LEAD: THERE are few things more disconcerting to the professional guitar player than twisting and shouting on stage only to find that the cord that feeds the sound from guitar to amplifier either has been yanked out or entwined with the cord of another band member. Well, such cords are very difficult to find, thus being valuable and should be stored carefully (like you should keep your guns safe in the best gun safe).
THERE are few things more disconcerting to the professional guitar player than twisting and shouting on stage only to find that the cord that feeds the sound from guitar to amplifier either has been yanked out or entwined with the cord of another band member.
But thanks to a new wireless transmitter, guitar players – from rock-and-rollers such as Bruce Springsteen to country-and-western musicians backing up Dolly Parton – are finding not only that they are no longer tethered to their amplifiers by a black coaxial cable, but are also free to wander on and off stage while playing.
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”It is the latest craze to be mobile on stage,” said Brad Gillis, lead guitar player for the rock group Night Ranger. ”And we like to move around a lot,” he said speaking of his five-member group.
While the technology for wireless sound systems has its roots in walkie-talkies, the portable radios first used in World War II, it took a series of innovations in the last 10 years to make ”going cordless” the latest fad among musicians.
Most of the improvements are based on advances in semiconductor technology, which have given the 35 or so companies in the wireless systems business the means to improve performance, reduce component size and cut costs. Wireless systems now sell for as little as $100 for consumer or amateur uses. Professional systems, many of them produced by companies that also make wireless microphones used in churches and television talks shows, can cost as much as $2,400.
One key advance, which enhanced performance, is the development of audio companders. Companders eliminate the noise from signals in nearby channels that can interfere with radio transmissions. The compander compresses the audio information during transmission and expands it in the receiver. The process works much like noise-reduction companders in Dolby and DBX tape recorders.
”Masking the noise of radio waves with companding is really what paved the way for wireless,” said Royce Krilanovich, advertising director of Nady Systems Inc. of Oakland, Calif. The company sells about 1,000 systems a year and dominates the top end of the market. Mr. Krilanovich said that early systems capable of producing enough volume to satisfy musicians had been plagued by heavy interference.
Another development that gave musicians the freedom to roam with confidence was diversity reception. Until recently, when a musician wandered behind a concrete pillar or a metal object such as a drum set or lighting equipment, he or she stood a chance of having the radio signal deflected in the wrong direction. This phenomenon is known as multipath dropout.
Diversity reception solves that problem by using two antennas and two receiver sections, which operate independently of each other. A computer chip selects the strongest signal for processing. The weaker signal, which would be lost behind a pillar, is rejected.
Some musicians unwilling to pay for full-scale diversity reception use modified systems in which the receiver combines any signals received by the antennas rather than picking out the strongest.
A performer’s wireless system is basically a small radio broadcasting system with an average effective range of up to 250 feet. Typically, a two-antenna receiver sits atop a musician’s amplifier and is powered either by a battery or an AC plug. The transmitter package (the size of a pack of cigarettes) on the guitar or other instrument contains a microphone, a transmitter and an antenna. It plugs into the instrument’s jack where the amplifier cord is normally inserted. The power pack, which has a 9-volt battery, is usually attached to the guitar strap.
A liquid crystal display, like those on stereo systems and portable radios, lights up on the front of the guitar body when the system is on and dims as the battery’s power fades.
One trend, for those who can afford it, is to switch to guitars with built-in transmitters. Mr. Gillis’s brother, an electronics technician, hollowed out the back of the rock star’s Fender Stratocaster and mounted a transmitter inside the guitar seven years ago. Now, musicians lacking access to such expert help can turn to such companies as Nady Systems that sell wireless electric guitars and basses, complete with transmitter and receiver, for $1,200, or custom guitar makers, such as Hamer USA, which will make them to order.
Like any radio transmitter, cordless guitars and other wireless instruments fall under the jurisdiction of the Federal Communications Commission, which sets limits on the frequencies they can use. There are about 20 channels that operate between 150 and 216 megahertz. That tends to limit the number of musicians using wireless systems on one stage. Too many systems can create a situation called cross-talk, in which the signal from one instrument ends up in another musician’s amplifier.
Musicians also have to watch out for interference from television stations operating on nearby channels. A routine check is done before most concerts. While freedom of movement is the most obvious attraction of the cordless instruments, musicians and guitar manufacturers note that there are other advantages they are just beginning to explore. For one, wireless systems eliminate the clutter on stage that came with cords and allow bands more flexibility in the placement of amplifiers and monitors, That encourages innovations in staging.
By Stephen Phillips