A Low Distortion Sinewave Oscillator

ricardo said:

...  but I would still like a software oscillator with a stepless knob ...  preferably free  ;D

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No specs available that I could find but the Sig gen in REW is stepless IIRC, and free
http://www.hometheatershack.com/roomeq/

Also it's been years since I tried it but I remember the generator in Signal Suite being stepless too, could be wrong on that
http://www.faberacoustical.com/products/signalsuite/

Not to be a "debbie downer", but any digitally generated sine wave will vary wavelength or pitch in discrete steps. These steps can be imperceptibly small.  Likewise the control input will be quantized, but sweeps or glides can be smoothed to sound less granular.

JR

Thanks for the links Mr. Flaherty.  Downloading REW now.  www.faberacoustical.com dun seem to want to know me.

JohnRoberts said:

... but any digitally generated sine wave will vary wavelength or pitch in discrete steps. These steps can be imperceptibly small.  Likewise the control input will be quantized, but sweeps or glides can be smoothed to sound less granular.

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There's no problem generating a sweep which is theoretically & practically 'stepless', even in 16b.  This is essential for Prof. Farina's log sweep to measure response and distortion simultaneously.  I generate & process this with old DOS C progs. cos I'm still firmly 20th century for programming.

The difficulty is, as you say, quantising the control input and devising some algorithm for smooth control of the continuously generated signal.  The criteria is that it 'sounds' stepless on either fast or very slow manual control.  The ear can pick up very small levels of 'FM' distortion.  'Loudspeaker Distortions - can we hear them?' Peter Fryer.  HFN & RR jul77