[sdiy] [synth-diy] numerically controlled superoscillator without hard sync

[cheater00 .]

On Mon, Feb 10, 2014 at 11:56 AM, Tom Wiltshire <tom at electricdruid.net> wrote:
> As Roman mentioned, this type of "wavetable" technique has quite a distinctive sound, probably due to everything being locked into tight harmonics. If you use more than 32 samples, you can get past "combo organ", but I still know what he means. Those combo organs used frequency division to get harmonics that were locked together, and this technique has the same fault.

32 samples are perfectly fine for the top 5 octaves. You can't even
hear more than 32 samples.

You mip-map below that.

> if the sample rate is not in a harmonic ratio to the oscillator
>> pitch, then the aliases will be non-harmonic, but they will have a
>> precise, constant spot in the spectrum, just like in any acoustical
>> instrument - stringed, brass, etc. They become part of the timbre as
>> long as the ratio stays precisely constant (and it does).
>
> That could be useful, but "precisely constant" isn't quite enough.
>
>
> You're going to have to be careful - if you've got complex non-integer ratios, the imaged frequencies won't fall neatly into the same sample every time, and you're back to having jitter in your signal. Think about why you don't get that when everything is harmonic.


No, in this case the aliased or imaged frequencies won't fall neatly
into the same samples, because they're not cyclic. But we're not
storing them in the wave table, those frequencies are generated by the
synthesis engine. I'm not sure what you mean about getting jitter. We
do get a signal which is aliased, but it's still locked in precise
frequency to the main frequency. Can you explain the jitter thing?

Cheers,
D.