Musical Instrument R-C Tuning Oscillator Employing Auto-Transformer Tappings to Give +/- 0.005% Interval Accuracy
In recent years much attention has been given to digital techniques for generating a series of semitones in equal-temperament frequency ratios (1)-(5). : The present contribution is concerned with a non-digital solution to the problem, which is both economical and capable of very high ratio accuracy and long-term stability. The new circuit (patent applied for) is basically an R-C oscillator of the double-integrator-loop variety (6), but the frequency of intervals are determined by varying the gain of one of the integrators by means of tappings on a small and quite cheap auto-transformer. Only the ratios of this transform are of first-order significance, not the inductance values as such.
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