Spot Sine Wave Generator - 1

A spot frequency generator is primarily used for distortion measurements. It derives its name from the fact that it delivers one or more fixed out- put frequencies (spots), rather than a continuous range. The use of fixed frequencies makes it possible to tailor the gener- ator such that it outputs each "spot" as a pure sine wave with significantly less distortion than would be attainable with a con- tinuously variable instrument. The spot sine wave generator described in this two-part article has technical features that make it suitable for a wide variety of applications having to do with the analysing, testing, and setting up of high-end audio equipment. Its excellent performance is the more sur- prising in view of its simplicity, relatively low cost, and the use of standard, off-the-shelf com- ponents. Design principles Figure 1 shows the functional blocks that make up the spot sine wave generator. In es- sence, the sine wave is obtained by first generating a square wave, integr...