When examining overload recovery in AC-coupled amplifiers or when testing the attack/release behavior of audio compressors, well-defined tone bursts come in really handy. This simple circuit accepts a steady tone from an ordinary audio oscillator at its input, and produces bursts at its output. The duration of the burst as well as their repetition rate are variable from less than a millisecond to several seconds. The amplitude and switching point are, of course, also adjustable.

Powered from a 9-volts supply the generator will accept input signals up to 5 Vpp before clipping. For more headroom the supply can be increased up to 15 V. The device works up to 20 kHz with input signals down to 400 mVpp. (With smaller signals the maximum frequency reduces somewhat.) The current consumption is less than 4 mA.

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