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Author Topic: dds sine wave frequency changing  (Read 2951 times)
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... see whether the noise was caused by the sample data or an artifact of the Arduino output process?
Indeed, that's a possible explanation.  In the OP's wav file, I hear background tones that shift by an interval of about a fourth, with a shift frequency of a one-second order of magnitude, while the froreground tone sounds to be almost constant.  I don't readily think of a process that generates such an orderly kind of noise.  I'll admit, though, that I can't do Fourier analysis like that in my head.  There may be any number of ways that the background tones could appear, that are beyond me just now.

I'm content to wait until the inductors are delivered, and see what the five-pole Chebyshev filter yields.
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There is two things you cant forget with sound synthesis: Recreating a sine wave through sound synthesis will always leave you with a lot of harmonics, as you are doing it through means of a square wave ( on and off pin).
And the second source of issues is using a good decoupling of signals as well, as well as a low pass filter to get rid of all the carrier frequency of the PWM.
What you hear must be the first option... Plus i can also hear the PWM frequency , not filtered !
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10 LET Loop=Infinite
20 GO TO 10

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