around the stage can operate at 59 Hz or 63 Hz, and nobody ever knows the difference.  

WHAT CAN BE DONE ABOUT THIS?

The first option is to find the generator man, and see if he's able to get the power stabilized to 60 Hz.  If his equipment is capable of fine frequency adjustment, you can probably work with him to lock it in.  I would strongly suggest you do this with your ears, comparing the Hammond to a known pitch (for example, another keyboard), and not with the dial or gauge on the truck.  Those dials live through a life of endless vibration on that truck, and may or may not be 100% accurate.  I would also strongly suggest you read the line frequency with one of the better digital voltmeters, such as a Fluke 85 or 87.  Just insert the probes into an outlet, set the meter for VOLTS AC, and read Hz on the meter by pressing the Hz button.  My own house reads 59.99 Hz as I'm writing this.

Many generator rental companies leave the generator on site, and don't return until after the concert is over to pick it up.  If the generator man is gone, or the control panel on the trailer is locked, you're in deep, deep trouble today.

A POSSIBLE SOLUTION

One possible preventative solution is to build your own stable power supply system.  This is quite simple to build, and doesn't cost very much, plus it's fairly lightweight and easy to transport.  And it can be easily built to work in foreign countries, using several different supply voltages.

The basis of a stable power supply is an amplifier.  I've used a Crown DC300 amp in the past, and these amps are commonly available and fairly inexpensive.  They're also built like a tank, and can take a lot of punishment.  

You'll need a stable signal generator, called a sine wave generator.  Many of these are crystal locked, so the output frequency doesn't shift, although the line power might fluctuate.  The sine wave output, at exactly 60 Hz, is fed into the amplifier's input, and the speaker output of the amplifier is now the power supply for the Hammond.  Using an AC voltmeter, raise the gain on the amplifier until the output reads around 110-120 volts.  If you have a scope available, view the signal generator output, and adjust it to just below clipping.  Some amplifiers may need to be bridged (ie; mono operation) to produce that much voltage to the speaker output terminals.  The speaker output voltage is connected to a standard type of wall outlet box, and the Hammond plugs right in.  The entire power supply should be enclosed in a small rack, protecting the components and making transport simple.  All the internal wiring can be permanent.  Once it's built, you just plug it in, and plug the Hammond into it, as if it were a regular wall outlet.  Changes in line frequency will no longer affect the Hammond, because it is now regulated to 60 Hz.  

I'd recommend using a large enough rack to accommodate at least one cooling fan.  You can fine tune the power at every gig, and make sure it's right on 60 Hz.  A small, panel mount frequency counter and AC voltmeter should be easy enough to find, and could be permanently mounted in the rack with the wave generator and amplifier.  This would make setup almost instantaneous.  Various power converters - such as a 220v to 110v - could also be mounted in this rack, which would enable it to be used in foreign countries as well.  The final design is determined by how elaborate and elegant you care to get with this project.  The possibilities are nearly endless.

At this point, I'm not certain exactly how much current a Crown DC300 will provide.  I recall using this system with two Leslies in England, but this was about 30 years ago.  I'm not sure if it could be used successfully with three, four, five, or more Leslies.  Obviously, if more power (meaning amperes) were needed, a more powerful amplifier could be substituted for the DC300.

I've heard suggestions that only the Hammond's run motor needs a stable power supply, and the Leslies, Hammond preamp, reverb, etc., could be operated on whatever power was available.  This is correct.  However, for the sake of simplicity, my preference would be to use a single power cable from the AC supply to the Hammond, and a single cable to each Leslie, rather than having any exotic connections, or special power cables for the run motor.  I'd rather keep this as simple as possible, making setup and teardown that much easier on everyone.

Other possibilities include various UPS systems and commercial power supplies.  Most of these will cost quite a bit, and some of them are large, heavy, and difficult to transport.  Some use internal backup batteries which will need replacement after some period of time, and are extremely expensive.