The Tone Plug-essentially a tiny audio generator built into a Neutrik XLR connector-is a dream tool for live sound engineers. And for project studio owners who have no test equipment, the GTC Industries Tone Plug could be the best preventive maintenance investment they could ever make.
This small unit generates five individually selected or automatically stepped sine waves at frequencies of 100, 250, 400, 1k and 10k Hz. Additional test signals include: a VLF 40/2400Hz combo tone for testing crossovers and subwoofers; a multifrequency pulse that’s perfect for adjusting speaker time delays and tweaking reverbs or delay units; an amplitude sweep function for adjusting compressor/limiters; plus a unique sweep tone for tracing wiring in racks and buildings.
The Tone Plug operates on phantom power and has a bright LED that glows when phantom power is present, the cable is working and the preamp is, well, preamping. It couldn’t be easier.
On power-up, Tone Plug generates a 1kHz pulse. Each time you press the small button on the XLR body the unit steps to another frequency, offering five choices (100/250/500/1k/10k Hz). If Tone Plug only delivered those five tones, it would be worth $49.95, but as late night TV always promises, “Wait! There’s more!” By holding the button down for two seconds when any frequency is selected, the unit enters a second-tier mode, offering five other functions: Multi-Frequency Pulse; an Auto Sequence (this steps through all five of the Tier One sine waves); Amplitude Sweep (a 1kHz tone that varies in amplitude over a 20dB range); Trace Tone (car alarm); and a VLF test signal-essentially a 40Hz sine wave superimposed with a 2,400Hz tone. The 2,400Hz signal is 20 dB lower in amplitude than the 40Hz tone-a good thing as the ear is very sensitive to midrange.
In the Pulse mode, a “pop” automatically repeats every four seconds or you can manually press the button to hear this environmentally friendly version of Chinese water torture. I have never had to adjust speaker cluster delays, but I am always trying to tweak reverb programs to make small rooms sound better, and a repeating pulse is a useful test signal.
The 20dB Amplitude Sweep is handy for checking threshold and ratio settings on dynamics modules. But one feature that reminded me of what I didn’t miss about New York City was the dreaded Sweep Trace Tone. Easily recognizable as the world-renowned car alarm sound, this tune makes millions of people wake up in the middle of the night. If you’ve ever used an inductive-type telephone line tracer, you know this signal makes wire tracing almost as much fun as snake charming.
LET’S MAKE SOME NOISEAn equally useful product is GTC Industries’ Noise Plug. Anytime you’re jonesin’ for some good old “pink” noise, there’s no need for smelly old seashells to hear the rush of the ocean: Just add phantom power, and you won’t believe how much continuous sound can come from a single XLR connector. While not as sophisticated as the Tone Plug, the Noise Plug is an ideal companion for use with a Sound Pressure Level (SPL) meter or a Real-Time Analyzer (RTA), which unfortunately can’t be squeezed into an XLR connector.
The Tone Plug and the Noise Plug are each priced at $49.95. I should also mention that the output of both of these units is a balanced mic-level signal and that no batteries are required. You’ll just have to feed the Energizer Bunny some carrots from now on and keep a Noise Plug and a Tone Plug in each pocket. Woof!
GTC Industries Inc., P.O. Box 2493, Naperville, IL 60567; 630/369-9815; fax 630/369-9198; www.gtcindustries.com.
