The RaneGain test set is a handy tool kit based on techniques first developed by Pat Brown of Syn-Aud-Con for use in quickly setting sound system gain controls. Using the RaneGain pair makes setting level controls a snap.
Comprised of a precision 400 Hz sine wave generator and a matching piezo transducer, the test set makes use of the Fourier principle that all periodic waves can be broken down into a sum of pure sine waves. If a pure 400 Hz tone is the source in a system, and the system is turned up until clipping, then what comes out is the 400 Hz fundamental, plus a whole string of predominately odd-order harmonics. Spectrum analysis of the output will show the 400 Hz fundamental, plus strong harmonics at the odd harmonic intervals of 1.2 kHz, 2 kHz, 2.8 kHz, 3.6 kHz, 4.4 kHz and so on. The RaneGain Transducer is a piezo tweeter designed to reproduce mid-to-high audio frequencies, so while it doesn't reproduce the 400 Hz fundamental worth a hoot, the harmonics make it scream (so loud it Hz).
