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Tuesday, May 19, 2015

Simple but precise 1KHz Distortion Analysis Tool

For my audio projects, I wanted to have a method of simply measuring distortion without buying (too costly) or building (too complex) a full-blown analyzer.

The most simple solution is to use a low distortion sine wave generator to feed the DUT, and at the output, filter the sine wave out again. What is left would be the distortion created by the DUT.

As it turns out, designing a very low distortion since wave generator is not that easy. Luckily I found a unit that is excellent for a reasonable price. It is called the Mickevich (the designer) Ultra Low Distortion  (<0.00001%) 1kHz Sine Wave Generator.

What was left was to design a precise filter, the required power supply and the box to put it all in to.

In addition, I needed an external sound card interface that is used as a front-end for the PC-based FFT analyzer.

I described this project on a diyaudio forum where much more information can be found about the oscillator, and the filter I used : 

In the meantime, I also purchased a high precision DIY capacitance meter, and also learned that the opamps I used are not the best. With time permitting, I will update the filter with better tuned filter capacitors, and change the OpAmps. Stay tuned.


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