Mar 17

100KHz square wave generator for testing audio amplifiers

 

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The musical signal's form does never resemble a square wave. The frequency range perceived by an average adult hardly goes above 17KHz. Hence I do not give a dime to those heated discussions whether it's appropriate to test audio amplifiers using a 100KHz meander signal. But being an electronic engineer in my heart as well as by education and passion - I can assure you that giving an audio amplifier a try with 100KHz square wave test signal can reveal quite some technical qualities (or lack of those) in the design. Overshots caused by negative feedback loops or signal slopes formed by input/Miller capacitances are amongst things that are easier to observe with meander than when using sound-frequency test signal.

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Mar 09

Simple high-quality saw-tooth test signal generator

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Honestly, I would not claim that a saw-tooth signal is crucial for tuning audio amplifiers and similar stuff. It's rather a matter of convenience and helps to spot several non-linearities easier than a sine-wave. I've assembled this generator in order to top off the Wien bridge based sine wave generator. Since then I use it regularly because it helps to reveal subtle oscillation issues in amplifiers way better that any sine or square wave can do.

In this article:

  • High quality saw-tooth generator using CMOS 555 timer chip
  • Buffer amplifier stage with nearly infinite input impedance
  • Variable gain buffer with gain from -1 to +1
  • Linearity of professional equipment using budget OpAmp

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