[sdiy] [AH] What would the ultimate LFO do?

[Tom Wiltshire]

On 18 Dec 2011, at 08:03, Paul Perry wrote:

> If it is digitally created - and I don't see why not - what I would definitely want to see is NO stepping. Because, any stepping is painfully obvious when you have a very slooow LFO - and the ultimate LFO will of course go down to .001 Hz at least!
> 
> paul perry Melbourne Australia

It's easily avoided. At very slow rates more or less any waveform data table will get stretched to the point at which the steps become visible, but it's easy to provide linear interpolation between the given data points. This allows you to output data which uses all the available DAC values even at the lowest rates.
I've done this with sample rates of 25KHz and 48KHz at 16-bit accuracy. There's absolutely no stepping perceptible in any situation. With modern chips, running an LFO (or even a few of 'em) isn't a big job, and you can push the sample rates into the audio range. This lets you filter the output at (say) 5KHz and remove any remaining trace of the digital origins. In practice, I don't bother beyond a roll-off cap here or there - I can't hear it at 16-bit.

Regards,
Tom