1) A frequency Selective Wave Analyzer is used for measurements in the audio frequency ranges between 20 Hz to 20 KHz.

2) The analyzer has a filter section with a very narrow pass band that can be tuned to the frequency of interest.

3) The block diagram is shown below

4) The waveform which is to be analyzed is applied to the input attenuator.

5) It acts a range multiplier and allows a large range of signal amplitudes to be analyzed without loading the amplifier.

6) The driver amplifier feeds the waveform to a high Q active filter.

7) The filter consists of a cascaded arrangement of RC resonant sections and filter amplifiers.

8) Close tolerance polystyrene capacitors are used for selecting the frequency ranges.

9) Precision potentiometers are used to tune the filter to any desired frequency within the selected pass band.

10) The final amplifier supplies the selected signal to the meter circuit and to an unturned buffer amplifier.

11) The buffer amplifier is used to drive output of devices like recorders, electronic counters etc.

12) The meter is driven by an average type detector and has several voltage ranges as well as decibel scale.

13) The instrument should have low input distortion.

14) Below is shown the response characteristics